OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​display/​drm_dp_mst_topology.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /*
  * Copyright © 2014 Red Hat
  *
  * Permission to use, copy, modify, distribute, and sell this software and its
  * documentation for any purpose is hereby granted without fee, provided that
  * the above copyright notice appear in all copies and that both that copyright
  * notice and this permission notice appear in supporting documentation, and
  * that the name of the copyright holders not be used in advertising or
  * publicity pertaining to distribution of the software without specific,
  * written prior permission.  The copyright holders make no representations
  * about the suitability of this software for any purpose.  It is provided "as
  * is" without express or implied warranty.
  *
  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
  * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  * OF THIS SOFTWARE.
  */
 
 #include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/iopoll.h>
 
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
 #include <linux/stacktrace.h>
 #include <linux/sort.h>
 #include <linux/timekeeping.h>
 #include <linux/math64.h>
 #endif
 
 #include <drm/display/drm_dp_mst_helper.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 
 #include "drm_dp_helper_internal.h"
 #include "drm_dp_mst_topology_internal.h"
 
 /**
  * DOC: dp mst helper
  *
  * These functions contain parts of the DisplayPort 1.2a MultiStream Transport
  * protocol. The helpers contain a topology manager and bandwidth manager.
  * The helpers encapsulate the sending and received of sideband msgs.
  */
 struct drm_dp_pending_up_req {
     struct drm_dp_sideband_msg_hdr hdr;
     struct drm_dp_sideband_msg_req_body msg;
     struct list_head next;
 };
 
 static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
                   char *buf);
 
 static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port);
 
 static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
                      int id,
                      struct drm_dp_payload *payload);
 
 static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
                  struct drm_dp_mst_port *port,
                  int offset, int size, u8 *bytes);
 static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
                   struct drm_dp_mst_port *port,
                   int offset, int size, u8 *bytes);
 
 static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_mst_branch *mstb);
 
 static void
 drm_dp_send_clear_payload_id_table(struct drm_dp_mst_topology_mgr *mgr,
                    struct drm_dp_mst_branch *mstb);
 
 static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
                        struct drm_dp_mst_branch *mstb,
                        struct drm_dp_mst_port *port);
 static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
                  u8 *guid);
 
 static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port);
 static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port);
 static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);
 
 static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
                          struct drm_dp_mst_branch *branch);
 
 #define DBG_PREFIX "[dp_mst]"
 
 #define DP_STR(x) [DP_ ## x] = #x
 
 static const char *drm_dp_mst_req_type_str(u8 req_type)
 {
     static const char * const req_type_str[] = {
         DP_STR(GET_MSG_TRANSACTION_VERSION),
         DP_STR(LINK_ADDRESS),
         DP_STR(CONNECTION_STATUS_NOTIFY),
         DP_STR(ENUM_PATH_RESOURCES),
         DP_STR(ALLOCATE_PAYLOAD),
         DP_STR(QUERY_PAYLOAD),
         DP_STR(RESOURCE_STATUS_NOTIFY),
         DP_STR(CLEAR_PAYLOAD_ID_TABLE),
         DP_STR(REMOTE_DPCD_READ),
         DP_STR(REMOTE_DPCD_WRITE),
         DP_STR(REMOTE_I2C_READ),
         DP_STR(REMOTE_I2C_WRITE),
         DP_STR(POWER_UP_PHY),
         DP_STR(POWER_DOWN_PHY),
         DP_STR(SINK_EVENT_NOTIFY),
         DP_STR(QUERY_STREAM_ENC_STATUS),
     };
 
     if (req_type >= ARRAY_SIZE(req_type_str) ||
         !req_type_str[req_type])
         return "unknown";
 
     return req_type_str[req_type];
 }
 
 #undef DP_STR
 #define DP_STR(x) [DP_NAK_ ## x] = #x
 
 static const char *drm_dp_mst_nak_reason_str(u8 nak_reason)
 {
     static const char * const nak_reason_str[] = {
         DP_STR(WRITE_FAILURE),
         DP_STR(INVALID_READ),
         DP_STR(CRC_FAILURE),
         DP_STR(BAD_PARAM),
         DP_STR(DEFER),
         DP_STR(LINK_FAILURE),
         DP_STR(NO_RESOURCES),
         DP_STR(DPCD_FAIL),
         DP_STR(I2C_NAK),
         DP_STR(ALLOCATE_FAIL),
     };
 
     if (nak_reason >= ARRAY_SIZE(nak_reason_str) ||
         !nak_reason_str[nak_reason])
         return "unknown";
 
     return nak_reason_str[nak_reason];
 }
 
 #undef DP_STR
 #define DP_STR(x) [DRM_DP_SIDEBAND_TX_ ## x] = #x
 
 static const char *drm_dp_mst_sideband_tx_state_str(int state)
 {
     static const char * const sideband_reason_str[] = {
         DP_STR(QUEUED),
         DP_STR(START_SEND),
         DP_STR(SENT),
         DP_STR(RX),
         DP_STR(TIMEOUT),
     };
 
     if (state >= ARRAY_SIZE(sideband_reason_str) ||
         !sideband_reason_str[state])
         return "unknown";
 
     return sideband_reason_str[state];
 }
 
 static int
 drm_dp_mst_rad_to_str(const u8 rad[8], u8 lct, char *out, size_t len)
 {
     int i;
     u8 unpacked_rad[16];
 
     for (i = 0; i < lct; i++) {
         if (i % 2)
             unpacked_rad[i] = rad[i / 2] >> 4;
         else
             unpacked_rad[i] = rad[i / 2] & BIT_MASK(4);
     }
 
     /* TODO: Eventually add something to printk so we can format the rad
      * like this: 1.2.3
      */
     return snprintf(out, len, "%*phC", lct, unpacked_rad);
 }
 
 /* sideband msg handling */
 static u8 drm_dp_msg_header_crc4(const uint8_t *data, size_t num_nibbles)
 {
     u8 bitmask = 0x80;
     u8 bitshift = 7;
     u8 array_index = 0;
     int number_of_bits = num_nibbles * 4;
     u8 remainder = 0;
 
     while (number_of_bits != 0) {
         number_of_bits--;
         remainder <<= 1;
         remainder |= (data[array_index] & bitmask) >> bitshift;
         bitmask >>= 1;
         bitshift--;
         if (bitmask == 0) {
             bitmask = 0x80;
             bitshift = 7;
             array_index++;
         }
         if ((remainder & 0x10) == 0x10)
             remainder ^= 0x13;
     }
 
     number_of_bits = 4;
     while (number_of_bits != 0) {
         number_of_bits--;
         remainder <<= 1;
         if ((remainder & 0x10) != 0)
             remainder ^= 0x13;
     }
 
     return remainder;
 }
 
 static u8 drm_dp_msg_data_crc4(const uint8_t *data, u8 number_of_bytes)
 {
     u8 bitmask = 0x80;
     u8 bitshift = 7;
     u8 array_index = 0;
     int number_of_bits = number_of_bytes * 8;
     u16 remainder = 0;
 
     while (number_of_bits != 0) {
         number_of_bits--;
         remainder <<= 1;
         remainder |= (data[array_index] & bitmask) >> bitshift;
         bitmask >>= 1;
         bitshift--;
         if (bitmask == 0) {
             bitmask = 0x80;
             bitshift = 7;
             array_index++;
         }
         if ((remainder & 0x100) == 0x100)
             remainder ^= 0xd5;
     }
 
     number_of_bits = 8;
     while (number_of_bits != 0) {
         number_of_bits--;
         remainder <<= 1;
         if ((remainder & 0x100) != 0)
             remainder ^= 0xd5;
     }
 
     return remainder & 0xff;
 }
 static inline u8 drm_dp_calc_sb_hdr_size(struct drm_dp_sideband_msg_hdr *hdr)
 {
     u8 size = 3;
 
     size += (hdr->lct / 2);
     return size;
 }
 
 static void drm_dp_encode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
                        u8 *buf, int *len)
 {
     int idx = 0;
     int i;
     u8 crc4;
 
     buf[idx++] = ((hdr->lct & 0xf) << 4) | (hdr->lcr & 0xf);
     for (i = 0; i < (hdr->lct / 2); i++)
         buf[idx++] = hdr->rad[i];
     buf[idx++] = (hdr->broadcast << 7) | (hdr->path_msg << 6) |
         (hdr->msg_len & 0x3f);
     buf[idx++] = (hdr->somt << 7) | (hdr->eomt << 6) | (hdr->seqno << 4);
 
     crc4 = drm_dp_msg_header_crc4(buf, (idx * 2) - 1);
     buf[idx - 1] |= (crc4 & 0xf);
 
     *len = idx;
 }
 
 static bool drm_dp_decode_sideband_msg_hdr(const struct drm_dp_mst_topology_mgr *mgr,
                        struct drm_dp_sideband_msg_hdr *hdr,
                        u8 *buf, int buflen, u8 *hdrlen)
 {
     u8 crc4;
     u8 len;
     int i;
     u8 idx;
 
     if (buf[0] == 0)
         return false;
     len = 3;
     len += ((buf[0] & 0xf0) >> 4) / 2;
     if (len > buflen)
         return false;
     crc4 = drm_dp_msg_header_crc4(buf, (len * 2) - 1);
 
     if ((crc4 & 0xf) != (buf[len - 1] & 0xf)) {
         drm_dbg_kms(mgr->dev, "crc4 mismatch 0x%x 0x%x\n", crc4, buf[len - 1]);
         return false;
     }
 
     hdr->lct = (buf[0] & 0xf0) >> 4;
     hdr->lcr = (buf[0] & 0xf);
     idx = 1;
     for (i = 0; i < (hdr->lct / 2); i++)
         hdr->rad[i] = buf[idx++];
     hdr->broadcast = (buf[idx] >> 7) & 0x1;
     hdr->path_msg = (buf[idx] >> 6) & 0x1;
     hdr->msg_len = buf[idx] & 0x3f;
     idx++;
     hdr->somt = (buf[idx] >> 7) & 0x1;
     hdr->eomt = (buf[idx] >> 6) & 0x1;
     hdr->seqno = (buf[idx] >> 4) & 0x1;
     idx++;
     *hdrlen = idx;
     return true;
 }
 
 void
 drm_dp_encode_sideband_req(const struct drm_dp_sideband_msg_req_body *req,
                struct drm_dp_sideband_msg_tx *raw)
 {
     int idx = 0;
     int i;
     u8 *buf = raw->msg;
 
     buf[idx++] = req->req_type & 0x7f;
 
     switch (req->req_type) {
     case DP_ENUM_PATH_RESOURCES:
     case DP_POWER_DOWN_PHY:
     case DP_POWER_UP_PHY:
         buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
         idx++;
         break;
     case DP_ALLOCATE_PAYLOAD:
         buf[idx] = (req->u.allocate_payload.port_number & 0xf) << 4 |
             (req->u.allocate_payload.number_sdp_streams & 0xf);
         idx++;
         buf[idx] = (req->u.allocate_payload.vcpi & 0x7f);
         idx++;
         buf[idx] = (req->u.allocate_payload.pbn >> 8);
         idx++;
         buf[idx] = (req->u.allocate_payload.pbn & 0xff);
         idx++;
         for (i = 0; i < req->u.allocate_payload.number_sdp_streams / 2; i++) {
             buf[idx] = ((req->u.allocate_payload.sdp_stream_sink[i * 2] & 0xf) << 4) |
                 (req->u.allocate_payload.sdp_stream_sink[i * 2 + 1] & 0xf);
             idx++;
         }
         if (req->u.allocate_payload.number_sdp_streams & 1) {
             i = req->u.allocate_payload.number_sdp_streams - 1;
             buf[idx] = (req->u.allocate_payload.sdp_stream_sink[i] & 0xf) << 4;
             idx++;
         }
         break;
     case DP_QUERY_PAYLOAD:
         buf[idx] = (req->u.query_payload.port_number & 0xf) << 4;
         idx++;
         buf[idx] = (req->u.query_payload.vcpi & 0x7f);
         idx++;
         break;
     case DP_REMOTE_DPCD_READ:
         buf[idx] = (req->u.dpcd_read.port_number & 0xf) << 4;
         buf[idx] |= ((req->u.dpcd_read.dpcd_address & 0xf0000) >> 16) & 0xf;
         idx++;
         buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff00) >> 8;
         idx++;
         buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff);
         idx++;
         buf[idx] = (req->u.dpcd_read.num_bytes);
         idx++;
         break;
 
     case DP_REMOTE_DPCD_WRITE:
         buf[idx] = (req->u.dpcd_write.port_number & 0xf) << 4;
         buf[idx] |= ((req->u.dpcd_write.dpcd_address & 0xf0000) >> 16) & 0xf;
         idx++;
         buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff00) >> 8;
         idx++;
         buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff);
         idx++;
         buf[idx] = (req->u.dpcd_write.num_bytes);
         idx++;
         memcpy(&buf[idx], req->u.dpcd_write.bytes, req->u.dpcd_write.num_bytes);
         idx += req->u.dpcd_write.num_bytes;
         break;
     case DP_REMOTE_I2C_READ:
         buf[idx] = (req->u.i2c_read.port_number & 0xf) << 4;
         buf[idx] |= (req->u.i2c_read.num_transactions & 0x3);
         idx++;
         for (i = 0; i < (req->u.i2c_read.num_transactions & 0x3); i++) {
             buf[idx] = req->u.i2c_read.transactions[i].i2c_dev_id & 0x7f;
             idx++;
             buf[idx] = req->u.i2c_read.transactions[i].num_bytes;
             idx++;
             memcpy(&buf[idx], req->u.i2c_read.transactions[i].bytes, req->u.i2c_read.transactions[i].num_bytes);
             idx += req->u.i2c_read.transactions[i].num_bytes;
 
             buf[idx] = (req->u.i2c_read.transactions[i].no_stop_bit & 0x1) << 4;
             buf[idx] |= (req->u.i2c_read.transactions[i].i2c_transaction_delay & 0xf);
             idx++;
         }
         buf[idx] = (req->u.i2c_read.read_i2c_device_id) & 0x7f;
         idx++;
         buf[idx] = (req->u.i2c_read.num_bytes_read);
         idx++;
         break;
 
     case DP_REMOTE_I2C_WRITE:
         buf[idx] = (req->u.i2c_write.port_number & 0xf) << 4;
         idx++;
         buf[idx] = (req->u.i2c_write.write_i2c_device_id) & 0x7f;
         idx++;
         buf[idx] = (req->u.i2c_write.num_bytes);
         idx++;
         memcpy(&buf[idx], req->u.i2c_write.bytes, req->u.i2c_write.num_bytes);
         idx += req->u.i2c_write.num_bytes;
         break;
     case DP_QUERY_STREAM_ENC_STATUS: {
         const struct drm_dp_query_stream_enc_status *msg;
 
         msg = &req->u.enc_status;
         buf[idx] = msg->stream_id;
         idx++;
         memcpy(&buf[idx], msg->client_id, sizeof(msg->client_id));
         idx += sizeof(msg->client_id);
         buf[idx] = 0;
         buf[idx] |= FIELD_PREP(GENMASK(1, 0), msg->stream_event);
         buf[idx] |= msg->valid_stream_event ? BIT(2) : 0;
         buf[idx] |= FIELD_PREP(GENMASK(4, 3), msg->stream_behavior);
         buf[idx] |= msg->valid_stream_behavior ? BIT(5) : 0;
         idx++;
         }
         break;
     }
     raw->cur_len = idx;
 }
 EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_encode_sideband_req);
 
 /* Decode a sideband request we've encoded, mainly used for debugging */
 int
 drm_dp_decode_sideband_req(const struct drm_dp_sideband_msg_tx *raw,
                struct drm_dp_sideband_msg_req_body *req)
 {
     const u8 *buf = raw->msg;
     int i, idx = 0;
 
     req->req_type = buf[idx++] & 0x7f;
     switch (req->req_type) {
     case DP_ENUM_PATH_RESOURCES:
     case DP_POWER_DOWN_PHY:
     case DP_POWER_UP_PHY:
         req->u.port_num.port_number = (buf[idx] >> 4) & 0xf;
         break;
     case DP_ALLOCATE_PAYLOAD:
         {
             struct drm_dp_allocate_payload *a =
                 &req->u.allocate_payload;
 
             a->number_sdp_streams = buf[idx] & 0xf;
             a->port_number = (buf[idx] >> 4) & 0xf;
 
             WARN_ON(buf[++idx] & 0x80);
             a->vcpi = buf[idx] & 0x7f;
 
             a->pbn = buf[++idx] << 8;
             a->pbn |= buf[++idx];
 
             idx++;
             for (i = 0; i < a->number_sdp_streams; i++) {
                 a->sdp_stream_sink[i] =
                     (buf[idx + (i / 2)] >> ((i % 2) ? 0 : 4)) & 0xf;
             }
         }
         break;
     case DP_QUERY_PAYLOAD:
         req->u.query_payload.port_number = (buf[idx] >> 4) & 0xf;
         WARN_ON(buf[++idx] & 0x80);
         req->u.query_payload.vcpi = buf[idx] & 0x7f;
         break;
     case DP_REMOTE_DPCD_READ:
         {
             struct drm_dp_remote_dpcd_read *r = &req->u.dpcd_read;
 
             r->port_number = (buf[idx] >> 4) & 0xf;
 
             r->dpcd_address = (buf[idx] << 16) & 0xf0000;
             r->dpcd_address |= (buf[++idx] << 8) & 0xff00;
             r->dpcd_address |= buf[++idx] & 0xff;
 
             r->num_bytes = buf[++idx];
         }
         break;
     case DP_REMOTE_DPCD_WRITE:
         {
             struct drm_dp_remote_dpcd_write *w =
                 &req->u.dpcd_write;
 
             w->port_number = (buf[idx] >> 4) & 0xf;
 
             w->dpcd_address = (buf[idx] << 16) & 0xf0000;
             w->dpcd_address |= (buf[++idx] << 8) & 0xff00;
             w->dpcd_address |= buf[++idx] & 0xff;
 
             w->num_bytes = buf[++idx];
 
             w->bytes = kmemdup(&buf[++idx], w->num_bytes,
                        GFP_KERNEL);
             if (!w->bytes)
                 return -ENOMEM;
         }
         break;
     case DP_REMOTE_I2C_READ:
         {
             struct drm_dp_remote_i2c_read *r = &req->u.i2c_read;
             struct drm_dp_remote_i2c_read_tx *tx;
             bool failed = false;
 
             r->num_transactions = buf[idx] & 0x3;
             r->port_number = (buf[idx] >> 4) & 0xf;
             for (i = 0; i < r->num_transactions; i++) {
                 tx = &r->transactions[i];
 
                 tx->i2c_dev_id = buf[++idx] & 0x7f;
                 tx->num_bytes = buf[++idx];
                 tx->bytes = kmemdup(&buf[++idx],
                             tx->num_bytes,
                             GFP_KERNEL);
                 if (!tx->bytes) {
                     failed = true;
                     break;
                 }
                 idx += tx->num_bytes;
                 tx->no_stop_bit = (buf[idx] >> 5) & 0x1;
                 tx->i2c_transaction_delay = buf[idx] & 0xf;
             }
 
             if (failed) {
                 for (i = 0; i < r->num_transactions; i++) {
                     tx = &r->transactions[i];
                     kfree(tx->bytes);
                 }
                 return -ENOMEM;
             }
 
             r->read_i2c_device_id = buf[++idx] & 0x7f;
             r->num_bytes_read = buf[++idx];
         }
         break;
     case DP_REMOTE_I2C_WRITE:
         {
             struct drm_dp_remote_i2c_write *w = &req->u.i2c_write;
 
             w->port_number = (buf[idx] >> 4) & 0xf;
             w->write_i2c_device_id = buf[++idx] & 0x7f;
             w->num_bytes = buf[++idx];
             w->bytes = kmemdup(&buf[++idx], w->num_bytes,
                        GFP_KERNEL);
             if (!w->bytes)
                 return -ENOMEM;
         }
         break;
     case DP_QUERY_STREAM_ENC_STATUS:
         req->u.enc_status.stream_id = buf[idx++];
         for (i = 0; i < sizeof(req->u.enc_status.client_id); i++)
             req->u.enc_status.client_id[i] = buf[idx++];
 
         req->u.enc_status.stream_event = FIELD_GET(GENMASK(1, 0),
                                buf[idx]);
         req->u.enc_status.valid_stream_event = FIELD_GET(BIT(2),
                                  buf[idx]);
         req->u.enc_status.stream_behavior = FIELD_GET(GENMASK(4, 3),
                                   buf[idx]);
         req->u.enc_status.valid_stream_behavior = FIELD_GET(BIT(5),
                                     buf[idx]);
         break;
     }
 
     return 0;
 }
 EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_decode_sideband_req);
 
 void
 drm_dp_dump_sideband_msg_req_body(const struct drm_dp_sideband_msg_req_body *req,
                   int indent, struct drm_printer *printer)
 {
     int i;
 
 #define P(f, ...) drm_printf_indent(printer, indent, f, ##__VA_ARGS__)
     if (req->req_type == DP_LINK_ADDRESS) {
         /* No contents to print */
         P("type=%s\n", drm_dp_mst_req_type_str(req->req_type));
         return;
     }
 
     P("type=%s contents:\n", drm_dp_mst_req_type_str(req->req_type));
     indent++;
 
     switch (req->req_type) {
     case DP_ENUM_PATH_RESOURCES:
     case DP_POWER_DOWN_PHY:
     case DP_POWER_UP_PHY:
         P("port=%d\n", req->u.port_num.port_number);
         break;
     case DP_ALLOCATE_PAYLOAD:
         P("port=%d vcpi=%d pbn=%d sdp_streams=%d %*ph\n",
           req->u.allocate_payload.port_number,
           req->u.allocate_payload.vcpi, req->u.allocate_payload.pbn,
           req->u.allocate_payload.number_sdp_streams,
           req->u.allocate_payload.number_sdp_streams,
           req->u.allocate_payload.sdp_stream_sink);
         break;
     case DP_QUERY_PAYLOAD:
         P("port=%d vcpi=%d\n",
           req->u.query_payload.port_number,
           req->u.query_payload.vcpi);
         break;
     case DP_REMOTE_DPCD_READ:
         P("port=%d dpcd_addr=%05x len=%d\n",
           req->u.dpcd_read.port_number, req->u.dpcd_read.dpcd_address,
           req->u.dpcd_read.num_bytes);
         break;
     case DP_REMOTE_DPCD_WRITE:
         P("port=%d addr=%05x len=%d: %*ph\n",
           req->u.dpcd_write.port_number,
           req->u.dpcd_write.dpcd_address,
           req->u.dpcd_write.num_bytes, req->u.dpcd_write.num_bytes,
           req->u.dpcd_write.bytes);
         break;
     case DP_REMOTE_I2C_READ:
         P("port=%d num_tx=%d id=%d size=%d:\n",
           req->u.i2c_read.port_number,
           req->u.i2c_read.num_transactions,
           req->u.i2c_read.read_i2c_device_id,
           req->u.i2c_read.num_bytes_read);
 
         indent++;
         for (i = 0; i < req->u.i2c_read.num_transactions; i++) {
             const struct drm_dp_remote_i2c_read_tx *rtx =
                 &req->u.i2c_read.transactions[i];
 
             P("%d: id=%03d size=%03d no_stop_bit=%d tx_delay=%03d: %*ph\n",
               i, rtx->i2c_dev_id, rtx->num_bytes,
               rtx->no_stop_bit, rtx->i2c_transaction_delay,
               rtx->num_bytes, rtx->bytes);
         }
         break;
     case DP_REMOTE_I2C_WRITE:
         P("port=%d id=%d size=%d: %*ph\n",
           req->u.i2c_write.port_number,
           req->u.i2c_write.write_i2c_device_id,
           req->u.i2c_write.num_bytes, req->u.i2c_write.num_bytes,
           req->u.i2c_write.bytes);
         break;
     case DP_QUERY_STREAM_ENC_STATUS:
         P("stream_id=%u client_id=%*ph stream_event=%x "
           "valid_event=%d stream_behavior=%x valid_behavior=%d",
           req->u.enc_status.stream_id,
           (int)ARRAY_SIZE(req->u.enc_status.client_id),
           req->u.enc_status.client_id, req->u.enc_status.stream_event,
           req->u.enc_status.valid_stream_event,
           req->u.enc_status.stream_behavior,
           req->u.enc_status.valid_stream_behavior);
         break;
     default:
         P("???\n");
         break;
     }
 #undef P
 }
 EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_dump_sideband_msg_req_body);
 
 static inline void
 drm_dp_mst_dump_sideband_msg_tx(struct drm_printer *p,
                 const struct drm_dp_sideband_msg_tx *txmsg)
 {
     struct drm_dp_sideband_msg_req_body req;
     char buf[64];
     int ret;
     int i;
 
     drm_dp_mst_rad_to_str(txmsg->dst->rad, txmsg->dst->lct, buf,
                   sizeof(buf));
     drm_printf(p, "txmsg cur_offset=%x cur_len=%x seqno=%x state=%s path_msg=%d dst=%s\n",
            txmsg->cur_offset, txmsg->cur_len, txmsg->seqno,
            drm_dp_mst_sideband_tx_state_str(txmsg->state),
            txmsg->path_msg, buf);
 
     ret = drm_dp_decode_sideband_req(txmsg, &req);
     if (ret) {
         drm_printf(p, "<failed to decode sideband req: %d>\n", ret);
         return;
     }
     drm_dp_dump_sideband_msg_req_body(&req, 1, p);
 
     switch (req.req_type) {
     case DP_REMOTE_DPCD_WRITE:
         kfree(req.u.dpcd_write.bytes);
         break;
     case DP_REMOTE_I2C_READ:
         for (i = 0; i < req.u.i2c_read.num_transactions; i++)
             kfree(req.u.i2c_read.transactions[i].bytes);
         break;
     case DP_REMOTE_I2C_WRITE:
         kfree(req.u.i2c_write.bytes);
         break;
     }
 }
 
 static void drm_dp_crc_sideband_chunk_req(u8 *msg, u8 len)
 {
     u8 crc4;
 
     crc4 = drm_dp_msg_data_crc4(msg, len);
     msg[len] = crc4;
 }
 
 static void drm_dp_encode_sideband_reply(struct drm_dp_sideband_msg_reply_body *rep,
                      struct drm_dp_sideband_msg_tx *raw)
 {
     int idx = 0;
     u8 *buf = raw->msg;
 
     buf[idx++] = (rep->reply_type & 0x1) << 7 | (rep->req_type & 0x7f);
 
     raw->cur_len = idx;
 }
 
 static int drm_dp_sideband_msg_set_header(struct drm_dp_sideband_msg_rx *msg,
                       struct drm_dp_sideband_msg_hdr *hdr,
                       u8 hdrlen)
 {
     /*
      * ignore out-of-order messages or messages that are part of a
      * failed transaction
      */
     if (!hdr->somt && !msg->have_somt)
         return false;
 
     /* get length contained in this portion */
     msg->curchunk_idx = 0;
     msg->curchunk_len = hdr->msg_len;
     msg->curchunk_hdrlen = hdrlen;
 
     /* we have already gotten an somt - don't bother parsing */
     if (hdr->somt && msg->have_somt)
         return false;
 
     if (hdr->somt) {
         memcpy(&msg->initial_hdr, hdr,
                sizeof(struct drm_dp_sideband_msg_hdr));
         msg->have_somt = true;
     }
     if (hdr->eomt)
         msg->have_eomt = true;
 
     return true;
 }
 
 /* this adds a chunk of msg to the builder to get the final msg */
 static bool drm_dp_sideband_append_payload(struct drm_dp_sideband_msg_rx *msg,
                        u8 *replybuf, u8 replybuflen)
 {
     u8 crc4;
 
     memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
     msg->curchunk_idx += replybuflen;
 
     if (msg->curchunk_idx >= msg->curchunk_len) {
         /* do CRC */
         crc4 = drm_dp_msg_data_crc4(msg->chunk, msg->curchunk_len - 1);
         if (crc4 != msg->chunk[msg->curchunk_len - 1])
             print_hex_dump(KERN_DEBUG, "wrong crc",
                        DUMP_PREFIX_NONE, 16, 1,
                        msg->chunk,  msg->curchunk_len, false);
         /* copy chunk into bigger msg */
         memcpy(&msg->msg[msg->curlen], msg->chunk, msg->curchunk_len - 1);
         msg->curlen += msg->curchunk_len - 1;
     }
     return true;
 }
 
 static bool drm_dp_sideband_parse_link_address(const struct drm_dp_mst_topology_mgr *mgr,
                            struct drm_dp_sideband_msg_rx *raw,
                            struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
     int i;
 
     memcpy(repmsg->u.link_addr.guid, &raw->msg[idx], 16);
     idx += 16;
     repmsg->u.link_addr.nports = raw->msg[idx] & 0xf;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     for (i = 0; i < repmsg->u.link_addr.nports; i++) {
         if (raw->msg[idx] & 0x80)
             repmsg->u.link_addr.ports[i].input_port = 1;
 
         repmsg->u.link_addr.ports[i].peer_device_type = (raw->msg[idx] >> 4) & 0x7;
         repmsg->u.link_addr.ports[i].port_number = (raw->msg[idx] & 0xf);
 
         idx++;
         if (idx > raw->curlen)
             goto fail_len;
         repmsg->u.link_addr.ports[i].mcs = (raw->msg[idx] >> 7) & 0x1;
         repmsg->u.link_addr.ports[i].ddps = (raw->msg[idx] >> 6) & 0x1;
         if (repmsg->u.link_addr.ports[i].input_port == 0)
             repmsg->u.link_addr.ports[i].legacy_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
         idx++;
         if (idx > raw->curlen)
             goto fail_len;
         if (repmsg->u.link_addr.ports[i].input_port == 0) {
             repmsg->u.link_addr.ports[i].dpcd_revision = (raw->msg[idx]);
             idx++;
             if (idx > raw->curlen)
                 goto fail_len;
             memcpy(repmsg->u.link_addr.ports[i].peer_guid, &raw->msg[idx], 16);
             idx += 16;
             if (idx > raw->curlen)
                 goto fail_len;
             repmsg->u.link_addr.ports[i].num_sdp_streams = (raw->msg[idx] >> 4) & 0xf;
             repmsg->u.link_addr.ports[i].num_sdp_stream_sinks = (raw->msg[idx] & 0xf);
             idx++;
 
         }
         if (idx > raw->curlen)
             goto fail_len;
     }
 
     return true;
 fail_len:
     DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx *raw,
                            struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.remote_dpcd_read_ack.port_number = raw->msg[idx] & 0xf;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
 
     memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes);
     return true;
 fail_len:
     DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_remote_dpcd_write(struct drm_dp_sideband_msg_rx *raw,
                               struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.remote_dpcd_write_ack.port_number = raw->msg[idx] & 0xf;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     return true;
 fail_len:
     DRM_DEBUG_KMS("parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg_rx *raw,
                               struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.remote_i2c_read_ack.port_number = (raw->msg[idx] & 0xf);
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx];
     idx++;
     /* TODO check */
     memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes);
     return true;
 fail_len:
     DRM_DEBUG_KMS("remote i2c reply parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband_msg_rx *raw,
                               struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
     repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
     idx += 2;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
     idx += 2;
     if (idx > raw->curlen)
         goto fail_len;
     return true;
 fail_len:
     DRM_DEBUG_KMS("enum resource parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_allocate_payload_ack(struct drm_dp_sideband_msg_rx *raw,
                               struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.allocate_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.allocate_payload.vcpi = raw->msg[idx];
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
     idx += 2;
     if (idx > raw->curlen)
         goto fail_len;
     return true;
 fail_len:
     DRM_DEBUG_KMS("allocate payload parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_rx *raw,
                             struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
     repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
     idx += 2;
     if (idx > raw->curlen)
         goto fail_len;
     return true;
 fail_len:
     DRM_DEBUG_KMS("query payload parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_power_updown_phy_ack(struct drm_dp_sideband_msg_rx *raw,
                                struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     int idx = 1;
 
     repmsg->u.port_number.port_number = (raw->msg[idx] >> 4) & 0xf;
     idx++;
     if (idx > raw->curlen) {
         DRM_DEBUG_KMS("power up/down phy parse length fail %d %d\n",
                   idx, raw->curlen);
         return false;
     }
     return true;
 }
 
 static bool
 drm_dp_sideband_parse_query_stream_enc_status(
                 struct drm_dp_sideband_msg_rx *raw,
                 struct drm_dp_sideband_msg_reply_body *repmsg)
 {
     struct drm_dp_query_stream_enc_status_ack_reply *reply;
 
     reply = &repmsg->u.enc_status;
 
     reply->stream_id = raw->msg[3];
 
     reply->reply_signed = raw->msg[2] & BIT(0);
 
     /*
      * NOTE: It's my impression from reading the spec that the below parsing
      * is correct. However I noticed while testing with an HDCP 1.4 display
      * through an HDCP 2.2 hub that only bit 3 was set. In that case, I
      * would expect both bits to be set. So keep the parsing following the
      * spec, but beware reality might not match the spec (at least for some
      * configurations).
      */
     reply->hdcp_1x_device_present = raw->msg[2] & BIT(4);
     reply->hdcp_2x_device_present = raw->msg[2] & BIT(3);
 
     reply->query_capable_device_present = raw->msg[2] & BIT(5);
     reply->legacy_device_present = raw->msg[2] & BIT(6);
     reply->unauthorizable_device_present = raw->msg[2] & BIT(7);
 
     reply->auth_completed = !!(raw->msg[1] & BIT(3));
     reply->encryption_enabled = !!(raw->msg[1] & BIT(4));
     reply->repeater_present = !!(raw->msg[1] & BIT(5));
     reply->state = (raw->msg[1] & GENMASK(7, 6)) >> 6;
 
     return true;
 }
 
 static bool drm_dp_sideband_parse_reply(const struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_sideband_msg_rx *raw,
                     struct drm_dp_sideband_msg_reply_body *msg)
 {
     memset(msg, 0, sizeof(*msg));
     msg->reply_type = (raw->msg[0] & 0x80) >> 7;
     msg->req_type = (raw->msg[0] & 0x7f);
 
     if (msg->reply_type == DP_SIDEBAND_REPLY_NAK) {
         memcpy(msg->u.nak.guid, &raw->msg[1], 16);
         msg->u.nak.reason = raw->msg[17];
         msg->u.nak.nak_data = raw->msg[18];
         return false;
     }
 
     switch (msg->req_type) {
     case DP_LINK_ADDRESS:
         return drm_dp_sideband_parse_link_address(mgr, raw, msg);
     case DP_QUERY_PAYLOAD:
         return drm_dp_sideband_parse_query_payload_ack(raw, msg);
     case DP_REMOTE_DPCD_READ:
         return drm_dp_sideband_parse_remote_dpcd_read(raw, msg);
     case DP_REMOTE_DPCD_WRITE:
         return drm_dp_sideband_parse_remote_dpcd_write(raw, msg);
     case DP_REMOTE_I2C_READ:
         return drm_dp_sideband_parse_remote_i2c_read_ack(raw, msg);
     case DP_REMOTE_I2C_WRITE:
         return true; /* since there's nothing to parse */
     case DP_ENUM_PATH_RESOURCES:
         return drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
     case DP_ALLOCATE_PAYLOAD:
         return drm_dp_sideband_parse_allocate_payload_ack(raw, msg);
     case DP_POWER_DOWN_PHY:
     case DP_POWER_UP_PHY:
         return drm_dp_sideband_parse_power_updown_phy_ack(raw, msg);
     case DP_CLEAR_PAYLOAD_ID_TABLE:
         return true; /* since there's nothing to parse */
     case DP_QUERY_STREAM_ENC_STATUS:
         return drm_dp_sideband_parse_query_stream_enc_status(raw, msg);
     default:
         drm_err(mgr->dev, "Got unknown reply 0x%02x (%s)\n",
             msg->req_type, drm_dp_mst_req_type_str(msg->req_type));
         return false;
     }
 }
 
 static bool
 drm_dp_sideband_parse_connection_status_notify(const struct drm_dp_mst_topology_mgr *mgr,
                            struct drm_dp_sideband_msg_rx *raw,
                            struct drm_dp_sideband_msg_req_body *msg)
 {
     int idx = 1;
 
     msg->u.conn_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
 
     memcpy(msg->u.conn_stat.guid, &raw->msg[idx], 16);
     idx += 16;
     if (idx > raw->curlen)
         goto fail_len;
 
     msg->u.conn_stat.legacy_device_plug_status = (raw->msg[idx] >> 6) & 0x1;
     msg->u.conn_stat.displayport_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
     msg->u.conn_stat.message_capability_status = (raw->msg[idx] >> 4) & 0x1;
     msg->u.conn_stat.input_port = (raw->msg[idx] >> 3) & 0x1;
     msg->u.conn_stat.peer_device_type = (raw->msg[idx] & 0x7);
     idx++;
     return true;
 fail_len:
     drm_dbg_kms(mgr->dev, "connection status reply parse length fail %d %d\n",
             idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_resource_status_notify(const struct drm_dp_mst_topology_mgr *mgr,
                              struct drm_dp_sideband_msg_rx *raw,
                              struct drm_dp_sideband_msg_req_body *msg)
 {
     int idx = 1;
 
     msg->u.resource_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
     idx++;
     if (idx > raw->curlen)
         goto fail_len;
 
     memcpy(msg->u.resource_stat.guid, &raw->msg[idx], 16);
     idx += 16;
     if (idx > raw->curlen)
         goto fail_len;
 
     msg->u.resource_stat.available_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
     idx++;
     return true;
 fail_len:
     drm_dbg_kms(mgr->dev, "resource status reply parse length fail %d %d\n", idx, raw->curlen);
     return false;
 }
 
 static bool drm_dp_sideband_parse_req(const struct drm_dp_mst_topology_mgr *mgr,
                       struct drm_dp_sideband_msg_rx *raw,
                       struct drm_dp_sideband_msg_req_body *msg)
 {
     memset(msg, 0, sizeof(*msg));
     msg->req_type = (raw->msg[0] & 0x7f);
 
     switch (msg->req_type) {
     case DP_CONNECTION_STATUS_NOTIFY:
         return drm_dp_sideband_parse_connection_status_notify(mgr, raw, msg);
     case DP_RESOURCE_STATUS_NOTIFY:
         return drm_dp_sideband_parse_resource_status_notify(mgr, raw, msg);
     default:
         drm_err(mgr->dev, "Got unknown request 0x%02x (%s)\n",
             msg->req_type, drm_dp_mst_req_type_str(msg->req_type));
         return false;
     }
 }
 
 static void build_dpcd_write(struct drm_dp_sideband_msg_tx *msg,
                  u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_REMOTE_DPCD_WRITE;
     req.u.dpcd_write.port_number = port_num;
     req.u.dpcd_write.dpcd_address = offset;
     req.u.dpcd_write.num_bytes = num_bytes;
     req.u.dpcd_write.bytes = bytes;
     drm_dp_encode_sideband_req(&req, msg);
 }
 
 static void build_link_address(struct drm_dp_sideband_msg_tx *msg)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_LINK_ADDRESS;
     drm_dp_encode_sideband_req(&req, msg);
 }
 
 static void build_clear_payload_id_table(struct drm_dp_sideband_msg_tx *msg)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_CLEAR_PAYLOAD_ID_TABLE;
     drm_dp_encode_sideband_req(&req, msg);
     msg->path_msg = true;
 }
 
 static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg,
                      int port_num)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_ENUM_PATH_RESOURCES;
     req.u.port_num.port_number = port_num;
     drm_dp_encode_sideband_req(&req, msg);
     msg->path_msg = true;
     return 0;
 }
 
 static void build_allocate_payload(struct drm_dp_sideband_msg_tx *msg,
                    int port_num,
                    u8 vcpi, uint16_t pbn,
                    u8 number_sdp_streams,
                    u8 *sdp_stream_sink)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     memset(&req, 0, sizeof(req));
     req.req_type = DP_ALLOCATE_PAYLOAD;
     req.u.allocate_payload.port_number = port_num;
     req.u.allocate_payload.vcpi = vcpi;
     req.u.allocate_payload.pbn = pbn;
     req.u.allocate_payload.number_sdp_streams = number_sdp_streams;
     memcpy(req.u.allocate_payload.sdp_stream_sink, sdp_stream_sink,
            number_sdp_streams);
     drm_dp_encode_sideband_req(&req, msg);
     msg->path_msg = true;
 }
 
 static void build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
                    int port_num, bool power_up)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     if (power_up)
         req.req_type = DP_POWER_UP_PHY;
     else
         req.req_type = DP_POWER_DOWN_PHY;
 
     req.u.port_num.port_number = port_num;
     drm_dp_encode_sideband_req(&req, msg);
     msg->path_msg = true;
 }
 
 static int
 build_query_stream_enc_status(struct drm_dp_sideband_msg_tx *msg, u8 stream_id,
                   u8 *q_id)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_QUERY_STREAM_ENC_STATUS;
     req.u.enc_status.stream_id = stream_id;
     memcpy(req.u.enc_status.client_id, q_id,
            sizeof(req.u.enc_status.client_id));
     req.u.enc_status.stream_event = 0;
     req.u.enc_status.valid_stream_event = false;
     req.u.enc_status.stream_behavior = 0;
     req.u.enc_status.valid_stream_behavior = false;
 
     drm_dp_encode_sideband_req(&req, msg);
     return 0;
 }
 
 static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_vcpi *vcpi)
 {
     int ret, vcpi_ret;
 
     mutex_lock(&mgr->payload_lock);
     ret = find_first_zero_bit(&mgr->payload_mask, mgr->max_payloads + 1);
     if (ret > mgr->max_payloads) {
         ret = -EINVAL;
         drm_dbg_kms(mgr->dev, "out of payload ids %d\n", ret);
         goto out_unlock;
     }
 
     vcpi_ret = find_first_zero_bit(&mgr->vcpi_mask, mgr->max_payloads + 1);
     if (vcpi_ret > mgr->max_payloads) {
         ret = -EINVAL;
         drm_dbg_kms(mgr->dev, "out of vcpi ids %d\n", ret);
         goto out_unlock;
     }
 
     set_bit(ret, &mgr->payload_mask);
     set_bit(vcpi_ret, &mgr->vcpi_mask);
     vcpi->vcpi = vcpi_ret + 1;
     mgr->proposed_vcpis[ret - 1] = vcpi;
 out_unlock:
     mutex_unlock(&mgr->payload_lock);
     return ret;
 }
 
 static void drm_dp_mst_put_payload_id(struct drm_dp_mst_topology_mgr *mgr,
                       int vcpi)
 {
     int i;
 
     if (vcpi == 0)
         return;
 
     mutex_lock(&mgr->payload_lock);
     drm_dbg_kms(mgr->dev, "putting payload %d\n", vcpi);
     clear_bit(vcpi - 1, &mgr->vcpi_mask);
 
     for (i = 0; i < mgr->max_payloads; i++) {
         if (mgr->proposed_vcpis[i] &&
             mgr->proposed_vcpis[i]->vcpi == vcpi) {
             mgr->proposed_vcpis[i] = NULL;
             clear_bit(i + 1, &mgr->payload_mask);
         }
     }
     mutex_unlock(&mgr->payload_lock);
 }
 
 static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr,
                   struct drm_dp_sideband_msg_tx *txmsg)
 {
     unsigned int state;
 
     /*
      * All updates to txmsg->state are protected by mgr->qlock, and the two
      * cases we check here are terminal states. For those the barriers
      * provided by the wake_up/wait_event pair are enough.
      */
     state = READ_ONCE(txmsg->state);
     return (state == DRM_DP_SIDEBAND_TX_RX ||
         state == DRM_DP_SIDEBAND_TX_TIMEOUT);
 }
 
 static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb,
                     struct drm_dp_sideband_msg_tx *txmsg)
 {
     struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
     unsigned long wait_timeout = msecs_to_jiffies(4000);
     unsigned long wait_expires = jiffies + wait_timeout;
     int ret;
 
     for (;;) {
         /*
          * If the driver provides a way for this, change to
          * poll-waiting for the MST reply interrupt if we didn't receive
          * it for 50 msec. This would cater for cases where the HPD
          * pulse signal got lost somewhere, even though the sink raised
          * the corresponding MST interrupt correctly. One example is the
          * Club 3D CAC-1557 TypeC -> DP adapter which for some reason
          * filters out short pulses with a duration less than ~540 usec.
          *
          * The poll period is 50 msec to avoid missing an interrupt
          * after the sink has cleared it (after a 110msec timeout
          * since it raised the interrupt).
          */
         ret = wait_event_timeout(mgr->tx_waitq,
                      check_txmsg_state(mgr, txmsg),
                      mgr->cbs->poll_hpd_irq ?
                         msecs_to_jiffies(50) :
                         wait_timeout);
 
         if (ret || !mgr->cbs->poll_hpd_irq ||
             time_after(jiffies, wait_expires))
             break;
 
         mgr->cbs->poll_hpd_irq(mgr);
     }
 
     mutex_lock(&mgr->qlock);
     if (ret > 0) {
         if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) {
             ret = -EIO;
             goto out;
         }
     } else {
         drm_dbg_kms(mgr->dev, "timedout msg send %p %d %d\n",
                 txmsg, txmsg->state, txmsg->seqno);
 
         /* dump some state */
         ret = -EIO;
 
         /* remove from q */
         if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED ||
             txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND ||
             txmsg->state == DRM_DP_SIDEBAND_TX_SENT)
             list_del(&txmsg->next);
     }
 out:
     if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) {
         struct drm_printer p = drm_debug_printer(DBG_PREFIX);
 
         drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
     }
     mutex_unlock(&mgr->qlock);
 
     drm_dp_mst_kick_tx(mgr);
     return ret;
 }
 
 static struct drm_dp_mst_branch *drm_dp_add_mst_branch_device(u8 lct, u8 *rad)
 {
     struct drm_dp_mst_branch *mstb;
 
     mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
     if (!mstb)
         return NULL;
 
     mstb->lct = lct;
     if (lct > 1)
         memcpy(mstb->rad, rad, lct / 2);
     INIT_LIST_HEAD(&mstb->ports);
     kref_init(&mstb->topology_kref);
     kref_init(&mstb->malloc_kref);
     return mstb;
 }
 
 static void drm_dp_free_mst_branch_device(struct kref *kref)
 {
     struct drm_dp_mst_branch *mstb =
         container_of(kref, struct drm_dp_mst_branch, malloc_kref);
 
     if (mstb->port_parent)
         drm_dp_mst_put_port_malloc(mstb->port_parent);
 
     kfree(mstb);
 }
 
 /**
  * DOC: Branch device and port refcounting
  *
  * Topology refcount overview
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * The refcounting schemes for &struct drm_dp_mst_branch and &struct
  * drm_dp_mst_port are somewhat unusual. Both ports and branch devices have
  * two different kinds of refcounts: topology refcounts, and malloc refcounts.
  *
  * Topology refcounts are not exposed to drivers, and are handled internally
  * by the DP MST helpers. The helpers use them in order to prevent the
  * in-memory topology state from being changed in the middle of critical
  * operations like changing the internal state of payload allocations. This
  * means each branch and port will be considered to be connected to the rest
  * of the topology until its topology refcount reaches zero. Additionally,
  * for ports this means that their associated &struct drm_connector will stay
  * registered with userspace until the port's refcount reaches 0.
  *
  * Malloc refcount overview
  * ~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * Malloc references are used to keep a &struct drm_dp_mst_port or &struct
  * drm_dp_mst_branch allocated even after all of its topology references have
  * been dropped, so that the driver or MST helpers can safely access each
  * branch's last known state before it was disconnected from the topology.
  * When the malloc refcount of a port or branch reaches 0, the memory
  * allocation containing the &struct drm_dp_mst_branch or &struct
  * drm_dp_mst_port respectively will be freed.
  *
  * For &struct drm_dp_mst_branch, malloc refcounts are not currently exposed
  * to drivers. As of writing this documentation, there are no drivers that
  * have a usecase for accessing &struct drm_dp_mst_branch outside of the MST
  * helpers. Exposing this API to drivers in a race-free manner would take more
  * tweaking of the refcounting scheme, however patches are welcome provided
  * there is a legitimate driver usecase for this.
  *
  * Refcount relationships in a topology
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * Let's take a look at why the relationship between topology and malloc
  * refcounts is designed the way it is.
  *
  * .. kernel-figure:: dp-mst/topology-figure-1.dot
  *
  *    An example of topology and malloc refs in a DP MST topology with two
  *    active payloads. Topology refcount increments are indicated by solid
  *    lines, and malloc refcount increments are indicated by dashed lines.
  *    Each starts from the branch which incremented the refcount, and ends at
  *    the branch to which the refcount belongs to, i.e. the arrow points the
  *    same way as the C pointers used to reference a structure.
  *
  * As you can see in the above figure, every branch increments the topology
  * refcount of its children, and increments the malloc refcount of its
  * parent. Additionally, every payload increments the malloc refcount of its
  * assigned port by 1.
  *
  * So, what would happen if MSTB #3 from the above figure was unplugged from
  * the system, but the driver hadn't yet removed payload #2 from port #3? The
  * topology would start to look like the figure below.
  *
  * .. kernel-figure:: dp-mst/topology-figure-2.dot
  *
  *    Ports and branch devices which have been released from memory are
  *    colored grey, and references which have been removed are colored red.
  *
  * Whenever a port or branch device's topology refcount reaches zero, it will
  * decrement the topology refcounts of all its children, the malloc refcount
  * of its parent, and finally its own malloc refcount. For MSTB #4 and port
  * #4, this means they both have been disconnected from the topology and freed
  * from memory. But, because payload #2 is still holding a reference to port
  * #3, port #3 is removed from the topology but its &struct drm_dp_mst_port
  * is still accessible from memory. This also means port #3 has not yet
  * decremented the malloc refcount of MSTB #3, so its &struct
  * drm_dp_mst_branch will also stay allocated in memory until port #3's
  * malloc refcount reaches 0.
  *
  * This relationship is necessary because in order to release payload #2, we
  * need to be able to figure out the last relative of port #3 that's still
  * connected to the topology. In this case, we would travel up the topology as
  * shown below.
  *
  * .. kernel-figure:: dp-mst/topology-figure-3.dot
  *
  * And finally, remove payload #2 by communicating with port #2 through
  * sideband transactions.
  */
 
 /**
  * drm_dp_mst_get_mstb_malloc() - Increment the malloc refcount of a branch
  * device
  * @mstb: The &struct drm_dp_mst_branch to increment the malloc refcount of
  *
  * Increments &drm_dp_mst_branch.malloc_kref. When
  * &drm_dp_mst_branch.malloc_kref reaches 0, the memory allocation for @mstb
  * will be released and @mstb may no longer be used.
  *
  * See also: drm_dp_mst_put_mstb_malloc()
  */
 static void
 drm_dp_mst_get_mstb_malloc(struct drm_dp_mst_branch *mstb)
 {
     kref_get(&mstb->malloc_kref);
     drm_dbg(mstb->mgr->dev, "mstb %p (%d)\n", mstb, kref_read(&mstb->malloc_kref));
 }
 
 /**
  * drm_dp_mst_put_mstb_malloc() - Decrement the malloc refcount of a branch
  * device
  * @mstb: The &struct drm_dp_mst_branch to decrement the malloc refcount of
  *
  * Decrements &drm_dp_mst_branch.malloc_kref. When
  * &drm_dp_mst_branch.malloc_kref reaches 0, the memory allocation for @mstb
  * will be released and @mstb may no longer be used.
  *
  * See also: drm_dp_mst_get_mstb_malloc()
  */
 static void
 drm_dp_mst_put_mstb_malloc(struct drm_dp_mst_branch *mstb)
 {
     drm_dbg(mstb->mgr->dev, "mstb %p (%d)\n", mstb, kref_read(&mstb->malloc_kref) - 1);
     kref_put(&mstb->malloc_kref, drm_dp_free_mst_branch_device);
 }
 
 static void drm_dp_free_mst_port(struct kref *kref)
 {
     struct drm_dp_mst_port *port =
         container_of(kref, struct drm_dp_mst_port, malloc_kref);
 
     drm_dp_mst_put_mstb_malloc(port->parent);
     kfree(port);
 }
 
 /**
  * drm_dp_mst_get_port_malloc() - Increment the malloc refcount of an MST port
  * @port: The &struct drm_dp_mst_port to increment the malloc refcount of
  *
  * Increments &drm_dp_mst_port.malloc_kref. When &drm_dp_mst_port.malloc_kref
  * reaches 0, the memory allocation for @port will be released and @port may
  * no longer be used.
  *
  * Because @port could potentially be freed at any time by the DP MST helpers
  * if &drm_dp_mst_port.malloc_kref reaches 0, including during a call to this
  * function, drivers that which to make use of &struct drm_dp_mst_port should
  * ensure that they grab at least one main malloc reference to their MST ports
  * in &drm_dp_mst_topology_cbs.add_connector. This callback is called before
  * there is any chance for &drm_dp_mst_port.malloc_kref to reach 0.
  *
  * See also: drm_dp_mst_put_port_malloc()
  */
 void
 drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port)
 {
     kref_get(&port->malloc_kref);
     drm_dbg(port->mgr->dev, "port %p (%d)\n", port, kref_read(&port->malloc_kref));
 }
 EXPORT_SYMBOL(drm_dp_mst_get_port_malloc);
 
 /**
  * drm_dp_mst_put_port_malloc() - Decrement the malloc refcount of an MST port
  * @port: The &struct drm_dp_mst_port to decrement the malloc refcount of
  *
  * Decrements &drm_dp_mst_port.malloc_kref. When &drm_dp_mst_port.malloc_kref
  * reaches 0, the memory allocation for @port will be released and @port may
  * no longer be used.
  *
  * See also: drm_dp_mst_get_port_malloc()
  */
 void
 drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port)
 {
     drm_dbg(port->mgr->dev, "port %p (%d)\n", port, kref_read(&port->malloc_kref) - 1);
     kref_put(&port->malloc_kref, drm_dp_free_mst_port);
 }
 EXPORT_SYMBOL(drm_dp_mst_put_port_malloc);
 
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
 
 #define STACK_DEPTH 8
 
 static noinline void
 __topology_ref_save(struct drm_dp_mst_topology_mgr *mgr,
             struct drm_dp_mst_topology_ref_history *history,
             enum drm_dp_mst_topology_ref_type type)
 {
     struct drm_dp_mst_topology_ref_entry *entry = NULL;
     depot_stack_handle_t backtrace;
     ulong stack_entries[STACK_DEPTH];
     uint n;
     int i;
 
     n = stack_trace_save(stack_entries, ARRAY_SIZE(stack_entries), 1);
     backtrace = stack_depot_save(stack_entries, n, GFP_KERNEL);
     if (!backtrace)
         return;
 
     /* Try to find an existing entry for this backtrace */
     for (i = 0; i < history->len; i++) {
         if (history->entries[i].backtrace == backtrace) {
             entry = &history->entries[i];
             break;
         }
     }
 
     /* Otherwise add one */
     if (!entry) {
         struct drm_dp_mst_topology_ref_entry *new;
         int new_len = history->len + 1;
 
         new = krealloc(history->entries, sizeof(*new) * new_len,
                    GFP_KERNEL);
         if (!new)
             return;
 
         entry = &new[history->len];
         history->len = new_len;
         history->entries = new;
 
         entry->backtrace = backtrace;
         entry->type = type;
         entry->count = 0;
     }
     entry->count++;
     entry->ts_nsec = ktime_get_ns();
 }
 
 static int
 topology_ref_history_cmp(const void *a, const void *b)
 {
     const struct drm_dp_mst_topology_ref_entry *entry_a = a, *entry_b = b;
 
     if (entry_a->ts_nsec > entry_b->ts_nsec)
         return 1;
     else if (entry_a->ts_nsec < entry_b->ts_nsec)
         return -1;
     else
         return 0;
 }
 
 static inline const char *
 topology_ref_type_to_str(enum drm_dp_mst_topology_ref_type type)
 {
     if (type == DRM_DP_MST_TOPOLOGY_REF_GET)
         return "get";
     else
         return "put";
 }
 
 static void
 __dump_topology_ref_history(struct drm_dp_mst_topology_ref_history *history,
                 void *ptr, const char *type_str)
 {
     struct drm_printer p = drm_debug_printer(DBG_PREFIX);
     char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
     int i;
 
     if (!buf)
         return;
 
     if (!history->len)
         goto out;
 
     /* First, sort the list so that it goes from oldest to newest
      * reference entry
      */
     sort(history->entries, history->len, sizeof(*history->entries),
          topology_ref_history_cmp, NULL);
 
     drm_printf(&p, "%s (%p) topology count reached 0, dumping history:\n",
            type_str, ptr);
 
     for (i = 0; i < history->len; i++) {
         const struct drm_dp_mst_topology_ref_entry *entry =
             &history->entries[i];
         u64 ts_nsec = entry->ts_nsec;
         u32 rem_nsec = do_div(ts_nsec, 1000000000);
 
         stack_depot_snprint(entry->backtrace, buf, PAGE_SIZE, 4);
 
         drm_printf(&p, "  %d %ss (last at %5llu.%06u):\n%s",
                entry->count,
                topology_ref_type_to_str(entry->type),
                ts_nsec, rem_nsec / 1000, buf);
     }
 
     /* Now free the history, since this is the only time we expose it */
     kfree(history->entries);
 out:
     kfree(buf);
 }
 
 static __always_inline void
 drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb)
 {
     __dump_topology_ref_history(&mstb->topology_ref_history, mstb,
                     "MSTB");
 }
 
 static __always_inline void
 drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port)
 {
     __dump_topology_ref_history(&port->topology_ref_history, port,
                     "Port");
 }
 
 static __always_inline void
 save_mstb_topology_ref(struct drm_dp_mst_branch *mstb,
                enum drm_dp_mst_topology_ref_type type)
 {
     __topology_ref_save(mstb->mgr, &mstb->topology_ref_history, type);
 }
 
 static __always_inline void
 save_port_topology_ref(struct drm_dp_mst_port *port,
                enum drm_dp_mst_topology_ref_type type)
 {
     __topology_ref_save(port->mgr, &port->topology_ref_history, type);
 }
 
 static inline void
 topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr)
 {
     mutex_lock(&mgr->topology_ref_history_lock);
 }
 
 static inline void
 topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr)
 {
     mutex_unlock(&mgr->topology_ref_history_lock);
 }
 #else
 static inline void
 topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) {}
 static inline void
 topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) {}
 static inline void
 drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) {}
 static inline void
 drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) {}
 #define save_mstb_topology_ref(mstb, type)
 #define save_port_topology_ref(port, type)
 #endif
 
 static void drm_dp_destroy_mst_branch_device(struct kref *kref)
 {
     struct drm_dp_mst_branch *mstb =
         container_of(kref, struct drm_dp_mst_branch, topology_kref);
     struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
 
     drm_dp_mst_dump_mstb_topology_history(mstb);
 
     INIT_LIST_HEAD(&mstb->destroy_next);
 
     /*
      * This can get called under mgr->mutex, so we need to perform the
      * actual destruction of the mstb in another worker
      */
     mutex_lock(&mgr->delayed_destroy_lock);
     list_add(&mstb->destroy_next, &mgr->destroy_branch_device_list);
     mutex_unlock(&mgr->delayed_destroy_lock);
     queue_work(mgr->delayed_destroy_wq, &mgr->delayed_destroy_work);
 }
 
 /**
  * drm_dp_mst_topology_try_get_mstb() - Increment the topology refcount of a
  * branch device unless it's zero
  * @mstb: &struct drm_dp_mst_branch to increment the topology refcount of
  *
  * Attempts to grab a topology reference to @mstb, if it hasn't yet been
  * removed from the topology (e.g. &drm_dp_mst_branch.topology_kref has
  * reached 0). Holding a topology reference implies that a malloc reference
  * will be held to @mstb as long as the user holds the topology reference.
  *
  * Care should be taken to ensure that the user has at least one malloc
  * reference to @mstb. If you already have a topology reference to @mstb, you
  * should use drm_dp_mst_topology_get_mstb() instead.
  *
  * See also:
  * drm_dp_mst_topology_get_mstb()
  * drm_dp_mst_topology_put_mstb()
  *
  * Returns:
  * * 1: A topology reference was grabbed successfully
  * * 0: @port is no longer in the topology, no reference was grabbed
  */
 static int __must_check
 drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb)
 {
     int ret;
 
     topology_ref_history_lock(mstb->mgr);
     ret = kref_get_unless_zero(&mstb->topology_kref);
     if (ret) {
         drm_dbg(mstb->mgr->dev, "mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref));
         save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET);
     }
 
     topology_ref_history_unlock(mstb->mgr);
 
     return ret;
 }
 
 /**
  * drm_dp_mst_topology_get_mstb() - Increment the topology refcount of a
  * branch device
  * @mstb: The &struct drm_dp_mst_branch to increment the topology refcount of
  *
  * Increments &drm_dp_mst_branch.topology_refcount without checking whether or
  * not it's already reached 0. This is only valid to use in scenarios where
  * you are already guaranteed to have at least one active topology reference
  * to @mstb. Otherwise, drm_dp_mst_topology_try_get_mstb() must be used.
  *
  * See also:
  * drm_dp_mst_topology_try_get_mstb()
  * drm_dp_mst_topology_put_mstb()
  */
 static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb)
 {
     topology_ref_history_lock(mstb->mgr);
 
     save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET);
     WARN_ON(kref_read(&mstb->topology_kref) == 0);
     kref_get(&mstb->topology_kref);
     drm_dbg(mstb->mgr->dev, "mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref));
 
     topology_ref_history_unlock(mstb->mgr);
 }
 
 /**
  * drm_dp_mst_topology_put_mstb() - release a topology reference to a branch
  * device
  * @mstb: The &struct drm_dp_mst_branch to release the topology reference from
  *
  * Releases a topology reference from @mstb by decrementing
  * &drm_dp_mst_branch.topology_kref.
  *
  * See also:
  * drm_dp_mst_topology_try_get_mstb()
  * drm_dp_mst_topology_get_mstb()
  */
 static void
 drm_dp_mst_topology_put_mstb(struct drm_dp_mst_branch *mstb)
 {
     topology_ref_history_lock(mstb->mgr);
 
     drm_dbg(mstb->mgr->dev, "mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref) - 1);
     save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_PUT);
 
     topology_ref_history_unlock(mstb->mgr);
     kref_put(&mstb->topology_kref, drm_dp_destroy_mst_branch_device);
 }
 
 static void drm_dp_destroy_port(struct kref *kref)
 {
     struct drm_dp_mst_port *port =
         container_of(kref, struct drm_dp_mst_port, topology_kref);
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
 
     drm_dp_mst_dump_port_topology_history(port);
 
     /* There's nothing that needs locking to destroy an input port yet */
     if (port->input) {
         drm_dp_mst_put_port_malloc(port);
         return;
     }
 
     kfree(port->cached_edid);
 
     /*
      * we can't destroy the connector here, as we might be holding the
      * mode_config.mutex from an EDID retrieval
      */
     mutex_lock(&mgr->delayed_destroy_lock);
     list_add(&port->next, &mgr->destroy_port_list);
     mutex_unlock(&mgr->delayed_destroy_lock);
     queue_work(mgr->delayed_destroy_wq, &mgr->delayed_destroy_work);
 }
 
 /**
  * drm_dp_mst_topology_try_get_port() - Increment the topology refcount of a
  * port unless it's zero
  * @port: &struct drm_dp_mst_port to increment the topology refcount of
  *
  * Attempts to grab a topology reference to @port, if it hasn't yet been
  * removed from the topology (e.g. &drm_dp_mst_port.topology_kref has reached
  * 0). Holding a topology reference implies that a malloc reference will be
  * held to @port as long as the user holds the topology reference.
  *
  * Care should be taken to ensure that the user has at least one malloc
  * reference to @port. If you already have a topology reference to @port, you
  * should use drm_dp_mst_topology_get_port() instead.
  *
  * See also:
  * drm_dp_mst_topology_get_port()
  * drm_dp_mst_topology_put_port()
  *
  * Returns:
  * * 1: A topology reference was grabbed successfully
  * * 0: @port is no longer in the topology, no reference was grabbed
  */
 static int __must_check
 drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port)
 {
     int ret;
 
     topology_ref_history_lock(port->mgr);
     ret = kref_get_unless_zero(&port->topology_kref);
     if (ret) {
         drm_dbg(port->mgr->dev, "port %p (%d)\n", port, kref_read(&port->topology_kref));
         save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET);
     }
 
     topology_ref_history_unlock(port->mgr);
     return ret;
 }
 
 /**
  * drm_dp_mst_topology_get_port() - Increment the topology refcount of a port
  * @port: The &struct drm_dp_mst_port to increment the topology refcount of
  *
  * Increments &drm_dp_mst_port.topology_refcount without checking whether or
  * not it's already reached 0. This is only valid to use in scenarios where
  * you are already guaranteed to have at least one active topology reference
  * to @port. Otherwise, drm_dp_mst_topology_try_get_port() must be used.
  *
  * See also:
  * drm_dp_mst_topology_try_get_port()
  * drm_dp_mst_topology_put_port()
  */
 static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port)
 {
     topology_ref_history_lock(port->mgr);
 
     WARN_ON(kref_read(&port->topology_kref) == 0);
     kref_get(&port->topology_kref);
     drm_dbg(port->mgr->dev, "port %p (%d)\n", port, kref_read(&port->topology_kref));
     save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET);
 
     topology_ref_history_unlock(port->mgr);
 }
 
 /**
  * drm_dp_mst_topology_put_port() - release a topology reference to a port
  * @port: The &struct drm_dp_mst_port to release the topology reference from
  *
  * Releases a topology reference from @port by decrementing
  * &drm_dp_mst_port.topology_kref.
  *
  * See also:
  * drm_dp_mst_topology_try_get_port()
  * drm_dp_mst_topology_get_port()
  */
 static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port)
 {
     topology_ref_history_lock(port->mgr);
 
     drm_dbg(port->mgr->dev, "port %p (%d)\n", port, kref_read(&port->topology_kref) - 1);
     save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_PUT);
 
     topology_ref_history_unlock(port->mgr);
     kref_put(&port->topology_kref, drm_dp_destroy_port);
 }
 
 static struct drm_dp_mst_branch *
 drm_dp_mst_topology_get_mstb_validated_locked(struct drm_dp_mst_branch *mstb,
                           struct drm_dp_mst_branch *to_find)
 {
     struct drm_dp_mst_port *port;
     struct drm_dp_mst_branch *rmstb;
 
     if (to_find == mstb)
         return mstb;
 
     list_for_each_entry(port, &mstb->ports, next) {
         if (port->mstb) {
             rmstb = drm_dp_mst_topology_get_mstb_validated_locked(
                 port->mstb, to_find);
             if (rmstb)
                 return rmstb;
         }
     }
     return NULL;
 }
 
 static struct drm_dp_mst_branch *
 drm_dp_mst_topology_get_mstb_validated(struct drm_dp_mst_topology_mgr *mgr,
                        struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_mst_branch *rmstb = NULL;
 
     mutex_lock(&mgr->lock);
     if (mgr->mst_primary) {
         rmstb = drm_dp_mst_topology_get_mstb_validated_locked(
             mgr->mst_primary, mstb);
 
         if (rmstb && !drm_dp_mst_topology_try_get_mstb(rmstb))
             rmstb = NULL;
     }
     mutex_unlock(&mgr->lock);
     return rmstb;
 }
 
 static struct drm_dp_mst_port *
 drm_dp_mst_topology_get_port_validated_locked(struct drm_dp_mst_branch *mstb,
                           struct drm_dp_mst_port *to_find)
 {
     struct drm_dp_mst_port *port, *mport;
 
     list_for_each_entry(port, &mstb->ports, next) {
         if (port == to_find)
             return port;
 
         if (port->mstb) {
             mport = drm_dp_mst_topology_get_port_validated_locked(
                 port->mstb, to_find);
             if (mport)
                 return mport;
         }
     }
     return NULL;
 }
 
 static struct drm_dp_mst_port *
 drm_dp_mst_topology_get_port_validated(struct drm_dp_mst_topology_mgr *mgr,
                        struct drm_dp_mst_port *port)
 {
     struct drm_dp_mst_port *rport = NULL;
 
     mutex_lock(&mgr->lock);
     if (mgr->mst_primary) {
         rport = drm_dp_mst_topology_get_port_validated_locked(
             mgr->mst_primary, port);
 
         if (rport && !drm_dp_mst_topology_try_get_port(rport))
             rport = NULL;
     }
     mutex_unlock(&mgr->lock);
     return rport;
 }
 
 static struct drm_dp_mst_port *drm_dp_get_port(struct drm_dp_mst_branch *mstb, u8 port_num)
 {
     struct drm_dp_mst_port *port;
     int ret;
 
     list_for_each_entry(port, &mstb->ports, next) {
         if (port->port_num == port_num) {
             ret = drm_dp_mst_topology_try_get_port(port);
             return ret ? port : NULL;
         }
     }
 
     return NULL;
 }
 
 /*
  * calculate a new RAD for this MST branch device
  * if parent has an LCT of 2 then it has 1 nibble of RAD,
  * if parent has an LCT of 3 then it has 2 nibbles of RAD,
  */
 static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port,
                  u8 *rad)
 {
     int parent_lct = port->parent->lct;
     int shift = 4;
     int idx = (parent_lct - 1) / 2;
 
     if (parent_lct > 1) {
         memcpy(rad, port->parent->rad, idx + 1);
         shift = (parent_lct % 2) ? 4 : 0;
     } else
         rad[0] = 0;
 
     rad[idx] |= port->port_num << shift;
     return parent_lct + 1;
 }
 
 static bool drm_dp_mst_is_end_device(u8 pdt, bool mcs)
 {
     switch (pdt) {
     case DP_PEER_DEVICE_DP_LEGACY_CONV:
     case DP_PEER_DEVICE_SST_SINK:
         return true;
     case DP_PEER_DEVICE_MST_BRANCHING:
         /* For sst branch device */
         if (!mcs)
             return true;
 
         return false;
     }
     return true;
 }
 
 static int
 drm_dp_port_set_pdt(struct drm_dp_mst_port *port, u8 new_pdt,
             bool new_mcs)
 {
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
     struct drm_dp_mst_branch *mstb;
     u8 rad[8], lct;
     int ret = 0;
 
     if (port->pdt == new_pdt && port->mcs == new_mcs)
         return 0;
 
     /* Teardown the old pdt, if there is one */
     if (port->pdt != DP_PEER_DEVICE_NONE) {
         if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
             /*
              * If the new PDT would also have an i2c bus,
              * don't bother with reregistering it
              */
             if (new_pdt != DP_PEER_DEVICE_NONE &&
                 drm_dp_mst_is_end_device(new_pdt, new_mcs)) {
                 port->pdt = new_pdt;
                 port->mcs = new_mcs;
                 return 0;
             }
 
             /* remove i2c over sideband */
             drm_dp_mst_unregister_i2c_bus(port);
         } else {
             mutex_lock(&mgr->lock);
             drm_dp_mst_topology_put_mstb(port->mstb);
             port->mstb = NULL;
             mutex_unlock(&mgr->lock);
         }
     }
 
     port->pdt = new_pdt;
     port->mcs = new_mcs;
 
     if (port->pdt != DP_PEER_DEVICE_NONE) {
         if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
             /* add i2c over sideband */
             ret = drm_dp_mst_register_i2c_bus(port);
         } else {
             lct = drm_dp_calculate_rad(port, rad);
             mstb = drm_dp_add_mst_branch_device(lct, rad);
             if (!mstb) {
                 ret = -ENOMEM;
                 drm_err(mgr->dev, "Failed to create MSTB for port %p", port);
                 goto out;
             }
 
             mutex_lock(&mgr->lock);
             port->mstb = mstb;
             mstb->mgr = port->mgr;
             mstb->port_parent = port;
 
             /*
              * Make sure this port's memory allocation stays
              * around until its child MSTB releases it
              */
             drm_dp_mst_get_port_malloc(port);
             mutex_unlock(&mgr->lock);
 
             /* And make sure we send a link address for this */
             ret = 1;
         }
     }
 
 out:
     if (ret < 0)
         port->pdt = DP_PEER_DEVICE_NONE;
     return ret;
 }
 
 /**
  * drm_dp_mst_dpcd_read() - read a series of bytes from the DPCD via sideband
  * @aux: Fake sideband AUX CH
  * @offset: address of the (first) register to read
  * @buffer: buffer to store the register values
  * @size: number of bytes in @buffer
  *
  * Performs the same functionality for remote devices via
  * sideband messaging as drm_dp_dpcd_read() does for local
  * devices via actual AUX CH.
  *
  * Return: Number of bytes read, or negative error code on failure.
  */
 ssize_t drm_dp_mst_dpcd_read(struct drm_dp_aux *aux,
                  unsigned int offset, void *buffer, size_t size)
 {
     struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port,
                             aux);
 
     return drm_dp_send_dpcd_read(port->mgr, port,
                      offset, size, buffer);
 }
 
 /**
  * drm_dp_mst_dpcd_write() - write a series of bytes to the DPCD via sideband
  * @aux: Fake sideband AUX CH
  * @offset: address of the (first) register to write
  * @buffer: buffer containing the values to write
  * @size: number of bytes in @buffer
  *
  * Performs the same functionality for remote devices via
  * sideband messaging as drm_dp_dpcd_write() does for local
  * devices via actual AUX CH.
  *
  * Return: number of bytes written on success, negative error code on failure.
  */
 ssize_t drm_dp_mst_dpcd_write(struct drm_dp_aux *aux,
                   unsigned int offset, void *buffer, size_t size)
 {
     struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port,
                             aux);
 
     return drm_dp_send_dpcd_write(port->mgr, port,
                       offset, size, buffer);
 }
 
 static int drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)
 {
     int ret = 0;
 
     memcpy(mstb->guid, guid, 16);
 
     if (!drm_dp_validate_guid(mstb->mgr, mstb->guid)) {
         if (mstb->port_parent) {
             ret = drm_dp_send_dpcd_write(mstb->mgr,
                              mstb->port_parent,
                              DP_GUID, 16, mstb->guid);
         } else {
             ret = drm_dp_dpcd_write(mstb->mgr->aux,
                         DP_GUID, mstb->guid, 16);
         }
     }
 
     if (ret < 16 && ret > 0)
         return -EPROTO;
 
     return ret == 16 ? 0 : ret;
 }
 
 static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
                 int pnum,
                 char *proppath,
                 size_t proppath_size)
 {
     int i;
     char temp[8];
 
     snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);
     for (i = 0; i < (mstb->lct - 1); i++) {
         int shift = (i % 2) ? 0 : 4;
         int port_num = (mstb->rad[i / 2] >> shift) & 0xf;
 
         snprintf(temp, sizeof(temp), "-%d", port_num);
         strlcat(proppath, temp, proppath_size);
     }
     snprintf(temp, sizeof(temp), "-%d", pnum);
     strlcat(proppath, temp, proppath_size);
 }
 
 /**
  * drm_dp_mst_connector_late_register() - Late MST connector registration
  * @connector: The MST connector
  * @port: The MST port for this connector
  *
  * Helper to register the remote aux device for this MST port. Drivers should
  * call this from their mst connector's late_register hook to enable MST aux
  * devices.
  *
  * Return: 0 on success, negative error code on failure.
  */
 int drm_dp_mst_connector_late_register(struct drm_connector *connector,
                        struct drm_dp_mst_port *port)
 {
     drm_dbg_kms(port->mgr->dev, "registering %s remote bus for %s\n",
             port->aux.name, connector->kdev->kobj.name);
 
     port->aux.dev = connector->kdev;
     return drm_dp_aux_register_devnode(&port->aux);
 }
 EXPORT_SYMBOL(drm_dp_mst_connector_late_register);
 
 /**
  * drm_dp_mst_connector_early_unregister() - Early MST connector unregistration
  * @connector: The MST connector
  * @port: The MST port for this connector
  *
  * Helper to unregister the remote aux device for this MST port, registered by
  * drm_dp_mst_connector_late_register(). Drivers should call this from their mst
  * connector's early_unregister hook.
  */
 void drm_dp_mst_connector_early_unregister(struct drm_connector *connector,
                        struct drm_dp_mst_port *port)
 {
     drm_dbg_kms(port->mgr->dev, "unregistering %s remote bus for %s\n",
             port->aux.name, connector->kdev->kobj.name);
     drm_dp_aux_unregister_devnode(&port->aux);
 }
 EXPORT_SYMBOL(drm_dp_mst_connector_early_unregister);
 
 static void
 drm_dp_mst_port_add_connector(struct drm_dp_mst_branch *mstb,
                   struct drm_dp_mst_port *port)
 {
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
     char proppath[255];
     int ret;
 
     build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath));
     port->connector = mgr->cbs->add_connector(mgr, port, proppath);
     if (!port->connector) {
         ret = -ENOMEM;
         goto error;
     }
 
     if (port->pdt != DP_PEER_DEVICE_NONE &&
         drm_dp_mst_is_end_device(port->pdt, port->mcs) &&
         port->port_num >= DP_MST_LOGICAL_PORT_0)
         port->cached_edid = drm_get_edid(port->connector,
                          &port->aux.ddc);
 
     drm_connector_register(port->connector);
     return;
 
 error:
     drm_err(mgr->dev, "Failed to create connector for port %p: %d\n", port, ret);
 }
 
 /*
  * Drop a topology reference, and unlink the port from the in-memory topology
  * layout
  */
 static void
 drm_dp_mst_topology_unlink_port(struct drm_dp_mst_topology_mgr *mgr,
                 struct drm_dp_mst_port *port)
 {
     mutex_lock(&mgr->lock);
     port->parent->num_ports--;
     list_del(&port->next);
     mutex_unlock(&mgr->lock);
     drm_dp_mst_topology_put_port(port);
 }
 
 static struct drm_dp_mst_port *
 drm_dp_mst_add_port(struct drm_device *dev,
             struct drm_dp_mst_topology_mgr *mgr,
             struct drm_dp_mst_branch *mstb, u8 port_number)
 {
     struct drm_dp_mst_port *port = kzalloc(sizeof(*port), GFP_KERNEL);
 
     if (!port)
         return NULL;
 
     kref_init(&port->topology_kref);
     kref_init(&port->malloc_kref);
     port->parent = mstb;
     port->port_num = port_number;
     port->mgr = mgr;
     port->aux.name = "DPMST";
     port->aux.dev = dev->dev;
     port->aux.is_remote = true;
 
     /* initialize the MST downstream port's AUX crc work queue */
     port->aux.drm_dev = dev;
     drm_dp_remote_aux_init(&port->aux);
 
     /*
      * Make sure the memory allocation for our parent branch stays
      * around until our own memory allocation is released
      */
     drm_dp_mst_get_mstb_malloc(mstb);
 
     return port;
 }
 
 static int
 drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
                     struct drm_device *dev,
                     struct drm_dp_link_addr_reply_port *port_msg)
 {
     struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
     struct drm_dp_mst_port *port;
     int old_ddps = 0, ret;
     u8 new_pdt = DP_PEER_DEVICE_NONE;
     bool new_mcs = 0;
     bool created = false, send_link_addr = false, changed = false;
 
     port = drm_dp_get_port(mstb, port_msg->port_number);
     if (!port) {
         port = drm_dp_mst_add_port(dev, mgr, mstb,
                        port_msg->port_number);
         if (!port)
             return -ENOMEM;
         created = true;
         changed = true;
     } else if (!port->input && port_msg->input_port && port->connector) {
         /* Since port->connector can't be changed here, we create a
          * new port if input_port changes from 0 to 1
          */
         drm_dp_mst_topology_unlink_port(mgr, port);
         drm_dp_mst_topology_put_port(port);
         port = drm_dp_mst_add_port(dev, mgr, mstb,
                        port_msg->port_number);
         if (!port)
             return -ENOMEM;
         changed = true;
         created = true;
     } else if (port->input && !port_msg->input_port) {
         changed = true;
     } else if (port->connector) {
         /* We're updating a port that's exposed to userspace, so do it
          * under lock
          */
         drm_modeset_lock(&mgr->base.lock, NULL);
 
         old_ddps = port->ddps;
         changed = port->ddps != port_msg->ddps ||
             (port->ddps &&
              (port->ldps != port_msg->legacy_device_plug_status ||
               port->dpcd_rev != port_msg->dpcd_revision ||
               port->mcs != port_msg->mcs ||
               port->pdt != port_msg->peer_device_type ||
               port->num_sdp_stream_sinks !=
               port_msg->num_sdp_stream_sinks));
     }
 
     port->input = port_msg->input_port;
     if (!port->input)
         new_pdt = port_msg->peer_device_type;
     new_mcs = port_msg->mcs;
     port->ddps = port_msg->ddps;
     port->ldps = port_msg->legacy_device_plug_status;
     port->dpcd_rev = port_msg->dpcd_revision;
     port->num_sdp_streams = port_msg->num_sdp_streams;
     port->num_sdp_stream_sinks = port_msg->num_sdp_stream_sinks;
 
     /* manage mstb port lists with mgr lock - take a reference
        for this list */
     if (created) {
         mutex_lock(&mgr->lock);
         drm_dp_mst_topology_get_port(port);
         list_add(&port->next, &mstb->ports);
         mstb->num_ports++;
         mutex_unlock(&mgr->lock);
     }
 
     /*
      * Reprobe PBN caps on both hotplug, and when re-probing the link
      * for our parent mstb
      */
     if (old_ddps != port->ddps || !created) {
         if (port->ddps && !port->input) {
             ret = drm_dp_send_enum_path_resources(mgr, mstb,
                                   port);
             if (ret == 1)
                 changed = true;
         } else {
             port->full_pbn = 0;
         }
     }
 
     ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);
     if (ret == 1) {
         send_link_addr = true;
     } else if (ret < 0) {
         drm_err(dev, "Failed to change PDT on port %p: %d\n", port, ret);
         goto fail;
     }
 
     /*
      * If this port wasn't just created, then we're reprobing because
      * we're coming out of suspend. In this case, always resend the link
      * address if there's an MSTB on this port
      */
     if (!created && port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
         port->mcs)
         send_link_addr = true;
 
     if (port->connector)
         drm_modeset_unlock(&mgr->base.lock);
     else if (!port->input)
         drm_dp_mst_port_add_connector(mstb, port);
 
     if (send_link_addr && port->mstb) {
         ret = drm_dp_send_link_address(mgr, port->mstb);
         if (ret == 1) /* MSTB below us changed */
             changed = true;
         else if (ret < 0)
             goto fail_put;
     }
 
     /* put reference to this port */
     drm_dp_mst_topology_put_port(port);
     return changed;
 
 fail:
     drm_dp_mst_topology_unlink_port(mgr, port);
     if (port->connector)
         drm_modeset_unlock(&mgr->base.lock);
 fail_put:
     drm_dp_mst_topology_put_port(port);
     return ret;
 }
 
 static void
 drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
                 struct drm_dp_connection_status_notify *conn_stat)
 {
     struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
     struct drm_dp_mst_port *port;
     int old_ddps, ret;
     u8 new_pdt;
     bool new_mcs;
     bool dowork = false, create_connector = false;
 
     port = drm_dp_get_port(mstb, conn_stat->port_number);
     if (!port)
         return;
 
     if (port->connector) {
         if (!port->input && conn_stat->input_port) {
             /*
              * We can't remove a connector from an already exposed
              * port, so just throw the port out and make sure we
              * reprobe the link address of it's parent MSTB
              */
             drm_dp_mst_topology_unlink_port(mgr, port);
             mstb->link_address_sent = false;
             dowork = true;
             goto out;
         }
 
         /* Locking is only needed if the port's exposed to userspace */
         drm_modeset_lock(&mgr->base.lock, NULL);
     } else if (port->input && !conn_stat->input_port) {
         create_connector = true;
         /* Reprobe link address so we get num_sdp_streams */
         mstb->link_address_sent = false;
         dowork = true;
     }
 
     old_ddps = port->ddps;
     port->input = conn_stat->input_port;
     port->ldps = conn_stat->legacy_device_plug_status;
     port->ddps = conn_stat->displayport_device_plug_status;
 
     if (old_ddps != port->ddps) {
         if (port->ddps && !port->input)
             drm_dp_send_enum_path_resources(mgr, mstb, port);
         else
             port->full_pbn = 0;
     }
 
     new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type;
     new_mcs = conn_stat->message_capability_status;
     ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);
     if (ret == 1) {
         dowork = true;
     } else if (ret < 0) {
         drm_err(mgr->dev, "Failed to change PDT for port %p: %d\n", port, ret);
         dowork = false;
     }
 
     if (port->connector)
         drm_modeset_unlock(&mgr->base.lock);
     else if (create_connector)
         drm_dp_mst_port_add_connector(mstb, port);
 
 out:
     drm_dp_mst_topology_put_port(port);
     if (dowork)
         queue_work(system_long_wq, &mstb->mgr->work);
 }
 
 static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr,
                                    u8 lct, u8 *rad)
 {
     struct drm_dp_mst_branch *mstb;
     struct drm_dp_mst_port *port;
     int i, ret;
     /* find the port by iterating down */
 
     mutex_lock(&mgr->lock);
     mstb = mgr->mst_primary;
 
     if (!mstb)
         goto out;
 
     for (i = 0; i < lct - 1; i++) {
         int shift = (i % 2) ? 0 : 4;
         int port_num = (rad[i / 2] >> shift) & 0xf;
 
         list_for_each_entry(port, &mstb->ports, next) {
             if (port->port_num == port_num) {
                 mstb = port->mstb;
                 if (!mstb) {
                     drm_err(mgr->dev,
                         "failed to lookup MSTB with lct %d, rad %02x\n",
                         lct, rad[0]);
                     goto out;
                 }
 
                 break;
             }
         }
     }
     ret = drm_dp_mst_topology_try_get_mstb(mstb);
     if (!ret)
         mstb = NULL;
 out:
     mutex_unlock(&mgr->lock);
     return mstb;
 }
 
 static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
     struct drm_dp_mst_branch *mstb,
     const uint8_t *guid)
 {
     struct drm_dp_mst_branch *found_mstb;
     struct drm_dp_mst_port *port;
 
     if (memcmp(mstb->guid, guid, 16) == 0)
         return mstb;
 
 
     list_for_each_entry(port, &mstb->ports, next) {
         if (!port->mstb)
             continue;
 
         found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);
 
         if (found_mstb)
             return found_mstb;
     }
 
     return NULL;
 }
 
 static struct drm_dp_mst_branch *
 drm_dp_get_mst_branch_device_by_guid(struct drm_dp_mst_topology_mgr *mgr,
                      const uint8_t *guid)
 {
     struct drm_dp_mst_branch *mstb;
     int ret;
 
     /* find the port by iterating down */
     mutex_lock(&mgr->lock);
 
     mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);
     if (mstb) {
         ret = drm_dp_mst_topology_try_get_mstb(mstb);
         if (!ret)
             mstb = NULL;
     }
 
     mutex_unlock(&mgr->lock);
     return mstb;
 }
 
 static int drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                            struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_mst_port *port;
     int ret;
     bool changed = false;
 
     if (!mstb->link_address_sent) {
         ret = drm_dp_send_link_address(mgr, mstb);
         if (ret == 1)
             changed = true;
         else if (ret < 0)
             return ret;
     }
 
     list_for_each_entry(port, &mstb->ports, next) {
         if (port->input || !port->ddps || !port->mstb)
             continue;
 
         ret = drm_dp_check_and_send_link_address(mgr, port->mstb);
         if (ret == 1)
             changed = true;
         else if (ret < 0)
             return ret;
     }
 
     return changed;
 }
 
 static void drm_dp_mst_link_probe_work(struct work_struct *work)
 {
     struct drm_dp_mst_topology_mgr *mgr =
         container_of(work, struct drm_dp_mst_topology_mgr, work);
     struct drm_device *dev = mgr->dev;
     struct drm_dp_mst_branch *mstb;
     int ret;
     bool clear_payload_id_table;
 
     mutex_lock(&mgr->probe_lock);
 
     mutex_lock(&mgr->lock);
     clear_payload_id_table = !mgr->payload_id_table_cleared;
     mgr->payload_id_table_cleared = true;
 
     mstb = mgr->mst_primary;
     if (mstb) {
         ret = drm_dp_mst_topology_try_get_mstb(mstb);
         if (!ret)
             mstb = NULL;
     }
     mutex_unlock(&mgr->lock);
     if (!mstb) {
         mutex_unlock(&mgr->probe_lock);
         return;
     }
 
     /*
      * Certain branch devices seem to incorrectly report an available_pbn
      * of 0 on downstream sinks, even after clearing the
      * DP_PAYLOAD_ALLOCATE_* registers in
      * drm_dp_mst_topology_mgr_set_mst(). Namely, the CableMatters USB-C
      * 2x DP hub. Sending a CLEAR_PAYLOAD_ID_TABLE message seems to make
      * things work again.
      */
     if (clear_payload_id_table) {
         drm_dbg_kms(dev, "Clearing payload ID table\n");
         drm_dp_send_clear_payload_id_table(mgr, mstb);
     }
 
     ret = drm_dp_check_and_send_link_address(mgr, mstb);
     drm_dp_mst_topology_put_mstb(mstb);
 
     mutex_unlock(&mgr->probe_lock);
     if (ret > 0)
         drm_kms_helper_hotplug_event(dev);
 }
 
 static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
                  u8 *guid)
 {
     u64 salt;
 
     if (memchr_inv(guid, 0, 16))
         return true;
 
     salt = get_jiffies_64();
 
     memcpy(&guid[0], &salt, sizeof(u64));
     memcpy(&guid[8], &salt, sizeof(u64));
 
     return false;
 }
 
 static void build_dpcd_read(struct drm_dp_sideband_msg_tx *msg,
                 u8 port_num, u32 offset, u8 num_bytes)
 {
     struct drm_dp_sideband_msg_req_body req;
 
     req.req_type = DP_REMOTE_DPCD_READ;
     req.u.dpcd_read.port_number = port_num;
     req.u.dpcd_read.dpcd_address = offset;
     req.u.dpcd_read.num_bytes = num_bytes;
     drm_dp_encode_sideband_req(&req, msg);
 }
 
 static int drm_dp_send_sideband_msg(struct drm_dp_mst_topology_mgr *mgr,
                     bool up, u8 *msg, int len)
 {
     int ret;
     int regbase = up ? DP_SIDEBAND_MSG_UP_REP_BASE : DP_SIDEBAND_MSG_DOWN_REQ_BASE;
     int tosend, total, offset;
     int retries = 0;
 
 retry:
     total = len;
     offset = 0;
     do {
         tosend = min3(mgr->max_dpcd_transaction_bytes, 16, total);
 
         ret = drm_dp_dpcd_write(mgr->aux, regbase + offset,
                     &msg[offset],
                     tosend);
         if (ret != tosend) {
             if (ret == -EIO && retries < 5) {
                 retries++;
                 goto retry;
             }
             drm_dbg_kms(mgr->dev, "failed to dpcd write %d %d\n", tosend, ret);
 
             return -EIO;
         }
         offset += tosend;
         total -= tosend;
     } while (total > 0);
     return 0;
 }
 
 static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr,
                   struct drm_dp_sideband_msg_tx *txmsg)
 {
     struct drm_dp_mst_branch *mstb = txmsg->dst;
     u8 req_type;
 
     req_type = txmsg->msg[0] & 0x7f;
     if (req_type == DP_CONNECTION_STATUS_NOTIFY ||
         req_type == DP_RESOURCE_STATUS_NOTIFY ||
         req_type == DP_CLEAR_PAYLOAD_ID_TABLE)
         hdr->broadcast = 1;
     else
         hdr->broadcast = 0;
     hdr->path_msg = txmsg->path_msg;
     if (hdr->broadcast) {
         hdr->lct = 1;
         hdr->lcr = 6;
     } else {
         hdr->lct = mstb->lct;
         hdr->lcr = mstb->lct - 1;
     }
 
     memcpy(hdr->rad, mstb->rad, hdr->lct / 2);
 
     return 0;
 }
 /*
  * process a single block of the next message in the sideband queue
  */
 static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
                    struct drm_dp_sideband_msg_tx *txmsg,
                    bool up)
 {
     u8 chunk[48];
     struct drm_dp_sideband_msg_hdr hdr;
     int len, space, idx, tosend;
     int ret;
 
     if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT)
         return 0;
 
     memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr));
 
     if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED)
         txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND;
 
     /* make hdr from dst mst */
     ret = set_hdr_from_dst_qlock(&hdr, txmsg);
     if (ret < 0)
         return ret;
 
     /* amount left to send in this message */
     len = txmsg->cur_len - txmsg->cur_offset;
 
     /* 48 - sideband msg size - 1 byte for data CRC, x header bytes */
     space = 48 - 1 - drm_dp_calc_sb_hdr_size(&hdr);
 
     tosend = min(len, space);
     if (len == txmsg->cur_len)
         hdr.somt = 1;
     if (space >= len)
         hdr.eomt = 1;
 
 
     hdr.msg_len = tosend + 1;
     drm_dp_encode_sideband_msg_hdr(&hdr, chunk, &idx);
     memcpy(&chunk[idx], &txmsg->msg[txmsg->cur_offset], tosend);
     /* add crc at end */
     drm_dp_crc_sideband_chunk_req(&chunk[idx], tosend);
     idx += tosend + 1;
 
     ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx);
     if (ret) {
         if (drm_debug_enabled(DRM_UT_DP)) {
             struct drm_printer p = drm_debug_printer(DBG_PREFIX);
 
             drm_printf(&p, "sideband msg failed to send\n");
             drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
         }
         return ret;
     }
 
     txmsg->cur_offset += tosend;
     if (txmsg->cur_offset == txmsg->cur_len) {
         txmsg->state = DRM_DP_SIDEBAND_TX_SENT;
         return 1;
     }
     return 0;
 }
 
 static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     int ret;
 
     WARN_ON(!mutex_is_locked(&mgr->qlock));
 
     /* construct a chunk from the first msg in the tx_msg queue */
     if (list_empty(&mgr->tx_msg_downq))
         return;
 
     txmsg = list_first_entry(&mgr->tx_msg_downq,
                  struct drm_dp_sideband_msg_tx, next);
     ret = process_single_tx_qlock(mgr, txmsg, false);
     if (ret < 0) {
         drm_dbg_kms(mgr->dev, "failed to send msg in q %d\n", ret);
         list_del(&txmsg->next);
         txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
         wake_up_all(&mgr->tx_waitq);
     }
 }
 
 static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
                  struct drm_dp_sideband_msg_tx *txmsg)
 {
     mutex_lock(&mgr->qlock);
     list_add_tail(&txmsg->next, &mgr->tx_msg_downq);
 
     if (drm_debug_enabled(DRM_UT_DP)) {
         struct drm_printer p = drm_debug_printer(DBG_PREFIX);
 
         drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
     }
 
     if (list_is_singular(&mgr->tx_msg_downq))
         process_single_down_tx_qlock(mgr);
     mutex_unlock(&mgr->qlock);
 }
 
 static void
 drm_dp_dump_link_address(const struct drm_dp_mst_topology_mgr *mgr,
              struct drm_dp_link_address_ack_reply *reply)
 {
     struct drm_dp_link_addr_reply_port *port_reply;
     int i;
 
     for (i = 0; i < reply->nports; i++) {
         port_reply = &reply->ports[i];
         drm_dbg_kms(mgr->dev,
                 "port %d: input %d, pdt: %d, pn: %d, dpcd_rev: %02x, mcs: %d, ddps: %d, ldps %d, sdp %d/%d\n",
                 i,
                 port_reply->input_port,
                 port_reply->peer_device_type,
                 port_reply->port_number,
                 port_reply->dpcd_revision,
                 port_reply->mcs,
                 port_reply->ddps,
                 port_reply->legacy_device_plug_status,
                 port_reply->num_sdp_streams,
                 port_reply->num_sdp_stream_sinks);
     }
 }
 
 static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                      struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     struct drm_dp_link_address_ack_reply *reply;
     struct drm_dp_mst_port *port, *tmp;
     int i, ret, port_mask = 0;
     bool changed = false;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg)
         return -ENOMEM;
 
     txmsg->dst = mstb;
     build_link_address(txmsg);
 
     mstb->link_address_sent = true;
     drm_dp_queue_down_tx(mgr, txmsg);
 
     /* FIXME: Actually do some real error handling here */
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret <= 0) {
         drm_err(mgr->dev, "Sending link address failed with %d\n", ret);
         goto out;
     }
     if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
         drm_err(mgr->dev, "link address NAK received\n");
         ret = -EIO;
         goto out;
     }
 
     reply = &txmsg->reply.u.link_addr;
     drm_dbg_kms(mgr->dev, "link address reply: %d\n", reply->nports);
     drm_dp_dump_link_address(mgr, reply);
 
     ret = drm_dp_check_mstb_guid(mstb, reply->guid);
     if (ret) {
         char buf[64];
 
         drm_dp_mst_rad_to_str(mstb->rad, mstb->lct, buf, sizeof(buf));
         drm_err(mgr->dev, "GUID check on %s failed: %d\n", buf, ret);
         goto out;
     }
 
     for (i = 0; i < reply->nports; i++) {
         port_mask |= BIT(reply->ports[i].port_number);
         ret = drm_dp_mst_handle_link_address_port(mstb, mgr->dev,
                               &reply->ports[i]);
         if (ret == 1)
             changed = true;
         else if (ret < 0)
             goto out;
     }
 
     /* Prune any ports that are currently a part of mstb in our in-memory
      * topology, but were not seen in this link address. Usually this
      * means that they were removed while the topology was out of sync,
      * e.g. during suspend/resume
      */
     mutex_lock(&mgr->lock);
     list_for_each_entry_safe(port, tmp, &mstb->ports, next) {
         if (port_mask & BIT(port->port_num))
             continue;
 
         drm_dbg_kms(mgr->dev, "port %d was not in link address, removing\n",
                 port->port_num);
         list_del(&port->next);
         drm_dp_mst_topology_put_port(port);
         changed = true;
     }
     mutex_unlock(&mgr->lock);
 
 out:
     if (ret <= 0)
         mstb->link_address_sent = false;
     kfree(txmsg);
     return ret < 0 ? ret : changed;
 }
 
 static void
 drm_dp_send_clear_payload_id_table(struct drm_dp_mst_topology_mgr *mgr,
                    struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     int ret;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg)
         return;
 
     txmsg->dst = mstb;
     build_clear_payload_id_table(txmsg);
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
         drm_dbg_kms(mgr->dev, "clear payload table id nak received\n");
 
     kfree(txmsg);
 }
 
 static int
 drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
                 struct drm_dp_mst_branch *mstb,
                 struct drm_dp_mst_port *port)
 {
     struct drm_dp_enum_path_resources_ack_reply *path_res;
     struct drm_dp_sideband_msg_tx *txmsg;
     int ret;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg)
         return -ENOMEM;
 
     txmsg->dst = mstb;
     build_enum_path_resources(txmsg, port->port_num);
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret > 0) {
         ret = 0;
         path_res = &txmsg->reply.u.path_resources;
 
         if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
             drm_dbg_kms(mgr->dev, "enum path resources nak received\n");
         } else {
             if (port->port_num != path_res->port_number)
                 DRM_ERROR("got incorrect port in response\n");
 
             drm_dbg_kms(mgr->dev, "enum path resources %d: %d %d\n",
                     path_res->port_number,
                     path_res->full_payload_bw_number,
                     path_res->avail_payload_bw_number);
 
             /*
              * If something changed, make sure we send a
              * hotplug
              */
             if (port->full_pbn != path_res->full_payload_bw_number ||
                 port->fec_capable != path_res->fec_capable)
                 ret = 1;
 
             port->full_pbn = path_res->full_payload_bw_number;
             port->fec_capable = path_res->fec_capable;
         }
     }
 
     kfree(txmsg);
     return ret;
 }
 
 static struct drm_dp_mst_port *drm_dp_get_last_connected_port_to_mstb(struct drm_dp_mst_branch *mstb)
 {
     if (!mstb->port_parent)
         return NULL;
 
     if (mstb->port_parent->mstb != mstb)
         return mstb->port_parent;
 
     return drm_dp_get_last_connected_port_to_mstb(mstb->port_parent->parent);
 }
 
 /*
  * Searches upwards in the topology starting from mstb to try to find the
  * closest available parent of mstb that's still connected to the rest of the
  * topology. This can be used in order to perform operations like releasing
  * payloads, where the branch device which owned the payload may no longer be
  * around and thus would require that the payload on the last living relative
  * be freed instead.
  */
 static struct drm_dp_mst_branch *
 drm_dp_get_last_connected_port_and_mstb(struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_mst_branch *mstb,
                     int *port_num)
 {
     struct drm_dp_mst_branch *rmstb = NULL;
     struct drm_dp_mst_port *found_port;
 
     mutex_lock(&mgr->lock);
     if (!mgr->mst_primary)
         goto out;
 
     do {
         found_port = drm_dp_get_last_connected_port_to_mstb(mstb);
         if (!found_port)
             break;
 
         if (drm_dp_mst_topology_try_get_mstb(found_port->parent)) {
             rmstb = found_port->parent;
             *port_num = found_port->port_num;
         } else {
             /* Search again, starting from this parent */
             mstb = found_port->parent;
         }
     } while (!rmstb);
 out:
     mutex_unlock(&mgr->lock);
     return rmstb;
 }
 
 static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
                    struct drm_dp_mst_port *port,
                    int id,
                    int pbn)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     struct drm_dp_mst_branch *mstb;
     int ret, port_num;
     u8 sinks[DRM_DP_MAX_SDP_STREAMS];
     int i;
 
     port_num = port->port_num;
     mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
     if (!mstb) {
         mstb = drm_dp_get_last_connected_port_and_mstb(mgr,
                                    port->parent,
                                    &port_num);
 
         if (!mstb)
             return -EINVAL;
     }
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         ret = -ENOMEM;
         goto fail_put;
     }
 
     for (i = 0; i < port->num_sdp_streams; i++)
         sinks[i] = i;
 
     txmsg->dst = mstb;
     build_allocate_payload(txmsg, port_num,
                    id,
                    pbn, port->num_sdp_streams, sinks);
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     /*
      * FIXME: there is a small chance that between getting the last
      * connected mstb and sending the payload message, the last connected
      * mstb could also be removed from the topology. In the future, this
      * needs to be fixed by restarting the
      * drm_dp_get_last_connected_port_and_mstb() search in the event of a
      * timeout if the topology is still connected to the system.
      */
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret > 0) {
         if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
             ret = -EINVAL;
         else
             ret = 0;
     }
     kfree(txmsg);
 fail_put:
     drm_dp_mst_topology_put_mstb(mstb);
     return ret;
 }
 
 int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
                  struct drm_dp_mst_port *port, bool power_up)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     int ret;
 
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port)
         return -EINVAL;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         drm_dp_mst_topology_put_port(port);
         return -ENOMEM;
     }
 
     txmsg->dst = port->parent;
     build_power_updown_phy(txmsg, port->port_num, power_up);
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(port->parent, txmsg);
     if (ret > 0) {
         if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
             ret = -EINVAL;
         else
             ret = 0;
     }
     kfree(txmsg);
     drm_dp_mst_topology_put_port(port);
 
     return ret;
 }
 EXPORT_SYMBOL(drm_dp_send_power_updown_phy);
 
 int drm_dp_send_query_stream_enc_status(struct drm_dp_mst_topology_mgr *mgr,
         struct drm_dp_mst_port *port,
         struct drm_dp_query_stream_enc_status_ack_reply *status)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     u8 nonce[7];
     int ret;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg)
         return -ENOMEM;
 
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port) {
         ret = -EINVAL;
         goto out_get_port;
     }
 
     get_random_bytes(nonce, sizeof(nonce));
 
     /*
      * "Source device targets the QUERY_STREAM_ENCRYPTION_STATUS message
      *  transaction at the MST Branch device directly connected to the
      *  Source"
      */
     txmsg->dst = mgr->mst_primary;
 
     build_query_stream_enc_status(txmsg, port->vcpi.vcpi, nonce);
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mgr->mst_primary, txmsg);
     if (ret < 0) {
         goto out;
     } else if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
         drm_dbg_kms(mgr->dev, "query encryption status nak received\n");
         ret = -ENXIO;
         goto out;
     }
 
     ret = 0;
     memcpy(status, &txmsg->reply.u.enc_status, sizeof(*status));
 
 out:
     drm_dp_mst_topology_put_port(port);
 out_get_port:
     kfree(txmsg);
     return ret;
 }
 EXPORT_SYMBOL(drm_dp_send_query_stream_enc_status);
 
 static int drm_dp_create_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
                        int id,
                        struct drm_dp_payload *payload)
 {
     int ret;
 
     ret = drm_dp_dpcd_write_payload(mgr, id, payload);
     if (ret < 0) {
         payload->payload_state = 0;
         return ret;
     }
     payload->payload_state = DP_PAYLOAD_LOCAL;
     return 0;
 }
 
 static int drm_dp_create_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
                        struct drm_dp_mst_port *port,
                        int id,
                        struct drm_dp_payload *payload)
 {
     int ret;
 
     ret = drm_dp_payload_send_msg(mgr, port, id, port->vcpi.pbn);
     if (ret < 0)
         return ret;
     payload->payload_state = DP_PAYLOAD_REMOTE;
     return ret;
 }
 
 static int drm_dp_destroy_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_mst_port *port,
                     int id,
                     struct drm_dp_payload *payload)
 {
     drm_dbg_kms(mgr->dev, "\n");
     /* it's okay for these to fail */
     if (port) {
         drm_dp_payload_send_msg(mgr, port, id, 0);
     }
 
     drm_dp_dpcd_write_payload(mgr, id, payload);
     payload->payload_state = DP_PAYLOAD_DELETE_LOCAL;
     return 0;
 }
 
 static int drm_dp_destroy_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
                     int id,
                     struct drm_dp_payload *payload)
 {
     payload->payload_state = 0;
     return 0;
 }
 
 /**
  * drm_dp_update_payload_part1() - Execute payload update part 1
  * @mgr: manager to use.
  * @start_slot: this is the cur slot
  *
  * NOTE: start_slot is a temporary workaround for non-atomic drivers,
  * this will be removed when non-atomic mst helpers are moved out of the helper
  *
  * This iterates over all proposed virtual channels, and tries to
  * allocate space in the link for them. For 0->slots transitions,
  * this step just writes the VCPI to the MST device. For slots->0
  * transitions, this writes the updated VCPIs and removes the
  * remote VC payloads.
  *
  * after calling this the driver should generate ACT and payload
  * packets.
  */
 int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr, int start_slot)
 {
     struct drm_dp_payload req_payload;
     struct drm_dp_mst_port *port;
     int i, j;
     int cur_slots = start_slot;
     bool skip;
 
     mutex_lock(&mgr->payload_lock);
     for (i = 0; i < mgr->max_payloads; i++) {
         struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i];
         struct drm_dp_payload *payload = &mgr->payloads[i];
         bool put_port = false;
 
         /* solve the current payloads - compare to the hw ones
            - update the hw view */
         req_payload.start_slot = cur_slots;
         if (vcpi) {
             port = container_of(vcpi, struct drm_dp_mst_port,
                         vcpi);
 
             mutex_lock(&mgr->lock);
             skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
             mutex_unlock(&mgr->lock);
 
             if (skip) {
                 drm_dbg_kms(mgr->dev,
                         "Virtual channel %d is not in current topology\n",
                         i);
                 continue;
             }
             /* Validated ports don't matter if we're releasing
              * VCPI
              */
             if (vcpi->num_slots) {
                 port = drm_dp_mst_topology_get_port_validated(
                     mgr, port);
                 if (!port) {
                     if (vcpi->num_slots == payload->num_slots) {
                         cur_slots += vcpi->num_slots;
                         payload->start_slot = req_payload.start_slot;
                         continue;
                     } else {
                         drm_dbg_kms(mgr->dev,
                                 "Fail:set payload to invalid sink");
                         mutex_unlock(&mgr->payload_lock);
                         return -EINVAL;
                     }
                 }
                 put_port = true;
             }
 
             req_payload.num_slots = vcpi->num_slots;
             req_payload.vcpi = vcpi->vcpi;
         } else {
             port = NULL;
             req_payload.num_slots = 0;
         }
 
         payload->start_slot = req_payload.start_slot;
         /* work out what is required to happen with this payload */
         if (payload->num_slots != req_payload.num_slots) {
 
             /* need to push an update for this payload */
             if (req_payload.num_slots) {
                 drm_dp_create_payload_step1(mgr, vcpi->vcpi,
                                 &req_payload);
                 payload->num_slots = req_payload.num_slots;
                 payload->vcpi = req_payload.vcpi;
 
             } else if (payload->num_slots) {
                 payload->num_slots = 0;
                 drm_dp_destroy_payload_step1(mgr, port,
                                  payload->vcpi,
                                  payload);
                 req_payload.payload_state =
                     payload->payload_state;
                 payload->start_slot = 0;
             }
             payload->payload_state = req_payload.payload_state;
         }
         cur_slots += req_payload.num_slots;
 
         if (put_port)
             drm_dp_mst_topology_put_port(port);
     }
 
     for (i = 0; i < mgr->max_payloads; /* do nothing */) {
         if (mgr->payloads[i].payload_state != DP_PAYLOAD_DELETE_LOCAL) {
             i++;
             continue;
         }
 
         drm_dbg_kms(mgr->dev, "removing payload %d\n", i);
         for (j = i; j < mgr->max_payloads - 1; j++) {
             mgr->payloads[j] = mgr->payloads[j + 1];
             mgr->proposed_vcpis[j] = mgr->proposed_vcpis[j + 1];
 
             if (mgr->proposed_vcpis[j] &&
                 mgr->proposed_vcpis[j]->num_slots) {
                 set_bit(j + 1, &mgr->payload_mask);
             } else {
                 clear_bit(j + 1, &mgr->payload_mask);
             }
         }
 
         memset(&mgr->payloads[mgr->max_payloads - 1], 0,
                sizeof(struct drm_dp_payload));
         mgr->proposed_vcpis[mgr->max_payloads - 1] = NULL;
         clear_bit(mgr->max_payloads, &mgr->payload_mask);
     }
     mutex_unlock(&mgr->payload_lock);
 
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_update_payload_part1);
 
 /**
  * drm_dp_update_payload_part2() - Execute payload update part 2
  * @mgr: manager to use.
  *
  * This iterates over all proposed virtual channels, and tries to
  * allocate space in the link for them. For 0->slots transitions,
  * this step writes the remote VC payload commands. For slots->0
  * this just resets some internal state.
  */
 int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
 {
     struct drm_dp_mst_port *port;
     int i;
     int ret = 0;
     bool skip;
 
     mutex_lock(&mgr->payload_lock);
     for (i = 0; i < mgr->max_payloads; i++) {
 
         if (!mgr->proposed_vcpis[i])
             continue;
 
         port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
 
         mutex_lock(&mgr->lock);
         skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
         mutex_unlock(&mgr->lock);
 
         if (skip)
             continue;
 
         drm_dbg_kms(mgr->dev, "payload %d %d\n", i, mgr->payloads[i].payload_state);
         if (mgr->payloads[i].payload_state == DP_PAYLOAD_LOCAL) {
             ret = drm_dp_create_payload_step2(mgr, port, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
         } else if (mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) {
             ret = drm_dp_destroy_payload_step2(mgr, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
         }
         if (ret) {
             mutex_unlock(&mgr->payload_lock);
             return ret;
         }
     }
     mutex_unlock(&mgr->payload_lock);
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_update_payload_part2);
 
 static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
                  struct drm_dp_mst_port *port,
                  int offset, int size, u8 *bytes)
 {
     int ret = 0;
     struct drm_dp_sideband_msg_tx *txmsg;
     struct drm_dp_mst_branch *mstb;
 
     mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
     if (!mstb)
         return -EINVAL;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         ret = -ENOMEM;
         goto fail_put;
     }
 
     build_dpcd_read(txmsg, port->port_num, offset, size);
     txmsg->dst = port->parent;
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret < 0)
         goto fail_free;
 
     if (txmsg->reply.reply_type == 1) {
         drm_dbg_kms(mgr->dev, "mstb %p port %d: DPCD read on addr 0x%x for %d bytes NAKed\n",
                 mstb, port->port_num, offset, size);
         ret = -EIO;
         goto fail_free;
     }
 
     if (txmsg->reply.u.remote_dpcd_read_ack.num_bytes != size) {
         ret = -EPROTO;
         goto fail_free;
     }
 
     ret = min_t(size_t, txmsg->reply.u.remote_dpcd_read_ack.num_bytes,
             size);
     memcpy(bytes, txmsg->reply.u.remote_dpcd_read_ack.bytes, ret);
 
 fail_free:
     kfree(txmsg);
 fail_put:
     drm_dp_mst_topology_put_mstb(mstb);
 
     return ret;
 }
 
 static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
                   struct drm_dp_mst_port *port,
                   int offset, int size, u8 *bytes)
 {
     int ret;
     struct drm_dp_sideband_msg_tx *txmsg;
     struct drm_dp_mst_branch *mstb;
 
     mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
     if (!mstb)
         return -EINVAL;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         ret = -ENOMEM;
         goto fail_put;
     }
 
     build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
     txmsg->dst = mstb;
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret > 0) {
         if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
             ret = -EIO;
         else
             ret = size;
     }
 
     kfree(txmsg);
 fail_put:
     drm_dp_mst_topology_put_mstb(mstb);
     return ret;
 }
 
 static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req_type)
 {
     struct drm_dp_sideband_msg_reply_body reply;
 
     reply.reply_type = DP_SIDEBAND_REPLY_ACK;
     reply.req_type = req_type;
     drm_dp_encode_sideband_reply(&reply, msg);
     return 0;
 }
 
 static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
                     struct drm_dp_mst_branch *mstb,
                     int req_type, bool broadcast)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg)
         return -ENOMEM;
 
     txmsg->dst = mstb;
     drm_dp_encode_up_ack_reply(txmsg, req_type);
 
     mutex_lock(&mgr->qlock);
     /* construct a chunk from the first msg in the tx_msg queue */
     process_single_tx_qlock(mgr, txmsg, true);
     mutex_unlock(&mgr->qlock);
 
     kfree(txmsg);
     return 0;
 }
 
 /**
  * drm_dp_get_vc_payload_bw - get the VC payload BW for an MST link
  * @mgr: The &drm_dp_mst_topology_mgr to use
  * @link_rate: link rate in 10kbits/s units
  * @link_lane_count: lane count
  *
  * Calculate the total bandwidth of a MultiStream Transport link. The returned
  * value is in units of PBNs/(timeslots/1 MTP). This value can be used to
  * convert the number of PBNs required for a given stream to the number of
  * timeslots this stream requires in each MTP.
  */
 int drm_dp_get_vc_payload_bw(const struct drm_dp_mst_topology_mgr *mgr,
                  int link_rate, int link_lane_count)
 {
     if (link_rate == 0 || link_lane_count == 0)
         drm_dbg_kms(mgr->dev, "invalid link rate/lane count: (%d / %d)\n",
                 link_rate, link_lane_count);
 
     /* See DP v2.0 2.6.4.2, VCPayload_Bandwidth_for_OneTimeSlotPer_MTP_Allocation */
     return link_rate * link_lane_count / 54000;
 }
 EXPORT_SYMBOL(drm_dp_get_vc_payload_bw);
 
 /**
  * drm_dp_read_mst_cap() - check whether or not a sink supports MST
  * @aux: The DP AUX channel to use
  * @dpcd: A cached copy of the DPCD capabilities for this sink
  *
  * Returns: %True if the sink supports MST, %false otherwise
  */
 bool drm_dp_read_mst_cap(struct drm_dp_aux *aux,
              const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
     u8 mstm_cap;
 
     if (dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
         return false;
 
     if (drm_dp_dpcd_readb(aux, DP_MSTM_CAP, &mstm_cap) != 1)
         return false;
 
     return mstm_cap & DP_MST_CAP;
 }
 EXPORT_SYMBOL(drm_dp_read_mst_cap);
 
 /**
  * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
  * @mgr: manager to set state for
  * @mst_state: true to enable MST on this connector - false to disable.
  *
  * This is called by the driver when it detects an MST capable device plugged
  * into a DP MST capable port, or when a DP MST capable device is unplugged.
  */
 int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)
 {
     int ret = 0;
     struct drm_dp_mst_branch *mstb = NULL;
 
     mutex_lock(&mgr->payload_lock);
     mutex_lock(&mgr->lock);
     if (mst_state == mgr->mst_state)
         goto out_unlock;
 
     mgr->mst_state = mst_state;
     /* set the device into MST mode */
     if (mst_state) {
         struct drm_dp_payload reset_pay;
         int lane_count;
         int link_rate;
 
         WARN_ON(mgr->mst_primary);
 
         /* get dpcd info */
         ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd);
         if (ret < 0) {
             drm_dbg_kms(mgr->dev, "%s: failed to read DPCD, ret %d\n",
                     mgr->aux->name, ret);
             goto out_unlock;
         }
 
         lane_count = min_t(int, mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK, mgr->max_lane_count);
         link_rate = min_t(int, drm_dp_bw_code_to_link_rate(mgr->dpcd[1]), mgr->max_link_rate);
         mgr->pbn_div = drm_dp_get_vc_payload_bw(mgr,
                             link_rate,
                             lane_count);
         if (mgr->pbn_div == 0) {
             ret = -EINVAL;
             goto out_unlock;
         }
 
         /* add initial branch device at LCT 1 */
         mstb = drm_dp_add_mst_branch_device(1, NULL);
         if (mstb == NULL) {
             ret = -ENOMEM;
             goto out_unlock;
         }
         mstb->mgr = mgr;
 
         /* give this the main reference */
         mgr->mst_primary = mstb;
         drm_dp_mst_topology_get_mstb(mgr->mst_primary);
 
         ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                      DP_MST_EN |
                      DP_UP_REQ_EN |
                      DP_UPSTREAM_IS_SRC);
         if (ret < 0)
             goto out_unlock;
 
         reset_pay.start_slot = 0;
         reset_pay.num_slots = 0x3f;
         drm_dp_dpcd_write_payload(mgr, 0, &reset_pay);
 
         queue_work(system_long_wq, &mgr->work);
 
         ret = 0;
     } else {
         /* disable MST on the device */
         mstb = mgr->mst_primary;
         mgr->mst_primary = NULL;
         /* this can fail if the device is gone */
         drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
         ret = 0;
         memset(mgr->payloads, 0,
                mgr->max_payloads * sizeof(mgr->payloads[0]));
         memset(mgr->proposed_vcpis, 0,
                mgr->max_payloads * sizeof(mgr->proposed_vcpis[0]));
         mgr->payload_mask = 0;
         set_bit(0, &mgr->payload_mask);
         mgr->vcpi_mask = 0;
         mgr->payload_id_table_cleared = false;
     }
 
 out_unlock:
     mutex_unlock(&mgr->lock);
     mutex_unlock(&mgr->payload_lock);
     if (mstb)
         drm_dp_mst_topology_put_mstb(mstb);
     return ret;
 
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_set_mst);
 
 static void
 drm_dp_mst_topology_mgr_invalidate_mstb(struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_mst_port *port;
 
     /* The link address will need to be re-sent on resume */
     mstb->link_address_sent = false;
 
     list_for_each_entry(port, &mstb->ports, next)
         if (port->mstb)
             drm_dp_mst_topology_mgr_invalidate_mstb(port->mstb);
 }
 
 /**
  * drm_dp_mst_topology_mgr_suspend() - suspend the MST manager
  * @mgr: manager to suspend
  *
  * This function tells the MST device that we can't handle UP messages
  * anymore. This should stop it from sending any since we are suspended.
  */
 void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr)
 {
     mutex_lock(&mgr->lock);
     drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                DP_MST_EN | DP_UPSTREAM_IS_SRC);
     mutex_unlock(&mgr->lock);
     flush_work(&mgr->up_req_work);
     flush_work(&mgr->work);
     flush_work(&mgr->delayed_destroy_work);
 
     mutex_lock(&mgr->lock);
     if (mgr->mst_state && mgr->mst_primary)
         drm_dp_mst_topology_mgr_invalidate_mstb(mgr->mst_primary);
     mutex_unlock(&mgr->lock);
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_suspend);
 
 /**
  * drm_dp_mst_topology_mgr_resume() - resume the MST manager
  * @mgr: manager to resume
  * @sync: whether or not to perform topology reprobing synchronously
  *
  * This will fetch DPCD and see if the device is still there,
  * if it is, it will rewrite the MSTM control bits, and return.
  *
  * If the device fails this returns -1, and the driver should do
  * a full MST reprobe, in case we were undocked.
  *
  * During system resume (where it is assumed that the driver will be calling
  * drm_atomic_helper_resume()) this function should be called beforehand with
  * @sync set to true. In contexts like runtime resume where the driver is not
  * expected to be calling drm_atomic_helper_resume(), this function should be
  * called with @sync set to false in order to avoid deadlocking.
  *
  * Returns: -1 if the MST topology was removed while we were suspended, 0
  * otherwise.
  */
 int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
                    bool sync)
 {
     int ret;
     u8 guid[16];
 
     mutex_lock(&mgr->lock);
     if (!mgr->mst_primary)
         goto out_fail;
 
     if (drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd) < 0) {
         drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
         goto out_fail;
     }
 
     ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                  DP_MST_EN |
                  DP_UP_REQ_EN |
                  DP_UPSTREAM_IS_SRC);
     if (ret < 0) {
         drm_dbg_kms(mgr->dev, "mst write failed - undocked during suspend?\n");
         goto out_fail;
     }
 
     /* Some hubs forget their guids after they resume */
     ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16);
     if (ret != 16) {
         drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
         goto out_fail;
     }
 
     ret = drm_dp_check_mstb_guid(mgr->mst_primary, guid);
     if (ret) {
         drm_dbg_kms(mgr->dev, "check mstb failed - undocked during suspend?\n");
         goto out_fail;
     }
 
     /*
      * For the final step of resuming the topology, we need to bring the
      * state of our in-memory topology back into sync with reality. So,
      * restart the probing process as if we're probing a new hub
      */
     queue_work(system_long_wq, &mgr->work);
     mutex_unlock(&mgr->lock);
 
     if (sync) {
         drm_dbg_kms(mgr->dev,
                 "Waiting for link probe work to finish re-syncing topology...\n");
         flush_work(&mgr->work);
     }
 
     return 0;
 
 out_fail:
     mutex_unlock(&mgr->lock);
     return -1;
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);
 
 static bool
 drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up,
               struct drm_dp_mst_branch **mstb)
 {
     int len;
     u8 replyblock[32];
     int replylen, curreply;
     int ret;
     u8 hdrlen;
     struct drm_dp_sideband_msg_hdr hdr;
     struct drm_dp_sideband_msg_rx *msg =
         up ? &mgr->up_req_recv : &mgr->down_rep_recv;
     int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE :
                DP_SIDEBAND_MSG_DOWN_REP_BASE;
 
     if (!up)
         *mstb = NULL;
 
     len = min(mgr->max_dpcd_transaction_bytes, 16);
     ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len);
     if (ret != len) {
         drm_dbg_kms(mgr->dev, "failed to read DPCD down rep %d %d\n", len, ret);
         return false;
     }
 
     ret = drm_dp_decode_sideband_msg_hdr(mgr, &hdr, replyblock, len, &hdrlen);
     if (ret == false) {
         print_hex_dump(KERN_DEBUG, "failed hdr", DUMP_PREFIX_NONE, 16,
                    1, replyblock, len, false);
         drm_dbg_kms(mgr->dev, "ERROR: failed header\n");
         return false;
     }
 
     if (!up) {
         /* Caller is responsible for giving back this reference */
         *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad);
         if (!*mstb) {
             drm_dbg_kms(mgr->dev, "Got MST reply from unknown device %d\n", hdr.lct);
             return false;
         }
     }
 
     if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) {
         drm_dbg_kms(mgr->dev, "sideband msg set header failed %d\n", replyblock[0]);
         return false;
     }
 
     replylen = min(msg->curchunk_len, (u8)(len - hdrlen));
     ret = drm_dp_sideband_append_payload(msg, replyblock + hdrlen, replylen);
     if (!ret) {
         drm_dbg_kms(mgr->dev, "sideband msg build failed %d\n", replyblock[0]);
         return false;
     }
 
     replylen = msg->curchunk_len + msg->curchunk_hdrlen - len;
     curreply = len;
     while (replylen > 0) {
         len = min3(replylen, mgr->max_dpcd_transaction_bytes, 16);
         ret = drm_dp_dpcd_read(mgr->aux, basereg + curreply,
                     replyblock, len);
         if (ret != len) {
             drm_dbg_kms(mgr->dev, "failed to read a chunk (len %d, ret %d)\n",
                     len, ret);
             return false;
         }
 
         ret = drm_dp_sideband_append_payload(msg, replyblock, len);
         if (!ret) {
             drm_dbg_kms(mgr->dev, "failed to build sideband msg\n");
             return false;
         }
 
         curreply += len;
         replylen -= len;
     }
     return true;
 }
 
 static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
 {
     struct drm_dp_sideband_msg_tx *txmsg;
     struct drm_dp_mst_branch *mstb = NULL;
     struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv;
 
     if (!drm_dp_get_one_sb_msg(mgr, false, &mstb))
         goto out;
 
     /* Multi-packet message transmission, don't clear the reply */
     if (!msg->have_eomt)
         goto out;
 
     /* find the message */
     mutex_lock(&mgr->qlock);
     txmsg = list_first_entry_or_null(&mgr->tx_msg_downq,
                      struct drm_dp_sideband_msg_tx, next);
     mutex_unlock(&mgr->qlock);
 
     /* Were we actually expecting a response, and from this mstb? */
     if (!txmsg || txmsg->dst != mstb) {
         struct drm_dp_sideband_msg_hdr *hdr;
 
         hdr = &msg->initial_hdr;
         drm_dbg_kms(mgr->dev, "Got MST reply with no msg %p %d %d %02x %02x\n",
                 mstb, hdr->seqno, hdr->lct, hdr->rad[0], msg->msg[0]);
         goto out_clear_reply;
     }
 
     drm_dp_sideband_parse_reply(mgr, msg, &txmsg->reply);
 
     if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
         drm_dbg_kms(mgr->dev,
                 "Got NAK reply: req 0x%02x (%s), reason 0x%02x (%s), nak data 0x%02x\n",
                 txmsg->reply.req_type,
                 drm_dp_mst_req_type_str(txmsg->reply.req_type),
                 txmsg->reply.u.nak.reason,
                 drm_dp_mst_nak_reason_str(txmsg->reply.u.nak.reason),
                 txmsg->reply.u.nak.nak_data);
     }
 
     memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
     drm_dp_mst_topology_put_mstb(mstb);
 
     mutex_lock(&mgr->qlock);
     txmsg->state = DRM_DP_SIDEBAND_TX_RX;
     list_del(&txmsg->next);
     mutex_unlock(&mgr->qlock);
 
     wake_up_all(&mgr->tx_waitq);
 
     return 0;
 
 out_clear_reply:
     memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
 out:
     if (mstb)
         drm_dp_mst_topology_put_mstb(mstb);
 
     return 0;
 }
 
 static inline bool
 drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr,
               struct drm_dp_pending_up_req *up_req)
 {
     struct drm_dp_mst_branch *mstb = NULL;
     struct drm_dp_sideband_msg_req_body *msg = &up_req->msg;
     struct drm_dp_sideband_msg_hdr *hdr = &up_req->hdr;
     bool hotplug = false;
 
     if (hdr->broadcast) {
         const u8 *guid = NULL;
 
         if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY)
             guid = msg->u.conn_stat.guid;
         else if (msg->req_type == DP_RESOURCE_STATUS_NOTIFY)
             guid = msg->u.resource_stat.guid;
 
         if (guid)
             mstb = drm_dp_get_mst_branch_device_by_guid(mgr, guid);
     } else {
         mstb = drm_dp_get_mst_branch_device(mgr, hdr->lct, hdr->rad);
     }
 
     if (!mstb) {
         drm_dbg_kms(mgr->dev, "Got MST reply from unknown device %d\n", hdr->lct);
         return false;
     }
 
     /* TODO: Add missing handler for DP_RESOURCE_STATUS_NOTIFY events */
     if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY) {
         drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat);
         hotplug = true;
     }
 
     drm_dp_mst_topology_put_mstb(mstb);
     return hotplug;
 }
 
 static void drm_dp_mst_up_req_work(struct work_struct *work)
 {
     struct drm_dp_mst_topology_mgr *mgr =
         container_of(work, struct drm_dp_mst_topology_mgr,
                  up_req_work);
     struct drm_dp_pending_up_req *up_req;
     bool send_hotplug = false;
 
     mutex_lock(&mgr->probe_lock);
     while (true) {
         mutex_lock(&mgr->up_req_lock);
         up_req = list_first_entry_or_null(&mgr->up_req_list,
                           struct drm_dp_pending_up_req,
                           next);
         if (up_req)
             list_del(&up_req->next);
         mutex_unlock(&mgr->up_req_lock);
 
         if (!up_req)
             break;
 
         send_hotplug |= drm_dp_mst_process_up_req(mgr, up_req);
         kfree(up_req);
     }
     mutex_unlock(&mgr->probe_lock);
 
     if (send_hotplug)
         drm_kms_helper_hotplug_event(mgr->dev);
 }
 
 static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
 {
     struct drm_dp_pending_up_req *up_req;
 
     if (!drm_dp_get_one_sb_msg(mgr, true, NULL))
         goto out;
 
     if (!mgr->up_req_recv.have_eomt)
         return 0;
 
     up_req = kzalloc(sizeof(*up_req), GFP_KERNEL);
     if (!up_req)
         return -ENOMEM;
 
     INIT_LIST_HEAD(&up_req->next);
 
     drm_dp_sideband_parse_req(mgr, &mgr->up_req_recv, &up_req->msg);
 
     if (up_req->msg.req_type != DP_CONNECTION_STATUS_NOTIFY &&
         up_req->msg.req_type != DP_RESOURCE_STATUS_NOTIFY) {
         drm_dbg_kms(mgr->dev, "Received unknown up req type, ignoring: %x\n",
                 up_req->msg.req_type);
         kfree(up_req);
         goto out;
     }
 
     drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type,
                  false);
 
     if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) {
         const struct drm_dp_connection_status_notify *conn_stat =
             &up_req->msg.u.conn_stat;
 
         drm_dbg_kms(mgr->dev, "Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n",
                 conn_stat->port_number,
                 conn_stat->legacy_device_plug_status,
                 conn_stat->displayport_device_plug_status,
                 conn_stat->message_capability_status,
                 conn_stat->input_port,
                 conn_stat->peer_device_type);
     } else if (up_req->msg.req_type == DP_RESOURCE_STATUS_NOTIFY) {
         const struct drm_dp_resource_status_notify *res_stat =
             &up_req->msg.u.resource_stat;
 
         drm_dbg_kms(mgr->dev, "Got RSN: pn: %d avail_pbn %d\n",
                 res_stat->port_number,
                 res_stat->available_pbn);
     }
 
     up_req->hdr = mgr->up_req_recv.initial_hdr;
     mutex_lock(&mgr->up_req_lock);
     list_add_tail(&up_req->next, &mgr->up_req_list);
     mutex_unlock(&mgr->up_req_lock);
     queue_work(system_long_wq, &mgr->up_req_work);
 
 out:
     memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
     return 0;
 }
 
 /**
  * drm_dp_mst_hpd_irq() - MST hotplug IRQ notify
  * @mgr: manager to notify irq for.
  * @esi: 4 bytes from SINK_COUNT_ESI
  * @handled: whether the hpd interrupt was consumed or not
  *
  * This should be called from the driver when it detects a short IRQ,
  * along with the value of the DEVICE_SERVICE_IRQ_VECTOR_ESI0. The
  * topology manager will process the sideband messages received as a result
  * of this.
  */
 int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled)
 {
     int ret = 0;
     int sc;
     *handled = false;
     sc = DP_GET_SINK_COUNT(esi[0]);
 
     if (sc != mgr->sink_count) {
         mgr->sink_count = sc;
         *handled = true;
     }
 
     if (esi[1] & DP_DOWN_REP_MSG_RDY) {
         ret = drm_dp_mst_handle_down_rep(mgr);
         *handled = true;
     }
 
     if (esi[1] & DP_UP_REQ_MSG_RDY) {
         ret |= drm_dp_mst_handle_up_req(mgr);
         *handled = true;
     }
 
     drm_dp_mst_kick_tx(mgr);
     return ret;
 }
 EXPORT_SYMBOL(drm_dp_mst_hpd_irq);
 
 /**
  * drm_dp_mst_detect_port() - get connection status for an MST port
  * @connector: DRM connector for this port
  * @ctx: The acquisition context to use for grabbing locks
  * @mgr: manager for this port
  * @port: pointer to a port
  *
  * This returns the current connection state for a port.
  */
 int
 drm_dp_mst_detect_port(struct drm_connector *connector,
                struct drm_modeset_acquire_ctx *ctx,
                struct drm_dp_mst_topology_mgr *mgr,
                struct drm_dp_mst_port *port)
 {
     int ret;
 
     /* we need to search for the port in the mgr in case it's gone */
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port)
         return connector_status_disconnected;
 
     ret = drm_modeset_lock(&mgr->base.lock, ctx);
     if (ret)
         goto out;
 
     ret = connector_status_disconnected;
 
     if (!port->ddps)
         goto out;
 
     switch (port->pdt) {
     case DP_PEER_DEVICE_NONE:
         break;
     case DP_PEER_DEVICE_MST_BRANCHING:
         if (!port->mcs)
             ret = connector_status_connected;
         break;
 
     case DP_PEER_DEVICE_SST_SINK:
         ret = connector_status_connected;
         /* for logical ports - cache the EDID */
         if (port->port_num >= DP_MST_LOGICAL_PORT_0 && !port->cached_edid)
             port->cached_edid = drm_get_edid(connector, &port->aux.ddc);
         break;
     case DP_PEER_DEVICE_DP_LEGACY_CONV:
         if (port->ldps)
             ret = connector_status_connected;
         break;
     }
 out:
     drm_dp_mst_topology_put_port(port);
     return ret;
 }
 EXPORT_SYMBOL(drm_dp_mst_detect_port);
 
 /**
  * drm_dp_mst_get_edid() - get EDID for an MST port
  * @connector: toplevel connector to get EDID for
  * @mgr: manager for this port
  * @port: unverified pointer to a port.
  *
  * This returns an EDID for the port connected to a connector,
  * It validates the pointer still exists so the caller doesn't require a
  * reference.
  */
 struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
 {
     struct edid *edid = NULL;
 
     /* we need to search for the port in the mgr in case it's gone */
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port)
         return NULL;
 
     if (port->cached_edid)
         edid = drm_edid_duplicate(port->cached_edid);
     else {
         edid = drm_get_edid(connector, &port->aux.ddc);
     }
     port->has_audio = drm_detect_monitor_audio(edid);
     drm_dp_mst_topology_put_port(port);
     return edid;
 }
 EXPORT_SYMBOL(drm_dp_mst_get_edid);
 
 /**
  * drm_dp_find_vcpi_slots() - Find VCPI slots for this PBN value
  * @mgr: manager to use
  * @pbn: payload bandwidth to convert into slots.
  *
  * Calculate the number of VCPI slots that will be required for the given PBN
  * value. This function is deprecated, and should not be used in atomic
  * drivers.
  *
  * RETURNS:
  * The total slots required for this port, or error.
  */
 int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr,
                int pbn)
 {
     int num_slots;
 
     num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
 
     /* max. time slots - one slot for MTP header */
     if (num_slots > 63)
         return -ENOSPC;
     return num_slots;
 }
 EXPORT_SYMBOL(drm_dp_find_vcpi_slots);
 
 static int drm_dp_init_vcpi(struct drm_dp_mst_topology_mgr *mgr,
                 struct drm_dp_vcpi *vcpi, int pbn, int slots)
 {
     int ret;
 
     vcpi->pbn = pbn;
     vcpi->aligned_pbn = slots * mgr->pbn_div;
     vcpi->num_slots = slots;
 
     ret = drm_dp_mst_assign_payload_id(mgr, vcpi);
     if (ret < 0)
         return ret;
     return 0;
 }
 
 /**
  * drm_dp_atomic_find_vcpi_slots() - Find and add VCPI slots to the state
  * @state: global atomic state
  * @mgr: MST topology manager for the port
  * @port: port to find vcpi slots for
  * @pbn: bandwidth required for the mode in PBN
  * @pbn_div: divider for DSC mode that takes FEC into account
  *
  * Allocates VCPI slots to @port, replacing any previous VCPI allocations it
  * may have had. Any atomic drivers which support MST must call this function
  * in their &drm_encoder_helper_funcs.atomic_check() callback to change the
  * current VCPI allocation for the new state, but only when
  * &drm_crtc_state.mode_changed or &drm_crtc_state.connectors_changed is set
  * to ensure compatibility with userspace applications that still use the
  * legacy modesetting UAPI.
  *
  * Allocations set by this function are not checked against the bandwidth
  * restraints of @mgr until the driver calls drm_dp_mst_atomic_check().
  *
  * Additionally, it is OK to call this function multiple times on the same
  * @port as needed. It is not OK however, to call this function and
  * drm_dp_atomic_release_vcpi_slots() in the same atomic check phase.
  *
  * See also:
  * drm_dp_atomic_release_vcpi_slots()
  * drm_dp_mst_atomic_check()
  *
  * Returns:
  * Total slots in the atomic state assigned for this port, or a negative error
  * code if the port no longer exists
  */
 int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
                   struct drm_dp_mst_topology_mgr *mgr,
                   struct drm_dp_mst_port *port, int pbn,
                   int pbn_div)
 {
     struct drm_dp_mst_topology_state *topology_state;
     struct drm_dp_vcpi_allocation *pos, *vcpi = NULL;
     int prev_slots, prev_bw, req_slots;
 
     topology_state = drm_atomic_get_mst_topology_state(state, mgr);
     if (IS_ERR(topology_state))
         return PTR_ERR(topology_state);
 
     /* Find the current allocation for this port, if any */
     list_for_each_entry(pos, &topology_state->vcpis, next) {
         if (pos->port == port) {
             vcpi = pos;
             prev_slots = vcpi->vcpi;
             prev_bw = vcpi->pbn;
 
             /*
              * This should never happen, unless the driver tries
              * releasing and allocating the same VCPI allocation,
              * which is an error
              */
             if (WARN_ON(!prev_slots)) {
                 drm_err(mgr->dev,
                     "cannot allocate and release VCPI on [MST PORT:%p] in the same state\n",
                     port);
                 return -EINVAL;
             }
 
             break;
         }
     }
     if (!vcpi) {
         prev_slots = 0;
         prev_bw = 0;
     }
 
     if (pbn_div <= 0)
         pbn_div = mgr->pbn_div;
 
     req_slots = DIV_ROUND_UP(pbn, pbn_div);
 
     drm_dbg_atomic(mgr->dev, "[CONNECTOR:%d:%s] [MST PORT:%p] VCPI %d -> %d\n",
                port->connector->base.id, port->connector->name,
                port, prev_slots, req_slots);
     drm_dbg_atomic(mgr->dev, "[CONNECTOR:%d:%s] [MST PORT:%p] PBN %d -> %d\n",
                port->connector->base.id, port->connector->name,
                port, prev_bw, pbn);
 
     /* Add the new allocation to the state */
     if (!vcpi) {
         vcpi = kzalloc(sizeof(*vcpi), GFP_KERNEL);
         if (!vcpi)
             return -ENOMEM;
 
         drm_dp_mst_get_port_malloc(port);
         vcpi->port = port;
         list_add(&vcpi->next, &topology_state->vcpis);
     }
     vcpi->vcpi = req_slots;
     vcpi->pbn = pbn;
 
     return req_slots;
 }
 EXPORT_SYMBOL(drm_dp_atomic_find_vcpi_slots);
 
 /**
  * drm_dp_atomic_release_vcpi_slots() - Release allocated vcpi slots
  * @state: global atomic state
  * @mgr: MST topology manager for the port
  * @port: The port to release the VCPI slots from
  *
  * Releases any VCPI slots that have been allocated to a port in the atomic
  * state. Any atomic drivers which support MST must call this function in
  * their &drm_connector_helper_funcs.atomic_check() callback when the
  * connector will no longer have VCPI allocated (e.g. because its CRTC was
  * removed) when it had VCPI allocated in the previous atomic state.
  *
  * It is OK to call this even if @port has been removed from the system.
  * Additionally, it is OK to call this function multiple times on the same
  * @port as needed. It is not OK however, to call this function and
  * drm_dp_atomic_find_vcpi_slots() on the same @port in a single atomic check
  * phase.
  *
  * See also:
  * drm_dp_atomic_find_vcpi_slots()
  * drm_dp_mst_atomic_check()
  *
  * Returns:
  * 0 if all slots for this port were added back to
  * &drm_dp_mst_topology_state.avail_slots or negative error code
  */
 int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
                      struct drm_dp_mst_topology_mgr *mgr,
                      struct drm_dp_mst_port *port)
 {
     struct drm_dp_mst_topology_state *topology_state;
     struct drm_dp_vcpi_allocation *pos;
     bool found = false;
 
     topology_state = drm_atomic_get_mst_topology_state(state, mgr);
     if (IS_ERR(topology_state))
         return PTR_ERR(topology_state);
 
     list_for_each_entry(pos, &topology_state->vcpis, next) {
         if (pos->port == port) {
             found = true;
             break;
         }
     }
     if (WARN_ON(!found)) {
         drm_err(mgr->dev, "no VCPI for [MST PORT:%p] found in mst state %p\n",
             port, &topology_state->base);
         return -EINVAL;
     }
 
     drm_dbg_atomic(mgr->dev, "[MST PORT:%p] VCPI %d -> 0\n", port, pos->vcpi);
     if (pos->vcpi) {
         drm_dp_mst_put_port_malloc(port);
         pos->vcpi = 0;
         pos->pbn = 0;
     }
 
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_atomic_release_vcpi_slots);
 
 /**
  * drm_dp_mst_update_slots() - updates the slot info depending on the DP ecoding format
  * @mst_state: mst_state to update
  * @link_encoding_cap: the ecoding format on the link
  */
 void drm_dp_mst_update_slots(struct drm_dp_mst_topology_state *mst_state, uint8_t link_encoding_cap)
 {
     if (link_encoding_cap == DP_CAP_ANSI_128B132B) {
         mst_state->total_avail_slots = 64;
         mst_state->start_slot = 0;
     } else {
         mst_state->total_avail_slots = 63;
         mst_state->start_slot = 1;
     }
 
     DRM_DEBUG_KMS("%s encoding format on mst_state 0x%p\n",
               (link_encoding_cap == DP_CAP_ANSI_128B132B) ? "128b/132b":"8b/10b",
               mst_state);
 }
 EXPORT_SYMBOL(drm_dp_mst_update_slots);
 
 /**
  * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
  * @mgr: manager for this port
  * @port: port to allocate a virtual channel for.
  * @pbn: payload bandwidth number to request
  * @slots: returned number of slots for this PBN.
  */
 bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
                   struct drm_dp_mst_port *port, int pbn, int slots)
 {
     int ret;
 
     if (slots < 0)
         return false;
 
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port)
         return false;
 
     if (port->vcpi.vcpi > 0) {
         drm_dbg_kms(mgr->dev,
                 "payload: vcpi %d already allocated for pbn %d - requested pbn %d\n",
                 port->vcpi.vcpi, port->vcpi.pbn, pbn);
         if (pbn == port->vcpi.pbn) {
             drm_dp_mst_topology_put_port(port);
             return true;
         }
     }
 
     ret = drm_dp_init_vcpi(mgr, &port->vcpi, pbn, slots);
     if (ret) {
         drm_dbg_kms(mgr->dev, "failed to init vcpi slots=%d ret=%d\n",
                 DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
         drm_dp_mst_topology_put_port(port);
         goto out;
     }
     drm_dbg_kms(mgr->dev, "initing vcpi for pbn=%d slots=%d\n", pbn, port->vcpi.num_slots);
 
     /* Keep port allocated until its payload has been removed */
     drm_dp_mst_get_port_malloc(port);
     drm_dp_mst_topology_put_port(port);
     return true;
 out:
     return false;
 }
 EXPORT_SYMBOL(drm_dp_mst_allocate_vcpi);
 
 int drm_dp_mst_get_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
 {
     int slots = 0;
 
     port = drm_dp_mst_topology_get_port_validated(mgr, port);
     if (!port)
         return slots;
 
     slots = port->vcpi.num_slots;
     drm_dp_mst_topology_put_port(port);
     return slots;
 }
 EXPORT_SYMBOL(drm_dp_mst_get_vcpi_slots);
 
 /**
  * drm_dp_mst_reset_vcpi_slots() - Reset number of slots to 0 for VCPI
  * @mgr: manager for this port
  * @port: unverified pointer to a port.
  *
  * This just resets the number of slots for the ports VCPI for later programming.
  */
 void drm_dp_mst_reset_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
 {
     /*
      * A port with VCPI will remain allocated until its VCPI is
      * released, no verified ref needed
      */
 
     port->vcpi.num_slots = 0;
 }
 EXPORT_SYMBOL(drm_dp_mst_reset_vcpi_slots);
 
 /**
  * drm_dp_mst_deallocate_vcpi() - deallocate a VCPI
  * @mgr: manager for this port
  * @port: port to deallocate vcpi for
  *
  * This can be called unconditionally, regardless of whether
  * drm_dp_mst_allocate_vcpi() succeeded or not.
  */
 void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
                 struct drm_dp_mst_port *port)
 {
     bool skip;
 
     if (!port->vcpi.vcpi)
         return;
 
     mutex_lock(&mgr->lock);
     skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
     mutex_unlock(&mgr->lock);
 
     if (skip)
         return;
 
     drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
     port->vcpi.num_slots = 0;
     port->vcpi.pbn = 0;
     port->vcpi.aligned_pbn = 0;
     port->vcpi.vcpi = 0;
     drm_dp_mst_put_port_malloc(port);
 }
 EXPORT_SYMBOL(drm_dp_mst_deallocate_vcpi);
 
 static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
                      int id, struct drm_dp_payload *payload)
 {
     u8 payload_alloc[3], status;
     int ret;
     int retries = 0;
 
     drm_dp_dpcd_writeb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS,
                DP_PAYLOAD_TABLE_UPDATED);
 
     payload_alloc[0] = id;
     payload_alloc[1] = payload->start_slot;
     payload_alloc[2] = payload->num_slots;
 
     ret = drm_dp_dpcd_write(mgr->aux, DP_PAYLOAD_ALLOCATE_SET, payload_alloc, 3);
     if (ret != 3) {
         drm_dbg_kms(mgr->dev, "failed to write payload allocation %d\n", ret);
         goto fail;
     }
 
 retry:
     ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
     if (ret < 0) {
         drm_dbg_kms(mgr->dev, "failed to read payload table status %d\n", ret);
         goto fail;
     }
 
     if (!(status & DP_PAYLOAD_TABLE_UPDATED)) {
         retries++;
         if (retries < 20) {
             usleep_range(10000, 20000);
             goto retry;
         }
         drm_dbg_kms(mgr->dev, "status not set after read payload table status %d\n",
                 status);
         ret = -EINVAL;
         goto fail;
     }
     ret = 0;
 fail:
     return ret;
 }
 
 static int do_get_act_status(struct drm_dp_aux *aux)
 {
     int ret;
     u8 status;
 
     ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
     if (ret < 0)
         return ret;
 
     return status;
 }
 
 /**
  * drm_dp_check_act_status() - Polls for ACT handled status.
  * @mgr: manager to use
  *
  * Tries waiting for the MST hub to finish updating it's payload table by
  * polling for the ACT handled bit for up to 3 seconds (yes-some hubs really
  * take that long).
  *
  * Returns:
  * 0 if the ACT was handled in time, negative error code on failure.
  */
 int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
 {
     /*
      * There doesn't seem to be any recommended retry count or timeout in
      * the MST specification. Since some hubs have been observed to take
      * over 1 second to update their payload allocations under certain
      * conditions, we use a rather large timeout value.
      */
     const int timeout_ms = 3000;
     int ret, status;
 
     ret = readx_poll_timeout(do_get_act_status, mgr->aux, status,
                  status & DP_PAYLOAD_ACT_HANDLED || status < 0,
                  200, timeout_ms * USEC_PER_MSEC);
     if (ret < 0 && status >= 0) {
         drm_err(mgr->dev, "Failed to get ACT after %dms, last status: %02x\n",
             timeout_ms, status);
         return -EINVAL;
     } else if (status < 0) {
         /*
          * Failure here isn't unexpected - the hub may have
          * just been unplugged
          */
         drm_dbg_kms(mgr->dev, "Failed to read payload table status: %d\n", status);
         return status;
     }
 
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_check_act_status);
 
 /**
  * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  * @clock: dot clock for the mode
  * @bpp: bpp for the mode.
  * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
  *
  * This uses the formula in the spec to calculate the PBN value for a mode.
  */
 int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
 {
     /*
      * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006
      * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on
      * common multiplier to render an integer PBN for all link rate/lane
      * counts combinations
      * calculate
      * peak_kbps *= (1006/1000)
      * peak_kbps *= (64/54)
      * peak_kbps *= 8    convert to bytes
      *
      * If the bpp is in units of 1/16, further divide by 16. Put this
      * factor in the numerator rather than the denominator to avoid
      * integer overflow
      */
 
     if (dsc)
         return DIV_ROUND_UP_ULL(mul_u32_u32(clock * (bpp / 16), 64 * 1006),
                     8 * 54 * 1000 * 1000);
 
     return DIV_ROUND_UP_ULL(mul_u32_u32(clock * bpp, 64 * 1006),
                 8 * 54 * 1000 * 1000);
 }
 EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
 
 /* we want to kick the TX after we've ack the up/down IRQs. */
 static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr)
 {
     queue_work(system_long_wq, &mgr->tx_work);
 }
 
 /*
  * Helper function for parsing DP device types into convenient strings
  * for use with dp_mst_topology
  */
 static const char *pdt_to_string(u8 pdt)
 {
     switch (pdt) {
     case DP_PEER_DEVICE_NONE:
         return "NONE";
     case DP_PEER_DEVICE_SOURCE_OR_SST:
         return "SOURCE OR SST";
     case DP_PEER_DEVICE_MST_BRANCHING:
         return "MST BRANCHING";
     case DP_PEER_DEVICE_SST_SINK:
         return "SST SINK";
     case DP_PEER_DEVICE_DP_LEGACY_CONV:
         return "DP LEGACY CONV";
     default:
         return "ERR";
     }
 }
 
 static void drm_dp_mst_dump_mstb(struct seq_file *m,
                  struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_mst_port *port;
     int tabs = mstb->lct;
     char prefix[10];
     int i;
 
     for (i = 0; i < tabs; i++)
         prefix[i] = '\t';
     prefix[i] = '\0';
 
     seq_printf(m, "%smstb - [%p]: num_ports: %d\n", prefix, mstb, mstb->num_ports);
     list_for_each_entry(port, &mstb->ports, next) {
         seq_printf(m, "%sport %d - [%p] (%s - %s): ddps: %d, ldps: %d, sdp: %d/%d, fec: %s, conn: %p\n",
                prefix,
                port->port_num,
                port,
                port->input ? "input" : "output",
                pdt_to_string(port->pdt),
                port->ddps,
                port->ldps,
                port->num_sdp_streams,
                port->num_sdp_stream_sinks,
                port->fec_capable ? "true" : "false",
                port->connector);
         if (port->mstb)
             drm_dp_mst_dump_mstb(m, port->mstb);
     }
 }
 
 #define DP_PAYLOAD_TABLE_SIZE       64
 
 static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
                   char *buf)
 {
     int i;
 
     for (i = 0; i < DP_PAYLOAD_TABLE_SIZE; i += 16) {
         if (drm_dp_dpcd_read(mgr->aux,
                      DP_PAYLOAD_TABLE_UPDATE_STATUS + i,
                      &buf[i], 16) != 16)
             return false;
     }
     return true;
 }
 
 static void fetch_monitor_name(struct drm_dp_mst_topology_mgr *mgr,
                    struct drm_dp_mst_port *port, char *name,
                    int namelen)
 {
     struct edid *mst_edid;
 
     mst_edid = drm_dp_mst_get_edid(port->connector, mgr, port);
     drm_edid_get_monitor_name(mst_edid, name, namelen);
     kfree(mst_edid);
 }
 
 /**
  * drm_dp_mst_dump_topology(): dump topology to seq file.
  * @m: seq_file to dump output to
  * @mgr: manager to dump current topology for.
  *
  * helper to dump MST topology to a seq file for debugfs.
  */
 void drm_dp_mst_dump_topology(struct seq_file *m,
                   struct drm_dp_mst_topology_mgr *mgr)
 {
     int i;
     struct drm_dp_mst_port *port;
 
     mutex_lock(&mgr->lock);
     if (mgr->mst_primary)
         drm_dp_mst_dump_mstb(m, mgr->mst_primary);
 
     /* dump VCPIs */
     mutex_unlock(&mgr->lock);
 
     mutex_lock(&mgr->payload_lock);
     seq_printf(m, "\n*** VCPI Info ***\n");
     seq_printf(m, "payload_mask: %lx, vcpi_mask: %lx, max_payloads: %d\n", mgr->payload_mask, mgr->vcpi_mask, mgr->max_payloads);
 
     seq_printf(m, "\n|   idx   |  port # |  vcp_id | # slots |     sink name     |\n");
     for (i = 0; i < mgr->max_payloads; i++) {
         if (mgr->proposed_vcpis[i]) {
             char name[14];
 
             port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
             fetch_monitor_name(mgr, port, name, sizeof(name));
             seq_printf(m, "%10d%10d%10d%10d%20s\n",
                    i,
                    port->port_num,
                    port->vcpi.vcpi,
                    port->vcpi.num_slots,
                    (*name != 0) ? name : "Unknown");
         } else
             seq_printf(m, "%6d - Unused\n", i);
     }
     seq_printf(m, "\n*** Payload Info ***\n");
     seq_printf(m, "|   idx   |  state  |  start slot  | # slots |\n");
     for (i = 0; i < mgr->max_payloads; i++) {
         seq_printf(m, "%10d%10d%15d%10d\n",
                i,
                mgr->payloads[i].payload_state,
                mgr->payloads[i].start_slot,
                mgr->payloads[i].num_slots);
     }
     mutex_unlock(&mgr->payload_lock);
 
     seq_printf(m, "\n*** DPCD Info ***\n");
     mutex_lock(&mgr->lock);
     if (mgr->mst_primary) {
         u8 buf[DP_PAYLOAD_TABLE_SIZE];
         int ret;
 
         if (drm_dp_read_dpcd_caps(mgr->aux, buf) < 0) {
             seq_printf(m, "dpcd read failed\n");
             goto out;
         }
         seq_printf(m, "dpcd: %*ph\n", DP_RECEIVER_CAP_SIZE, buf);
 
         ret = drm_dp_dpcd_read(mgr->aux, DP_FAUX_CAP, buf, 2);
         if (ret) {
             seq_printf(m, "faux/mst read failed\n");
             goto out;
         }
         seq_printf(m, "faux/mst: %*ph\n", 2, buf);
 
         ret = drm_dp_dpcd_read(mgr->aux, DP_MSTM_CTRL, buf, 1);
         if (ret) {
             seq_printf(m, "mst ctrl read failed\n");
             goto out;
         }
         seq_printf(m, "mst ctrl: %*ph\n", 1, buf);
 
         /* dump the standard OUI branch header */
         ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_BRANCH_OUI_HEADER_SIZE);
         if (ret) {
             seq_printf(m, "branch oui read failed\n");
             goto out;
         }
         seq_printf(m, "branch oui: %*phN devid: ", 3, buf);
 
         for (i = 0x3; i < 0x8 && buf[i]; i++)
             seq_printf(m, "%c", buf[i]);
         seq_printf(m, " revision: hw: %x.%x sw: %x.%x\n",
                buf[0x9] >> 4, buf[0x9] & 0xf, buf[0xa], buf[0xb]);
         if (dump_dp_payload_table(mgr, buf))
             seq_printf(m, "payload table: %*ph\n", DP_PAYLOAD_TABLE_SIZE, buf);
     }
 
 out:
     mutex_unlock(&mgr->lock);
 
 }
 EXPORT_SYMBOL(drm_dp_mst_dump_topology);
 
 static void drm_dp_tx_work(struct work_struct *work)
 {
     struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work);
 
     mutex_lock(&mgr->qlock);
     if (!list_empty(&mgr->tx_msg_downq))
         process_single_down_tx_qlock(mgr);
     mutex_unlock(&mgr->qlock);
 }
 
 static inline void
 drm_dp_delayed_destroy_port(struct drm_dp_mst_port *port)
 {
     drm_dp_port_set_pdt(port, DP_PEER_DEVICE_NONE, port->mcs);
 
     if (port->connector) {
         drm_connector_unregister(port->connector);
         drm_connector_put(port->connector);
     }
 
     drm_dp_mst_put_port_malloc(port);
 }
 
 static inline void
 drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb)
 {
     struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
     struct drm_dp_mst_port *port, *port_tmp;
     struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp;
     bool wake_tx = false;
 
     mutex_lock(&mgr->lock);
     list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) {
         list_del(&port->next);
         drm_dp_mst_topology_put_port(port);
     }
     mutex_unlock(&mgr->lock);
 
     /* drop any tx slot msg */
     mutex_lock(&mstb->mgr->qlock);
     list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) {
         if (txmsg->dst != mstb)
             continue;
 
         txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
         list_del(&txmsg->next);
         wake_tx = true;
     }
     mutex_unlock(&mstb->mgr->qlock);
 
     if (wake_tx)
         wake_up_all(&mstb->mgr->tx_waitq);
 
     drm_dp_mst_put_mstb_malloc(mstb);
 }
 
 static void drm_dp_delayed_destroy_work(struct work_struct *work)
 {
     struct drm_dp_mst_topology_mgr *mgr =
         container_of(work, struct drm_dp_mst_topology_mgr,
                  delayed_destroy_work);
     bool send_hotplug = false, go_again;
 
     /*
      * Not a regular list traverse as we have to drop the destroy
      * connector lock before destroying the mstb/port, to avoid AB->BA
      * ordering between this lock and the config mutex.
      */
     do {
         go_again = false;
 
         for (;;) {
             struct drm_dp_mst_branch *mstb;
 
             mutex_lock(&mgr->delayed_destroy_lock);
             mstb = list_first_entry_or_null(&mgr->destroy_branch_device_list,
                             struct drm_dp_mst_branch,
                             destroy_next);
             if (mstb)
                 list_del(&mstb->destroy_next);
             mutex_unlock(&mgr->delayed_destroy_lock);
 
             if (!mstb)
                 break;
 
             drm_dp_delayed_destroy_mstb(mstb);
             go_again = true;
         }
 
         for (;;) {
             struct drm_dp_mst_port *port;
 
             mutex_lock(&mgr->delayed_destroy_lock);
             port = list_first_entry_or_null(&mgr->destroy_port_list,
                             struct drm_dp_mst_port,
                             next);
             if (port)
                 list_del(&port->next);
             mutex_unlock(&mgr->delayed_destroy_lock);
 
             if (!port)
                 break;
 
             drm_dp_delayed_destroy_port(port);
             send_hotplug = true;
             go_again = true;
         }
     } while (go_again);
 
     if (send_hotplug)
         drm_kms_helper_hotplug_event(mgr->dev);
 }
 
 static struct drm_private_state *
 drm_dp_mst_duplicate_state(struct drm_private_obj *obj)
 {
     struct drm_dp_mst_topology_state *state, *old_state =
         to_dp_mst_topology_state(obj->state);
     struct drm_dp_vcpi_allocation *pos, *vcpi;
 
     state = kmemdup(old_state, sizeof(*state), GFP_KERNEL);
     if (!state)
         return NULL;
 
     __drm_atomic_helper_private_obj_duplicate_state(obj, &state->base);
 
     INIT_LIST_HEAD(&state->vcpis);
 
     list_for_each_entry(pos, &old_state->vcpis, next) {
         /* Prune leftover freed VCPI allocations */
         if (!pos->vcpi)
             continue;
 
         vcpi = kmemdup(pos, sizeof(*vcpi), GFP_KERNEL);
         if (!vcpi)
             goto fail;
 
         drm_dp_mst_get_port_malloc(vcpi->port);
         list_add(&vcpi->next, &state->vcpis);
     }
 
     return &state->base;
 
 fail:
     list_for_each_entry_safe(pos, vcpi, &state->vcpis, next) {
         drm_dp_mst_put_port_malloc(pos->port);
         kfree(pos);
     }
     kfree(state);
 
     return NULL;
 }
 
 static void drm_dp_mst_destroy_state(struct drm_private_obj *obj,
                      struct drm_private_state *state)
 {
     struct drm_dp_mst_topology_state *mst_state =
         to_dp_mst_topology_state(state);
     struct drm_dp_vcpi_allocation *pos, *tmp;
 
     list_for_each_entry_safe(pos, tmp, &mst_state->vcpis, next) {
         /* We only keep references to ports with non-zero VCPIs */
         if (pos->vcpi)
             drm_dp_mst_put_port_malloc(pos->port);
         kfree(pos);
     }
 
     kfree(mst_state);
 }
 
 static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
                          struct drm_dp_mst_branch *branch)
 {
     while (port->parent) {
         if (port->parent == branch)
             return true;
 
         if (port->parent->port_parent)
             port = port->parent->port_parent;
         else
             break;
     }
     return false;
 }
 
 static int
 drm_dp_mst_atomic_check_port_bw_limit(struct drm_dp_mst_port *port,
                       struct drm_dp_mst_topology_state *state);
 
 static int
 drm_dp_mst_atomic_check_mstb_bw_limit(struct drm_dp_mst_branch *mstb,
                       struct drm_dp_mst_topology_state *state)
 {
     struct drm_dp_vcpi_allocation *vcpi;
     struct drm_dp_mst_port *port;
     int pbn_used = 0, ret;
     bool found = false;
 
     /* Check that we have at least one port in our state that's downstream
      * of this branch, otherwise we can skip this branch
      */
     list_for_each_entry(vcpi, &state->vcpis, next) {
         if (!vcpi->pbn ||
             !drm_dp_mst_port_downstream_of_branch(vcpi->port, mstb))
             continue;
 
         found = true;
         break;
     }
     if (!found)
         return 0;
 
     if (mstb->port_parent)
         drm_dbg_atomic(mstb->mgr->dev,
                    "[MSTB:%p] [MST PORT:%p] Checking bandwidth limits on [MSTB:%p]\n",
                    mstb->port_parent->parent, mstb->port_parent, mstb);
     else
         drm_dbg_atomic(mstb->mgr->dev, "[MSTB:%p] Checking bandwidth limits\n", mstb);
 
     list_for_each_entry(port, &mstb->ports, next) {
         ret = drm_dp_mst_atomic_check_port_bw_limit(port, state);
         if (ret < 0)
             return ret;
 
         pbn_used += ret;
     }
 
     return pbn_used;
 }
 
 static int
 drm_dp_mst_atomic_check_port_bw_limit(struct drm_dp_mst_port *port,
                       struct drm_dp_mst_topology_state *state)
 {
     struct drm_dp_vcpi_allocation *vcpi;
     int pbn_used = 0;
 
     if (port->pdt == DP_PEER_DEVICE_NONE)
         return 0;
 
     if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
         bool found = false;
 
         list_for_each_entry(vcpi, &state->vcpis, next) {
             if (vcpi->port != port)
                 continue;
             if (!vcpi->pbn)
                 return 0;
 
             found = true;
             break;
         }
         if (!found)
             return 0;
 
         /*
          * This could happen if the sink deasserted its HPD line, but
          * the branch device still reports it as attached (PDT != NONE).
          */
         if (!port->full_pbn) {
             drm_dbg_atomic(port->mgr->dev,
                        "[MSTB:%p] [MST PORT:%p] no BW available for the port\n",
                        port->parent, port);
             return -EINVAL;
         }
 
         pbn_used = vcpi->pbn;
     } else {
         pbn_used = drm_dp_mst_atomic_check_mstb_bw_limit(port->mstb,
                                  state);
         if (pbn_used <= 0)
             return pbn_used;
     }
 
     if (pbn_used > port->full_pbn) {
         drm_dbg_atomic(port->mgr->dev,
                    "[MSTB:%p] [MST PORT:%p] required PBN of %d exceeds port limit of %d\n",
                    port->parent, port, pbn_used, port->full_pbn);
         return -ENOSPC;
     }
 
     drm_dbg_atomic(port->mgr->dev, "[MSTB:%p] [MST PORT:%p] uses %d out of %d PBN\n",
                port->parent, port, pbn_used, port->full_pbn);
 
     return pbn_used;
 }
 
 static inline int
 drm_dp_mst_atomic_check_vcpi_alloc_limit(struct drm_dp_mst_topology_mgr *mgr,
                      struct drm_dp_mst_topology_state *mst_state)
 {
     struct drm_dp_vcpi_allocation *vcpi;
     int avail_slots = mst_state->total_avail_slots, payload_count = 0;
 
     list_for_each_entry(vcpi, &mst_state->vcpis, next) {
         /* Releasing VCPI is always OK-even if the port is gone */
         if (!vcpi->vcpi) {
             drm_dbg_atomic(mgr->dev, "[MST PORT:%p] releases all VCPI slots\n",
                        vcpi->port);
             continue;
         }
 
         drm_dbg_atomic(mgr->dev, "[MST PORT:%p] requires %d vcpi slots\n",
                    vcpi->port, vcpi->vcpi);
 
         avail_slots -= vcpi->vcpi;
         if (avail_slots < 0) {
             drm_dbg_atomic(mgr->dev,
                        "[MST PORT:%p] not enough VCPI slots in mst state %p (avail=%d)\n",
                        vcpi->port, mst_state, avail_slots + vcpi->vcpi);
             return -ENOSPC;
         }
 
         if (++payload_count > mgr->max_payloads) {
             drm_dbg_atomic(mgr->dev,
                        "[MST MGR:%p] state %p has too many payloads (max=%d)\n",
                        mgr, mst_state, mgr->max_payloads);
             return -EINVAL;
         }
     }
     drm_dbg_atomic(mgr->dev, "[MST MGR:%p] mst state %p VCPI avail=%d used=%d\n",
                mgr, mst_state, avail_slots, mst_state->total_avail_slots - avail_slots);
 
     return 0;
 }
 
 /**
  * drm_dp_mst_add_affected_dsc_crtcs
  * @state: Pointer to the new struct drm_dp_mst_topology_state
  * @mgr: MST topology manager
  *
  * Whenever there is a change in mst topology
  * DSC configuration would have to be recalculated
  * therefore we need to trigger modeset on all affected
  * CRTCs in that topology
  *
  * See also:
  * drm_dp_mst_atomic_enable_dsc()
  */
 int drm_dp_mst_add_affected_dsc_crtcs(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr)
 {
     struct drm_dp_mst_topology_state *mst_state;
     struct drm_dp_vcpi_allocation *pos;
     struct drm_connector *connector;
     struct drm_connector_state *conn_state;
     struct drm_crtc *crtc;
     struct drm_crtc_state *crtc_state;
 
     mst_state = drm_atomic_get_mst_topology_state(state, mgr);
 
     if (IS_ERR(mst_state))
         return -EINVAL;
 
     list_for_each_entry(pos, &mst_state->vcpis, next) {
 
         connector = pos->port->connector;
 
         if (!connector)
             return -EINVAL;
 
         conn_state = drm_atomic_get_connector_state(state, connector);
 
         if (IS_ERR(conn_state))
             return PTR_ERR(conn_state);
 
         crtc = conn_state->crtc;
 
         if (!crtc)
             continue;
 
         if (!drm_dp_mst_dsc_aux_for_port(pos->port))
             continue;
 
         crtc_state = drm_atomic_get_crtc_state(mst_state->base.state, crtc);
 
         if (IS_ERR(crtc_state))
             return PTR_ERR(crtc_state);
 
         drm_dbg_atomic(mgr->dev, "[MST MGR:%p] Setting mode_changed flag on CRTC %p\n",
                    mgr, crtc);
 
         crtc_state->mode_changed = true;
     }
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_mst_add_affected_dsc_crtcs);
 
 /**
  * drm_dp_mst_atomic_enable_dsc - Set DSC Enable Flag to On/Off
  * @state: Pointer to the new drm_atomic_state
  * @port: Pointer to the affected MST Port
  * @pbn: Newly recalculated bw required for link with DSC enabled
  * @pbn_div: Divider to calculate correct number of pbn per slot
  * @enable: Boolean flag to enable or disable DSC on the port
  *
  * This function enables DSC on the given Port
  * by recalculating its vcpi from pbn provided
  * and sets dsc_enable flag to keep track of which
  * ports have DSC enabled
  *
  */
 int drm_dp_mst_atomic_enable_dsc(struct drm_atomic_state *state,
                  struct drm_dp_mst_port *port,
                  int pbn, int pbn_div,
                  bool enable)
 {
     struct drm_dp_mst_topology_state *mst_state;
     struct drm_dp_vcpi_allocation *pos;
     bool found = false;
     int vcpi = 0;
 
     mst_state = drm_atomic_get_mst_topology_state(state, port->mgr);
 
     if (IS_ERR(mst_state))
         return PTR_ERR(mst_state);
 
     list_for_each_entry(pos, &mst_state->vcpis, next) {
         if (pos->port == port) {
             found = true;
             break;
         }
     }
 
     if (!found) {
         drm_dbg_atomic(state->dev,
                    "[MST PORT:%p] Couldn't find VCPI allocation in mst state %p\n",
                    port, mst_state);
         return -EINVAL;
     }
 
     if (pos->dsc_enabled == enable) {
         drm_dbg_atomic(state->dev,
                    "[MST PORT:%p] DSC flag is already set to %d, returning %d VCPI slots\n",
                    port, enable, pos->vcpi);
         vcpi = pos->vcpi;
     }
 
     if (enable) {
         vcpi = drm_dp_atomic_find_vcpi_slots(state, port->mgr, port, pbn, pbn_div);
         drm_dbg_atomic(state->dev,
                    "[MST PORT:%p] Enabling DSC flag, reallocating %d VCPI slots on the port\n",
                    port, vcpi);
         if (vcpi < 0)
             return -EINVAL;
     }
 
     pos->dsc_enabled = enable;
 
     return vcpi;
 }
 EXPORT_SYMBOL(drm_dp_mst_atomic_enable_dsc);
 /**
  * drm_dp_mst_atomic_check - Check that the new state of an MST topology in an
  * atomic update is valid
  * @state: Pointer to the new &struct drm_dp_mst_topology_state
  *
  * Checks the given topology state for an atomic update to ensure that it's
  * valid. This includes checking whether there's enough bandwidth to support
  * the new VCPI allocations in the atomic update.
  *
  * Any atomic drivers supporting DP MST must make sure to call this after
  * checking the rest of their state in their
  * &drm_mode_config_funcs.atomic_check() callback.
  *
  * See also:
  * drm_dp_atomic_find_vcpi_slots()
  * drm_dp_atomic_release_vcpi_slots()
  *
  * Returns:
  *
  * 0 if the new state is valid, negative error code otherwise.
  */
 int drm_dp_mst_atomic_check(struct drm_atomic_state *state)
 {
     struct drm_dp_mst_topology_mgr *mgr;
     struct drm_dp_mst_topology_state *mst_state;
     int i, ret = 0;
 
     for_each_new_mst_mgr_in_state(state, mgr, mst_state, i) {
         if (!mgr->mst_state)
             continue;
 
         ret = drm_dp_mst_atomic_check_vcpi_alloc_limit(mgr, mst_state);
         if (ret)
             break;
 
         mutex_lock(&mgr->lock);
         ret = drm_dp_mst_atomic_check_mstb_bw_limit(mgr->mst_primary,
                                 mst_state);
         mutex_unlock(&mgr->lock);
         if (ret < 0)
             break;
         else
             ret = 0;
     }
 
     return ret;
 }
 EXPORT_SYMBOL(drm_dp_mst_atomic_check);
 
 const struct drm_private_state_funcs drm_dp_mst_topology_state_funcs = {
     .atomic_duplicate_state = drm_dp_mst_duplicate_state,
     .atomic_destroy_state = drm_dp_mst_destroy_state,
 };
 EXPORT_SYMBOL(drm_dp_mst_topology_state_funcs);
 
 /**
  * drm_atomic_get_mst_topology_state: get MST topology state
  *
  * @state: global atomic state
  * @mgr: MST topology manager, also the private object in this case
  *
  * This function wraps drm_atomic_get_priv_obj_state() passing in the MST atomic
  * state vtable so that the private object state returned is that of a MST
  * topology object.
  *
  * RETURNS:
  *
  * The MST topology state or error pointer.
  */
 struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
                                     struct drm_dp_mst_topology_mgr *mgr)
 {
     return to_dp_mst_topology_state(drm_atomic_get_private_obj_state(state, &mgr->base));
 }
 EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
 
 /**
  * drm_dp_mst_topology_mgr_init - initialise a topology manager
  * @mgr: manager struct to initialise
  * @dev: device providing this structure - for i2c addition.
  * @aux: DP helper aux channel to talk to this device
  * @max_dpcd_transaction_bytes: hw specific DPCD transaction limit
  * @max_payloads: maximum number of payloads this GPU can source
  * @max_lane_count: maximum number of lanes this GPU supports
  * @max_link_rate: maximum link rate per lane this GPU supports in kHz
  * @conn_base_id: the connector object ID the MST device is connected to.
  *
  * Return 0 for success, or negative error code on failure
  */
 int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
                  struct drm_device *dev, struct drm_dp_aux *aux,
                  int max_dpcd_transaction_bytes, int max_payloads,
                  int max_lane_count, int max_link_rate,
                  int conn_base_id)
 {
     struct drm_dp_mst_topology_state *mst_state;
 
     mutex_init(&mgr->lock);
     mutex_init(&mgr->qlock);
     mutex_init(&mgr->payload_lock);
     mutex_init(&mgr->delayed_destroy_lock);
     mutex_init(&mgr->up_req_lock);
     mutex_init(&mgr->probe_lock);
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
     mutex_init(&mgr->topology_ref_history_lock);
     stack_depot_init();
 #endif
     INIT_LIST_HEAD(&mgr->tx_msg_downq);
     INIT_LIST_HEAD(&mgr->destroy_port_list);
     INIT_LIST_HEAD(&mgr->destroy_branch_device_list);
     INIT_LIST_HEAD(&mgr->up_req_list);
 
     /*
      * delayed_destroy_work will be queued on a dedicated WQ, so that any
      * requeuing will be also flushed when deiniting the topology manager.
      */
     mgr->delayed_destroy_wq = alloc_ordered_workqueue("drm_dp_mst_wq", 0);
     if (mgr->delayed_destroy_wq == NULL)
         return -ENOMEM;
 
     INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work);
     INIT_WORK(&mgr->tx_work, drm_dp_tx_work);
     INIT_WORK(&mgr->delayed_destroy_work, drm_dp_delayed_destroy_work);
     INIT_WORK(&mgr->up_req_work, drm_dp_mst_up_req_work);
     init_waitqueue_head(&mgr->tx_waitq);
     mgr->dev = dev;
     mgr->aux = aux;
     mgr->max_dpcd_transaction_bytes = max_dpcd_transaction_bytes;
     mgr->max_payloads = max_payloads;
     mgr->max_lane_count = max_lane_count;
     mgr->max_link_rate = max_link_rate;
     mgr->conn_base_id = conn_base_id;
     if (max_payloads + 1 > sizeof(mgr->payload_mask) * 8 ||
         max_payloads + 1 > sizeof(mgr->vcpi_mask) * 8)
         return -EINVAL;
     mgr->payloads = kcalloc(max_payloads, sizeof(struct drm_dp_payload), GFP_KERNEL);
     if (!mgr->payloads)
         return -ENOMEM;
     mgr->proposed_vcpis = kcalloc(max_payloads, sizeof(struct drm_dp_vcpi *), GFP_KERNEL);
     if (!mgr->proposed_vcpis)
         return -ENOMEM;
     set_bit(0, &mgr->payload_mask);
 
     mst_state = kzalloc(sizeof(*mst_state), GFP_KERNEL);
     if (mst_state == NULL)
         return -ENOMEM;
 
     mst_state->total_avail_slots = 63;
     mst_state->start_slot = 1;
 
     mst_state->mgr = mgr;
     INIT_LIST_HEAD(&mst_state->vcpis);
 
     drm_atomic_private_obj_init(dev, &mgr->base,
                     &mst_state->base,
                     &drm_dp_mst_topology_state_funcs);
 
     return 0;
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init);
 
 /**
  * drm_dp_mst_topology_mgr_destroy() - destroy topology manager.
  * @mgr: manager to destroy
  */
 void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
 {
     drm_dp_mst_topology_mgr_set_mst(mgr, false);
     flush_work(&mgr->work);
     /* The following will also drain any requeued work on the WQ. */
     if (mgr->delayed_destroy_wq) {
         destroy_workqueue(mgr->delayed_destroy_wq);
         mgr->delayed_destroy_wq = NULL;
     }
     mutex_lock(&mgr->payload_lock);
     kfree(mgr->payloads);
     mgr->payloads = NULL;
     kfree(mgr->proposed_vcpis);
     mgr->proposed_vcpis = NULL;
     mutex_unlock(&mgr->payload_lock);
     mgr->dev = NULL;
     mgr->aux = NULL;
     drm_atomic_private_obj_fini(&mgr->base);
     mgr->funcs = NULL;
 
     mutex_destroy(&mgr->delayed_destroy_lock);
     mutex_destroy(&mgr->payload_lock);
     mutex_destroy(&mgr->qlock);
     mutex_destroy(&mgr->lock);
     mutex_destroy(&mgr->up_req_lock);
     mutex_destroy(&mgr->probe_lock);
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
     mutex_destroy(&mgr->topology_ref_history_lock);
 #endif
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);
 
 static bool remote_i2c_read_ok(const struct i2c_msg msgs[], int num)
 {
     int i;
 
     if (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)
         return false;
 
     for (i = 0; i < num - 1; i++) {
         if (msgs[i].flags & I2C_M_RD ||
             msgs[i].len > 0xff)
             return false;
     }
 
     return msgs[num - 1].flags & I2C_M_RD &&
         msgs[num - 1].len <= 0xff;
 }
 
 static bool remote_i2c_write_ok(const struct i2c_msg msgs[], int num)
 {
     int i;
 
     for (i = 0; i < num - 1; i++) {
         if (msgs[i].flags & I2C_M_RD || !(msgs[i].flags & I2C_M_STOP) ||
             msgs[i].len > 0xff)
             return false;
     }
 
     return !(msgs[num - 1].flags & I2C_M_RD) && msgs[num - 1].len <= 0xff;
 }
 
 static int drm_dp_mst_i2c_read(struct drm_dp_mst_branch *mstb,
                    struct drm_dp_mst_port *port,
                    struct i2c_msg *msgs, int num)
 {
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
     unsigned int i;
     struct drm_dp_sideband_msg_req_body msg;
     struct drm_dp_sideband_msg_tx *txmsg = NULL;
     int ret;
 
     memset(&msg, 0, sizeof(msg));
     msg.req_type = DP_REMOTE_I2C_READ;
     msg.u.i2c_read.num_transactions = num - 1;
     msg.u.i2c_read.port_number = port->port_num;
     for (i = 0; i < num - 1; i++) {
         msg.u.i2c_read.transactions[i].i2c_dev_id = msgs[i].addr;
         msg.u.i2c_read.transactions[i].num_bytes = msgs[i].len;
         msg.u.i2c_read.transactions[i].bytes = msgs[i].buf;
         msg.u.i2c_read.transactions[i].no_stop_bit = !(msgs[i].flags & I2C_M_STOP);
     }
     msg.u.i2c_read.read_i2c_device_id = msgs[num - 1].addr;
     msg.u.i2c_read.num_bytes_read = msgs[num - 1].len;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         ret = -ENOMEM;
         goto out;
     }
 
     txmsg->dst = mstb;
     drm_dp_encode_sideband_req(&msg, txmsg);
 
     drm_dp_queue_down_tx(mgr, txmsg);
 
     ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
     if (ret > 0) {
 
         if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
             ret = -EREMOTEIO;
             goto out;
         }
         if (txmsg->reply.u.remote_i2c_read_ack.num_bytes != msgs[num - 1].len) {
             ret = -EIO;
             goto out;
         }
         memcpy(msgs[num - 1].buf, txmsg->reply.u.remote_i2c_read_ack.bytes, msgs[num - 1].len);
         ret = num;
     }
 out:
     kfree(txmsg);
     return ret;
 }
 
 static int drm_dp_mst_i2c_write(struct drm_dp_mst_branch *mstb,
                 struct drm_dp_mst_port *port,
                 struct i2c_msg *msgs, int num)
 {
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
     unsigned int i;
     struct drm_dp_sideband_msg_req_body msg;
     struct drm_dp_sideband_msg_tx *txmsg = NULL;
     int ret;
 
     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
     if (!txmsg) {
         ret = -ENOMEM;
         goto out;
     }
     for (i = 0; i < num; i++) {
         memset(&msg, 0, sizeof(msg));
         msg.req_type = DP_REMOTE_I2C_WRITE;
         msg.u.i2c_write.port_number = port->port_num;
         msg.u.i2c_write.write_i2c_device_id = msgs[i].addr;
         msg.u.i2c_write.num_bytes = msgs[i].len;
         msg.u.i2c_write.bytes = msgs[i].buf;
 
         memset(txmsg, 0, sizeof(*txmsg));
         txmsg->dst = mstb;
 
         drm_dp_encode_sideband_req(&msg, txmsg);
         drm_dp_queue_down_tx(mgr, txmsg);
 
         ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
         if (ret > 0) {
             if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
                 ret = -EREMOTEIO;
                 goto out;
             }
         } else {
             goto out;
         }
     }
     ret = num;
 out:
     kfree(txmsg);
     return ret;
 }
 
 /* I2C device */
 static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter,
                    struct i2c_msg *msgs, int num)
 {
     struct drm_dp_aux *aux = adapter->algo_data;
     struct drm_dp_mst_port *port =
         container_of(aux, struct drm_dp_mst_port, aux);
     struct drm_dp_mst_branch *mstb;
     struct drm_dp_mst_topology_mgr *mgr = port->mgr;
     int ret;
 
     mstb = drm_dp_mst_topology_get_mstb_validated(mgr, port->parent);
     if (!mstb)
         return -EREMOTEIO;
 
     if (remote_i2c_read_ok(msgs, num)) {
         ret = drm_dp_mst_i2c_read(mstb, port, msgs, num);
     } else if (remote_i2c_write_ok(msgs, num)) {
         ret = drm_dp_mst_i2c_write(mstb, port, msgs, num);
     } else {
         drm_dbg_kms(mgr->dev, "Unsupported I2C transaction for MST device\n");
         ret = -EIO;
     }
 
     drm_dp_mst_topology_put_mstb(mstb);
     return ret;
 }
 
 static u32 drm_dp_mst_i2c_functionality(struct i2c_adapter *adapter)
 {
     return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
            I2C_FUNC_SMBUS_READ_BLOCK_DATA |
            I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
            I2C_FUNC_10BIT_ADDR;
 }
 
 static const struct i2c_algorithm drm_dp_mst_i2c_algo = {
     .functionality = drm_dp_mst_i2c_functionality,
     .master_xfer = drm_dp_mst_i2c_xfer,
 };
 
 /**
  * drm_dp_mst_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
  * @port: The port to add the I2C bus on
  *
  * Returns 0 on success or a negative error code on failure.
  */
 static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port)
 {
     struct drm_dp_aux *aux = &port->aux;
     struct device *parent_dev = port->mgr->dev->dev;
 
     aux->ddc.algo = &drm_dp_mst_i2c_algo;
     aux->ddc.algo_data = aux;
     aux->ddc.retries = 3;
 
     aux->ddc.class = I2C_CLASS_DDC;
     aux->ddc.owner = THIS_MODULE;
     /* FIXME: set the kdev of the port's connector as parent */
     aux->ddc.dev.parent = parent_dev;
     aux->ddc.dev.of_node = parent_dev->of_node;
 
     strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(parent_dev),
         sizeof(aux->ddc.name));
 
     return i2c_add_adapter(&aux->ddc);
 }
 
 /**
  * drm_dp_mst_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
  * @port: The port to remove the I2C bus from
  */
 static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port)
 {
     i2c_del_adapter(&port->aux.ddc);
 }
 
 /**
  * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer Device
  * @port: The port to check
  *
  * A single physical MST hub object can be represented in the topology
  * by multiple branches, with virtual ports between those branches.
  *
  * As of DP1.4, An MST hub with internal (virtual) ports must expose
  * certain DPCD registers over those ports. See sections 2.6.1.1.1
  * and 2.6.1.1.2 of Display Port specification v1.4 for details.
  *
  * May acquire mgr->lock
  *
  * Returns:
  * true if the port is a virtual DP peer device, false otherwise
  */
 static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
 {
     struct drm_dp_mst_port *downstream_port;
 
     if (!port || port->dpcd_rev < DP_DPCD_REV_14)
         return false;
 
     /* Virtual DP Sink (Internal Display Panel) */
     if (port->port_num >= 8)
         return true;
 
     /* DP-to-HDMI Protocol Converter */
     if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
         !port->mcs &&
         port->ldps)
         return true;
 
     /* DP-to-DP */
     mutex_lock(&port->mgr->lock);
     if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
         port->mstb &&
         port->mstb->num_ports == 2) {
         list_for_each_entry(downstream_port, &port->mstb->ports, next) {
             if (downstream_port->pdt == DP_PEER_DEVICE_SST_SINK &&
                 !downstream_port->input) {
                 mutex_unlock(&port->mgr->lock);
                 return true;
             }
         }
     }
     mutex_unlock(&port->mgr->lock);
 
     return false;
 }
 
 /**
  * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
  * @port: The port to check. A leaf of the MST tree with an attached display.
  *
  * Depending on the situation, DSC may be enabled via the endpoint aux,
  * the immediately upstream aux, or the connector's physical aux.
  *
  * This is both the correct aux to read DSC_CAPABILITY and the
  * correct aux to write DSC_ENABLED.
  *
  * This operation can be expensive (up to four aux reads), so
  * the caller should cache the return.
  *
  * Returns:
  * NULL if DSC cannot be enabled on this port, otherwise the aux device
  */
 struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 {
     struct drm_dp_mst_port *immediate_upstream_port;
     struct drm_dp_mst_port *fec_port;
     struct drm_dp_desc desc = {};
     u8 endpoint_fec;
     u8 endpoint_dsc;
 
     if (!port)
         return NULL;
 
     if (port->parent->port_parent)
         immediate_upstream_port = port->parent->port_parent;
     else
         immediate_upstream_port = NULL;
 
     fec_port = immediate_upstream_port;
     while (fec_port) {
         /*
          * Each physical link (i.e. not a virtual port) between the
          * output and the primary device must support FEC
          */
         if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
             !fec_port->fec_capable)
             return NULL;
 
         fec_port = fec_port->parent->port_parent;
     }
 
     /* DP-to-DP peer device */
     if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
         u8 upstream_dsc;
 
         if (drm_dp_dpcd_read(&port->aux,
                      DP_DSC_SUPPORT, &endpoint_dsc, 1) != 1)
             return NULL;
         if (drm_dp_dpcd_read(&port->aux,
                      DP_FEC_CAPABILITY, &endpoint_fec, 1) != 1)
             return NULL;
         if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
                      DP_DSC_SUPPORT, &upstream_dsc, 1) != 1)
             return NULL;
 
         /* Enpoint decompression with DP-to-DP peer device */
         if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED) &&
             (endpoint_fec & DP_FEC_CAPABLE) &&
             (upstream_dsc & 0x2) /* DSC passthrough */)
             return &port->aux;
 
         /* Virtual DPCD decompression with DP-to-DP peer device */
         return &immediate_upstream_port->aux;
     }
 
     /* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
     if (drm_dp_mst_is_virtual_dpcd(port))
         return &port->aux;
 
     /*
      * Synaptics quirk
      * Applies to ports for which:
      * - Physical aux has Synaptics OUI
      * - DPv1.4 or higher
      * - Port is on primary branch device
      * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
      */
     if (drm_dp_read_desc(port->mgr->aux, &desc, true))
         return NULL;
 
     if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
         port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
         port->parent == port->mgr->mst_primary) {
         u8 dpcd_ext[DP_RECEIVER_CAP_SIZE];
 
         if (drm_dp_read_dpcd_caps(port->mgr->aux, dpcd_ext) < 0)
             return NULL;
 
         if ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT) &&
             ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK)
              != DP_DWN_STRM_PORT_TYPE_ANALOG))
             return port->mgr->aux;
     }
 
     /*
      * The check below verifies if the MST sink
      * connected to the GPU is capable of DSC -
      * therefore the endpoint needs to be
      * both DSC and FEC capable.
      */
     if (drm_dp_dpcd_read(&port->aux,
        DP_DSC_SUPPORT, &endpoint_dsc, 1) != 1)
         return NULL;
     if (drm_dp_dpcd_read(&port->aux,
        DP_FEC_CAPABILITY, &endpoint_fec, 1) != 1)
         return NULL;
     if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED) &&
        (endpoint_fec & DP_FEC_CAPABLE))
         return &port->aux;
 
     return NULL;
 }
 EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);