firmware/arm_scmi/shmem.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * For transport using shared mem structure.
0004  *
0005  * Copyright (C) 2019 ARM Ltd.
0006  */
0007
0008 #include <linux/io.h>
0009 #include <linux/processor.h>
0010 #include <linux/types.h>
0011
0012 #include "common.h"
0013
0014 /*
0015  * SCMI specification requires all parameters, message headers, return
0016  * arguments or any protocol data to be expressed in little endian
0017  * format only.
0018  */
0019 struct scmi_shared_mem {
0020     __le32 reserved;
0021     __le32 channel_status;
0022 #define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR  BIT(1)
0023 #define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE   BIT(0)
0024     __le32 reserved1[2];
0025     __le32 flags;
0026 #define SCMI_SHMEM_FLAG_INTR_ENABLED    BIT(0)
0027     __le32 length;
0028     __le32 msg_header;
0029     u8 msg_payload[];
0030 };
0031
0032 void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
0033               struct scmi_xfer *xfer)
0034 {
0035     /*
0036      * Ideally channel must be free by now unless OS timeout last
0037      * request and platform continued to process the same, wait
0038      * until it releases the shared memory, otherwise we may endup
0039      * overwriting its response with new message payload or vice-versa
0040      */
0041     spin_until_cond(ioread32(&shmem->channel_status) &
0042             SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
0043     /* Mark channel busy + clear error */
0044     iowrite32(0x0, &shmem->channel_status);
0045     iowrite32(xfer->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
0046           &shmem->flags);
0047     iowrite32(sizeof(shmem->msg_header) + xfer->tx.len, &shmem->length);
0048     iowrite32(pack_scmi_header(&xfer->hdr), &shmem->msg_header);
0049     if (xfer->tx.buf)
0050         memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
0051 }
0052
0053 u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
0054 {
0055     return ioread32(&shmem->msg_header);
0056 }
0057
0058 void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
0059               struct scmi_xfer *xfer)
0060 {
0061     xfer->hdr.status = ioread32(shmem->msg_payload);
0062     /* Skip the length of header and status in shmem area i.e 8 bytes */
0063     xfer->rx.len = min_t(size_t, xfer->rx.len,
0064                  ioread32(&shmem->length) - 8);
0065
0066     /* Take a copy to the rx buffer.. */
0067     memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
0068 }
0069
0070 void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
0071                   size_t max_len, struct scmi_xfer *xfer)
0072 {
0073     /* Skip only the length of header in shmem area i.e 4 bytes */
0074     xfer->rx.len = min_t(size_t, max_len, ioread32(&shmem->length) - 4);
0075
0076     /* Take a copy to the rx buffer.. */
0077     memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
0078 }
0079
0080 void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
0081 {
0082     iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
0083 }
0084
0085 bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
0086              struct scmi_xfer *xfer)
0087 {
0088     u16 xfer_id;
0089
0090     xfer_id = MSG_XTRACT_TOKEN(ioread32(&shmem->msg_header));
0091
0092     if (xfer->hdr.seq != xfer_id)
0093         return false;
0094
0095     return ioread32(&shmem->channel_status) &
0096         (SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
0097          SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
0098 }