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 // SPDX-License-Identifier: GPL-2.0
 /* Copyright(c) 2013 - 2019 Intel Corporation. */
 
 #include "fm10k_common.h"
 
 /**
  *  fm10k_fifo_init - Initialize a message FIFO
  *  @fifo: pointer to FIFO
  *  @buffer: pointer to memory to be used to store FIFO
  *  @size: maximum message size to store in FIFO, must be 2^n - 1
  **/
 static void fm10k_fifo_init(struct fm10k_mbx_fifo *fifo, u32 *buffer, u16 size)
 {
     fifo->buffer = buffer;
     fifo->size = size;
     fifo->head = 0;
     fifo->tail = 0;
 }
 
 /**
  *  fm10k_fifo_used - Retrieve used space in FIFO
  *  @fifo: pointer to FIFO
  *
  *  This function returns the number of DWORDs used in the FIFO
  **/
 static u16 fm10k_fifo_used(struct fm10k_mbx_fifo *fifo)
 {
     return fifo->tail - fifo->head;
 }
 
 /**
  *  fm10k_fifo_unused - Retrieve unused space in FIFO
  *  @fifo: pointer to FIFO
  *
  *  This function returns the number of unused DWORDs in the FIFO
  **/
 static u16 fm10k_fifo_unused(struct fm10k_mbx_fifo *fifo)
 {
     return fifo->size + fifo->head - fifo->tail;
 }
 
 /**
  *  fm10k_fifo_empty - Test to verify if FIFO is empty
  *  @fifo: pointer to FIFO
  *
  *  This function returns true if the FIFO is empty, else false
  **/
 static bool fm10k_fifo_empty(struct fm10k_mbx_fifo *fifo)
 {
     return fifo->head == fifo->tail;
 }
 
 /**
  *  fm10k_fifo_head_offset - returns indices of head with given offset
  *  @fifo: pointer to FIFO
  *  @offset: offset to add to head
  *
  *  This function returns the indices into the FIFO based on head + offset
  **/
 static u16 fm10k_fifo_head_offset(struct fm10k_mbx_fifo *fifo, u16 offset)
 {
     return (fifo->head + offset) & (fifo->size - 1);
 }
 
 /**
  *  fm10k_fifo_tail_offset - returns indices of tail with given offset
  *  @fifo: pointer to FIFO
  *  @offset: offset to add to tail
  *
  *  This function returns the indices into the FIFO based on tail + offset
  **/
 static u16 fm10k_fifo_tail_offset(struct fm10k_mbx_fifo *fifo, u16 offset)
 {
     return (fifo->tail + offset) & (fifo->size - 1);
 }
 
 /**
  *  fm10k_fifo_head_len - Retrieve length of first message in FIFO
  *  @fifo: pointer to FIFO
  *
  *  This function returns the size of the first message in the FIFO
  **/
 static u16 fm10k_fifo_head_len(struct fm10k_mbx_fifo *fifo)
 {
     u32 *head = fifo->buffer + fm10k_fifo_head_offset(fifo, 0);
 
     /* verify there is at least 1 DWORD in the fifo so *head is valid */
     if (fm10k_fifo_empty(fifo))
         return 0;
 
     /* retieve the message length */
     return FM10K_TLV_DWORD_LEN(*head);
 }
 
 /**
  *  fm10k_fifo_head_drop - Drop the first message in FIFO
  *  @fifo: pointer to FIFO
  *
  *  This function returns the size of the message dropped from the FIFO
  **/
 static u16 fm10k_fifo_head_drop(struct fm10k_mbx_fifo *fifo)
 {
     u16 len = fm10k_fifo_head_len(fifo);
 
     /* update head so it is at the start of next frame */
     fifo->head += len;
 
     return len;
 }
 
 /**
  *  fm10k_fifo_drop_all - Drop all messages in FIFO
  *  @fifo: pointer to FIFO
  *
  *  This function resets the head pointer to drop all messages in the FIFO and
  *  ensure the FIFO is empty.
  **/
 static void fm10k_fifo_drop_all(struct fm10k_mbx_fifo *fifo)
 {
     fifo->head = fifo->tail;
 }
 
 /**
  *  fm10k_mbx_index_len - Convert a head/tail index into a length value
  *  @mbx: pointer to mailbox
  *  @head: head index
  *  @tail: head index
  *
  *  This function takes the head and tail index and determines the length
  *  of the data indicated by this pair.
  **/
 static u16 fm10k_mbx_index_len(struct fm10k_mbx_info *mbx, u16 head, u16 tail)
 {
     u16 len = tail - head;
 
     /* we wrapped so subtract 2, one for index 0, one for all 1s index */
     if (len > tail)
         len -= 2;
 
     return len & ((mbx->mbmem_len << 1) - 1);
 }
 
 /**
  *  fm10k_mbx_tail_add - Determine new tail value with added offset
  *  @mbx: pointer to mailbox
  *  @offset: length to add to tail offset
  *
  *  This function takes the local tail index and recomputes it for
  *  a given length added as an offset.
  **/
 static u16 fm10k_mbx_tail_add(struct fm10k_mbx_info *mbx, u16 offset)
 {
     u16 tail = (mbx->tail + offset + 1) & ((mbx->mbmem_len << 1) - 1);
 
     /* add/sub 1 because we cannot have offset 0 or all 1s */
     return (tail > mbx->tail) ? --tail : ++tail;
 }
 
 /**
  *  fm10k_mbx_tail_sub - Determine new tail value with subtracted offset
  *  @mbx: pointer to mailbox
  *  @offset: length to add to tail offset
  *
  *  This function takes the local tail index and recomputes it for
  *  a given length added as an offset.
  **/
 static u16 fm10k_mbx_tail_sub(struct fm10k_mbx_info *mbx, u16 offset)
 {
     u16 tail = (mbx->tail - offset - 1) & ((mbx->mbmem_len << 1) - 1);
 
     /* sub/add 1 because we cannot have offset 0 or all 1s */
     return (tail < mbx->tail) ? ++tail : --tail;
 }
 
 /**
  *  fm10k_mbx_head_add - Determine new head value with added offset
  *  @mbx: pointer to mailbox
  *  @offset: length to add to head offset
  *
  *  This function takes the local head index and recomputes it for
  *  a given length added as an offset.
  **/
 static u16 fm10k_mbx_head_add(struct fm10k_mbx_info *mbx, u16 offset)
 {
     u16 head = (mbx->head + offset + 1) & ((mbx->mbmem_len << 1) - 1);
 
     /* add/sub 1 because we cannot have offset 0 or all 1s */
     return (head > mbx->head) ? --head : ++head;
 }
 
 /**
  *  fm10k_mbx_head_sub - Determine new head value with subtracted offset
  *  @mbx: pointer to mailbox
  *  @offset: length to add to head offset
  *
  *  This function takes the local head index and recomputes it for
  *  a given length added as an offset.
  **/
 static u16 fm10k_mbx_head_sub(struct fm10k_mbx_info *mbx, u16 offset)
 {
     u16 head = (mbx->head - offset - 1) & ((mbx->mbmem_len << 1) - 1);
 
     /* sub/add 1 because we cannot have offset 0 or all 1s */
     return (head < mbx->head) ? ++head : --head;
 }
 
 /**
  *  fm10k_mbx_pushed_tail_len - Retrieve the length of message being pushed
  *  @mbx: pointer to mailbox
  *
  *  This function will return the length of the message currently being
  *  pushed onto the tail of the Rx queue.
  **/
 static u16 fm10k_mbx_pushed_tail_len(struct fm10k_mbx_info *mbx)
 {
     u32 *tail = mbx->rx.buffer + fm10k_fifo_tail_offset(&mbx->rx, 0);
 
     /* pushed tail is only valid if pushed is set */
     if (!mbx->pushed)
         return 0;
 
     return FM10K_TLV_DWORD_LEN(*tail);
 }
 
 /**
  *  fm10k_fifo_write_copy - pulls data off of msg and places it in FIFO
  *  @fifo: pointer to FIFO
  *  @msg: message array to populate
  *  @tail_offset: additional offset to add to tail pointer
  *  @len: length of FIFO to copy into message header
  *
  *  This function will take a message and copy it into a section of the
  *  FIFO.  In order to get something into a location other than just
  *  the tail you can use tail_offset to adjust the pointer.
  **/
 static void fm10k_fifo_write_copy(struct fm10k_mbx_fifo *fifo,
                   const u32 *msg, u16 tail_offset, u16 len)
 {
     u16 end = fm10k_fifo_tail_offset(fifo, tail_offset);
     u32 *tail = fifo->buffer + end;
 
     /* track when we should cross the end of the FIFO */
     end = fifo->size - end;
 
     /* copy end of message before start of message */
     if (end < len)
         memcpy(fifo->buffer, msg + end, (len - end) << 2);
     else
         end = len;
 
     /* Copy remaining message into Tx FIFO */
     memcpy(tail, msg, end << 2);
 }
 
 /**
  *  fm10k_fifo_enqueue - Enqueues the message to the tail of the FIFO
  *  @fifo: pointer to FIFO
  *  @msg: message array to read
  *
  *  This function enqueues a message up to the size specified by the length
  *  contained in the first DWORD of the message and will place at the tail
  *  of the FIFO.  It will return 0 on success, or a negative value on error.
  **/
 static s32 fm10k_fifo_enqueue(struct fm10k_mbx_fifo *fifo, const u32 *msg)
 {
     u16 len = FM10K_TLV_DWORD_LEN(*msg);
 
     /* verify parameters */
     if (len > fifo->size)
         return FM10K_MBX_ERR_SIZE;
 
     /* verify there is room for the message */
     if (len > fm10k_fifo_unused(fifo))
         return FM10K_MBX_ERR_NO_SPACE;
 
     /* Copy message into FIFO */
     fm10k_fifo_write_copy(fifo, msg, 0, len);
 
     /* memory barrier to guarantee FIFO is written before tail update */
     wmb();
 
     /* Update Tx FIFO tail */
     fifo->tail += len;
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_validate_msg_size - Validate incoming message based on size
  *  @mbx: pointer to mailbox
  *  @len: length of data pushed onto buffer
  *
  *  This function analyzes the frame and will return a non-zero value when
  *  the start of a message larger than the mailbox is detected.
  **/
 static u16 fm10k_mbx_validate_msg_size(struct fm10k_mbx_info *mbx, u16 len)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->rx;
     u16 total_len = 0, msg_len;
 
     /* length should include previous amounts pushed */
     len += mbx->pushed;
 
     /* offset in message is based off of current message size */
     do {
         u32 *msg;
 
         msg = fifo->buffer + fm10k_fifo_tail_offset(fifo, total_len);
         msg_len = FM10K_TLV_DWORD_LEN(*msg);
         total_len += msg_len;
     } while (total_len < len);
 
     /* message extends out of pushed section, but fits in FIFO */
     if ((len < total_len) && (msg_len <= mbx->max_size))
         return 0;
 
     /* return length of invalid section */
     return (len < total_len) ? len : (len - total_len);
 }
 
 /**
  *  fm10k_mbx_write_copy - pulls data off of Tx FIFO and places it in mbmem
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will take a section of the Tx FIFO and copy it into the
  *  mailbox memory.  The offset in mbmem is based on the lower bits of the
  *  tail and len determines the length to copy.
  **/
 static void fm10k_mbx_write_copy(struct fm10k_hw *hw,
                  struct fm10k_mbx_info *mbx)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->tx;
     u32 mbmem = mbx->mbmem_reg;
     u32 *head = fifo->buffer;
     u16 end, len, tail, mask;
 
     if (!mbx->tail_len)
         return;
 
     /* determine data length and mbmem tail index */
     mask = mbx->mbmem_len - 1;
     len = mbx->tail_len;
     tail = fm10k_mbx_tail_sub(mbx, len);
     if (tail > mask)
         tail++;
 
     /* determine offset in the ring */
     end = fm10k_fifo_head_offset(fifo, mbx->pulled);
     head += end;
 
     /* memory barrier to guarantee data is ready to be read */
     rmb();
 
     /* Copy message from Tx FIFO */
     for (end = fifo->size - end; len; head = fifo->buffer) {
         do {
             /* adjust tail to match offset for FIFO */
             tail &= mask;
             if (!tail)
                 tail++;
 
             mbx->tx_mbmem_pulled++;
 
             /* write message to hardware FIFO */
             fm10k_write_reg(hw, mbmem + tail++, *(head++));
         } while (--len && --end);
     }
 }
 
 /**
  *  fm10k_mbx_pull_head - Pulls data off of head of Tx FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @head: acknowledgement number last received
  *
  *  This function will push the tail index forward based on the remote
  *  head index.  It will then pull up to mbmem_len DWORDs off of the
  *  head of the FIFO and will place it in the MBMEM registers
  *  associated with the mailbox.
  **/
 static void fm10k_mbx_pull_head(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx, u16 head)
 {
     u16 mbmem_len, len, ack = fm10k_mbx_index_len(mbx, head, mbx->tail);
     struct fm10k_mbx_fifo *fifo = &mbx->tx;
 
     /* update number of bytes pulled and update bytes in transit */
     mbx->pulled += mbx->tail_len - ack;
 
     /* determine length of data to pull, reserve space for mbmem header */
     mbmem_len = mbx->mbmem_len - 1;
     len = fm10k_fifo_used(fifo) - mbx->pulled;
     if (len > mbmem_len)
         len = mbmem_len;
 
     /* update tail and record number of bytes in transit */
     mbx->tail = fm10k_mbx_tail_add(mbx, len - ack);
     mbx->tail_len = len;
 
     /* drop pulled messages from the FIFO */
     for (len = fm10k_fifo_head_len(fifo);
          len && (mbx->pulled >= len);
          len = fm10k_fifo_head_len(fifo)) {
         mbx->pulled -= fm10k_fifo_head_drop(fifo);
         mbx->tx_messages++;
         mbx->tx_dwords += len;
     }
 
     /* Copy message out from the Tx FIFO */
     fm10k_mbx_write_copy(hw, mbx);
 }
 
 /**
  *  fm10k_mbx_read_copy - pulls data off of mbmem and places it in Rx FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will take a section of the mailbox memory and copy it
  *  into the Rx FIFO.  The offset is based on the lower bits of the
  *  head and len determines the length to copy.
  **/
 static void fm10k_mbx_read_copy(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->rx;
     u32 mbmem = mbx->mbmem_reg ^ mbx->mbmem_len;
     u32 *tail = fifo->buffer;
     u16 end, len, head;
 
     /* determine data length and mbmem head index */
     len = mbx->head_len;
     head = fm10k_mbx_head_sub(mbx, len);
     if (head >= mbx->mbmem_len)
         head++;
 
     /* determine offset in the ring */
     end = fm10k_fifo_tail_offset(fifo, mbx->pushed);
     tail += end;
 
     /* Copy message into Rx FIFO */
     for (end = fifo->size - end; len; tail = fifo->buffer) {
         do {
             /* adjust head to match offset for FIFO */
             head &= mbx->mbmem_len - 1;
             if (!head)
                 head++;
 
             mbx->rx_mbmem_pushed++;
 
             /* read message from hardware FIFO */
             *(tail++) = fm10k_read_reg(hw, mbmem + head++);
         } while (--len && --end);
     }
 
     /* memory barrier to guarantee FIFO is written before tail update */
     wmb();
 }
 
 /**
  *  fm10k_mbx_push_tail - Pushes up to 15 DWORDs on to tail of FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @tail: tail index of message
  *
  *  This function will first validate the tail index and size for the
  *  incoming message.  It then updates the acknowledgment number and
  *  copies the data into the FIFO.  It will return the number of messages
  *  dequeued on success and a negative value on error.
  **/
 static s32 fm10k_mbx_push_tail(struct fm10k_hw *hw,
                    struct fm10k_mbx_info *mbx,
                    u16 tail)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->rx;
     u16 len, seq = fm10k_mbx_index_len(mbx, mbx->head, tail);
 
     /* determine length of data to push */
     len = fm10k_fifo_unused(fifo) - mbx->pushed;
     if (len > seq)
         len = seq;
 
     /* update head and record bytes received */
     mbx->head = fm10k_mbx_head_add(mbx, len);
     mbx->head_len = len;
 
     /* nothing to do if there is no data */
     if (!len)
         return 0;
 
     /* Copy msg into Rx FIFO */
     fm10k_mbx_read_copy(hw, mbx);
 
     /* determine if there are any invalid lengths in message */
     if (fm10k_mbx_validate_msg_size(mbx, len))
         return FM10K_MBX_ERR_SIZE;
 
     /* Update pushed */
     mbx->pushed += len;
 
     /* flush any completed messages */
     for (len = fm10k_mbx_pushed_tail_len(mbx);
          len && (mbx->pushed >= len);
          len = fm10k_mbx_pushed_tail_len(mbx)) {
         fifo->tail += len;
         mbx->pushed -= len;
         mbx->rx_messages++;
         mbx->rx_dwords += len;
     }
 
     return 0;
 }
 
 /* pre-generated data for generating the CRC based on the poly 0xAC9A. */
 static const u16 fm10k_crc_16b_table[256] = {
     0x0000, 0x7956, 0xF2AC, 0x8BFA, 0xBC6D, 0xC53B, 0x4EC1, 0x3797,
     0x21EF, 0x58B9, 0xD343, 0xAA15, 0x9D82, 0xE4D4, 0x6F2E, 0x1678,
     0x43DE, 0x3A88, 0xB172, 0xC824, 0xFFB3, 0x86E5, 0x0D1F, 0x7449,
     0x6231, 0x1B67, 0x909D, 0xE9CB, 0xDE5C, 0xA70A, 0x2CF0, 0x55A6,
     0x87BC, 0xFEEA, 0x7510, 0x0C46, 0x3BD1, 0x4287, 0xC97D, 0xB02B,
     0xA653, 0xDF05, 0x54FF, 0x2DA9, 0x1A3E, 0x6368, 0xE892, 0x91C4,
     0xC462, 0xBD34, 0x36CE, 0x4F98, 0x780F, 0x0159, 0x8AA3, 0xF3F5,
     0xE58D, 0x9CDB, 0x1721, 0x6E77, 0x59E0, 0x20B6, 0xAB4C, 0xD21A,
     0x564D, 0x2F1B, 0xA4E1, 0xDDB7, 0xEA20, 0x9376, 0x188C, 0x61DA,
     0x77A2, 0x0EF4, 0x850E, 0xFC58, 0xCBCF, 0xB299, 0x3963, 0x4035,
     0x1593, 0x6CC5, 0xE73F, 0x9E69, 0xA9FE, 0xD0A8, 0x5B52, 0x2204,
     0x347C, 0x4D2A, 0xC6D0, 0xBF86, 0x8811, 0xF147, 0x7ABD, 0x03EB,
     0xD1F1, 0xA8A7, 0x235D, 0x5A0B, 0x6D9C, 0x14CA, 0x9F30, 0xE666,
     0xF01E, 0x8948, 0x02B2, 0x7BE4, 0x4C73, 0x3525, 0xBEDF, 0xC789,
     0x922F, 0xEB79, 0x6083, 0x19D5, 0x2E42, 0x5714, 0xDCEE, 0xA5B8,
     0xB3C0, 0xCA96, 0x416C, 0x383A, 0x0FAD, 0x76FB, 0xFD01, 0x8457,
     0xAC9A, 0xD5CC, 0x5E36, 0x2760, 0x10F7, 0x69A1, 0xE25B, 0x9B0D,
     0x8D75, 0xF423, 0x7FD9, 0x068F, 0x3118, 0x484E, 0xC3B4, 0xBAE2,
     0xEF44, 0x9612, 0x1DE8, 0x64BE, 0x5329, 0x2A7F, 0xA185, 0xD8D3,
     0xCEAB, 0xB7FD, 0x3C07, 0x4551, 0x72C6, 0x0B90, 0x806A, 0xF93C,
     0x2B26, 0x5270, 0xD98A, 0xA0DC, 0x974B, 0xEE1D, 0x65E7, 0x1CB1,
     0x0AC9, 0x739F, 0xF865, 0x8133, 0xB6A4, 0xCFF2, 0x4408, 0x3D5E,
     0x68F8, 0x11AE, 0x9A54, 0xE302, 0xD495, 0xADC3, 0x2639, 0x5F6F,
     0x4917, 0x3041, 0xBBBB, 0xC2ED, 0xF57A, 0x8C2C, 0x07D6, 0x7E80,
     0xFAD7, 0x8381, 0x087B, 0x712D, 0x46BA, 0x3FEC, 0xB416, 0xCD40,
     0xDB38, 0xA26E, 0x2994, 0x50C2, 0x6755, 0x1E03, 0x95F9, 0xECAF,
     0xB909, 0xC05F, 0x4BA5, 0x32F3, 0x0564, 0x7C32, 0xF7C8, 0x8E9E,
     0x98E6, 0xE1B0, 0x6A4A, 0x131C, 0x248B, 0x5DDD, 0xD627, 0xAF71,
     0x7D6B, 0x043D, 0x8FC7, 0xF691, 0xC106, 0xB850, 0x33AA, 0x4AFC,
     0x5C84, 0x25D2, 0xAE28, 0xD77E, 0xE0E9, 0x99BF, 0x1245, 0x6B13,
     0x3EB5, 0x47E3, 0xCC19, 0xB54F, 0x82D8, 0xFB8E, 0x7074, 0x0922,
     0x1F5A, 0x660C, 0xEDF6, 0x94A0, 0xA337, 0xDA61, 0x519B, 0x28CD };
 
 /**
  *  fm10k_crc_16b - Generate a 16 bit CRC for a region of 16 bit data
  *  @data: pointer to data to process
  *  @seed: seed value for CRC
  *  @len: length measured in 16 bits words
  *
  *  This function will generate a CRC based on the polynomial 0xAC9A and
  *  whatever value is stored in the seed variable.  Note that this
  *  value inverts the local seed and the result in order to capture all
  *  leading and trailing zeros.
  */
 static u16 fm10k_crc_16b(const u32 *data, u16 seed, u16 len)
 {
     u32 result = seed;
 
     while (len--) {
         result ^= *(data++);
         result = (result >> 8) ^ fm10k_crc_16b_table[result & 0xFF];
         result = (result >> 8) ^ fm10k_crc_16b_table[result & 0xFF];
 
         if (!(len--))
             break;
 
         result = (result >> 8) ^ fm10k_crc_16b_table[result & 0xFF];
         result = (result >> 8) ^ fm10k_crc_16b_table[result & 0xFF];
     }
 
     return (u16)result;
 }
 
 /**
  *  fm10k_fifo_crc - generate a CRC based off of FIFO data
  *  @fifo: pointer to FIFO
  *  @offset: offset point for start of FIFO
  *  @len: number of DWORDS words to process
  *  @seed: seed value for CRC
  *
  *  This function generates a CRC for some region of the FIFO
  **/
 static u16 fm10k_fifo_crc(struct fm10k_mbx_fifo *fifo, u16 offset,
               u16 len, u16 seed)
 {
     u32 *data = fifo->buffer + offset;
 
     /* track when we should cross the end of the FIFO */
     offset = fifo->size - offset;
 
     /* if we are in 2 blocks process the end of the FIFO first */
     if (offset < len) {
         seed = fm10k_crc_16b(data, seed, offset * 2);
         data = fifo->buffer;
         len -= offset;
     }
 
     /* process any remaining bits */
     return fm10k_crc_16b(data, seed, len * 2);
 }
 
 /**
  *  fm10k_mbx_update_local_crc - Update the local CRC for outgoing data
  *  @mbx: pointer to mailbox
  *  @head: head index provided by remote mailbox
  *
  *  This function will generate the CRC for all data from the end of the
  *  last head update to the current one.  It uses the result of the
  *  previous CRC as the seed for this update.  The result is stored in
  *  mbx->local.
  **/
 static void fm10k_mbx_update_local_crc(struct fm10k_mbx_info *mbx, u16 head)
 {
     u16 len = mbx->tail_len - fm10k_mbx_index_len(mbx, head, mbx->tail);
 
     /* determine the offset for the start of the region to be pulled */
     head = fm10k_fifo_head_offset(&mbx->tx, mbx->pulled);
 
     /* update local CRC to include all of the pulled data */
     mbx->local = fm10k_fifo_crc(&mbx->tx, head, len, mbx->local);
 }
 
 /**
  *  fm10k_mbx_verify_remote_crc - Verify the CRC is correct for current data
  *  @mbx: pointer to mailbox
  *
  *  This function will take all data that has been provided from the remote
  *  end and generate a CRC for it.  This is stored in mbx->remote.  The
  *  CRC for the header is then computed and if the result is non-zero this
  *  is an error and we signal an error dropping all data and resetting the
  *  connection.
  */
 static s32 fm10k_mbx_verify_remote_crc(struct fm10k_mbx_info *mbx)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->rx;
     u16 len = mbx->head_len;
     u16 offset = fm10k_fifo_tail_offset(fifo, mbx->pushed) - len;
     u16 crc;
 
     /* update the remote CRC if new data has been received */
     if (len)
         mbx->remote = fm10k_fifo_crc(fifo, offset, len, mbx->remote);
 
     /* process the full header as we have to validate the CRC */
     crc = fm10k_crc_16b(&mbx->mbx_hdr, mbx->remote, 1);
 
     /* notify other end if we have a problem */
     return crc ? FM10K_MBX_ERR_CRC : 0;
 }
 
 /**
  *  fm10k_mbx_rx_ready - Indicates that a message is ready in the Rx FIFO
  *  @mbx: pointer to mailbox
  *
  *  This function returns true if there is a message in the Rx FIFO to dequeue.
  **/
 static bool fm10k_mbx_rx_ready(struct fm10k_mbx_info *mbx)
 {
     u16 msg_size = fm10k_fifo_head_len(&mbx->rx);
 
     return msg_size && (fm10k_fifo_used(&mbx->rx) >= msg_size);
 }
 
 /**
  *  fm10k_mbx_tx_ready - Indicates that the mailbox is in state ready for Tx
  *  @mbx: pointer to mailbox
  *  @len: verify free space is >= this value
  *
  *  This function returns true if the mailbox is in a state ready to transmit.
  **/
 static bool fm10k_mbx_tx_ready(struct fm10k_mbx_info *mbx, u16 len)
 {
     u16 fifo_unused = fm10k_fifo_unused(&mbx->tx);
 
     return (mbx->state == FM10K_STATE_OPEN) && (fifo_unused >= len);
 }
 
 /**
  *  fm10k_mbx_tx_complete - Indicates that the Tx FIFO has been emptied
  *  @mbx: pointer to mailbox
  *
  *  This function returns true if the Tx FIFO is empty.
  **/
 static bool fm10k_mbx_tx_complete(struct fm10k_mbx_info *mbx)
 {
     return fm10k_fifo_empty(&mbx->tx);
 }
 
 /**
  *  fm10k_mbx_dequeue_rx - Dequeues the message from the head in the Rx FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function dequeues messages and hands them off to the TLV parser.
  *  It will return the number of messages processed when called.
  **/
 static u16 fm10k_mbx_dequeue_rx(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->rx;
     s32 err;
     u16 cnt;
 
     /* parse Rx messages out of the Rx FIFO to empty it */
     for (cnt = 0; !fm10k_fifo_empty(fifo); cnt++) {
         err = fm10k_tlv_msg_parse(hw, fifo->buffer + fifo->head,
                       mbx, mbx->msg_data);
         if (err < 0)
             mbx->rx_parse_err++;
 
         fm10k_fifo_head_drop(fifo);
     }
 
     /* shift remaining bytes back to start of FIFO */
     memmove(fifo->buffer, fifo->buffer + fifo->tail, mbx->pushed << 2);
 
     /* shift head and tail based on the memory we moved */
     fifo->tail -= fifo->head;
     fifo->head = 0;
 
     return cnt;
 }
 
 /**
  *  fm10k_mbx_enqueue_tx - Enqueues the message to the tail of the Tx FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @msg: message array to read
  *
  *  This function enqueues a message up to the size specified by the length
  *  contained in the first DWORD of the message and will place at the tail
  *  of the FIFO.  It will return 0 on success, or a negative value on error.
  **/
 static s32 fm10k_mbx_enqueue_tx(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx, const u32 *msg)
 {
     u32 countdown = mbx->timeout;
     s32 err;
 
     switch (mbx->state) {
     case FM10K_STATE_CLOSED:
     case FM10K_STATE_DISCONNECT:
         return FM10K_MBX_ERR_NO_MBX;
     default:
         break;
     }
 
     /* enqueue the message on the Tx FIFO */
     err = fm10k_fifo_enqueue(&mbx->tx, msg);
 
     /* if it failed give the FIFO a chance to drain */
     while (err && countdown) {
         countdown--;
         udelay(mbx->udelay);
         mbx->ops.process(hw, mbx);
         err = fm10k_fifo_enqueue(&mbx->tx, msg);
     }
 
     /* if we failed treat the error */
     if (err) {
         mbx->timeout = 0;
         mbx->tx_busy++;
     }
 
     /* begin processing message, ignore errors as this is just meant
      * to start the mailbox flow so we are not concerned if there
      * is a bad error, or the mailbox is already busy with a request
      */
     if (!mbx->tail_len)
         mbx->ops.process(hw, mbx);
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_read - Copies the mbmem to local message buffer
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function copies the message from the mbmem to the message array
  **/
 static s32 fm10k_mbx_read(struct fm10k_hw *hw, struct fm10k_mbx_info *mbx)
 {
     /* only allow one reader in here at a time */
     if (mbx->mbx_hdr)
         return FM10K_MBX_ERR_BUSY;
 
     /* read to capture initial interrupt bits */
     if (fm10k_read_reg(hw, mbx->mbx_reg) & FM10K_MBX_REQ_INTERRUPT)
         mbx->mbx_lock = FM10K_MBX_ACK;
 
     /* write back interrupt bits to clear */
     fm10k_write_reg(hw, mbx->mbx_reg,
             FM10K_MBX_REQ_INTERRUPT | FM10K_MBX_ACK_INTERRUPT);
 
     /* read remote header */
     mbx->mbx_hdr = fm10k_read_reg(hw, mbx->mbmem_reg ^ mbx->mbmem_len);
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_write - Copies the local message buffer to mbmem
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function copies the message from the message array to mbmem
  **/
 static void fm10k_mbx_write(struct fm10k_hw *hw, struct fm10k_mbx_info *mbx)
 {
     u32 mbmem = mbx->mbmem_reg;
 
     /* write new msg header to notify recipient of change */
     fm10k_write_reg(hw, mbmem, mbx->mbx_hdr);
 
     /* write mailbox to send interrupt */
     if (mbx->mbx_lock)
         fm10k_write_reg(hw, mbx->mbx_reg, mbx->mbx_lock);
 
     /* we no longer are using the header so free it */
     mbx->mbx_hdr = 0;
     mbx->mbx_lock = 0;
 }
 
 /**
  *  fm10k_mbx_create_connect_hdr - Generate a connect mailbox header
  *  @mbx: pointer to mailbox
  *
  *  This function returns a connection mailbox header
  **/
 static void fm10k_mbx_create_connect_hdr(struct fm10k_mbx_info *mbx)
 {
     mbx->mbx_lock |= FM10K_MBX_REQ;
 
     mbx->mbx_hdr = FM10K_MSG_HDR_FIELD_SET(FM10K_MSG_CONNECT, TYPE) |
                FM10K_MSG_HDR_FIELD_SET(mbx->head, HEAD) |
                FM10K_MSG_HDR_FIELD_SET(mbx->rx.size - 1, CONNECT_SIZE);
 }
 
 /**
  *  fm10k_mbx_create_data_hdr - Generate a data mailbox header
  *  @mbx: pointer to mailbox
  *
  *  This function returns a data mailbox header
  **/
 static void fm10k_mbx_create_data_hdr(struct fm10k_mbx_info *mbx)
 {
     u32 hdr = FM10K_MSG_HDR_FIELD_SET(FM10K_MSG_DATA, TYPE) |
           FM10K_MSG_HDR_FIELD_SET(mbx->tail, TAIL) |
           FM10K_MSG_HDR_FIELD_SET(mbx->head, HEAD);
     struct fm10k_mbx_fifo *fifo = &mbx->tx;
     u16 crc;
 
     if (mbx->tail_len)
         mbx->mbx_lock |= FM10K_MBX_REQ;
 
     /* generate CRC for data in flight and header */
     crc = fm10k_fifo_crc(fifo, fm10k_fifo_head_offset(fifo, mbx->pulled),
                  mbx->tail_len, mbx->local);
     crc = fm10k_crc_16b(&hdr, crc, 1);
 
     /* load header to memory to be written */
     mbx->mbx_hdr = hdr | FM10K_MSG_HDR_FIELD_SET(crc, CRC);
 }
 
 /**
  *  fm10k_mbx_create_disconnect_hdr - Generate a disconnect mailbox header
  *  @mbx: pointer to mailbox
  *
  *  This function returns a disconnect mailbox header
  **/
 static void fm10k_mbx_create_disconnect_hdr(struct fm10k_mbx_info *mbx)
 {
     u32 hdr = FM10K_MSG_HDR_FIELD_SET(FM10K_MSG_DISCONNECT, TYPE) |
           FM10K_MSG_HDR_FIELD_SET(mbx->tail, TAIL) |
           FM10K_MSG_HDR_FIELD_SET(mbx->head, HEAD);
     u16 crc = fm10k_crc_16b(&hdr, mbx->local, 1);
 
     mbx->mbx_lock |= FM10K_MBX_ACK;
 
     /* load header to memory to be written */
     mbx->mbx_hdr = hdr | FM10K_MSG_HDR_FIELD_SET(crc, CRC);
 }
 
 /**
  *  fm10k_mbx_create_fake_disconnect_hdr - Generate a false disconnect mbox hdr
  *  @mbx: pointer to mailbox
  *
  *  This function creates a fake disconnect header for loading into remote
  *  mailbox header. The primary purpose is to prevent errors on immediate
  *  start up after mbx->connect.
  **/
 static void fm10k_mbx_create_fake_disconnect_hdr(struct fm10k_mbx_info *mbx)
 {
     u32 hdr = FM10K_MSG_HDR_FIELD_SET(FM10K_MSG_DISCONNECT, TYPE) |
           FM10K_MSG_HDR_FIELD_SET(mbx->head, TAIL) |
           FM10K_MSG_HDR_FIELD_SET(mbx->tail, HEAD);
     u16 crc = fm10k_crc_16b(&hdr, mbx->local, 1);
 
     mbx->mbx_lock |= FM10K_MBX_ACK;
 
     /* load header to memory to be written */
     mbx->mbx_hdr = hdr | FM10K_MSG_HDR_FIELD_SET(crc, CRC);
 }
 
 /**
  *  fm10k_mbx_create_error_msg - Generate an error message
  *  @mbx: pointer to mailbox
  *  @err: local error encountered
  *
  *  This function will interpret the error provided by err, and based on
  *  that it may shift the message by 1 DWORD and then place an error header
  *  at the start of the message.
  **/
 static void fm10k_mbx_create_error_msg(struct fm10k_mbx_info *mbx, s32 err)
 {
     /* only generate an error message for these types */
     switch (err) {
     case FM10K_MBX_ERR_TAIL:
     case FM10K_MBX_ERR_HEAD:
     case FM10K_MBX_ERR_TYPE:
     case FM10K_MBX_ERR_SIZE:
     case FM10K_MBX_ERR_RSVD0:
     case FM10K_MBX_ERR_CRC:
         break;
     default:
         return;
     }
 
     mbx->mbx_lock |= FM10K_MBX_REQ;
 
     mbx->mbx_hdr = FM10K_MSG_HDR_FIELD_SET(FM10K_MSG_ERROR, TYPE) |
                FM10K_MSG_HDR_FIELD_SET(err, ERR_NO) |
                FM10K_MSG_HDR_FIELD_SET(mbx->head, HEAD);
 }
 
 /**
  *  fm10k_mbx_validate_msg_hdr - Validate common fields in the message header
  *  @mbx: pointer to mailbox
  *
  *  This function will parse up the fields in the mailbox header and return
  *  an error if the header contains any of a number of invalid configurations
  *  including unrecognized type, invalid route, or a malformed message.
  **/
 static s32 fm10k_mbx_validate_msg_hdr(struct fm10k_mbx_info *mbx)
 {
     u16 type, rsvd0, head, tail, size;
     const u32 *hdr = &mbx->mbx_hdr;
 
     type = FM10K_MSG_HDR_FIELD_GET(*hdr, TYPE);
     rsvd0 = FM10K_MSG_HDR_FIELD_GET(*hdr, RSVD0);
     tail = FM10K_MSG_HDR_FIELD_GET(*hdr, TAIL);
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
     size = FM10K_MSG_HDR_FIELD_GET(*hdr, CONNECT_SIZE);
 
     if (rsvd0)
         return FM10K_MBX_ERR_RSVD0;
 
     switch (type) {
     case FM10K_MSG_DISCONNECT:
         /* validate that all data has been received */
         if (tail != mbx->head)
             return FM10K_MBX_ERR_TAIL;
 
         fallthrough;
     case FM10K_MSG_DATA:
         /* validate that head is moving correctly */
         if (!head || (head == FM10K_MSG_HDR_MASK(HEAD)))
             return FM10K_MBX_ERR_HEAD;
         if (fm10k_mbx_index_len(mbx, head, mbx->tail) > mbx->tail_len)
             return FM10K_MBX_ERR_HEAD;
 
         /* validate that tail is moving correctly */
         if (!tail || (tail == FM10K_MSG_HDR_MASK(TAIL)))
             return FM10K_MBX_ERR_TAIL;
         if (fm10k_mbx_index_len(mbx, mbx->head, tail) < mbx->mbmem_len)
             break;
 
         return FM10K_MBX_ERR_TAIL;
     case FM10K_MSG_CONNECT:
         /* validate size is in range and is power of 2 mask */
         if ((size < FM10K_VFMBX_MSG_MTU) || (size & (size + 1)))
             return FM10K_MBX_ERR_SIZE;
 
         fallthrough;
     case FM10K_MSG_ERROR:
         if (!head || (head == FM10K_MSG_HDR_MASK(HEAD)))
             return FM10K_MBX_ERR_HEAD;
         /* neither create nor error include a tail offset */
         if (tail)
             return FM10K_MBX_ERR_TAIL;
 
         break;
     default:
         return FM10K_MBX_ERR_TYPE;
     }
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_create_reply - Generate reply based on state and remote head
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @head: acknowledgement number
  *
  *  This function will generate an outgoing message based on the current
  *  mailbox state and the remote FIFO head.  It will return the length
  *  of the outgoing message excluding header on success, and a negative value
  *  on error.
  **/
 static s32 fm10k_mbx_create_reply(struct fm10k_hw *hw,
                   struct fm10k_mbx_info *mbx, u16 head)
 {
     switch (mbx->state) {
     case FM10K_STATE_OPEN:
     case FM10K_STATE_DISCONNECT:
         /* update our checksum for the outgoing data */
         fm10k_mbx_update_local_crc(mbx, head);
 
         /* as long as other end recognizes us keep sending data */
         fm10k_mbx_pull_head(hw, mbx, head);
 
         /* generate new header based on data */
         if (mbx->tail_len || (mbx->state == FM10K_STATE_OPEN))
             fm10k_mbx_create_data_hdr(mbx);
         else
             fm10k_mbx_create_disconnect_hdr(mbx);
         break;
     case FM10K_STATE_CONNECT:
         /* send disconnect even if we aren't connected */
         fm10k_mbx_create_connect_hdr(mbx);
         break;
     case FM10K_STATE_CLOSED:
         /* generate new header based on data */
         fm10k_mbx_create_disconnect_hdr(mbx);
         break;
     default:
         break;
     }
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_reset_work- Reset internal pointers for any pending work
  *  @mbx: pointer to mailbox
  *
  *  This function will reset all internal pointers so any work in progress
  *  is dropped.  This call should occur every time we transition from the
  *  open state to the connect state.
  **/
 static void fm10k_mbx_reset_work(struct fm10k_mbx_info *mbx)
 {
     u16 len, head, ack;
 
     /* reset our outgoing max size back to Rx limits */
     mbx->max_size = mbx->rx.size - 1;
 
     /* update mbx->pulled to account for tail_len and ack */
     head = FM10K_MSG_HDR_FIELD_GET(mbx->mbx_hdr, HEAD);
     ack = fm10k_mbx_index_len(mbx, head, mbx->tail);
     mbx->pulled += mbx->tail_len - ack;
 
     /* now drop any messages which have started or finished transmitting */
     while (fm10k_fifo_head_len(&mbx->tx) && mbx->pulled) {
         len = fm10k_fifo_head_drop(&mbx->tx);
         mbx->tx_dropped++;
         if (mbx->pulled >= len)
             mbx->pulled -= len;
         else
             mbx->pulled = 0;
     }
 
     /* just do a quick resysnc to start of message */
     mbx->pushed = 0;
     mbx->pulled = 0;
     mbx->tail_len = 0;
     mbx->head_len = 0;
     mbx->rx.tail = 0;
     mbx->rx.head = 0;
 }
 
 /**
  *  fm10k_mbx_update_max_size - Update the max_size and drop any large messages
  *  @mbx: pointer to mailbox
  *  @size: new value for max_size
  *
  *  This function updates the max_size value and drops any outgoing messages
  *  at the head of the Tx FIFO if they are larger than max_size. It does not
  *  drop all messages, as this is too difficult to parse and remove them from
  *  the FIFO. Instead, rely on the checking to ensure that messages larger
  *  than max_size aren't pushed into the memory buffer.
  **/
 static void fm10k_mbx_update_max_size(struct fm10k_mbx_info *mbx, u16 size)
 {
     u16 len;
 
     mbx->max_size = size;
 
     /* flush any oversized messages from the queue */
     for (len = fm10k_fifo_head_len(&mbx->tx);
          len > size;
          len = fm10k_fifo_head_len(&mbx->tx)) {
         fm10k_fifo_head_drop(&mbx->tx);
         mbx->tx_dropped++;
     }
 }
 
 /**
  *  fm10k_mbx_connect_reset - Reset following request for reset
  *  @mbx: pointer to mailbox
  *
  *  This function resets the mailbox to either a disconnected state
  *  or a connect state depending on the current mailbox state
  **/
 static void fm10k_mbx_connect_reset(struct fm10k_mbx_info *mbx)
 {
     /* just do a quick resysnc to start of frame */
     fm10k_mbx_reset_work(mbx);
 
     /* reset CRC seeds */
     mbx->local = FM10K_MBX_CRC_SEED;
     mbx->remote = FM10K_MBX_CRC_SEED;
 
     /* we cannot exit connect until the size is good */
     if (mbx->state == FM10K_STATE_OPEN)
         mbx->state = FM10K_STATE_CONNECT;
     else
         mbx->state = FM10K_STATE_CLOSED;
 }
 
 /**
  *  fm10k_mbx_process_connect - Process connect header
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will read an incoming connect header and reply with the
  *  appropriate message.  It will return a value indicating the number of
  *  data DWORDs on success, or will return a negative value on failure.
  **/
 static s32 fm10k_mbx_process_connect(struct fm10k_hw *hw,
                      struct fm10k_mbx_info *mbx)
 {
     const enum fm10k_mbx_state state = mbx->state;
     const u32 *hdr = &mbx->mbx_hdr;
     u16 size, head;
 
     /* we will need to pull all of the fields for verification */
     size = FM10K_MSG_HDR_FIELD_GET(*hdr, CONNECT_SIZE);
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
 
     switch (state) {
     case FM10K_STATE_DISCONNECT:
     case FM10K_STATE_OPEN:
         /* reset any in-progress work */
         fm10k_mbx_connect_reset(mbx);
         break;
     case FM10K_STATE_CONNECT:
         /* we cannot exit connect until the size is good */
         if (size > mbx->rx.size) {
             mbx->max_size = mbx->rx.size - 1;
         } else {
             /* record the remote system requesting connection */
             mbx->state = FM10K_STATE_OPEN;
 
             fm10k_mbx_update_max_size(mbx, size);
         }
         break;
     default:
         break;
     }
 
     /* align our tail index to remote head index */
     mbx->tail = head;
 
     return fm10k_mbx_create_reply(hw, mbx, head);
 }
 
 /**
  *  fm10k_mbx_process_data - Process data header
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will read an incoming data header and reply with the
  *  appropriate message.  It will return a value indicating the number of
  *  data DWORDs on success, or will return a negative value on failure.
  **/
 static s32 fm10k_mbx_process_data(struct fm10k_hw *hw,
                   struct fm10k_mbx_info *mbx)
 {
     const u32 *hdr = &mbx->mbx_hdr;
     u16 head, tail;
     s32 err;
 
     /* we will need to pull all of the fields for verification */
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
     tail = FM10K_MSG_HDR_FIELD_GET(*hdr, TAIL);
 
     /* if we are in connect just update our data and go */
     if (mbx->state == FM10K_STATE_CONNECT) {
         mbx->tail = head;
         mbx->state = FM10K_STATE_OPEN;
     }
 
     /* abort on message size errors */
     err = fm10k_mbx_push_tail(hw, mbx, tail);
     if (err < 0)
         return err;
 
     /* verify the checksum on the incoming data */
     err = fm10k_mbx_verify_remote_crc(mbx);
     if (err)
         return err;
 
     /* process messages if we have received any */
     fm10k_mbx_dequeue_rx(hw, mbx);
 
     return fm10k_mbx_create_reply(hw, mbx, head);
 }
 
 /**
  *  fm10k_mbx_process_disconnect - Process disconnect header
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will read an incoming disconnect header and reply with the
  *  appropriate message.  It will return a value indicating the number of
  *  data DWORDs on success, or will return a negative value on failure.
  **/
 static s32 fm10k_mbx_process_disconnect(struct fm10k_hw *hw,
                     struct fm10k_mbx_info *mbx)
 {
     const enum fm10k_mbx_state state = mbx->state;
     const u32 *hdr = &mbx->mbx_hdr;
     u16 head;
     s32 err;
 
     /* we will need to pull the header field for verification */
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
 
     /* We should not be receiving disconnect if Rx is incomplete */
     if (mbx->pushed)
         return FM10K_MBX_ERR_TAIL;
 
     /* we have already verified mbx->head == tail so we know this is 0 */
     mbx->head_len = 0;
 
     /* verify the checksum on the incoming header is correct */
     err = fm10k_mbx_verify_remote_crc(mbx);
     if (err)
         return err;
 
     switch (state) {
     case FM10K_STATE_DISCONNECT:
     case FM10K_STATE_OPEN:
         /* state doesn't change if we still have work to do */
         if (!fm10k_mbx_tx_complete(mbx))
             break;
 
         /* verify the head indicates we completed all transmits */
         if (head != mbx->tail)
             return FM10K_MBX_ERR_HEAD;
 
         /* reset any in-progress work */
         fm10k_mbx_connect_reset(mbx);
         break;
     default:
         break;
     }
 
     return fm10k_mbx_create_reply(hw, mbx, head);
 }
 
 /**
  *  fm10k_mbx_process_error - Process error header
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will read an incoming error header and reply with the
  *  appropriate message.  It will return a value indicating the number of
  *  data DWORDs on success, or will return a negative value on failure.
  **/
 static s32 fm10k_mbx_process_error(struct fm10k_hw *hw,
                    struct fm10k_mbx_info *mbx)
 {
     const u32 *hdr = &mbx->mbx_hdr;
     u16 head;
 
     /* we will need to pull all of the fields for verification */
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
 
     switch (mbx->state) {
     case FM10K_STATE_OPEN:
     case FM10K_STATE_DISCONNECT:
         /* flush any uncompleted work */
         fm10k_mbx_reset_work(mbx);
 
         /* reset CRC seeds */
         mbx->local = FM10K_MBX_CRC_SEED;
         mbx->remote = FM10K_MBX_CRC_SEED;
 
         /* reset tail index and size to prepare for reconnect */
         mbx->tail = head;
 
         /* if open then reset max_size and go back to connect */
         if (mbx->state == FM10K_STATE_OPEN) {
             mbx->state = FM10K_STATE_CONNECT;
             break;
         }
 
         /* send a connect message to get data flowing again */
         fm10k_mbx_create_connect_hdr(mbx);
         return 0;
     default:
         break;
     }
 
     return fm10k_mbx_create_reply(hw, mbx, mbx->tail);
 }
 
 /**
  *  fm10k_mbx_process - Process mailbox interrupt
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will process incoming mailbox events and generate mailbox
  *  replies.  It will return a value indicating the number of DWORDs
  *  transmitted excluding header on success or a negative value on error.
  **/
 static s32 fm10k_mbx_process(struct fm10k_hw *hw,
                  struct fm10k_mbx_info *mbx)
 {
     s32 err;
 
     /* we do not read mailbox if closed */
     if (mbx->state == FM10K_STATE_CLOSED)
         return 0;
 
     /* copy data from mailbox */
     err = fm10k_mbx_read(hw, mbx);
     if (err)
         return err;
 
     /* validate type, source, and destination */
     err = fm10k_mbx_validate_msg_hdr(mbx);
     if (err < 0)
         goto msg_err;
 
     switch (FM10K_MSG_HDR_FIELD_GET(mbx->mbx_hdr, TYPE)) {
     case FM10K_MSG_CONNECT:
         err = fm10k_mbx_process_connect(hw, mbx);
         break;
     case FM10K_MSG_DATA:
         err = fm10k_mbx_process_data(hw, mbx);
         break;
     case FM10K_MSG_DISCONNECT:
         err = fm10k_mbx_process_disconnect(hw, mbx);
         break;
     case FM10K_MSG_ERROR:
         err = fm10k_mbx_process_error(hw, mbx);
         break;
     default:
         err = FM10K_MBX_ERR_TYPE;
         break;
     }
 
 msg_err:
     /* notify partner of errors on our end */
     if (err < 0)
         fm10k_mbx_create_error_msg(mbx, err);
 
     /* copy data from mailbox */
     fm10k_mbx_write(hw, mbx);
 
     return err;
 }
 
 /**
  *  fm10k_mbx_disconnect - Shutdown mailbox connection
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will shut down the mailbox.  It places the mailbox first
  *  in the disconnect state, it then allows up to a predefined timeout for
  *  the mailbox to transition to close on its own.  If this does not occur
  *  then the mailbox will be forced into the closed state.
  *
  *  Any mailbox transactions not completed before calling this function
  *  are not guaranteed to complete and may be dropped.
  **/
 static void fm10k_mbx_disconnect(struct fm10k_hw *hw,
                  struct fm10k_mbx_info *mbx)
 {
     int timeout = mbx->timeout ? FM10K_MBX_DISCONNECT_TIMEOUT : 0;
 
     /* Place mbx in ready to disconnect state */
     mbx->state = FM10K_STATE_DISCONNECT;
 
     /* trigger interrupt to start shutdown process */
     fm10k_write_reg(hw, mbx->mbx_reg, FM10K_MBX_REQ |
                       FM10K_MBX_INTERRUPT_DISABLE);
     do {
         udelay(FM10K_MBX_POLL_DELAY);
         mbx->ops.process(hw, mbx);
         timeout -= FM10K_MBX_POLL_DELAY;
     } while ((timeout > 0) && (mbx->state != FM10K_STATE_CLOSED));
 
     /* in case we didn't close, just force the mailbox into shutdown and
      * drop all left over messages in the FIFO.
      */
     fm10k_mbx_connect_reset(mbx);
     fm10k_fifo_drop_all(&mbx->tx);
 
     fm10k_write_reg(hw, mbx->mbmem_reg, 0);
 }
 
 /**
  *  fm10k_mbx_connect - Start mailbox connection
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will initiate a mailbox connection.  It will populate the
  *  mailbox with a broadcast connect message and then initialize the lock.
  *  This is safe since the connect message is a single DWORD so the mailbox
  *  transaction is guaranteed to be atomic.
  *
  *  This function will return an error if the mailbox has not been initiated
  *  or is currently in use.
  **/
 static s32 fm10k_mbx_connect(struct fm10k_hw *hw, struct fm10k_mbx_info *mbx)
 {
     /* we cannot connect an uninitialized mailbox */
     if (!mbx->rx.buffer)
         return FM10K_MBX_ERR_NO_SPACE;
 
     /* we cannot connect an already connected mailbox */
     if (mbx->state != FM10K_STATE_CLOSED)
         return FM10K_MBX_ERR_BUSY;
 
     /* mailbox timeout can now become active */
     mbx->timeout = FM10K_MBX_INIT_TIMEOUT;
 
     /* Place mbx in ready to connect state */
     mbx->state = FM10K_STATE_CONNECT;
 
     fm10k_mbx_reset_work(mbx);
 
     /* initialize header of remote mailbox */
     fm10k_mbx_create_fake_disconnect_hdr(mbx);
     fm10k_write_reg(hw, mbx->mbmem_reg ^ mbx->mbmem_len, mbx->mbx_hdr);
 
     /* enable interrupt and notify other party of new message */
     mbx->mbx_lock = FM10K_MBX_REQ_INTERRUPT | FM10K_MBX_ACK_INTERRUPT |
             FM10K_MBX_INTERRUPT_ENABLE;
 
     /* generate and load connect header into mailbox */
     fm10k_mbx_create_connect_hdr(mbx);
     fm10k_mbx_write(hw, mbx);
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_validate_handlers - Validate layout of message parsing data
  *  @msg_data: handlers for mailbox events
  *
  *  This function validates the layout of the message parsing data.  This
  *  should be mostly static, but it is important to catch any errors that
  *  are made when constructing the parsers.
  **/
 static s32 fm10k_mbx_validate_handlers(const struct fm10k_msg_data *msg_data)
 {
     const struct fm10k_tlv_attr *attr;
     unsigned int id;
 
     /* Allow NULL mailboxes that transmit but don't receive */
     if (!msg_data)
         return 0;
 
     while (msg_data->id != FM10K_TLV_ERROR) {
         /* all messages should have a function handler */
         if (!msg_data->func)
             return FM10K_ERR_PARAM;
 
         /* parser is optional */
         attr = msg_data->attr;
         if (attr) {
             while (attr->id != FM10K_TLV_ERROR) {
                 id = attr->id;
                 attr++;
                 /* ID should always be increasing */
                 if (id >= attr->id)
                     return FM10K_ERR_PARAM;
                 /* ID should fit in results array */
                 if (id >= FM10K_TLV_RESULTS_MAX)
                     return FM10K_ERR_PARAM;
             }
 
             /* verify terminator is in the list */
             if (attr->id != FM10K_TLV_ERROR)
                 return FM10K_ERR_PARAM;
         }
 
         id = msg_data->id;
         msg_data++;
         /* ID should always be increasing */
         if (id >= msg_data->id)
             return FM10K_ERR_PARAM;
     }
 
     /* verify terminator is in the list */
     if ((msg_data->id != FM10K_TLV_ERROR) || !msg_data->func)
         return FM10K_ERR_PARAM;
 
     return 0;
 }
 
 /**
  *  fm10k_mbx_register_handlers - Register a set of handler ops for mailbox
  *  @mbx: pointer to mailbox
  *  @msg_data: handlers for mailbox events
  *
  *  This function associates a set of message handling ops with a mailbox.
  **/
 static s32 fm10k_mbx_register_handlers(struct fm10k_mbx_info *mbx,
                        const struct fm10k_msg_data *msg_data)
 {
     /* validate layout of handlers before assigning them */
     if (fm10k_mbx_validate_handlers(msg_data))
         return FM10K_ERR_PARAM;
 
     /* initialize the message handlers */
     mbx->msg_data = msg_data;
 
     return 0;
 }
 
 /**
  *  fm10k_pfvf_mbx_init - Initialize mailbox memory for PF/VF mailbox
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @msg_data: handlers for mailbox events
  *  @id: ID reference for PF as it supports up to 64 PF/VF mailboxes
  *
  *  This function initializes the mailbox for use.  It will split the
  *  buffer provided and use that to populate both the Tx and Rx FIFO by
  *  evenly splitting it.  In order to allow for easy masking of head/tail
  *  the value reported in size must be a power of 2 and is reported in
  *  DWORDs, not bytes.  Any invalid values will cause the mailbox to return
  *  error.
  **/
 s32 fm10k_pfvf_mbx_init(struct fm10k_hw *hw, struct fm10k_mbx_info *mbx,
             const struct fm10k_msg_data *msg_data, u8 id)
 {
     /* initialize registers */
     switch (hw->mac.type) {
     case fm10k_mac_vf:
         mbx->mbx_reg = FM10K_VFMBX;
         mbx->mbmem_reg = FM10K_VFMBMEM(FM10K_VFMBMEM_VF_XOR);
         break;
     case fm10k_mac_pf:
         /* there are only 64 VF <-> PF mailboxes */
         if (id < 64) {
             mbx->mbx_reg = FM10K_MBX(id);
             mbx->mbmem_reg = FM10K_MBMEM_VF(id, 0);
             break;
         }
         fallthrough;
     default:
         return FM10K_MBX_ERR_NO_MBX;
     }
 
     /* start out in closed state */
     mbx->state = FM10K_STATE_CLOSED;
 
     /* validate layout of handlers before assigning them */
     if (fm10k_mbx_validate_handlers(msg_data))
         return FM10K_ERR_PARAM;
 
     /* initialize the message handlers */
     mbx->msg_data = msg_data;
 
     /* start mailbox as timed out and let the reset_hw call
      * set the timeout value to begin communications
      */
     mbx->timeout = 0;
     mbx->udelay = FM10K_MBX_INIT_DELAY;
 
     /* initialize tail and head */
     mbx->tail = 1;
     mbx->head = 1;
 
     /* initialize CRC seeds */
     mbx->local = FM10K_MBX_CRC_SEED;
     mbx->remote = FM10K_MBX_CRC_SEED;
 
     /* Split buffer for use by Tx/Rx FIFOs */
     mbx->max_size = FM10K_MBX_MSG_MAX_SIZE;
     mbx->mbmem_len = FM10K_VFMBMEM_VF_XOR;
 
     /* initialize the FIFOs, sizes are in 4 byte increments */
     fm10k_fifo_init(&mbx->tx, mbx->buffer, FM10K_MBX_TX_BUFFER_SIZE);
     fm10k_fifo_init(&mbx->rx, &mbx->buffer[FM10K_MBX_TX_BUFFER_SIZE],
             FM10K_MBX_RX_BUFFER_SIZE);
 
     /* initialize function pointers */
     mbx->ops.connect = fm10k_mbx_connect;
     mbx->ops.disconnect = fm10k_mbx_disconnect;
     mbx->ops.rx_ready = fm10k_mbx_rx_ready;
     mbx->ops.tx_ready = fm10k_mbx_tx_ready;
     mbx->ops.tx_complete = fm10k_mbx_tx_complete;
     mbx->ops.enqueue_tx = fm10k_mbx_enqueue_tx;
     mbx->ops.process = fm10k_mbx_process;
     mbx->ops.register_handlers = fm10k_mbx_register_handlers;
 
     return 0;
 }
 
 /**
  *  fm10k_sm_mbx_create_data_hdr - Generate a mailbox header for local FIFO
  *  @mbx: pointer to mailbox
  *
  *  This function returns a data mailbox header
  **/
 static void fm10k_sm_mbx_create_data_hdr(struct fm10k_mbx_info *mbx)
 {
     if (mbx->tail_len)
         mbx->mbx_lock |= FM10K_MBX_REQ;
 
     mbx->mbx_hdr = FM10K_MSG_HDR_FIELD_SET(mbx->tail, SM_TAIL) |
                FM10K_MSG_HDR_FIELD_SET(mbx->remote, SM_VER) |
                FM10K_MSG_HDR_FIELD_SET(mbx->head, SM_HEAD);
 }
 
 /**
  *  fm10k_sm_mbx_create_connect_hdr - Generate a mailbox header for local FIFO
  *  @mbx: pointer to mailbox
  *  @err: error flags to report if any
  *
  *  This function returns a connection mailbox header
  **/
 static void fm10k_sm_mbx_create_connect_hdr(struct fm10k_mbx_info *mbx, u8 err)
 {
     if (mbx->local)
         mbx->mbx_lock |= FM10K_MBX_REQ;
 
     mbx->mbx_hdr = FM10K_MSG_HDR_FIELD_SET(mbx->tail, SM_TAIL) |
                FM10K_MSG_HDR_FIELD_SET(mbx->remote, SM_VER) |
                FM10K_MSG_HDR_FIELD_SET(mbx->head, SM_HEAD) |
                FM10K_MSG_HDR_FIELD_SET(err, SM_ERR);
 }
 
 /**
  *  fm10k_sm_mbx_connect_reset - Reset following request for reset
  *  @mbx: pointer to mailbox
  *
  *  This function resets the mailbox to a just connected state
  **/
 static void fm10k_sm_mbx_connect_reset(struct fm10k_mbx_info *mbx)
 {
     /* flush any uncompleted work */
     fm10k_mbx_reset_work(mbx);
 
     /* set local version to max and remote version to 0 */
     mbx->local = FM10K_SM_MBX_VERSION;
     mbx->remote = 0;
 
     /* initialize tail and head */
     mbx->tail = 1;
     mbx->head = 1;
 
     /* reset state back to connect */
     mbx->state = FM10K_STATE_CONNECT;
 }
 
 /**
  *  fm10k_sm_mbx_connect - Start switch manager mailbox connection
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will initiate a mailbox connection with the switch
  *  manager.  To do this it will first disconnect the mailbox, and then
  *  reconnect it in order to complete a reset of the mailbox.
  *
  *  This function will return an error if the mailbox has not been initiated
  *  or is currently in use.
  **/
 static s32 fm10k_sm_mbx_connect(struct fm10k_hw *hw, struct fm10k_mbx_info *mbx)
 {
     /* we cannot connect an uninitialized mailbox */
     if (!mbx->rx.buffer)
         return FM10K_MBX_ERR_NO_SPACE;
 
     /* we cannot connect an already connected mailbox */
     if (mbx->state != FM10K_STATE_CLOSED)
         return FM10K_MBX_ERR_BUSY;
 
     /* mailbox timeout can now become active */
     mbx->timeout = FM10K_MBX_INIT_TIMEOUT;
 
     /* Place mbx in ready to connect state */
     mbx->state = FM10K_STATE_CONNECT;
     mbx->max_size = FM10K_MBX_MSG_MAX_SIZE;
 
     /* reset interface back to connect */
     fm10k_sm_mbx_connect_reset(mbx);
 
     /* enable interrupt and notify other party of new message */
     mbx->mbx_lock = FM10K_MBX_REQ_INTERRUPT | FM10K_MBX_ACK_INTERRUPT |
             FM10K_MBX_INTERRUPT_ENABLE;
 
     /* generate and load connect header into mailbox */
     fm10k_sm_mbx_create_connect_hdr(mbx, 0);
     fm10k_mbx_write(hw, mbx);
 
     return 0;
 }
 
 /**
  *  fm10k_sm_mbx_disconnect - Shutdown mailbox connection
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will shut down the mailbox.  It places the mailbox first
  *  in the disconnect state, it then allows up to a predefined timeout for
  *  the mailbox to transition to close on its own.  If this does not occur
  *  then the mailbox will be forced into the closed state.
  *
  *  Any mailbox transactions not completed before calling this function
  *  are not guaranteed to complete and may be dropped.
  **/
 static void fm10k_sm_mbx_disconnect(struct fm10k_hw *hw,
                     struct fm10k_mbx_info *mbx)
 {
     int timeout = mbx->timeout ? FM10K_MBX_DISCONNECT_TIMEOUT : 0;
 
     /* Place mbx in ready to disconnect state */
     mbx->state = FM10K_STATE_DISCONNECT;
 
     /* trigger interrupt to start shutdown process */
     fm10k_write_reg(hw, mbx->mbx_reg, FM10K_MBX_REQ |
                       FM10K_MBX_INTERRUPT_DISABLE);
     do {
         udelay(FM10K_MBX_POLL_DELAY);
         mbx->ops.process(hw, mbx);
         timeout -= FM10K_MBX_POLL_DELAY;
     } while ((timeout > 0) && (mbx->state != FM10K_STATE_CLOSED));
 
     /* in case we didn't close just force the mailbox into shutdown */
     mbx->state = FM10K_STATE_CLOSED;
     mbx->remote = 0;
     fm10k_mbx_reset_work(mbx);
     fm10k_fifo_drop_all(&mbx->tx);
 
     fm10k_write_reg(hw, mbx->mbmem_reg, 0);
 }
 
 /**
  *  fm10k_sm_mbx_validate_fifo_hdr - Validate fields in the remote FIFO header
  *  @mbx: pointer to mailbox
  *
  *  This function will parse up the fields in the mailbox header and return
  *  an error if the header contains any of a number of invalid configurations
  *  including unrecognized offsets or version numbers.
  **/
 static s32 fm10k_sm_mbx_validate_fifo_hdr(struct fm10k_mbx_info *mbx)
 {
     const u32 *hdr = &mbx->mbx_hdr;
     u16 tail, head, ver;
 
     tail = FM10K_MSG_HDR_FIELD_GET(*hdr, SM_TAIL);
     ver = FM10K_MSG_HDR_FIELD_GET(*hdr, SM_VER);
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, SM_HEAD);
 
     switch (ver) {
     case 0:
         break;
     case FM10K_SM_MBX_VERSION:
         if (!head || head > FM10K_SM_MBX_FIFO_LEN)
             return FM10K_MBX_ERR_HEAD;
         if (!tail || tail > FM10K_SM_MBX_FIFO_LEN)
             return FM10K_MBX_ERR_TAIL;
         if (mbx->tail < head)
             head += mbx->mbmem_len - 1;
         if (tail < mbx->head)
             tail += mbx->mbmem_len - 1;
         if (fm10k_mbx_index_len(mbx, head, mbx->tail) > mbx->tail_len)
             return FM10K_MBX_ERR_HEAD;
         if (fm10k_mbx_index_len(mbx, mbx->head, tail) < mbx->mbmem_len)
             break;
         return FM10K_MBX_ERR_TAIL;
     default:
         return FM10K_MBX_ERR_SRC;
     }
 
     return 0;
 }
 
 /**
  *  fm10k_sm_mbx_process_error - Process header with error flag set
  *  @mbx: pointer to mailbox
  *
  *  This function is meant to respond to a request where the error flag
  *  is set.  As a result we will terminate a connection if one is present
  *  and fall back into the reset state with a connection header of version
  *  0 (RESET).
  **/
 static void fm10k_sm_mbx_process_error(struct fm10k_mbx_info *mbx)
 {
     const enum fm10k_mbx_state state = mbx->state;
 
     switch (state) {
     case FM10K_STATE_DISCONNECT:
         /* if there is an error just disconnect */
         mbx->remote = 0;
         break;
     case FM10K_STATE_OPEN:
         /* flush any uncompleted work */
         fm10k_sm_mbx_connect_reset(mbx);
         break;
     case FM10K_STATE_CONNECT:
         /* try connecting at lower version */
         if (mbx->remote) {
             while (mbx->local > 1)
                 mbx->local--;
             mbx->remote = 0;
         }
         break;
     default:
         break;
     }
 
     fm10k_sm_mbx_create_connect_hdr(mbx, 0);
 }
 
 /**
  *  fm10k_sm_mbx_create_error_msg - Process an error in FIFO header
  *  @mbx: pointer to mailbox
  *  @err: local error encountered
  *
  *  This function will interpret the error provided by err, and based on
  *  that it may set the error bit in the local message header
  **/
 static void fm10k_sm_mbx_create_error_msg(struct fm10k_mbx_info *mbx, s32 err)
 {
     /* only generate an error message for these types */
     switch (err) {
     case FM10K_MBX_ERR_TAIL:
     case FM10K_MBX_ERR_HEAD:
     case FM10K_MBX_ERR_SRC:
     case FM10K_MBX_ERR_SIZE:
     case FM10K_MBX_ERR_RSVD0:
         break;
     default:
         return;
     }
 
     /* process it as though we received an error, and send error reply */
     fm10k_sm_mbx_process_error(mbx);
     fm10k_sm_mbx_create_connect_hdr(mbx, 1);
 }
 
 /**
  *  fm10k_sm_mbx_receive - Take message from Rx mailbox FIFO and put it in Rx
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @tail: tail index of message
  *
  *  This function will dequeue one message from the Rx switch manager mailbox
  *  FIFO and place it in the Rx mailbox FIFO for processing by software.
  **/
 static s32 fm10k_sm_mbx_receive(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx,
                 u16 tail)
 {
     /* reduce length by 1 to convert to a mask */
     u16 mbmem_len = mbx->mbmem_len - 1;
     s32 err;
 
     /* push tail in front of head */
     if (tail < mbx->head)
         tail += mbmem_len;
 
     /* copy data to the Rx FIFO */
     err = fm10k_mbx_push_tail(hw, mbx, tail);
     if (err < 0)
         return err;
 
     /* process messages if we have received any */
     fm10k_mbx_dequeue_rx(hw, mbx);
 
     /* guarantee head aligns with the end of the last message */
     mbx->head = fm10k_mbx_head_sub(mbx, mbx->pushed);
     mbx->pushed = 0;
 
     /* clear any extra bits left over since index adds 1 extra bit */
     if (mbx->head > mbmem_len)
         mbx->head -= mbmem_len;
 
     return err;
 }
 
 /**
  *  fm10k_sm_mbx_transmit - Take message from Tx and put it in Tx mailbox FIFO
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @head: head index of message
  *
  *  This function will dequeue one message from the Tx mailbox FIFO and place
  *  it in the Tx switch manager mailbox FIFO for processing by hardware.
  **/
 static void fm10k_sm_mbx_transmit(struct fm10k_hw *hw,
                   struct fm10k_mbx_info *mbx, u16 head)
 {
     struct fm10k_mbx_fifo *fifo = &mbx->tx;
     /* reduce length by 1 to convert to a mask */
     u16 mbmem_len = mbx->mbmem_len - 1;
     u16 tail_len, len = 0;
 
     /* push head behind tail */
     if (mbx->tail < head)
         head += mbmem_len;
 
     fm10k_mbx_pull_head(hw, mbx, head);
 
     /* determine msg aligned offset for end of buffer */
     do {
         u32 *msg;
 
         msg = fifo->buffer + fm10k_fifo_head_offset(fifo, len);
         tail_len = len;
         len += FM10K_TLV_DWORD_LEN(*msg);
     } while ((len <= mbx->tail_len) && (len < mbmem_len));
 
     /* guarantee we stop on a message boundary */
     if (mbx->tail_len > tail_len) {
         mbx->tail = fm10k_mbx_tail_sub(mbx, mbx->tail_len - tail_len);
         mbx->tail_len = tail_len;
     }
 
     /* clear any extra bits left over since index adds 1 extra bit */
     if (mbx->tail > mbmem_len)
         mbx->tail -= mbmem_len;
 }
 
 /**
  *  fm10k_sm_mbx_create_reply - Generate reply based on state and remote head
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @head: acknowledgement number
  *
  *  This function will generate an outgoing message based on the current
  *  mailbox state and the remote FIFO head.  It will return the length
  *  of the outgoing message excluding header on success, and a negative value
  *  on error.
  **/
 static void fm10k_sm_mbx_create_reply(struct fm10k_hw *hw,
                       struct fm10k_mbx_info *mbx, u16 head)
 {
     switch (mbx->state) {
     case FM10K_STATE_OPEN:
     case FM10K_STATE_DISCONNECT:
         /* flush out Tx data */
         fm10k_sm_mbx_transmit(hw, mbx, head);
 
         /* generate new header based on data */
         if (mbx->tail_len || (mbx->state == FM10K_STATE_OPEN)) {
             fm10k_sm_mbx_create_data_hdr(mbx);
         } else {
             mbx->remote = 0;
             fm10k_sm_mbx_create_connect_hdr(mbx, 0);
         }
         break;
     case FM10K_STATE_CONNECT:
     case FM10K_STATE_CLOSED:
         fm10k_sm_mbx_create_connect_hdr(mbx, 0);
         break;
     default:
         break;
     }
 }
 
 /**
  *  fm10k_sm_mbx_process_reset - Process header with version == 0 (RESET)
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function is meant to respond to a request where the version data
  *  is set to 0.  As such we will either terminate the connection or go
  *  into the connect state in order to re-establish the connection.  This
  *  function can also be used to respond to an error as the connection
  *  resetting would also be a means of dealing with errors.
  **/
 static s32 fm10k_sm_mbx_process_reset(struct fm10k_hw *hw,
                       struct fm10k_mbx_info *mbx)
 {
     s32 err = 0;
     const enum fm10k_mbx_state state = mbx->state;
 
     switch (state) {
     case FM10K_STATE_DISCONNECT:
         /* drop remote connections and disconnect */
         mbx->state = FM10K_STATE_CLOSED;
         mbx->remote = 0;
         mbx->local = 0;
         break;
     case FM10K_STATE_OPEN:
         /* flush any incomplete work */
         fm10k_sm_mbx_connect_reset(mbx);
         err = FM10K_ERR_RESET_REQUESTED;
         break;
     case FM10K_STATE_CONNECT:
         /* Update remote value to match local value */
         mbx->remote = mbx->local;
         break;
     default:
         break;
     }
 
     fm10k_sm_mbx_create_reply(hw, mbx, mbx->tail);
 
     return err;
 }
 
 /**
  *  fm10k_sm_mbx_process_version_1 - Process header with version == 1
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function is meant to process messages received when the remote
  *  mailbox is active.
  **/
 static s32 fm10k_sm_mbx_process_version_1(struct fm10k_hw *hw,
                       struct fm10k_mbx_info *mbx)
 {
     const u32 *hdr = &mbx->mbx_hdr;
     u16 head, tail;
     s32 len;
 
     /* pull all fields needed for verification */
     tail = FM10K_MSG_HDR_FIELD_GET(*hdr, SM_TAIL);
     head = FM10K_MSG_HDR_FIELD_GET(*hdr, SM_HEAD);
 
     /* if we are in connect and wanting version 1 then start up and go */
     if (mbx->state == FM10K_STATE_CONNECT) {
         if (!mbx->remote)
             goto send_reply;
         if (mbx->remote != 1)
             return FM10K_MBX_ERR_SRC;
 
         mbx->state = FM10K_STATE_OPEN;
     }
 
     do {
         /* abort on message size errors */
         len = fm10k_sm_mbx_receive(hw, mbx, tail);
         if (len < 0)
             return len;
 
         /* continue until we have flushed the Rx FIFO */
     } while (len);
 
 send_reply:
     fm10k_sm_mbx_create_reply(hw, mbx, head);
 
     return 0;
 }
 
 /**
  *  fm10k_sm_mbx_process - Process switch manager mailbox interrupt
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *
  *  This function will process incoming mailbox events and generate mailbox
  *  replies.  It will return a value indicating the number of DWORDs
  *  transmitted excluding header on success or a negative value on error.
  **/
 static s32 fm10k_sm_mbx_process(struct fm10k_hw *hw,
                 struct fm10k_mbx_info *mbx)
 {
     s32 err;
 
     /* we do not read mailbox if closed */
     if (mbx->state == FM10K_STATE_CLOSED)
         return 0;
 
     /* retrieve data from switch manager */
     err = fm10k_mbx_read(hw, mbx);
     if (err)
         return err;
 
     err = fm10k_sm_mbx_validate_fifo_hdr(mbx);
     if (err < 0)
         goto fifo_err;
 
     if (FM10K_MSG_HDR_FIELD_GET(mbx->mbx_hdr, SM_ERR)) {
         fm10k_sm_mbx_process_error(mbx);
         goto fifo_err;
     }
 
     switch (FM10K_MSG_HDR_FIELD_GET(mbx->mbx_hdr, SM_VER)) {
     case 0:
         err = fm10k_sm_mbx_process_reset(hw, mbx);
         break;
     case FM10K_SM_MBX_VERSION:
         err = fm10k_sm_mbx_process_version_1(hw, mbx);
         break;
     }
 
 fifo_err:
     if (err < 0)
         fm10k_sm_mbx_create_error_msg(mbx, err);
 
     /* report data to switch manager */
     fm10k_mbx_write(hw, mbx);
 
     return err;
 }
 
 /**
  *  fm10k_sm_mbx_init - Initialize mailbox memory for PF/SM mailbox
  *  @hw: pointer to hardware structure
  *  @mbx: pointer to mailbox
  *  @msg_data: handlers for mailbox events
  *
  *  This function initializes the PF/SM mailbox for use.  It will split the
  *  buffer provided and use that to populate both the Tx and Rx FIFO by
  *  evenly splitting it.  In order to allow for easy masking of head/tail
  *  the value reported in size must be a power of 2 and is reported in
  *  DWORDs, not bytes.  Any invalid values will cause the mailbox to return
  *  error.
  **/
 s32 fm10k_sm_mbx_init(struct fm10k_hw __always_unused *hw,
               struct fm10k_mbx_info *mbx,
               const struct fm10k_msg_data *msg_data)
 {
     mbx->mbx_reg = FM10K_GMBX;
     mbx->mbmem_reg = FM10K_MBMEM_PF(0);
 
     /* start out in closed state */
     mbx->state = FM10K_STATE_CLOSED;
 
     /* validate layout of handlers before assigning them */
     if (fm10k_mbx_validate_handlers(msg_data))
         return FM10K_ERR_PARAM;
 
     /* initialize the message handlers */
     mbx->msg_data = msg_data;
 
     /* start mailbox as timed out and let the reset_hw call
      * set the timeout value to begin communications
      */
     mbx->timeout = 0;
     mbx->udelay = FM10K_MBX_INIT_DELAY;
 
     /* Split buffer for use by Tx/Rx FIFOs */
     mbx->max_size = FM10K_MBX_MSG_MAX_SIZE;
     mbx->mbmem_len = FM10K_MBMEM_PF_XOR;
 
     /* initialize the FIFOs, sizes are in 4 byte increments */
     fm10k_fifo_init(&mbx->tx, mbx->buffer, FM10K_MBX_TX_BUFFER_SIZE);
     fm10k_fifo_init(&mbx->rx, &mbx->buffer[FM10K_MBX_TX_BUFFER_SIZE],
             FM10K_MBX_RX_BUFFER_SIZE);
 
     /* initialize function pointers */
     mbx->ops.connect = fm10k_sm_mbx_connect;
     mbx->ops.disconnect = fm10k_sm_mbx_disconnect;
     mbx->ops.rx_ready = fm10k_mbx_rx_ready;
     mbx->ops.tx_ready = fm10k_mbx_tx_ready;
     mbx->ops.tx_complete = fm10k_mbx_tx_complete;
     mbx->ops.enqueue_tx = fm10k_mbx_enqueue_tx;
     mbx->ops.process = fm10k_sm_mbx_process;
     mbx->ops.register_handlers = fm10k_mbx_register_handlers;
 
     return 0;
 }

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