gpio: rcar: Fix runtime PM imbalance on error

[linux/fpc-iii.git] / drivers / net / ethernet / intel / fm10k / fm10k_mbx.c

// 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_deqeueue_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 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;

                /* fall through */
        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;

                /* fall through */
        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);
        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;
                }
                /* fall through */
        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 connnecting 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;
        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;
}