GNU Linux-libre 6.7.9-gnu

[releases.git] / drivers / usb / cdns3 / cdnsp-ring.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Cadence CDNSP DRD Driver.
 *
 * Copyright (C) 2020 Cadence.
 *
 * Author: Pawel Laszczak <pawell@cadence.com>
 *
 * Code based on Linux XHCI driver.
 * Origin: Copyright (C) 2008 Intel Corp
 */

/*
 * Ring initialization rules:
 * 1. Each segment is initialized to zero, except for link TRBs.
 * 2. Ring cycle state = 0. This represents Producer Cycle State (PCS) or
 *    Consumer Cycle State (CCS), depending on ring function.
 * 3. Enqueue pointer = dequeue pointer = address of first TRB in the segment.
 *
 * Ring behavior rules:
 * 1. A ring is empty if enqueue == dequeue. This means there will always be at
 *    least one free TRB in the ring. This is useful if you want to turn that
 *    into a link TRB and expand the ring.
 * 2. When incrementing an enqueue or dequeue pointer, if the next TRB is a
 *    link TRB, then load the pointer with the address in the link TRB. If the
 *    link TRB had its toggle bit set, you may need to update the ring cycle
 *    state (see cycle bit rules). You may have to do this multiple times
 *    until you reach a non-link TRB.
 * 3. A ring is full if enqueue++ (for the definition of increment above)
 *    equals the dequeue pointer.
 *
 * Cycle bit rules:
 * 1. When a consumer increments a dequeue pointer and encounters a toggle bit
 *    in a link TRB, it must toggle the ring cycle state.
 * 2. When a producer increments an enqueue pointer and encounters a toggle bit
 *    in a link TRB, it must toggle the ring cycle state.
 *
 * Producer rules:
 * 1. Check if ring is full before you enqueue.
 * 2. Write the ring cycle state to the cycle bit in the TRB you're enqueuing.
 *    Update enqueue pointer between each write (which may update the ring
 *    cycle state).
 * 3. Notify consumer. If SW is producer, it rings the doorbell for command
 *    and endpoint rings. If controller is the producer for the event ring,
 *    and it generates an interrupt according to interrupt modulation rules.
 *
 * Consumer rules:
 * 1. Check if TRB belongs to you. If the cycle bit == your ring cycle state,
 *    the TRB is owned by the consumer.
 * 2. Update dequeue pointer (which may update the ring cycle state) and
 *    continue processing TRBs until you reach a TRB which is not owned by you.
 * 3. Notify the producer. SW is the consumer for the event ring, and it
 *    updates event ring dequeue pointer. Controller is the consumer for the
 *    command and endpoint rings; it generates events on the event ring
 *    for these.
 */

#include <linux/scatterlist.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/irq.h>

#include "cdnsp-trace.h"
#include "cdnsp-gadget.h"

/*
 * Returns zero if the TRB isn't in this segment, otherwise it returns the DMA
 * address of the TRB.
 */
dma_addr_t cdnsp_trb_virt_to_dma(struct cdnsp_segment *seg,
                                 union cdnsp_trb *trb)
{
        unsigned long segment_offset = trb - seg->trbs;

        if (trb < seg->trbs || segment_offset >= TRBS_PER_SEGMENT)
                return 0;

        return seg->dma + (segment_offset * sizeof(*trb));
}

static bool cdnsp_trb_is_noop(union cdnsp_trb *trb)
{
        return TRB_TYPE_NOOP_LE32(trb->generic.field[3]);
}

static bool cdnsp_trb_is_link(union cdnsp_trb *trb)
{
        return TRB_TYPE_LINK_LE32(trb->link.control);
}

bool cdnsp_last_trb_on_seg(struct cdnsp_segment *seg, union cdnsp_trb *trb)
{
        return trb == &seg->trbs[TRBS_PER_SEGMENT - 1];
}

bool cdnsp_last_trb_on_ring(struct cdnsp_ring *ring,
                            struct cdnsp_segment *seg,
                            union cdnsp_trb *trb)
{
        return cdnsp_last_trb_on_seg(seg, trb) && (seg->next == ring->first_seg);
}

static bool cdnsp_link_trb_toggles_cycle(union cdnsp_trb *trb)
{
        return le32_to_cpu(trb->link.control) & LINK_TOGGLE;
}

static void cdnsp_trb_to_noop(union cdnsp_trb *trb, u32 noop_type)
{
        if (cdnsp_trb_is_link(trb)) {
                /* Unchain chained link TRBs. */
                trb->link.control &= cpu_to_le32(~TRB_CHAIN);
        } else {
                trb->generic.field[0] = 0;
                trb->generic.field[1] = 0;
                trb->generic.field[2] = 0;
                /* Preserve only the cycle bit of this TRB. */
                trb->generic.field[3] &= cpu_to_le32(TRB_CYCLE);
                trb->generic.field[3] |= cpu_to_le32(TRB_TYPE(noop_type));
        }
}

/*
 * Updates trb to point to the next TRB in the ring, and updates seg if the next
 * TRB is in a new segment. This does not skip over link TRBs, and it does not
 * effect the ring dequeue or enqueue pointers.
 */
static void cdnsp_next_trb(struct cdnsp_device *pdev,
                           struct cdnsp_ring *ring,
                           struct cdnsp_segment **seg,
                           union cdnsp_trb **trb)
{
        if (cdnsp_trb_is_link(*trb)) {
                *seg = (*seg)->next;
                *trb = ((*seg)->trbs);
        } else {
                (*trb)++;
        }
}

/*
 * See Cycle bit rules. SW is the consumer for the event ring only.
 * Don't make a ring full of link TRBs. That would be dumb and this would loop.
 */
void cdnsp_inc_deq(struct cdnsp_device *pdev, struct cdnsp_ring *ring)
{
        /* event ring doesn't have link trbs, check for last trb. */
        if (ring->type == TYPE_EVENT) {
                if (!cdnsp_last_trb_on_seg(ring->deq_seg, ring->dequeue)) {
                        ring->dequeue++;
                        goto out;
                }

                if (cdnsp_last_trb_on_ring(ring, ring->deq_seg, ring->dequeue))
                        ring->cycle_state ^= 1;

                ring->deq_seg = ring->deq_seg->next;
                ring->dequeue = ring->deq_seg->trbs;
                goto out;
        }

        /* All other rings have link trbs. */
        if (!cdnsp_trb_is_link(ring->dequeue)) {
                ring->dequeue++;
                ring->num_trbs_free++;
        }
        while (cdnsp_trb_is_link(ring->dequeue)) {
                ring->deq_seg = ring->deq_seg->next;
                ring->dequeue = ring->deq_seg->trbs;
        }
out:
        trace_cdnsp_inc_deq(ring);
}

/*
 * See Cycle bit rules. SW is the consumer for the event ring only.
 * Don't make a ring full of link TRBs. That would be dumb and this would loop.
 *
 * If we've just enqueued a TRB that is in the middle of a TD (meaning the
 * chain bit is set), then set the chain bit in all the following link TRBs.
 * If we've enqueued the last TRB in a TD, make sure the following link TRBs
 * have their chain bit cleared (so that each Link TRB is a separate TD).
 *
 * @more_trbs_coming:   Will you enqueue more TRBs before ringing the doorbell.
 */
static void cdnsp_inc_enq(struct cdnsp_device *pdev,
                          struct cdnsp_ring *ring,
                          bool more_trbs_coming)
{
        union cdnsp_trb *next;
        u32 chain;

        chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;

        /* If this is not event ring, there is one less usable TRB. */
        if (!cdnsp_trb_is_link(ring->enqueue))
                ring->num_trbs_free--;
        next = ++(ring->enqueue);

        /* Update the dequeue pointer further if that was a link TRB */
        while (cdnsp_trb_is_link(next)) {
                /*
                 * If the caller doesn't plan on enqueuing more TDs before
                 * ringing the doorbell, then we don't want to give the link TRB
                 * to the hardware just yet. We'll give the link TRB back in
                 * cdnsp_prepare_ring() just before we enqueue the TD at the
                 * top of the ring.
                 */
                if (!chain && !more_trbs_coming)
                        break;

                next->link.control &= cpu_to_le32(~TRB_CHAIN);
                next->link.control |= cpu_to_le32(chain);

                /* Give this link TRB to the hardware */
                wmb();
                next->link.control ^= cpu_to_le32(TRB_CYCLE);

                /* Toggle the cycle bit after the last ring segment. */
                if (cdnsp_link_trb_toggles_cycle(next))
                        ring->cycle_state ^= 1;

                ring->enq_seg = ring->enq_seg->next;
                ring->enqueue = ring->enq_seg->trbs;
                next = ring->enqueue;
        }

        trace_cdnsp_inc_enq(ring);
}

/*
 * Check to see if there's room to enqueue num_trbs on the ring and make sure
 * enqueue pointer will not advance into dequeue segment.
 */
static bool cdnsp_room_on_ring(struct cdnsp_device *pdev,
                               struct cdnsp_ring *ring,
                               unsigned int num_trbs)
{
        int num_trbs_in_deq_seg;

        if (ring->num_trbs_free < num_trbs)
                return false;

        if (ring->type != TYPE_COMMAND && ring->type != TYPE_EVENT) {
                num_trbs_in_deq_seg = ring->dequeue - ring->deq_seg->trbs;

                if (ring->num_trbs_free < num_trbs + num_trbs_in_deq_seg)
                        return false;
        }

        return true;
}

/*
 * Workaround for L1: controller has issue with resuming from L1 after
 * setting doorbell for endpoint during L1 state. This function forces
 * resume signal in such case.
 */
static void cdnsp_force_l0_go(struct cdnsp_device *pdev)
{
        if (pdev->active_port == &pdev->usb2_port && pdev->gadget.lpm_capable)
                cdnsp_set_link_state(pdev, &pdev->active_port->regs->portsc, XDEV_U0);
}

/* Ring the doorbell after placing a command on the ring. */
void cdnsp_ring_cmd_db(struct cdnsp_device *pdev)
{
        writel(DB_VALUE_CMD, &pdev->dba->cmd_db);
}

/*
 * Ring the doorbell after placing a transfer on the ring.
 * Returns true if doorbell was set, otherwise false.
 */
static bool cdnsp_ring_ep_doorbell(struct cdnsp_device *pdev,
                                   struct cdnsp_ep *pep,
                                   unsigned int stream_id)
{
        __le32 __iomem *reg_addr = &pdev->dba->ep_db;
        unsigned int ep_state = pep->ep_state;
        unsigned int db_value;

        /*
         * Don't ring the doorbell for this endpoint if endpoint is halted or
         * disabled.
         */
        if (ep_state & EP_HALTED || !(ep_state & EP_ENABLED))
                return false;

        /* For stream capable endpoints driver can ring doorbell only twice. */
        if (pep->ep_state & EP_HAS_STREAMS) {
                if (pep->stream_info.drbls_count >= 2)
                        return false;

                pep->stream_info.drbls_count++;
        }

        pep->ep_state &= ~EP_STOPPED;

        if (pep->idx == 0 && pdev->ep0_stage == CDNSP_DATA_STAGE &&
            !pdev->ep0_expect_in)
                db_value = DB_VALUE_EP0_OUT(pep->idx, stream_id);
        else
                db_value = DB_VALUE(pep->idx, stream_id);

        trace_cdnsp_tr_drbl(pep, stream_id);

        writel(db_value, reg_addr);

        cdnsp_force_l0_go(pdev);

        /* Doorbell was set. */
        return true;
}

/*
 * Get the right ring for the given pep and stream_id.
 * If the endpoint supports streams, boundary check the USB request's stream ID.
 * If the endpoint doesn't support streams, return the singular endpoint ring.
 */
static struct cdnsp_ring *cdnsp_get_transfer_ring(struct cdnsp_device *pdev,
                                                  struct cdnsp_ep *pep,
                                                  unsigned int stream_id)
{
        if (!(pep->ep_state & EP_HAS_STREAMS))
                return pep->ring;

        if (stream_id == 0 || stream_id >= pep->stream_info.num_streams) {
                dev_err(pdev->dev, "ERR: %s ring doesn't exist for SID: %d.\n",
                        pep->name, stream_id);
                return NULL;
        }

        return pep->stream_info.stream_rings[stream_id];
}

static struct cdnsp_ring *
        cdnsp_request_to_transfer_ring(struct cdnsp_device *pdev,
                                       struct cdnsp_request *preq)
{
        return cdnsp_get_transfer_ring(pdev, preq->pep,
                                       preq->request.stream_id);
}

/* Ring the doorbell for any rings with pending requests. */
void cdnsp_ring_doorbell_for_active_rings(struct cdnsp_device *pdev,
                                          struct cdnsp_ep *pep)
{
        struct cdnsp_stream_info *stream_info;
        unsigned int stream_id;
        int ret;

        if (pep->ep_state & EP_DIS_IN_RROGRESS)
                return;

        /* A ring has pending Request if its TD list is not empty. */
        if (!(pep->ep_state & EP_HAS_STREAMS) && pep->number) {
                if (pep->ring && !list_empty(&pep->ring->td_list))
                        cdnsp_ring_ep_doorbell(pdev, pep, 0);
                return;
        }

        stream_info = &pep->stream_info;

        for (stream_id = 1; stream_id < stream_info->num_streams; stream_id++) {
                struct cdnsp_td *td, *td_temp;
                struct cdnsp_ring *ep_ring;

                if (stream_info->drbls_count >= 2)
                        return;

                ep_ring = cdnsp_get_transfer_ring(pdev, pep, stream_id);
                if (!ep_ring)
                        continue;

                if (!ep_ring->stream_active || ep_ring->stream_rejected)
                        continue;

                list_for_each_entry_safe(td, td_temp, &ep_ring->td_list,
                                         td_list) {
                        if (td->drbl)
                                continue;

                        ret = cdnsp_ring_ep_doorbell(pdev, pep, stream_id);
                        if (ret)
                                td->drbl = 1;
                }
        }
}

/*
 * Get the hw dequeue pointer controller stopped on, either directly from the
 * endpoint context, or if streams are in use from the stream context.
 * The returned hw_dequeue contains the lowest four bits with cycle state
 * and possible stream context type.
 */
static u64 cdnsp_get_hw_deq(struct cdnsp_device *pdev,
                            unsigned int ep_index,
                            unsigned int stream_id)
{
        struct cdnsp_stream_ctx *st_ctx;
        struct cdnsp_ep *pep;

        pep = &pdev->eps[stream_id];

        if (pep->ep_state & EP_HAS_STREAMS) {
                st_ctx = &pep->stream_info.stream_ctx_array[stream_id];
                return le64_to_cpu(st_ctx->stream_ring);
        }

        return le64_to_cpu(pep->out_ctx->deq);
}

/*
 * Move the controller endpoint ring dequeue pointer past cur_td.
 * Record the new state of the controller endpoint ring dequeue segment,
 * dequeue pointer, and new consumer cycle state in state.
 * Update internal representation of the ring's dequeue pointer.
 *
 * We do this in three jumps:
 *  - First we update our new ring state to be the same as when the
 *    controller stopped.
 *  - Then we traverse the ring to find the segment that contains
 *    the last TRB in the TD. We toggle the controller new cycle state
 *    when we pass any link TRBs with the toggle cycle bit set.
 *  - Finally we move the dequeue state one TRB further, toggling the cycle bit
 *    if we've moved it past a link TRB with the toggle cycle bit set.
 */
static void cdnsp_find_new_dequeue_state(struct cdnsp_device *pdev,
                                         struct cdnsp_ep *pep,
                                         unsigned int stream_id,
                                         struct cdnsp_td *cur_td,
                                         struct cdnsp_dequeue_state *state)
{
        bool td_last_trb_found = false;
        struct cdnsp_segment *new_seg;
        struct cdnsp_ring *ep_ring;
        union cdnsp_trb *new_deq;
        bool cycle_found = false;
        u64 hw_dequeue;

        ep_ring = cdnsp_get_transfer_ring(pdev, pep, stream_id);
        if (!ep_ring)
                return;

        /*
         * Dig out the cycle state saved by the controller during the
         * stop endpoint command.
         */
        hw_dequeue = cdnsp_get_hw_deq(pdev, pep->idx, stream_id);
        new_seg = ep_ring->deq_seg;
        new_deq = ep_ring->dequeue;
        state->new_cycle_state = hw_dequeue & 0x1;
        state->stream_id = stream_id;

        /*
         * We want to find the pointer, segment and cycle state of the new trb
         * (the one after current TD's last_trb). We know the cycle state at
         * hw_dequeue, so walk the ring until both hw_dequeue and last_trb are
         * found.
         */
        do {
                if (!cycle_found && cdnsp_trb_virt_to_dma(new_seg, new_deq)
                    == (dma_addr_t)(hw_dequeue & ~0xf)) {
                        cycle_found = true;

                        if (td_last_trb_found)
                                break;
                }

                if (new_deq == cur_td->last_trb)
                        td_last_trb_found = true;

                if (cycle_found && cdnsp_trb_is_link(new_deq) &&
                    cdnsp_link_trb_toggles_cycle(new_deq))
                        state->new_cycle_state ^= 0x1;

                cdnsp_next_trb(pdev, ep_ring, &new_seg, &new_deq);

                /* Search wrapped around, bail out. */
                if (new_deq == pep->ring->dequeue) {
                        dev_err(pdev->dev,
                                "Error: Failed finding new dequeue state\n");
                        state->new_deq_seg = NULL;
                        state->new_deq_ptr = NULL;
                        return;
                }

        } while (!cycle_found || !td_last_trb_found);

        state->new_deq_seg = new_seg;
        state->new_deq_ptr = new_deq;

        trace_cdnsp_new_deq_state(state);
}

/*
 * flip_cycle means flip the cycle bit of all but the first and last TRB.
 * (The last TRB actually points to the ring enqueue pointer, which is not part
 * of this TD.) This is used to remove partially enqueued isoc TDs from a ring.
 */
static void cdnsp_td_to_noop(struct cdnsp_device *pdev,
                             struct cdnsp_ring *ep_ring,
                             struct cdnsp_td *td,
                             bool flip_cycle)
{
        struct cdnsp_segment *seg = td->start_seg;
        union cdnsp_trb *trb = td->first_trb;

        while (1) {
                cdnsp_trb_to_noop(trb, TRB_TR_NOOP);

                /* flip cycle if asked to */
                if (flip_cycle && trb != td->first_trb && trb != td->last_trb)
                        trb->generic.field[3] ^= cpu_to_le32(TRB_CYCLE);

                if (trb == td->last_trb)
                        break;

                cdnsp_next_trb(pdev, ep_ring, &seg, &trb);
        }
}

/*
 * This TD is defined by the TRBs starting at start_trb in start_seg and ending
 * at end_trb, which may be in another segment. If the suspect DMA address is a
 * TRB in this TD, this function returns that TRB's segment. Otherwise it
 * returns 0.
 */
static struct cdnsp_segment *cdnsp_trb_in_td(struct cdnsp_device *pdev,
                                             struct cdnsp_segment *start_seg,
                                             union cdnsp_trb *start_trb,
                                             union cdnsp_trb *end_trb,
                                             dma_addr_t suspect_dma)
{
        struct cdnsp_segment *cur_seg;
        union cdnsp_trb *temp_trb;
        dma_addr_t end_seg_dma;
        dma_addr_t end_trb_dma;
        dma_addr_t start_dma;

        start_dma = cdnsp_trb_virt_to_dma(start_seg, start_trb);
        cur_seg = start_seg;

        do {
                if (start_dma == 0)
                        return NULL;

                temp_trb = &cur_seg->trbs[TRBS_PER_SEGMENT - 1];
                /* We may get an event for a Link TRB in the middle of a TD */
                end_seg_dma = cdnsp_trb_virt_to_dma(cur_seg, temp_trb);
                /* If the end TRB isn't in this segment, this is set to 0 */
                end_trb_dma = cdnsp_trb_virt_to_dma(cur_seg, end_trb);

                trace_cdnsp_looking_trb_in_td(suspect_dma, start_dma,
                                              end_trb_dma, cur_seg->dma,
                                              end_seg_dma);

                if (end_trb_dma > 0) {
                        /*
                         * The end TRB is in this segment, so suspect should
                         * be here
                         */
                        if (start_dma <= end_trb_dma) {
                                if (suspect_dma >= start_dma &&
                                    suspect_dma <= end_trb_dma) {
                                        return cur_seg;
                                }
                        } else {
                                /*
                                 * Case for one segment with a
                                 * TD wrapped around to the top
                                 */
                                if ((suspect_dma >= start_dma &&
                                     suspect_dma <= end_seg_dma) ||
                                    (suspect_dma >= cur_seg->dma &&
                                     suspect_dma <= end_trb_dma)) {
                                        return cur_seg;
                                }
                        }

                        return NULL;
                }

                /* Might still be somewhere in this segment */
                if (suspect_dma >= start_dma && suspect_dma <= end_seg_dma)
                        return cur_seg;

                cur_seg = cur_seg->next;
                start_dma = cdnsp_trb_virt_to_dma(cur_seg, &cur_seg->trbs[0]);
        } while (cur_seg != start_seg);

        return NULL;
}

static void cdnsp_unmap_td_bounce_buffer(struct cdnsp_device *pdev,
                                         struct cdnsp_ring *ring,
                                         struct cdnsp_td *td)
{
        struct cdnsp_segment *seg = td->bounce_seg;
        struct cdnsp_request *preq;
        size_t len;

        if (!seg)
                return;

        preq = td->preq;

        trace_cdnsp_bounce_unmap(td->preq, seg->bounce_len, seg->bounce_offs,
                                 seg->bounce_dma, 0);

        if (!preq->direction) {
                dma_unmap_single(pdev->dev, seg->bounce_dma,
                                 ring->bounce_buf_len,  DMA_TO_DEVICE);
                return;
        }

        dma_unmap_single(pdev->dev, seg->bounce_dma, ring->bounce_buf_len,
                         DMA_FROM_DEVICE);

        /* For in transfers we need to copy the data from bounce to sg */
        len = sg_pcopy_from_buffer(preq->request.sg, preq->request.num_sgs,
                                   seg->bounce_buf, seg->bounce_len,
                                   seg->bounce_offs);
        if (len != seg->bounce_len)
                dev_warn(pdev->dev, "WARN Wrong bounce buffer read length: %zu != %d\n",
                         len, seg->bounce_len);

        seg->bounce_len = 0;
        seg->bounce_offs = 0;
}

static int cdnsp_cmd_set_deq(struct cdnsp_device *pdev,
                             struct cdnsp_ep *pep,
                             struct cdnsp_dequeue_state *deq_state)
{
        struct cdnsp_ring *ep_ring;
        int ret;

        if (!deq_state->new_deq_ptr || !deq_state->new_deq_seg) {
                cdnsp_ring_doorbell_for_active_rings(pdev, pep);
                return 0;
        }

        cdnsp_queue_new_dequeue_state(pdev, pep, deq_state);
        cdnsp_ring_cmd_db(pdev);
        ret = cdnsp_wait_for_cmd_compl(pdev);

        trace_cdnsp_handle_cmd_set_deq(cdnsp_get_slot_ctx(&pdev->out_ctx));
        trace_cdnsp_handle_cmd_set_deq_ep(pep->out_ctx);

        /*
         * Update the ring's dequeue segment and dequeue pointer
         * to reflect the new position.
         */
        ep_ring = cdnsp_get_transfer_ring(pdev, pep, deq_state->stream_id);

        if (cdnsp_trb_is_link(ep_ring->dequeue)) {
                ep_ring->deq_seg = ep_ring->deq_seg->next;
                ep_ring->dequeue = ep_ring->deq_seg->trbs;
        }

        while (ep_ring->dequeue != deq_state->new_deq_ptr) {
                ep_ring->num_trbs_free++;
                ep_ring->dequeue++;

                if (cdnsp_trb_is_link(ep_ring->dequeue)) {
                        if (ep_ring->dequeue == deq_state->new_deq_ptr)
                                break;

                        ep_ring->deq_seg = ep_ring->deq_seg->next;
                        ep_ring->dequeue = ep_ring->deq_seg->trbs;
                }
        }

        /*
         * Probably there was TIMEOUT during handling Set Dequeue Pointer
         * command. It's critical error and controller will be stopped.
         */
        if (ret)
                return -ESHUTDOWN;

        /* Restart any rings with pending requests */
        cdnsp_ring_doorbell_for_active_rings(pdev, pep);

        return 0;
}

int cdnsp_remove_request(struct cdnsp_device *pdev,
                         struct cdnsp_request *preq,
                         struct cdnsp_ep *pep)
{
        struct cdnsp_dequeue_state deq_state;
        struct cdnsp_td *cur_td = NULL;
        struct cdnsp_ring *ep_ring;
        struct cdnsp_segment *seg;
        int status = -ECONNRESET;
        int ret = 0;
        u64 hw_deq;

        memset(&deq_state, 0, sizeof(deq_state));

        trace_cdnsp_remove_request(pep->out_ctx);
        trace_cdnsp_remove_request_td(preq);

        cur_td = &preq->td;
        ep_ring = cdnsp_request_to_transfer_ring(pdev, preq);

        /*
         * If we stopped on the TD we need to cancel, then we have to
         * move the controller endpoint ring dequeue pointer past
         * this TD.
         */
        hw_deq = cdnsp_get_hw_deq(pdev, pep->idx, preq->request.stream_id);
        hw_deq &= ~0xf;

        seg = cdnsp_trb_in_td(pdev, cur_td->start_seg, cur_td->first_trb,
                              cur_td->last_trb, hw_deq);

        if (seg && (pep->ep_state & EP_ENABLED))
                cdnsp_find_new_dequeue_state(pdev, pep, preq->request.stream_id,
                                             cur_td, &deq_state);
        else
                cdnsp_td_to_noop(pdev, ep_ring, cur_td, false);

        /*
         * The event handler won't see a completion for this TD anymore,
         * so remove it from the endpoint ring's TD list.
         */
        list_del_init(&cur_td->td_list);
        ep_ring->num_tds--;
        pep->stream_info.td_count--;

        /*
         * During disconnecting all endpoint will be disabled so we don't
         * have to worry about updating dequeue pointer.
         */
        if (pdev->cdnsp_state & CDNSP_STATE_DISCONNECT_PENDING) {
                status = -ESHUTDOWN;
                ret = cdnsp_cmd_set_deq(pdev, pep, &deq_state);
        }

        cdnsp_unmap_td_bounce_buffer(pdev, ep_ring, cur_td);
        cdnsp_gadget_giveback(pep, cur_td->preq, status);

        return ret;
}

static int cdnsp_update_port_id(struct cdnsp_device *pdev, u32 port_id)
{
        struct cdnsp_port *port = pdev->active_port;
        u8 old_port = 0;

        if (port && port->port_num == port_id)
                return 0;

        if (port)
                old_port = port->port_num;

        if (port_id == pdev->usb2_port.port_num) {
                port = &pdev->usb2_port;
        } else if (port_id == pdev->usb3_port.port_num) {
                port  = &pdev->usb3_port;
        } else {
                dev_err(pdev->dev, "Port event with invalid port ID %d\n",
                        port_id);
                return -EINVAL;
        }

        if (port_id != old_port) {
                cdnsp_disable_slot(pdev);
                pdev->active_port = port;
                cdnsp_enable_slot(pdev);
        }

        if (port_id == pdev->usb2_port.port_num)
                cdnsp_set_usb2_hardware_lpm(pdev, NULL, 1);
        else
                writel(PORT_U1_TIMEOUT(1) | PORT_U2_TIMEOUT(1),
                       &pdev->usb3_port.regs->portpmsc);

        return 0;
}

static void cdnsp_handle_port_status(struct cdnsp_device *pdev,
                                     union cdnsp_trb *event)
{
        struct cdnsp_port_regs __iomem *port_regs;
        u32 portsc, cmd_regs;
        bool port2 = false;
        u32 link_state;
        u32 port_id;

        /* Port status change events always have a successful completion code */
        if (GET_COMP_CODE(le32_to_cpu(event->generic.field[2])) != COMP_SUCCESS)
                dev_err(pdev->dev, "ERR: incorrect PSC event\n");

        port_id = GET_PORT_ID(le32_to_cpu(event->generic.field[0]));

        if (cdnsp_update_port_id(pdev, port_id))
                goto cleanup;

        port_regs = pdev->active_port->regs;

        if (port_id == pdev->usb2_port.port_num)
                port2 = true;

new_event:
        portsc = readl(&port_regs->portsc);
        writel(cdnsp_port_state_to_neutral(portsc) |
               (portsc & PORT_CHANGE_BITS), &port_regs->portsc);

        trace_cdnsp_handle_port_status(pdev->active_port->port_num, portsc);

        pdev->gadget.speed = cdnsp_port_speed(portsc);
        link_state = portsc & PORT_PLS_MASK;

        /* Port Link State change detected. */
        if ((portsc & PORT_PLC)) {
                if (!(pdev->cdnsp_state & CDNSP_WAKEUP_PENDING)  &&
                    link_state == XDEV_RESUME) {
                        cmd_regs = readl(&pdev->op_regs->command);
                        if (!(cmd_regs & CMD_R_S))
                                goto cleanup;

                        if (DEV_SUPERSPEED_ANY(portsc)) {
                                cdnsp_set_link_state(pdev, &port_regs->portsc,
                                                     XDEV_U0);

                                cdnsp_resume_gadget(pdev);
                        }
                }

                if ((pdev->cdnsp_state & CDNSP_WAKEUP_PENDING) &&
                    link_state == XDEV_U0) {
                        pdev->cdnsp_state &= ~CDNSP_WAKEUP_PENDING;

                        cdnsp_force_header_wakeup(pdev, 1);
                        cdnsp_ring_cmd_db(pdev);
                        cdnsp_wait_for_cmd_compl(pdev);
                }

                if (link_state == XDEV_U0 && pdev->link_state == XDEV_U3 &&
                    !DEV_SUPERSPEED_ANY(portsc))
                        cdnsp_resume_gadget(pdev);

                if (link_state == XDEV_U3 &&  pdev->link_state != XDEV_U3)
                        cdnsp_suspend_gadget(pdev);

                pdev->link_state = link_state;
        }

        if (portsc & PORT_CSC) {
                /* Detach device. */
                if (pdev->gadget.connected && !(portsc & PORT_CONNECT))
                        cdnsp_disconnect_gadget(pdev);

                /* Attach device. */
                if (portsc & PORT_CONNECT) {
                        if (!port2)
                                cdnsp_irq_reset(pdev);

                        usb_gadget_set_state(&pdev->gadget, USB_STATE_ATTACHED);
                }
        }

        /* Port reset. */
        if ((portsc & (PORT_RC | PORT_WRC)) && (portsc & PORT_CONNECT)) {
                cdnsp_irq_reset(pdev);
                pdev->u1_allowed = 0;
                pdev->u2_allowed = 0;
                pdev->may_wakeup = 0;
        }

        if (portsc & PORT_CEC)
                dev_err(pdev->dev, "Port Over Current detected\n");

        if (portsc & PORT_CEC)
                dev_err(pdev->dev, "Port Configure Error detected\n");

        if (readl(&port_regs->portsc) & PORT_CHANGE_BITS)
                goto new_event;

cleanup:
        cdnsp_inc_deq(pdev, pdev->event_ring);
}

static void cdnsp_td_cleanup(struct cdnsp_device *pdev,
                             struct cdnsp_td *td,
                             struct cdnsp_ring *ep_ring,
                             int *status)
{
        struct cdnsp_request *preq = td->preq;

        /* if a bounce buffer was used to align this td then unmap it */
        cdnsp_unmap_td_bounce_buffer(pdev, ep_ring, td);

        /*
         * If the controller said we transferred more data than the buffer
         * length, Play it safe and say we didn't transfer anything.
         */
        if (preq->request.actual > preq->request.length) {
                preq->request.actual = 0;
                *status = 0;
        }

        list_del_init(&td->td_list);
        ep_ring->num_tds--;
        preq->pep->stream_info.td_count--;

        cdnsp_gadget_giveback(preq->pep, preq, *status);
}

static void cdnsp_finish_td(struct cdnsp_device *pdev,
                            struct cdnsp_td *td,
                            struct cdnsp_transfer_event *event,
                            struct cdnsp_ep *ep,
                            int *status)
{
        struct cdnsp_ring *ep_ring;
        u32 trb_comp_code;

        ep_ring = cdnsp_dma_to_transfer_ring(ep, le64_to_cpu(event->buffer));
        trb_comp_code = GET_COMP_CODE(le32_to_cpu(event->transfer_len));

        if (trb_comp_code == COMP_STOPPED_LENGTH_INVALID ||
            trb_comp_code == COMP_STOPPED ||
            trb_comp_code == COMP_STOPPED_SHORT_PACKET) {
                /*
                 * The Endpoint Stop Command completion will take care of any
                 * stopped TDs. A stopped TD may be restarted, so don't update
                 * the ring dequeue pointer or take this TD off any lists yet.
                 */
                return;
        }

        /* Update ring dequeue pointer */
        while (ep_ring->dequeue != td->last_trb)
                cdnsp_inc_deq(pdev, ep_ring);

        cdnsp_inc_deq(pdev, ep_ring);

        cdnsp_td_cleanup(pdev, td, ep_ring, status);
}

/* sum trb lengths from ring dequeue up to stop_trb, _excluding_ stop_trb */
static int cdnsp_sum_trb_lengths(struct cdnsp_device *pdev,
                                 struct cdnsp_ring *ring,
                                 union cdnsp_trb *stop_trb)
{
        struct cdnsp_segment *seg = ring->deq_seg;
        union cdnsp_trb *trb = ring->dequeue;
        u32 sum;

        for (sum = 0; trb != stop_trb; cdnsp_next_trb(pdev, ring, &seg, &trb)) {
                if (!cdnsp_trb_is_noop(trb) && !cdnsp_trb_is_link(trb))
                        sum += TRB_LEN(le32_to_cpu(trb->generic.field[2]));
        }
        return sum;
}

static int cdnsp_giveback_first_trb(struct cdnsp_device *pdev,
                                    struct cdnsp_ep *pep,
                                    unsigned int stream_id,
                                    int start_cycle,
                                    struct cdnsp_generic_trb *start_trb)
{
        /*
         * Pass all the TRBs to the hardware at once and make sure this write
         * isn't reordered.
         */
        wmb();

        if (start_cycle)
                start_trb->field[3] |= cpu_to_le32(start_cycle);
        else
                start_trb->field[3] &= cpu_to_le32(~TRB_CYCLE);

        if ((pep->ep_state & EP_HAS_STREAMS) &&
            !pep->stream_info.first_prime_det) {
                trace_cdnsp_wait_for_prime(pep, stream_id);
                return 0;
        }

        return cdnsp_ring_ep_doorbell(pdev, pep, stream_id);
}

/*
 * Process control tds, update USB request status and actual_length.
 */
static void cdnsp_process_ctrl_td(struct cdnsp_device *pdev,
                                  struct cdnsp_td *td,
                                  union cdnsp_trb *event_trb,
                                  struct cdnsp_transfer_event *event,
                                  struct cdnsp_ep *pep,
                                  int *status)
{
        struct cdnsp_ring *ep_ring;
        u32 remaining;
        u32 trb_type;

        trb_type = TRB_FIELD_TO_TYPE(le32_to_cpu(event_trb->generic.field[3]));
        ep_ring = cdnsp_dma_to_transfer_ring(pep, le64_to_cpu(event->buffer));
        remaining = EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));

        /*
         * if on data stage then update the actual_length of the USB
         * request and flag it as set, so it won't be overwritten in the event
         * for the last TRB.
         */
        if (trb_type == TRB_DATA) {
                td->request_length_set = true;
                td->preq->request.actual = td->preq->request.length - remaining;
        }

        /* at status stage */
        if (!td->request_length_set)
                td->preq->request.actual = td->preq->request.length;

        if (pdev->ep0_stage == CDNSP_DATA_STAGE && pep->number == 0 &&
            pdev->three_stage_setup) {
                td = list_entry(ep_ring->td_list.next, struct cdnsp_td,
                                td_list);
                pdev->ep0_stage = CDNSP_STATUS_STAGE;

                cdnsp_giveback_first_trb(pdev, pep, 0, ep_ring->cycle_state,
                                         &td->last_trb->generic);
                return;
        }

        *status = 0;

        cdnsp_finish_td(pdev, td, event, pep, status);
}

/*
 * Process isochronous tds, update usb request status and actual_length.
 */
static void cdnsp_process_isoc_td(struct cdnsp_device *pdev,
                                  struct cdnsp_td *td,
                                  union cdnsp_trb *ep_trb,
                                  struct cdnsp_transfer_event *event,
                                  struct cdnsp_ep *pep,
                                  int status)
{
        struct cdnsp_request *preq = td->preq;
        u32 remaining, requested, ep_trb_len;
        bool sum_trbs_for_length = false;
        struct cdnsp_ring *ep_ring;
        u32 trb_comp_code;
        u32 td_length;

        ep_ring = cdnsp_dma_to_transfer_ring(pep, le64_to_cpu(event->buffer));
        trb_comp_code = GET_COMP_CODE(le32_to_cpu(event->transfer_len));
        remaining = EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));
        ep_trb_len = TRB_LEN(le32_to_cpu(ep_trb->generic.field[2]));

        requested = preq->request.length;

        /* handle completion code */
        switch (trb_comp_code) {
        case COMP_SUCCESS:
                preq->request.status = 0;
                break;
        case COMP_SHORT_PACKET:
                preq->request.status = 0;
                sum_trbs_for_length = true;
                break;
        case COMP_ISOCH_BUFFER_OVERRUN:
        case COMP_BABBLE_DETECTED_ERROR:
                preq->request.status = -EOVERFLOW;
                break;
        case COMP_STOPPED:
                sum_trbs_for_length = true;
                break;
        case COMP_STOPPED_SHORT_PACKET:
                /* field normally containing residue now contains transferred */
                preq->request.status  = 0;
                requested = remaining;
                break;
        case COMP_STOPPED_LENGTH_INVALID:
                requested = 0;
                remaining = 0;
                break;
        default:
                sum_trbs_for_length = true;
                preq->request.status = -1;
                break;
        }

        if (sum_trbs_for_length) {
                td_length = cdnsp_sum_trb_lengths(pdev, ep_ring, ep_trb);
                td_length += ep_trb_len - remaining;
        } else {
                td_length = requested;
        }

        td->preq->request.actual += td_length;

        cdnsp_finish_td(pdev, td, event, pep, &status);
}

static void cdnsp_skip_isoc_td(struct cdnsp_device *pdev,
                               struct cdnsp_td *td,
                               struct cdnsp_transfer_event *event,
                               struct cdnsp_ep *pep,
                               int status)
{
        struct cdnsp_ring *ep_ring;

        ep_ring = cdnsp_dma_to_transfer_ring(pep, le64_to_cpu(event->buffer));
        td->preq->request.status = -EXDEV;
        td->preq->request.actual = 0;

        /* Update ring dequeue pointer */
        while (ep_ring->dequeue != td->last_trb)
                cdnsp_inc_deq(pdev, ep_ring);

        cdnsp_inc_deq(pdev, ep_ring);

        cdnsp_td_cleanup(pdev, td, ep_ring, &status);
}

/*
 * Process bulk and interrupt tds, update usb request status and actual_length.
 */
static void cdnsp_process_bulk_intr_td(struct cdnsp_device *pdev,
                                       struct cdnsp_td *td,
                                       union cdnsp_trb *ep_trb,
                                       struct cdnsp_transfer_event *event,
                                       struct cdnsp_ep *ep,
                                       int *status)
{
        u32 remaining, requested, ep_trb_len;
        struct cdnsp_ring *ep_ring;
        u32 trb_comp_code;

        ep_ring = cdnsp_dma_to_transfer_ring(ep, le64_to_cpu(event->buffer));
        trb_comp_code = GET_COMP_CODE(le32_to_cpu(event->transfer_len));
        remaining = EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));
        ep_trb_len = TRB_LEN(le32_to_cpu(ep_trb->generic.field[2]));
        requested = td->preq->request.length;

        switch (trb_comp_code) {
        case COMP_SUCCESS:
        case COMP_SHORT_PACKET:
                *status = 0;
                break;
        case COMP_STOPPED_SHORT_PACKET:
                td->preq->request.actual = remaining;
                goto finish_td;
        case COMP_STOPPED_LENGTH_INVALID:
                /* Stopped on ep trb with invalid length, exclude it. */
                ep_trb_len = 0;
                remaining = 0;
                break;
        }

        if (ep_trb == td->last_trb)
                ep_trb_len = requested - remaining;
        else
                ep_trb_len = cdnsp_sum_trb_lengths(pdev, ep_ring, ep_trb) +
                                                   ep_trb_len - remaining;
        td->preq->request.actual = ep_trb_len;

finish_td:
        ep->stream_info.drbls_count--;

        cdnsp_finish_td(pdev, td, event, ep, status);
}

static void cdnsp_handle_tx_nrdy(struct cdnsp_device *pdev,
                                 struct cdnsp_transfer_event *event)
{
        struct cdnsp_generic_trb *generic;
        struct cdnsp_ring *ep_ring;
        struct cdnsp_ep *pep;
        int cur_stream;
        int ep_index;
        int host_sid;
        int dev_sid;

        generic = (struct cdnsp_generic_trb *)event;
        ep_index = TRB_TO_EP_ID(le32_to_cpu(event->flags)) - 1;
        dev_sid = TRB_TO_DEV_STREAM(le32_to_cpu(generic->field[0]));
        host_sid = TRB_TO_HOST_STREAM(le32_to_cpu(generic->field[2]));

        pep = &pdev->eps[ep_index];

        if (!(pep->ep_state & EP_HAS_STREAMS))
                return;

        if (host_sid == STREAM_PRIME_ACK) {
                pep->stream_info.first_prime_det = 1;
                for (cur_stream = 1; cur_stream < pep->stream_info.num_streams;
                    cur_stream++) {
                        ep_ring = pep->stream_info.stream_rings[cur_stream];
                        ep_ring->stream_active = 1;
                        ep_ring->stream_rejected = 0;
                }
        }

        if (host_sid == STREAM_REJECTED) {
                struct cdnsp_td *td, *td_temp;

                pep->stream_info.drbls_count--;
                ep_ring = pep->stream_info.stream_rings[dev_sid];
                ep_ring->stream_active = 0;
                ep_ring->stream_rejected = 1;

                list_for_each_entry_safe(td, td_temp, &ep_ring->td_list,
                                         td_list) {
                        td->drbl = 0;
                }
        }

        cdnsp_ring_doorbell_for_active_rings(pdev, pep);
}

/*
 * If this function returns an error condition, it means it got a Transfer
 * event with a corrupted TRB DMA address or endpoint is disabled.
 */
static int cdnsp_handle_tx_event(struct cdnsp_device *pdev,
                                 struct cdnsp_transfer_event *event)
{
        const struct usb_endpoint_descriptor *desc;
        bool handling_skipped_tds = false;
        struct cdnsp_segment *ep_seg;
        struct cdnsp_ring *ep_ring;
        int status = -EINPROGRESS;
        union cdnsp_trb *ep_trb;
        dma_addr_t ep_trb_dma;
        struct cdnsp_ep *pep;
        struct cdnsp_td *td;
        u32 trb_comp_code;
        int invalidate;
        int ep_index;

        invalidate = le32_to_cpu(event->flags) & TRB_EVENT_INVALIDATE;
        ep_index = TRB_TO_EP_ID(le32_to_cpu(event->flags)) - 1;
        trb_comp_code = GET_COMP_CODE(le32_to_cpu(event->transfer_len));
        ep_trb_dma = le64_to_cpu(event->buffer);

        pep = &pdev->eps[ep_index];
        ep_ring = cdnsp_dma_to_transfer_ring(pep, le64_to_cpu(event->buffer));

        /*
         * If device is disconnect then all requests will be dequeued
         * by upper layers as part of disconnect sequence.
         * We don't want handle such event to avoid racing.
         */
        if (invalidate || !pdev->gadget.connected)
                goto cleanup;

        if (GET_EP_CTX_STATE(pep->out_ctx) == EP_STATE_DISABLED) {
                trace_cdnsp_ep_disabled(pep->out_ctx);
                goto err_out;
        }

        /* Some transfer events don't always point to a trb*/
        if (!ep_ring) {
                switch (trb_comp_code) {
                case COMP_INVALID_STREAM_TYPE_ERROR:
                case COMP_INVALID_STREAM_ID_ERROR:
                case COMP_RING_UNDERRUN:
                case COMP_RING_OVERRUN:
                        goto cleanup;
                default:
                        dev_err(pdev->dev, "ERROR: %s event for unknown ring\n",
                                pep->name);
                        goto err_out;
                }
        }

        /* Look for some error cases that need special treatment. */
        switch (trb_comp_code) {
        case COMP_BABBLE_DETECTED_ERROR:
                status = -EOVERFLOW;
                break;
        case COMP_RING_UNDERRUN:
        case COMP_RING_OVERRUN:
                /*
                 * When the Isoch ring is empty, the controller will generate
                 * a Ring Overrun Event for IN Isoch endpoint or Ring
                 * Underrun Event for OUT Isoch endpoint.
                 */
                goto cleanup;
        case COMP_MISSED_SERVICE_ERROR:
                /*
                 * When encounter missed service error, one or more isoc tds
                 * may be missed by controller.
                 * Set skip flag of the ep_ring; Complete the missed tds as
                 * short transfer when process the ep_ring next time.
                 */
                pep->skip = true;
                break;
        }

        do {
                /*
                 * This TRB should be in the TD at the head of this ring's TD
                 * list.
                 */
                if (list_empty(&ep_ring->td_list)) {
                        /*
                         * Don't print warnings if it's due to a stopped
                         * endpoint generating an extra completion event, or
                         * a event for the last TRB of a short TD we already
                         * got a short event for.
                         * The short TD is already removed from the TD list.
                         */
                        if (!(trb_comp_code == COMP_STOPPED ||
                              trb_comp_code == COMP_STOPPED_LENGTH_INVALID ||
                              ep_ring->last_td_was_short))
                                trace_cdnsp_trb_without_td(ep_ring,
                                        (struct cdnsp_generic_trb *)event);

                        if (pep->skip) {
                                pep->skip = false;
                                trace_cdnsp_ep_list_empty_with_skip(pep, 0);
                        }

                        goto cleanup;
                }

                td = list_entry(ep_ring->td_list.next, struct cdnsp_td,
                                td_list);

                /* Is this a TRB in the currently executing TD? */
                ep_seg = cdnsp_trb_in_td(pdev, ep_ring->deq_seg,
                                         ep_ring->dequeue, td->last_trb,
                                         ep_trb_dma);

                desc = td->preq->pep->endpoint.desc;

                if (ep_seg) {
                        ep_trb = &ep_seg->trbs[(ep_trb_dma - ep_seg->dma)
                                               / sizeof(*ep_trb)];

                        trace_cdnsp_handle_transfer(ep_ring,
                                        (struct cdnsp_generic_trb *)ep_trb);

                        if (pep->skip && usb_endpoint_xfer_isoc(desc) &&
                            td->last_trb != ep_trb)
                                return -EAGAIN;
                }

                /*
                 * Skip the Force Stopped Event. The event_trb(ep_trb_dma)
                 * of FSE is not in the current TD pointed by ep_ring->dequeue
                 * because that the hardware dequeue pointer still at the
                 * previous TRB of the current TD. The previous TRB maybe a
                 * Link TD or the last TRB of the previous TD. The command
                 * completion handle will take care the rest.
                 */
                if (!ep_seg && (trb_comp_code == COMP_STOPPED ||
                                trb_comp_code == COMP_STOPPED_LENGTH_INVALID)) {
                        pep->skip = false;
                        goto cleanup;
                }

                if (!ep_seg) {
                        if (!pep->skip || !usb_endpoint_xfer_isoc(desc)) {
                                /* Something is busted, give up! */
                                dev_err(pdev->dev,
                                        "ERROR Transfer event TRB DMA ptr not "
                                        "part of current TD ep_index %d "
                                        "comp_code %u\n", ep_index,
                                        trb_comp_code);
                                return -EINVAL;
                        }

                        cdnsp_skip_isoc_td(pdev, td, event, pep, status);
                        goto cleanup;
                }

                if (trb_comp_code == COMP_SHORT_PACKET)
                        ep_ring->last_td_was_short = true;
                else
                        ep_ring->last_td_was_short = false;

                if (pep->skip) {
                        pep->skip = false;
                        cdnsp_skip_isoc_td(pdev, td, event, pep, status);
                        goto cleanup;
                }

                if (cdnsp_trb_is_noop(ep_trb))
                        goto cleanup;

                if (usb_endpoint_xfer_control(desc))
                        cdnsp_process_ctrl_td(pdev, td, ep_trb, event, pep,
                                              &status);
                else if (usb_endpoint_xfer_isoc(desc))
                        cdnsp_process_isoc_td(pdev, td, ep_trb, event, pep,
                                              status);
                else
                        cdnsp_process_bulk_intr_td(pdev, td, ep_trb, event, pep,
                                                   &status);
cleanup:
                handling_skipped_tds = pep->skip;

                /*
                 * Do not update event ring dequeue pointer if we're in a loop
                 * processing missed tds.
                 */
                if (!handling_skipped_tds)
                        cdnsp_inc_deq(pdev, pdev->event_ring);

        /*
         * If ep->skip is set, it means there are missed tds on the
         * endpoint ring need to take care of.
         * Process them as short transfer until reach the td pointed by
         * the event.
         */
        } while (handling_skipped_tds);
        return 0;

err_out:
        dev_err(pdev->dev, "@%016llx %08x %08x %08x %08x\n",
                (unsigned long long)
                cdnsp_trb_virt_to_dma(pdev->event_ring->deq_seg,
                                      pdev->event_ring->dequeue),
                 lower_32_bits(le64_to_cpu(event->buffer)),
                 upper_32_bits(le64_to_cpu(event->buffer)),
                 le32_to_cpu(event->transfer_len),
                 le32_to_cpu(event->flags));
        return -EINVAL;
}

/*
 * This function handles all events on the event ring.
 * Returns true for "possibly more events to process" (caller should call
 * again), otherwise false if done.
 */
static bool cdnsp_handle_event(struct cdnsp_device *pdev)
{
        unsigned int comp_code;
        union cdnsp_trb *event;
        bool update_ptrs = true;
        u32 cycle_bit;
        int ret = 0;
        u32 flags;

        event = pdev->event_ring->dequeue;
        flags = le32_to_cpu(event->event_cmd.flags);
        cycle_bit = (flags & TRB_CYCLE);

        /* Does the controller or driver own the TRB? */
        if (cycle_bit != pdev->event_ring->cycle_state)
                return false;

        trace_cdnsp_handle_event(pdev->event_ring, &event->generic);

        /*
         * Barrier between reading the TRB_CYCLE (valid) flag above and any
         * reads of the event's flags/data below.
         */
        rmb();

        switch (flags & TRB_TYPE_BITMASK) {
        case TRB_TYPE(TRB_COMPLETION):
                /*
                 * Command can't be handled in interrupt context so just
                 * increment command ring dequeue pointer.
                 */
                cdnsp_inc_deq(pdev, pdev->cmd_ring);
                break;
        case TRB_TYPE(TRB_PORT_STATUS):
                cdnsp_handle_port_status(pdev, event);
                update_ptrs = false;
                break;
        case TRB_TYPE(TRB_TRANSFER):
                ret = cdnsp_handle_tx_event(pdev, &event->trans_event);
                if (ret >= 0)
                        update_ptrs = false;
                break;
        case TRB_TYPE(TRB_SETUP):
                pdev->ep0_stage = CDNSP_SETUP_STAGE;
                pdev->setup_id = TRB_SETUPID_TO_TYPE(flags);
                pdev->setup_speed = TRB_SETUP_SPEEDID(flags);
                pdev->setup = *((struct usb_ctrlrequest *)
                                &event->trans_event.buffer);

                cdnsp_setup_analyze(pdev);
                break;
        case TRB_TYPE(TRB_ENDPOINT_NRDY):
                cdnsp_handle_tx_nrdy(pdev, &event->trans_event);
                break;
        case TRB_TYPE(TRB_HC_EVENT): {
                comp_code = GET_COMP_CODE(le32_to_cpu(event->generic.field[2]));

                switch (comp_code) {
                case COMP_EVENT_RING_FULL_ERROR:
                        dev_err(pdev->dev, "Event Ring Full\n");
                        break;
                default:
                        dev_err(pdev->dev, "Controller error code 0x%02x\n",
                                comp_code);
                }

                break;
        }
        case TRB_TYPE(TRB_MFINDEX_WRAP):
        case TRB_TYPE(TRB_DRB_OVERFLOW):
                break;
        default:
                dev_warn(pdev->dev, "ERROR unknown event type %ld\n",
                         TRB_FIELD_TO_TYPE(flags));
        }

        if (update_ptrs)
                /* Update SW event ring dequeue pointer. */
                cdnsp_inc_deq(pdev, pdev->event_ring);

        /*
         * Caller will call us again to check if there are more items
         * on the event ring.
         */
        return true;
}

irqreturn_t cdnsp_thread_irq_handler(int irq, void *data)
{
        struct cdnsp_device *pdev = (struct cdnsp_device *)data;
        union cdnsp_trb *event_ring_deq;
        unsigned long flags;
        int counter = 0;

        local_bh_disable();
        spin_lock_irqsave(&pdev->lock, flags);

        if (pdev->cdnsp_state & (CDNSP_STATE_HALTED | CDNSP_STATE_DYING)) {
                /*
                 * While removing or stopping driver there may still be deferred
                 * not handled interrupt which should not be treated as error.
                 * Driver should simply ignore it.
                 */
                if (pdev->gadget_driver)
                        cdnsp_died(pdev);

                spin_unlock_irqrestore(&pdev->lock, flags);
                local_bh_enable();
                return IRQ_HANDLED;
        }

        event_ring_deq = pdev->event_ring->dequeue;

        while (cdnsp_handle_event(pdev)) {
                if (++counter >= TRBS_PER_EV_DEQ_UPDATE) {
                        cdnsp_update_erst_dequeue(pdev, event_ring_deq, 0);
                        event_ring_deq = pdev->event_ring->dequeue;
                        counter = 0;
                }
        }

        cdnsp_update_erst_dequeue(pdev, event_ring_deq, 1);

        spin_unlock_irqrestore(&pdev->lock, flags);
        local_bh_enable();

        return IRQ_HANDLED;
}

irqreturn_t cdnsp_irq_handler(int irq, void *priv)
{
        struct cdnsp_device *pdev = (struct cdnsp_device *)priv;
        u32 irq_pending;
        u32 status;

        status = readl(&pdev->op_regs->status);

        if (status == ~(u32)0) {
                cdnsp_died(pdev);
                return IRQ_HANDLED;
        }

        if (!(status & STS_EINT))
                return IRQ_NONE;

        writel(status | STS_EINT, &pdev->op_regs->status);
        irq_pending = readl(&pdev->ir_set->irq_pending);
        irq_pending |= IMAN_IP;
        writel(irq_pending, &pdev->ir_set->irq_pending);

        if (status & STS_FATAL) {
                cdnsp_died(pdev);
                return IRQ_HANDLED;
        }

        return IRQ_WAKE_THREAD;
}

/*
 * Generic function for queuing a TRB on a ring.
 * The caller must have checked to make sure there's room on the ring.
 *
 * @more_trbs_coming:   Will you enqueue more TRBs before setting doorbell?
 */
static void cdnsp_queue_trb(struct cdnsp_device *pdev, struct cdnsp_ring *ring,
                            bool more_trbs_coming, u32 field1, u32 field2,
                            u32 field3, u32 field4)
{
        struct cdnsp_generic_trb *trb;

        trb = &ring->enqueue->generic;

        trb->field[0] = cpu_to_le32(field1);
        trb->field[1] = cpu_to_le32(field2);
        trb->field[2] = cpu_to_le32(field3);
        trb->field[3] = cpu_to_le32(field4);

        trace_cdnsp_queue_trb(ring, trb);
        cdnsp_inc_enq(pdev, ring, more_trbs_coming);
}

/*
 * Does various checks on the endpoint ring, and makes it ready to
 * queue num_trbs.
 */
static int cdnsp_prepare_ring(struct cdnsp_device *pdev,
                              struct cdnsp_ring *ep_ring,
                              u32 ep_state, unsigned
                              int num_trbs,
                              gfp_t mem_flags)
{
        unsigned int num_trbs_needed;

        /* Make sure the endpoint has been added to controller schedule. */
        switch (ep_state) {
        case EP_STATE_STOPPED:
        case EP_STATE_RUNNING:
        case EP_STATE_HALTED:
                break;
        default:
                dev_err(pdev->dev, "ERROR: incorrect endpoint state\n");
                return -EINVAL;
        }

        while (1) {
                if (cdnsp_room_on_ring(pdev, ep_ring, num_trbs))
                        break;

                trace_cdnsp_no_room_on_ring("try ring expansion");

                num_trbs_needed = num_trbs - ep_ring->num_trbs_free;
                if (cdnsp_ring_expansion(pdev, ep_ring, num_trbs_needed,
                                         mem_flags)) {
                        dev_err(pdev->dev, "Ring expansion failed\n");
                        return -ENOMEM;
                }
        }

        while (cdnsp_trb_is_link(ep_ring->enqueue)) {
                ep_ring->enqueue->link.control |= cpu_to_le32(TRB_CHAIN);
                /* The cycle bit must be set as the last operation. */
                wmb();
                ep_ring->enqueue->link.control ^= cpu_to_le32(TRB_CYCLE);

                /* Toggle the cycle bit after the last ring segment. */
                if (cdnsp_link_trb_toggles_cycle(ep_ring->enqueue))
                        ep_ring->cycle_state ^= 1;
                ep_ring->enq_seg = ep_ring->enq_seg->next;
                ep_ring->enqueue = ep_ring->enq_seg->trbs;
        }
        return 0;
}

static int cdnsp_prepare_transfer(struct cdnsp_device *pdev,
                                  struct cdnsp_request *preq,
                                  unsigned int num_trbs)
{
        struct cdnsp_ring *ep_ring;
        int ret;

        ep_ring = cdnsp_get_transfer_ring(pdev, preq->pep,
                                          preq->request.stream_id);
        if (!ep_ring)
                return -EINVAL;

        ret = cdnsp_prepare_ring(pdev, ep_ring,
                                 GET_EP_CTX_STATE(preq->pep->out_ctx),
                                 num_trbs, GFP_ATOMIC);
        if (ret)
                return ret;

        INIT_LIST_HEAD(&preq->td.td_list);
        preq->td.preq = preq;

        /* Add this TD to the tail of the endpoint ring's TD list. */
        list_add_tail(&preq->td.td_list, &ep_ring->td_list);
        ep_ring->num_tds++;
        preq->pep->stream_info.td_count++;

        preq->td.start_seg = ep_ring->enq_seg;
        preq->td.first_trb = ep_ring->enqueue;

        return 0;
}

static unsigned int cdnsp_count_trbs(u64 addr, u64 len)
{
        unsigned int num_trbs;

        num_trbs = DIV_ROUND_UP(len + (addr & (TRB_MAX_BUFF_SIZE - 1)),
                                TRB_MAX_BUFF_SIZE);
        if (num_trbs == 0)
                num_trbs++;

        return num_trbs;
}

static unsigned int count_trbs_needed(struct cdnsp_request *preq)
{
        return cdnsp_count_trbs(preq->request.dma, preq->request.length);
}

static unsigned int count_sg_trbs_needed(struct cdnsp_request *preq)
{
        unsigned int i, len, full_len, num_trbs = 0;
        struct scatterlist *sg;

        full_len = preq->request.length;

        for_each_sg(preq->request.sg, sg, preq->request.num_sgs, i) {
                len = sg_dma_len(sg);
                num_trbs += cdnsp_count_trbs(sg_dma_address(sg), len);
                len = min(len, full_len);
                full_len -= len;
                if (full_len == 0)
                        break;
        }

        return num_trbs;
}

static void cdnsp_check_trb_math(struct cdnsp_request *preq, int running_total)
{
        if (running_total != preq->request.length)
                dev_err(preq->pep->pdev->dev,
                        "%s - Miscalculated tx length, "
                        "queued %#x, asked for %#x (%d)\n",
                        preq->pep->name, running_total,
                        preq->request.length, preq->request.actual);
}

/*
 * TD size is the number of max packet sized packets remaining in the TD
 * (*not* including this TRB).
 *
 * Total TD packet count = total_packet_count =
 *     DIV_ROUND_UP(TD size in bytes / wMaxPacketSize)
 *
 * Packets transferred up to and including this TRB = packets_transferred =
 *     rounddown(total bytes transferred including this TRB / wMaxPacketSize)
 *
 * TD size = total_packet_count - packets_transferred
 *
 * It must fit in bits 21:17, so it can't be bigger than 31.
 * This is taken care of in the TRB_TD_SIZE() macro
 *
 * The last TRB in a TD must have the TD size set to zero.
 */
static u32 cdnsp_td_remainder(struct cdnsp_device *pdev,
                              int transferred,
                              int trb_buff_len,
                              unsigned int td_total_len,
                              struct cdnsp_request *preq,
                              bool more_trbs_coming,
                              bool zlp)
{
        u32 maxp, total_packet_count;

        /* Before ZLP driver needs set TD_SIZE = 1. */
        if (zlp)
                return 1;

        /* One TRB with a zero-length data packet. */
        if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
            trb_buff_len == td_total_len)
                return 0;

        maxp = usb_endpoint_maxp(preq->pep->endpoint.desc);
        total_packet_count = DIV_ROUND_UP(td_total_len, maxp);

        /* Queuing functions don't count the current TRB into transferred. */
        return (total_packet_count - ((transferred + trb_buff_len) / maxp));
}

static int cdnsp_align_td(struct cdnsp_device *pdev,
                          struct cdnsp_request *preq, u32 enqd_len,
                          u32 *trb_buff_len, struct cdnsp_segment *seg)
{
        struct device *dev = pdev->dev;
        unsigned int unalign;
        unsigned int max_pkt;
        u32 new_buff_len;

        max_pkt = usb_endpoint_maxp(preq->pep->endpoint.desc);
        unalign = (enqd_len + *trb_buff_len) % max_pkt;

        /* We got lucky, last normal TRB data on segment is packet aligned. */
        if (unalign == 0)
                return 0;

        /* Is the last nornal TRB alignable by splitting it. */
        if (*trb_buff_len > unalign) {
                *trb_buff_len -= unalign;
                trace_cdnsp_bounce_align_td_split(preq, *trb_buff_len,
                                                  enqd_len, 0, unalign);
                return 0;
        }

        /*
         * We want enqd_len + trb_buff_len to sum up to a number aligned to
         * number which is divisible by the endpoint's wMaxPacketSize. IOW:
         * (size of currently enqueued TRBs + remainder) % wMaxPacketSize == 0.
         */
        new_buff_len = max_pkt - (enqd_len % max_pkt);

        if (new_buff_len > (preq->request.length - enqd_len))
                new_buff_len = (preq->request.length - enqd_len);

        /* Create a max max_pkt sized bounce buffer pointed to by last trb. */
        if (preq->direction) {
                sg_pcopy_to_buffer(preq->request.sg,
                                   preq->request.num_mapped_sgs,
                                   seg->bounce_buf, new_buff_len, enqd_len);
                seg->bounce_dma = dma_map_single(dev, seg->bounce_buf,
                                                 max_pkt, DMA_TO_DEVICE);
        } else {
                seg->bounce_dma = dma_map_single(dev, seg->bounce_buf,
                                                 max_pkt, DMA_FROM_DEVICE);
        }

        if (dma_mapping_error(dev, seg->bounce_dma)) {
                /* Try without aligning.*/
                dev_warn(pdev->dev,
                         "Failed mapping bounce buffer, not aligning\n");
                return 0;
        }

        *trb_buff_len = new_buff_len;
        seg->bounce_len = new_buff_len;
        seg->bounce_offs = enqd_len;

        trace_cdnsp_bounce_map(preq, new_buff_len, enqd_len, seg->bounce_dma,
                               unalign);

        /*
         * Bounce buffer successful aligned and seg->bounce_dma will be used
         * in transfer TRB as new transfer buffer address.
         */
        return 1;
}

int cdnsp_queue_bulk_tx(struct cdnsp_device *pdev, struct cdnsp_request *preq)
{
        unsigned int enqd_len, block_len, trb_buff_len, full_len;
        unsigned int start_cycle, num_sgs = 0;
        struct cdnsp_generic_trb *start_trb;
        u32 field, length_field, remainder;
        struct scatterlist *sg = NULL;
        bool more_trbs_coming = true;
        bool need_zero_pkt = false;
        bool zero_len_trb = false;
        struct cdnsp_ring *ring;
        bool first_trb = true;
        unsigned int num_trbs;
        struct cdnsp_ep *pep;
        u64 addr, send_addr;
        int sent_len, ret;

        ring = cdnsp_request_to_transfer_ring(pdev, preq);
        if (!ring)
                return -EINVAL;

        full_len = preq->request.length;

        if (preq->request.num_sgs) {
                num_sgs = preq->request.num_sgs;
                sg = preq->request.sg;
                addr = (u64)sg_dma_address(sg);
                block_len = sg_dma_len(sg);
                num_trbs = count_sg_trbs_needed(preq);
        } else {
                num_trbs = count_trbs_needed(preq);
                addr = (u64)preq->request.dma;
                block_len = full_len;
        }

        pep = preq->pep;

        /* Deal with request.zero - need one more td/trb. */
        if (preq->request.zero && preq->request.length &&
            IS_ALIGNED(full_len, usb_endpoint_maxp(pep->endpoint.desc))) {
                need_zero_pkt = true;
                num_trbs++;
        }

        ret = cdnsp_prepare_transfer(pdev, preq, num_trbs);
        if (ret)
                return ret;

        /*
         * Don't give the first TRB to the hardware (by toggling the cycle bit)
         * until we've finished creating all the other TRBs. The ring's cycle
         * state may change as we enqueue the other TRBs, so save it too.
         */
        start_trb = &ring->enqueue->generic;
        start_cycle = ring->cycle_state;
        send_addr = addr;

        /* Queue the TRBs, even if they are zero-length */
        for (enqd_len = 0; zero_len_trb || first_trb || enqd_len < full_len;
             enqd_len += trb_buff_len) {
                field = TRB_TYPE(TRB_NORMAL);

                /* TRB buffer should not cross 64KB boundaries */
                trb_buff_len = TRB_BUFF_LEN_UP_TO_BOUNDARY(addr);
                trb_buff_len = min(trb_buff_len, block_len);
                if (enqd_len + trb_buff_len > full_len)
                        trb_buff_len = full_len - enqd_len;

                /* Don't change the cycle bit of the first TRB until later */
                if (first_trb) {
                        first_trb = false;
                        if (start_cycle == 0)
                                field |= TRB_CYCLE;
                } else {
                        field |= ring->cycle_state;
                }

                /*
                 * Chain all the TRBs together; clear the chain bit in the last
                 * TRB to indicate it's the last TRB in the chain.
                 */
                if (enqd_len + trb_buff_len < full_len || need_zero_pkt) {
                        field |= TRB_CHAIN;
                        if (cdnsp_trb_is_link(ring->enqueue + 1)) {
                                if (cdnsp_align_td(pdev, preq, enqd_len,
                                                   &trb_buff_len,
                                                   ring->enq_seg)) {
                                        send_addr = ring->enq_seg->bounce_dma;
                                        /* Assuming TD won't span 2 segs */
                                        preq->td.bounce_seg = ring->enq_seg;
                                }
                        }
                }

                if (enqd_len + trb_buff_len >= full_len) {
                        if (need_zero_pkt && !zero_len_trb) {
                                zero_len_trb = true;
                        } else {
                                zero_len_trb = false;
                                field &= ~TRB_CHAIN;
                                field |= TRB_IOC;
                                more_trbs_coming = false;
                                need_zero_pkt = false;
                                preq->td.last_trb = ring->enqueue;
                        }
                }

                /* Only set interrupt on short packet for OUT endpoints. */
                if (!preq->direction)
                        field |= TRB_ISP;

                /* Set the TRB length, TD size, and interrupter fields. */
                remainder = cdnsp_td_remainder(pdev, enqd_len, trb_buff_len,
                                               full_len, preq,
                                               more_trbs_coming,
                                               zero_len_trb);

                length_field = TRB_LEN(trb_buff_len) | TRB_TD_SIZE(remainder) |
                        TRB_INTR_TARGET(0);

                cdnsp_queue_trb(pdev, ring, more_trbs_coming,
                                lower_32_bits(send_addr),
                                upper_32_bits(send_addr),
                                length_field,
                                field);

                addr += trb_buff_len;
                sent_len = trb_buff_len;
                while (sg && sent_len >= block_len) {
                        /* New sg entry */
                        --num_sgs;
                        sent_len -= block_len;
                        if (num_sgs != 0) {
                                sg = sg_next(sg);
                                block_len = sg_dma_len(sg);
                                addr = (u64)sg_dma_address(sg);
                                addr += sent_len;
                        }
                }
                block_len -= sent_len;
                send_addr = addr;
        }

        cdnsp_check_trb_math(preq, enqd_len);
        ret = cdnsp_giveback_first_trb(pdev, pep, preq->request.stream_id,
                                       start_cycle, start_trb);

        if (ret)
                preq->td.drbl = 1;

        return 0;
}

int cdnsp_queue_ctrl_tx(struct cdnsp_device *pdev, struct cdnsp_request *preq)
{
        u32 field, length_field, zlp = 0;
        struct cdnsp_ep *pep = preq->pep;
        struct cdnsp_ring *ep_ring;
        int num_trbs;
        u32 maxp;
        int ret;

        ep_ring = cdnsp_request_to_transfer_ring(pdev, preq);
        if (!ep_ring)
                return -EINVAL;

        /* 1 TRB for data, 1 for status */
        num_trbs = (pdev->three_stage_setup) ? 2 : 1;

        maxp = usb_endpoint_maxp(pep->endpoint.desc);

        if (preq->request.zero && preq->request.length &&
            (preq->request.length % maxp == 0)) {
                num_trbs++;
                zlp = 1;
        }

        ret = cdnsp_prepare_transfer(pdev, preq, num_trbs);
        if (ret)
                return ret;

        /* If there's data, queue data TRBs */
        if (preq->request.length > 0) {
                field = TRB_TYPE(TRB_DATA);

                if (zlp)
                        field |= TRB_CHAIN;
                else
                        field |= TRB_IOC | (pdev->ep0_expect_in ? 0 : TRB_ISP);

                if (pdev->ep0_expect_in)
                        field |= TRB_DIR_IN;

                length_field = TRB_LEN(preq->request.length) |
                               TRB_TD_SIZE(zlp) | TRB_INTR_TARGET(0);

                cdnsp_queue_trb(pdev, ep_ring, true,
                                lower_32_bits(preq->request.dma),
                                upper_32_bits(preq->request.dma), length_field,
                                field | ep_ring->cycle_state |
                                TRB_SETUPID(pdev->setup_id) |
                                pdev->setup_speed);

                if (zlp) {
                        field = TRB_TYPE(TRB_NORMAL) | TRB_IOC;

                        if (!pdev->ep0_expect_in)
                                field = TRB_ISP;

                        cdnsp_queue_trb(pdev, ep_ring, true,
                                        lower_32_bits(preq->request.dma),
                                        upper_32_bits(preq->request.dma), 0,
                                        field | ep_ring->cycle_state |
                                        TRB_SETUPID(pdev->setup_id) |
                                        pdev->setup_speed);
                }

                pdev->ep0_stage = CDNSP_DATA_STAGE;
        }

        /* Save the DMA address of the last TRB in the TD. */
        preq->td.last_trb = ep_ring->enqueue;

        /* Queue status TRB. */
        if (preq->request.length == 0)
                field = ep_ring->cycle_state;
        else
                field = (ep_ring->cycle_state ^ 1);

        if (preq->request.length > 0 && pdev->ep0_expect_in)
                field |= TRB_DIR_IN;

        if (pep->ep_state & EP0_HALTED_STATUS) {
                pep->ep_state &= ~EP0_HALTED_STATUS;
                field |= TRB_SETUPSTAT(TRB_SETUPSTAT_STALL);
        } else {
                field |= TRB_SETUPSTAT(TRB_SETUPSTAT_ACK);
        }

        cdnsp_queue_trb(pdev, ep_ring, false, 0, 0, TRB_INTR_TARGET(0),
                        field | TRB_IOC | TRB_SETUPID(pdev->setup_id) |
                        TRB_TYPE(TRB_STATUS) | pdev->setup_speed);

        cdnsp_ring_ep_doorbell(pdev, pep, preq->request.stream_id);

        return 0;
}

int cdnsp_cmd_stop_ep(struct cdnsp_device *pdev, struct cdnsp_ep *pep)
{
        u32 ep_state = GET_EP_CTX_STATE(pep->out_ctx);
        int ret = 0;

        if (ep_state == EP_STATE_STOPPED || ep_state == EP_STATE_DISABLED ||
            ep_state == EP_STATE_HALTED) {
                trace_cdnsp_ep_stopped_or_disabled(pep->out_ctx);
                goto ep_stopped;
        }

        cdnsp_queue_stop_endpoint(pdev, pep->idx);
        cdnsp_ring_cmd_db(pdev);
        ret = cdnsp_wait_for_cmd_compl(pdev);

        trace_cdnsp_handle_cmd_stop_ep(pep->out_ctx);

ep_stopped:
        pep->ep_state |= EP_STOPPED;
        return ret;
}

/*
 * The transfer burst count field of the isochronous TRB defines the number of
 * bursts that are required to move all packets in this TD. Only SuperSpeed
 * devices can burst up to bMaxBurst number of packets per service interval.
 * This field is zero based, meaning a value of zero in the field means one
 * burst. Basically, for everything but SuperSpeed devices, this field will be
 * zero.
 */
static unsigned int cdnsp_get_burst_count(struct cdnsp_device *pdev,
                                          struct cdnsp_request *preq,
                                          unsigned int total_packet_count)
{
        unsigned int max_burst;

        if (pdev->gadget.speed < USB_SPEED_SUPER)
                return 0;

        max_burst = preq->pep->endpoint.comp_desc->bMaxBurst;
        return DIV_ROUND_UP(total_packet_count, max_burst + 1) - 1;
}

/*
 * Returns the number of packets in the last "burst" of packets. This field is
 * valid for all speeds of devices. USB 2.0 devices can only do one "burst", so
 * the last burst packet count is equal to the total number of packets in the
 * TD. SuperSpeed endpoints can have up to 3 bursts. All but the last burst
 * must contain (bMaxBurst + 1) number of packets, but the last burst can
 * contain 1 to (bMaxBurst + 1) packets.
 */
static unsigned int
        cdnsp_get_last_burst_packet_count(struct cdnsp_device *pdev,
                                          struct cdnsp_request *preq,
                                          unsigned int total_packet_count)
{
        unsigned int max_burst;
        unsigned int residue;

        if (pdev->gadget.speed >= USB_SPEED_SUPER) {
                /* bMaxBurst is zero based: 0 means 1 packet per burst. */
                max_burst = preq->pep->endpoint.comp_desc->bMaxBurst;
                residue = total_packet_count % (max_burst + 1);

                /*
                 * If residue is zero, the last burst contains (max_burst + 1)
                 * number of packets, but the TLBPC field is zero-based.
                 */
                if (residue == 0)
                        return max_burst;

                return residue - 1;
        }
        if (total_packet_count == 0)
                return 0;

        return total_packet_count - 1;
}

/* Queue function isoc transfer */
int cdnsp_queue_isoc_tx(struct cdnsp_device *pdev,
                        struct cdnsp_request *preq)
{
        unsigned int trb_buff_len, td_len, td_remain_len, block_len;
        unsigned int burst_count, last_burst_pkt;
        unsigned int total_pkt_count, max_pkt;
        struct cdnsp_generic_trb *start_trb;
        struct scatterlist *sg = NULL;
        bool more_trbs_coming = true;
        struct cdnsp_ring *ep_ring;
        unsigned int num_sgs = 0;
        int running_total = 0;
        u32 field, length_field;
        u64 addr, send_addr;
        int start_cycle;
        int trbs_per_td;
        int i, sent_len, ret;

        ep_ring = preq->pep->ring;

        td_len = preq->request.length;

        if (preq->request.num_sgs) {
                num_sgs = preq->request.num_sgs;
                sg = preq->request.sg;
                addr = (u64)sg_dma_address(sg);
                block_len = sg_dma_len(sg);
                trbs_per_td = count_sg_trbs_needed(preq);
        } else {
                addr = (u64)preq->request.dma;
                block_len = td_len;
                trbs_per_td = count_trbs_needed(preq);
        }

        ret = cdnsp_prepare_transfer(pdev, preq, trbs_per_td);
        if (ret)
                return ret;

        start_trb = &ep_ring->enqueue->generic;
        start_cycle = ep_ring->cycle_state;
        td_remain_len = td_len;
        send_addr = addr;

        max_pkt = usb_endpoint_maxp(preq->pep->endpoint.desc);
        total_pkt_count = DIV_ROUND_UP(td_len, max_pkt);

        /* A zero-length transfer still involves at least one packet. */
        if (total_pkt_count == 0)
                total_pkt_count++;

        burst_count = cdnsp_get_burst_count(pdev, preq, total_pkt_count);
        last_burst_pkt = cdnsp_get_last_burst_packet_count(pdev, preq,
                                                           total_pkt_count);

        /*
         * Set isoc specific data for the first TRB in a TD.
         * Prevent HW from getting the TRBs by keeping the cycle state
         * inverted in the first TDs isoc TRB.
         */
        field = TRB_TYPE(TRB_ISOC) | TRB_TLBPC(last_burst_pkt) |
                TRB_SIA | TRB_TBC(burst_count);

        if (!start_cycle)
                field |= TRB_CYCLE;

        /* Fill the rest of the TRB fields, and remaining normal TRBs. */
        for (i = 0; i < trbs_per_td; i++) {
                u32 remainder;

                /* Calculate TRB length. */
                trb_buff_len = TRB_BUFF_LEN_UP_TO_BOUNDARY(addr);
                trb_buff_len = min(trb_buff_len, block_len);
                if (trb_buff_len > td_remain_len)
                        trb_buff_len = td_remain_len;

                /* Set the TRB length, TD size, & interrupter fields. */
                remainder = cdnsp_td_remainder(pdev, running_total,
                                               trb_buff_len, td_len, preq,
                                               more_trbs_coming, 0);

                length_field = TRB_LEN(trb_buff_len) | TRB_TD_SIZE(remainder) |
                        TRB_INTR_TARGET(0);

                /* Only first TRB is isoc, overwrite otherwise. */
                if (i) {
                        field = TRB_TYPE(TRB_NORMAL) | ep_ring->cycle_state;
                        length_field |= TRB_TD_SIZE(remainder);
                } else {
                        length_field |= TRB_TD_SIZE_TBC(burst_count);
                }

                /* Only set interrupt on short packet for OUT EPs. */
                if (usb_endpoint_dir_out(preq->pep->endpoint.desc))
                        field |= TRB_ISP;

                /* Set the chain bit for all except the last TRB. */
                if (i < trbs_per_td - 1) {
                        more_trbs_coming = true;
                        field |= TRB_CHAIN;
                } else {
                        more_trbs_coming = false;
                        preq->td.last_trb = ep_ring->enqueue;
                        field |= TRB_IOC;
                }

                cdnsp_queue_trb(pdev, ep_ring, more_trbs_coming,
                                lower_32_bits(send_addr), upper_32_bits(send_addr),
                                length_field, field);

                running_total += trb_buff_len;
                addr += trb_buff_len;
                td_remain_len -= trb_buff_len;

                sent_len = trb_buff_len;
                while (sg && sent_len >= block_len) {
                        /* New sg entry */
                        --num_sgs;
                        sent_len -= block_len;
                        if (num_sgs != 0) {
                                sg = sg_next(sg);
                                block_len = sg_dma_len(sg);
                                addr = (u64)sg_dma_address(sg);
                                addr += sent_len;
                        }
                }
                block_len -= sent_len;
                send_addr = addr;
        }

        /* Check TD length */
        if (running_total != td_len) {
                dev_err(pdev->dev, "ISOC TD length unmatch\n");
                ret = -EINVAL;
                goto cleanup;
        }

        cdnsp_giveback_first_trb(pdev, preq->pep, preq->request.stream_id,
                                 start_cycle, start_trb);

        return 0;

cleanup:
        /* Clean up a partially enqueued isoc transfer. */
        list_del_init(&preq->td.td_list);
        ep_ring->num_tds--;

        /*
         * Use the first TD as a temporary variable to turn the TDs we've
         * queued into No-ops with a software-owned cycle bit.
         * That way the hardware won't accidentally start executing bogus TDs
         * when we partially overwrite them.
         * td->first_trb and td->start_seg are already set.
         */
        preq->td.last_trb = ep_ring->enqueue;
        /* Every TRB except the first & last will have its cycle bit flipped. */
        cdnsp_td_to_noop(pdev, ep_ring, &preq->td, true);

        /* Reset the ring enqueue back to the first TRB and its cycle bit. */
        ep_ring->enqueue = preq->td.first_trb;
        ep_ring->enq_seg = preq->td.start_seg;
        ep_ring->cycle_state = start_cycle;
        return ret;
}

/****           Command Ring Operations         ****/
/*
 * Generic function for queuing a command TRB on the command ring.
 * Driver queue only one command to ring in the moment.
 */
static void cdnsp_queue_command(struct cdnsp_device *pdev,
                                u32 field1,
                                u32 field2,
                                u32 field3,
                                u32 field4)
{
        cdnsp_prepare_ring(pdev, pdev->cmd_ring, EP_STATE_RUNNING, 1,
                           GFP_ATOMIC);

        pdev->cmd.command_trb = pdev->cmd_ring->enqueue;

        cdnsp_queue_trb(pdev, pdev->cmd_ring, false, field1, field2,
                        field3, field4 | pdev->cmd_ring->cycle_state);
}

/* Queue a slot enable or disable request on the command ring */
void cdnsp_queue_slot_control(struct cdnsp_device *pdev, u32 trb_type)
{
        cdnsp_queue_command(pdev, 0, 0, 0, TRB_TYPE(trb_type) |
                            SLOT_ID_FOR_TRB(pdev->slot_id));
}

/* Queue an address device command TRB */
void cdnsp_queue_address_device(struct cdnsp_device *pdev,
                                dma_addr_t in_ctx_ptr,
                                enum cdnsp_setup_dev setup)
{
        cdnsp_queue_command(pdev, lower_32_bits(in_ctx_ptr),
                            upper_32_bits(in_ctx_ptr), 0,
                            TRB_TYPE(TRB_ADDR_DEV) |
                            SLOT_ID_FOR_TRB(pdev->slot_id) |
                            (setup == SETUP_CONTEXT_ONLY ? TRB_BSR : 0));
}

/* Queue a reset device command TRB */
void cdnsp_queue_reset_device(struct cdnsp_device *pdev)
{
        cdnsp_queue_command(pdev, 0, 0, 0, TRB_TYPE(TRB_RESET_DEV) |
                            SLOT_ID_FOR_TRB(pdev->slot_id));
}

/* Queue a configure endpoint command TRB */
void cdnsp_queue_configure_endpoint(struct cdnsp_device *pdev,
                                    dma_addr_t in_ctx_ptr)
{
        cdnsp_queue_command(pdev, lower_32_bits(in_ctx_ptr),
                            upper_32_bits(in_ctx_ptr), 0,
                            TRB_TYPE(TRB_CONFIG_EP) |
                            SLOT_ID_FOR_TRB(pdev->slot_id));
}

/*
 * Suspend is set to indicate "Stop Endpoint Command" is being issued to stop
 * activity on an endpoint that is about to be suspended.
 */
void cdnsp_queue_stop_endpoint(struct cdnsp_device *pdev, unsigned int ep_index)
{
        cdnsp_queue_command(pdev, 0, 0, 0, SLOT_ID_FOR_TRB(pdev->slot_id) |
                            EP_ID_FOR_TRB(ep_index) | TRB_TYPE(TRB_STOP_RING));
}

/* Set Transfer Ring Dequeue Pointer command. */
void cdnsp_queue_new_dequeue_state(struct cdnsp_device *pdev,
                                   struct cdnsp_ep *pep,
                                   struct cdnsp_dequeue_state *deq_state)
{
        u32 trb_stream_id = STREAM_ID_FOR_TRB(deq_state->stream_id);
        u32 trb_slot_id = SLOT_ID_FOR_TRB(pdev->slot_id);
        u32 type = TRB_TYPE(TRB_SET_DEQ);
        u32 trb_sct = 0;
        dma_addr_t addr;

        addr = cdnsp_trb_virt_to_dma(deq_state->new_deq_seg,
                                     deq_state->new_deq_ptr);

        if (deq_state->stream_id)
                trb_sct = SCT_FOR_TRB(SCT_PRI_TR);

        cdnsp_queue_command(pdev, lower_32_bits(addr) | trb_sct |
                            deq_state->new_cycle_state, upper_32_bits(addr),
                            trb_stream_id, trb_slot_id |
                            EP_ID_FOR_TRB(pep->idx) | type);
}

void cdnsp_queue_reset_ep(struct cdnsp_device *pdev, unsigned int ep_index)
{
        return cdnsp_queue_command(pdev, 0, 0, 0,
                                   SLOT_ID_FOR_TRB(pdev->slot_id) |
                                   EP_ID_FOR_TRB(ep_index) |
                                   TRB_TYPE(TRB_RESET_EP));
}

/*
 * Queue a halt endpoint request on the command ring.
 */
void cdnsp_queue_halt_endpoint(struct cdnsp_device *pdev, unsigned int ep_index)
{
        cdnsp_queue_command(pdev, 0, 0, 0, TRB_TYPE(TRB_HALT_ENDPOINT) |
                            SLOT_ID_FOR_TRB(pdev->slot_id) |
                            EP_ID_FOR_TRB(ep_index));
}

void cdnsp_force_header_wakeup(struct cdnsp_device *pdev, int intf_num)
{
        u32 lo, mid;

        lo = TRB_FH_TO_PACKET_TYPE(TRB_FH_TR_PACKET) |
             TRB_FH_TO_DEVICE_ADDRESS(pdev->device_address);
        mid = TRB_FH_TR_PACKET_DEV_NOT |
              TRB_FH_TO_NOT_TYPE(TRB_FH_TR_PACKET_FUNCTION_WAKE) |
              TRB_FH_TO_INTERFACE(intf_num);

        cdnsp_queue_command(pdev, lo, mid, 0,
                            TRB_TYPE(TRB_FORCE_HEADER) | SET_PORT_ID(2));
}