// SPDX-License-Identifier: GPL-2.0+
/*
 * USB HOST XHCI Controller stack
 *
 * Based on xHCI host controller driver in linux-kernel
 * by Sarah Sharp.
 *
 * Copyright (C) 2008 Intel Corp.
 * Author: Sarah Sharp
 *
 * Copyright (C) 2013 Samsung Electronics Co.Ltd
 * Authors: Vivek Gautam <gautam.vivek@samsung.com>
 *          Vikas Sajjan <vikas.sajjan@samsung.com>
 */

#include <common.h>
#include <cpu_func.h>
#include <log.h>
#include <asm/byteorder.h>
#include <usb.h>
#include <asm/unaligned.h>
#include <linux/bug.h>
#include <linux/errno.h>

#include <usb/xhci.h>

/**
 * Is this TRB a link TRB or was the last TRB the last TRB in this event ring
 * segment?  I.e. would the updated event TRB pointer step off the end of the
 * event seg ?
 *
 * @param ctrl  Host controller data structure
 * @param ring  pointer to the ring
 * @param seg   poniter to the segment to which TRB belongs
 * @param trb   poniter to the ring trb
 * @return 1 if this TRB a link TRB else 0
 */
static int last_trb(struct xhci_ctrl *ctrl, struct xhci_ring *ring,
                        struct xhci_segment *seg, union xhci_trb *trb)
{
        if (ring == ctrl->event_ring)
                return trb == &seg->trbs[TRBS_PER_SEGMENT];
        else
                return TRB_TYPE_LINK_LE32(trb->link.control);
}

/**
 * Does this link TRB point to the first segment in a ring,
 * or was the previous TRB the last TRB on the last segment in the ERST?
 *
 * @param ctrl  Host controller data structure
 * @param ring  pointer to the ring
 * @param seg   poniter to the segment to which TRB belongs
 * @param trb   poniter to the ring trb
 * @return 1 if this TRB is the last TRB on the last segment else 0
 */
static bool last_trb_on_last_seg(struct xhci_ctrl *ctrl,
                                 struct xhci_ring *ring,
                                 struct xhci_segment *seg,
                                 union xhci_trb *trb)
{
        if (ring == ctrl->event_ring)
                return ((trb == &seg->trbs[TRBS_PER_SEGMENT]) &&
                        (seg->next == ring->first_seg));
        else
                return le32_to_cpu(trb->link.control) & LINK_TOGGLE;
}

/**
 * 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).
 *
 * Section 6.4.4.1 of the 0.95 spec says link TRBs cannot have the chain bit
 * set, but other sections talk about dealing with the chain bit set.  This was
 * fixed in the 0.96 specification errata, but we have to assume that all 0.95
 * xHCI hardware can't handle the chain bit being cleared on a link TRB.
 *
 * @param ctrl  Host controller data structure
 * @param ring  pointer to the ring
 * @param more_trbs_coming      flag to indicate whether more trbs
 *                              are expected or NOT.
 *                              Will you enqueue more TRBs before calling
 *                              prepare_ring()?
 * @return none
 */
static void inc_enq(struct xhci_ctrl *ctrl, struct xhci_ring *ring,
                                                bool more_trbs_coming)
{
        u32 chain;
        union xhci_trb *next;

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

        /*
         * Update the dequeue pointer further if that was a link TRB or we're at
         * the end of an event ring segment (which doesn't have link TRBS)
         */
        while (last_trb(ctrl, ring, ring->enq_seg, next)) {
                if (ring != ctrl->event_ring) {
                        /*
                         * If the caller doesn't plan on enqueueing 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 prepare_ring() just before we enqueue
                         * the TD at the top of the ring.
                         */
                        if (!chain && !more_trbs_coming)
                                break;

                        /*
                         * If we're not dealing with 0.95 hardware or
                         * isoc rings on AMD 0.96 host,
                         * carry over the chain bit of the previous TRB
                         * (which may mean the chain bit is cleared).
                         */
                        next->link.control &= cpu_to_le32(~TRB_CHAIN);
                        next->link.control |= cpu_to_le32(chain);

                        next->link.control ^= cpu_to_le32(TRB_CYCLE);
                        xhci_flush_cache((uintptr_t)next,
                                         sizeof(union xhci_trb));
                }
                /* Toggle the cycle bit after the last ring segment. */
                if (last_trb_on_last_seg(ctrl, ring,
                                        ring->enq_seg, next))
                        ring->cycle_state = (ring->cycle_state ? 0 : 1);

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

/**
 * 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.
 *
 * @param ctrl  Host controller data structure
 * @param ring  Ring whose Dequeue TRB pointer needs to be incremented.
 * return none
 */
static void inc_deq(struct xhci_ctrl *ctrl, struct xhci_ring *ring)
{
        do {
                /*
                 * Update the dequeue pointer further if that was a link TRB or
                 * we're at the end of an event ring segment (which doesn't have
                 * link TRBS)
                 */
                if (last_trb(ctrl, ring, ring->deq_seg, ring->dequeue)) {
                        if (ring == ctrl->event_ring &&
                                        last_trb_on_last_seg(ctrl, ring,
                                                ring->deq_seg, ring->dequeue)) {
                                ring->cycle_state = (ring->cycle_state ? 0 : 1);
                        }
                        ring->deq_seg = ring->deq_seg->next;
                        ring->dequeue = ring->deq_seg->trbs;
                } else {
                        ring->dequeue++;
                }
        } while (last_trb(ctrl, ring, ring->deq_seg, ring->dequeue));
}

/**
 * Generic function for queueing a TRB on a ring.
 * The caller must have checked to make sure there's room on the ring.
 *
 * @param       more_trbs_coming:   Will you enqueue more TRBs before calling
 *                              prepare_ring()?
 * @param ctrl  Host controller data structure
 * @param ring  pointer to the ring
 * @param more_trbs_coming      flag to indicate whether more trbs
 * @param trb_fields    pointer to trb field array containing TRB contents
 * @return pointer to the enqueued trb
 */
static struct xhci_generic_trb *queue_trb(struct xhci_ctrl *ctrl,
                                          struct xhci_ring *ring,
                                          bool more_trbs_coming,
                                          unsigned int *trb_fields)
{
        struct xhci_generic_trb *trb;
        int i;

        trb = &ring->enqueue->generic;

        for (i = 0; i < 4; i++)
                trb->field[i] = cpu_to_le32(trb_fields[i]);

        xhci_flush_cache((uintptr_t)trb, sizeof(struct xhci_generic_trb));

        inc_enq(ctrl, ring, more_trbs_coming);

        return trb;
}

/**
 * Does various checks on the endpoint ring, and makes it ready
 * to queue num_trbs.
 *
 * @param ctrl          Host controller data structure
 * @param ep_ring       pointer to the EP Transfer Ring
 * @param ep_state      State of the End Point
 * @return error code in case of invalid ep_state, 0 on success
 */
static int prepare_ring(struct xhci_ctrl *ctrl, struct xhci_ring *ep_ring,
                                                        u32 ep_state)
{
        union xhci_trb *next = ep_ring->enqueue;

        /* Make sure the endpoint has been added to xHC schedule */
        switch (ep_state) {
        case EP_STATE_DISABLED:
                /*
                 * USB core changed config/interfaces without notifying us,
                 * or hardware is reporting the wrong state.
                 */
                puts("WARN urb submitted to disabled ep\n");
                return -ENOENT;
        case EP_STATE_ERROR:
                puts("WARN waiting for error on ep to be cleared\n");
                return -EINVAL;
        case EP_STATE_HALTED:
                puts("WARN halted endpoint, queueing URB anyway.\n");
        case EP_STATE_STOPPED:
        case EP_STATE_RUNNING:
                debug("EP STATE RUNNING.\n");
                break;
        default:
                puts("ERROR unknown endpoint state for ep\n");
                return -EINVAL;
        }

        while (last_trb(ctrl, ep_ring, ep_ring->enq_seg, next)) {
                /*
                 * If we're not dealing with 0.95 hardware or isoc rings
                 * on AMD 0.96 host, clear the chain bit.
                 */
                next->link.control &= cpu_to_le32(~TRB_CHAIN);

                next->link.control ^= cpu_to_le32(TRB_CYCLE);

                xhci_flush_cache((uintptr_t)next, sizeof(union xhci_trb));

                /* Toggle the cycle bit after the last ring segment. */
                if (last_trb_on_last_seg(ctrl, ep_ring,
                                        ep_ring->enq_seg, next))
                        ep_ring->cycle_state = (ep_ring->cycle_state ? 0 : 1);
                ep_ring->enq_seg = ep_ring->enq_seg->next;
                ep_ring->enqueue = ep_ring->enq_seg->trbs;
                next = ep_ring->enqueue;
        }

        return 0;
}

/**
 * Generic function for queueing a command TRB on the command ring.
 * Check to make sure there's room on the command ring for one command TRB.
 *
 * @param ctrl          Host controller data structure
 * @param ptr           Pointer address to write in the first two fields (opt.)
 * @param slot_id       Slot ID to encode in the flags field (opt.)
 * @param ep_index      Endpoint index to encode in the flags field (opt.)
 * @param cmd           Command type to enqueue
 * @return none
 */
void xhci_queue_command(struct xhci_ctrl *ctrl, u8 *ptr, u32 slot_id,
                        u32 ep_index, trb_type cmd)
{
        u32 fields[4];
        u64 val_64 = 0;

        BUG_ON(prepare_ring(ctrl, ctrl->cmd_ring, EP_STATE_RUNNING));

        if (ptr)
                val_64 = xhci_virt_to_bus(ctrl, ptr);

        fields[0] = lower_32_bits(val_64);
        fields[1] = upper_32_bits(val_64);
        fields[2] = 0;
        fields[3] = TRB_TYPE(cmd) | SLOT_ID_FOR_TRB(slot_id) |
                    ctrl->cmd_ring->cycle_state;

        /*
         * Only 'reset endpoint', 'stop endpoint' and 'set TR dequeue pointer'
         * commands need endpoint id encoded.
         */
        if (cmd >= TRB_RESET_EP && cmd <= TRB_SET_DEQ)
                fields[3] |= EP_ID_FOR_TRB(ep_index);

        queue_trb(ctrl, ctrl->cmd_ring, false, fields);

        /* Ring the command ring doorbell */
        xhci_writel(&ctrl->dba->doorbell[0], DB_VALUE_HOST);
}

/*
 * For xHCI 1.0 host controllers, 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
 *
 * For xHCI 0.96 and older, TD size field should be the remaining bytes
 * including this TRB, right shifted by 10
 *
 * For all hosts 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.
 *
 * @param ctrl  host controller data structure
 * @param transferred   total size sent so far
 * @param trb_buff_len  length of the TRB Buffer
 * @param td_total_len  total packet count
 * @param maxp  max packet size of current pipe
 * @param more_trbs_coming      indicate last trb in TD
 * @return remainder
 */
static u32 xhci_td_remainder(struct xhci_ctrl *ctrl, int transferred,
                             int trb_buff_len, unsigned int td_total_len,
                             int maxp, bool more_trbs_coming)
{
        u32 total_packet_count;

        /* MTK xHCI 0.96 contains some features from 1.0 */
        if (ctrl->hci_version < 0x100 && !(ctrl->quirks & XHCI_MTK_HOST))
                return ((td_total_len - transferred) >> 10);

        /* 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;

        /* for MTK xHCI 0.96, TD size include this TRB, but not in 1.x */
        if ((ctrl->quirks & XHCI_MTK_HOST) && (ctrl->hci_version < 0x100))
                trb_buff_len = 0;

        total_packet_count = DIV_ROUND_UP(td_total_len, maxp);

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

/**
 * Ring the doorbell of the End Point
 *
 * @param udev          pointer to the USB device structure
 * @param ep_index      index of the endpoint
 * @param start_cycle   cycle flag of the first TRB
 * @param start_trb     pionter to the first TRB
 * @return none
 */
static void giveback_first_trb(struct usb_device *udev, int ep_index,
                                int start_cycle,
                                struct xhci_generic_trb *start_trb)
{
        struct xhci_ctrl *ctrl = xhci_get_ctrl(udev);

        /*
         * Pass all the TRBs to the hardware at once and make sure this write
         * isn't reordered.
         */
        if (start_cycle)
                start_trb->field[3] |= cpu_to_le32(start_cycle);
        else
                start_trb->field[3] &= cpu_to_le32(~TRB_CYCLE);

        xhci_flush_cache((uintptr_t)start_trb, sizeof(struct xhci_generic_trb));

        /* Ringing EP doorbell here */
        xhci_writel(&ctrl->dba->doorbell[udev->slot_id],
                                DB_VALUE(ep_index, 0));

        return;
}

/**** POLLING mechanism for XHCI ****/

/**
 * Finalizes a handled event TRB by advancing our dequeue pointer and giving
 * the TRB back to the hardware for recycling. Must call this exactly once at
 * the end of each event handler, and not touch the TRB again afterwards.
 *
 * @param ctrl  Host controller data structure
 * @return none
 */
void xhci_acknowledge_event(struct xhci_ctrl *ctrl)
{
        /* Advance our dequeue pointer to the next event */
        inc_deq(ctrl, ctrl->event_ring);

        /* Inform the hardware */
        xhci_writeq(&ctrl->ir_set->erst_dequeue,
                    xhci_virt_to_bus(ctrl, ctrl->event_ring->dequeue) | ERST_EHB);
}

/**
 * Checks if there is a new event to handle on the event ring.
 *
 * @param ctrl  Host controller data structure
 * @return 0 if failure else 1 on success
 */
static int event_ready(struct xhci_ctrl *ctrl)
{
        union xhci_trb *event;

        xhci_inval_cache((uintptr_t)ctrl->event_ring->dequeue,
                         sizeof(union xhci_trb));

        event = ctrl->event_ring->dequeue;

        /* Does the HC or OS own the TRB? */
        if ((le32_to_cpu(event->event_cmd.flags) & TRB_CYCLE) !=
                ctrl->event_ring->cycle_state)
                return 0;

        return 1;
}

/**
 * Waits for a specific type of event and returns it. Discards unexpected
 * events. Caller *must* call xhci_acknowledge_event() after it is finished
 * processing the event, and must not access the returned pointer afterwards.
 *
 * @param ctrl          Host controller data structure
 * @param expected      TRB type expected from Event TRB
 * @return pointer to event trb
 */
union xhci_trb *xhci_wait_for_event(struct xhci_ctrl *ctrl, trb_type expected)
{
        trb_type type;
        unsigned long ts = get_timer(0);

        do {
                union xhci_trb *event = ctrl->event_ring->dequeue;

                if (!event_ready(ctrl))
                        continue;

                type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->event_cmd.flags));
                if (type == expected)
                        return event;

                if (type == TRB_PORT_STATUS)
                /* TODO: remove this once enumeration has been reworked */
                        /*
                         * Port status change events always have a
                         * successful completion code
                         */
                        BUG_ON(GET_COMP_CODE(
                                le32_to_cpu(event->generic.field[2])) !=
                                                                COMP_SUCCESS);
                else
                        printf("Unexpected XHCI event TRB, skipping... "
                                "(%08x %08x %08x %08x)\n",
                                le32_to_cpu(event->generic.field[0]),
                                le32_to_cpu(event->generic.field[1]),
                                le32_to_cpu(event->generic.field[2]),
                                le32_to_cpu(event->generic.field[3]));

                xhci_acknowledge_event(ctrl);
        } while (get_timer(ts) < XHCI_TIMEOUT);

        if (expected == TRB_TRANSFER)
                return NULL;

        printf("XHCI timeout on event type %d... cannot recover.\n", expected);
        BUG();
}

/*
 * Stops transfer processing for an endpoint and throws away all unprocessed
 * TRBs by setting the xHC's dequeue pointer to our enqueue pointer. The next
 * xhci_bulk_tx/xhci_ctrl_tx on this enpoint will add new transfers there and
 * ring the doorbell, causing this endpoint to start working again.
 * (Careful: This will BUG() when there was no transfer in progress. Shouldn't
 * happen in practice for current uses and is too complicated to fix right now.)
 */
static void abort_td(struct usb_device *udev, int ep_index)
{
        struct xhci_ctrl *ctrl = xhci_get_ctrl(udev);
        struct xhci_ring *ring =  ctrl->devs[udev->slot_id]->eps[ep_index].ring;
        union xhci_trb *event;
        u32 field;

        xhci_queue_command(ctrl, NULL, udev->slot_id, ep_index, TRB_STOP_RING);

        event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
        field = le32_to_cpu(event->trans_event.flags);
        BUG_ON(TRB_TO_SLOT_ID(field) != udev->slot_id);
        BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);
        BUG_ON(GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len
                != COMP_STOP)));
        xhci_acknowledge_event(ctrl);

        event = xhci_wait_for_event(ctrl, TRB_COMPLETION);
        BUG_ON(TRB_TO_SLOT_ID(le32_to_cpu(event->event_cmd.flags))
                != udev->slot_id || GET_COMP_CODE(le32_to_cpu(
                event->event_cmd.status)) != COMP_SUCCESS);
        xhci_acknowledge_event(ctrl);

        xhci_queue_command(ctrl, (void *)((uintptr_t)ring->enqueue |
                ring->cycle_state), udev->slot_id, ep_index, TRB_SET_DEQ);
        event = xhci_wait_for_event(ctrl, TRB_COMPLETION);
        BUG_ON(TRB_TO_SLOT_ID(le32_to_cpu(event->event_cmd.flags))
                != udev->slot_id || GET_COMP_CODE(le32_to_cpu(
                event->event_cmd.status)) != COMP_SUCCESS);
        xhci_acknowledge_event(ctrl);
}

static void record_transfer_result(struct usb_device *udev,
                                   union xhci_trb *event, int length)
{
        udev->act_len = min(length, length -
                (int)EVENT_TRB_LEN(le32_to_cpu(event->trans_event.transfer_len)));

        switch (GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len))) {
        case COMP_SUCCESS:
                BUG_ON(udev->act_len != length);
                /* fallthrough */
        case COMP_SHORT_TX:
                udev->status = 0;
                break;
        case COMP_STALL:
                udev->status = USB_ST_STALLED;
                break;
        case COMP_DB_ERR:
        case COMP_TRB_ERR:
                udev->status = USB_ST_BUF_ERR;
                break;
        case COMP_BABBLE:
                udev->status = USB_ST_BABBLE_DET;
                break;
        default:
                udev->status = 0x80;  /* USB_ST_TOO_LAZY_TO_MAKE_A_NEW_MACRO */
        }
}

/**** Bulk and Control transfer methods ****/
/**
 * Queues up the BULK Request
 *
 * @param udev          pointer to the USB device structure
 * @param pipe          contains the DIR_IN or OUT , devnum
 * @param length        length of the buffer
 * @param buffer        buffer to be read/written based on the request
 * @return returns 0 if successful else -1 on failure
 */
int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
                        int length, void *buffer)
{
        int num_trbs = 0;
        struct xhci_generic_trb *start_trb;
        bool first_trb = false;
        int start_cycle;
        u32 field = 0;
        u32 length_field = 0;
        struct xhci_ctrl *ctrl = xhci_get_ctrl(udev);
        int slot_id = udev->slot_id;
        int ep_index;
        struct xhci_virt_device *virt_dev;
        struct xhci_ep_ctx *ep_ctx;
        struct xhci_ring *ring;         /* EP transfer ring */
        union xhci_trb *event;

        int running_total, trb_buff_len;
        bool more_trbs_coming = true;
        int maxpacketsize;
        u64 addr;
        int ret;
        u32 trb_fields[4];
        u64 val_64 = xhci_virt_to_bus(ctrl, buffer);
        void *last_transfer_trb_addr;
        int available_length;

        debug("dev=%p, pipe=%lx, buffer=%p, length=%d\n",
                udev, pipe, buffer, length);

        available_length = length;
        ep_index = usb_pipe_ep_index(pipe);
        virt_dev = ctrl->devs[slot_id];

        xhci_inval_cache((uintptr_t)virt_dev->out_ctx->bytes,
                         virt_dev->out_ctx->size);

        ep_ctx = xhci_get_ep_ctx(ctrl, virt_dev->out_ctx, ep_index);

        ring = virt_dev->eps[ep_index].ring;
        /*
         * How much data is (potentially) left before the 64KB boundary?
         * XHCI Spec puts restriction( TABLE 49 and 6.4.1 section of XHCI Spec)
         * that the buffer should not span 64KB boundary. if so
         * we send request in more than 1 TRB by chaining them.
         */
        running_total = TRB_MAX_BUFF_SIZE -
                        (lower_32_bits(val_64) & (TRB_MAX_BUFF_SIZE - 1));
        trb_buff_len = running_total;
        running_total &= TRB_MAX_BUFF_SIZE - 1;

        /*
         * If there's some data on this 64KB chunk, or we have to send a
         * zero-length transfer, we need at least one TRB
         */
        if (running_total != 0 || length == 0)
                num_trbs++;

        /* How many more 64KB chunks to transfer, how many more TRBs? */
        while (running_total < length) {
                num_trbs++;
                running_total += TRB_MAX_BUFF_SIZE;
        }

        /*
         * XXX: Calling routine prepare_ring() called in place of
         * prepare_trasfer() as there in 'Linux' since we are not
         * maintaining multiple TDs/transfer at the same time.
         */
        ret = prepare_ring(ctrl, ring,
                           le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK);
        if (ret < 0)
                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;

        running_total = 0;
        maxpacketsize = usb_maxpacket(udev, pipe);

        /* How much data is in the first TRB? */
        /*
         * How much data is (potentially) left before the 64KB boundary?
         * XHCI Spec puts restriction( TABLE 49 and 6.4.1 section of XHCI Spec)
         * that the buffer should not span 64KB boundary. if so
         * we send request in more than 1 TRB by chaining them.
         */
        addr = val_64;

        if (trb_buff_len > length)
                trb_buff_len = length;

        first_trb = true;

        /* flush the buffer before use */
        xhci_flush_cache((uintptr_t)buffer, length);

        /* Queue the first TRB, even if it's zero-length */
        do {
                u32 remainder = 0;
                field = 0;
                /* 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 (num_trbs > 1) {
                        field |= TRB_CHAIN;
                } else {
                        field |= TRB_IOC;
                        more_trbs_coming = false;
                }

                /* Only set interrupt on short packet for IN endpoints */
                if (usb_pipein(pipe))
                        field |= TRB_ISP;

                /* Set the TRB length, TD size, and interrupter fields. */
                remainder = xhci_td_remainder(ctrl, running_total, trb_buff_len,
                                              length, maxpacketsize,
                                              more_trbs_coming);

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

                trb_fields[0] = lower_32_bits(addr);
                trb_fields[1] = upper_32_bits(addr);
                trb_fields[2] = length_field;
                trb_fields[3] = field | TRB_TYPE(TRB_NORMAL);

                last_transfer_trb_addr = queue_trb(ctrl, ring, (num_trbs > 1), trb_fields);

                --num_trbs;

                running_total += trb_buff_len;

                /* Calculate length for next transfer */
                addr += trb_buff_len;
                trb_buff_len = min((length - running_total), TRB_MAX_BUFF_SIZE);
        } while (running_total < length);

        giveback_first_trb(udev, ep_index, start_cycle, start_trb);

again:
        event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
        if (!event) {
                debug("XHCI bulk transfer timed out, aborting...\n");
                abort_td(udev, ep_index);
                udev->status = USB_ST_NAK_REC;  /* closest thing to a timeout */
                udev->act_len = 0;
                return -ETIMEDOUT;
        }

        if ((uintptr_t)(le64_to_cpu(event->trans_event.buffer)) !=
            (uintptr_t)xhci_virt_to_bus(ctrl, last_transfer_trb_addr)) {
                available_length -=
                        (int)EVENT_TRB_LEN(le32_to_cpu(event->trans_event.transfer_len));
                xhci_acknowledge_event(ctrl);
                goto again;
        }

        field = le32_to_cpu(event->trans_event.flags);
        BUG_ON(TRB_TO_SLOT_ID(field) != slot_id);
        BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);

        record_transfer_result(udev, event, available_length);
        xhci_acknowledge_event(ctrl);
        xhci_inval_cache((uintptr_t)buffer, length);

        return (udev->status != USB_ST_NOT_PROC) ? 0 : -1;
}

/**
 * Queues up the Control Transfer Request
 *
 * @param udev  pointer to the USB device structure
 * @param pipe          contains the DIR_IN or OUT , devnum
 * @param req           request type
 * @param length        length of the buffer
 * @param buffer        buffer to be read/written based on the request
 * @return returns 0 if successful else error code on failure
 */
int xhci_ctrl_tx(struct usb_device *udev, unsigned long pipe,
                        struct devrequest *req, int length,
                        void *buffer)
{
        int ret;
        int start_cycle;
        int num_trbs;
        u32 field;
        u32 length_field;
        u64 buf_64 = 0;
        struct xhci_generic_trb *start_trb;
        struct xhci_ctrl *ctrl = xhci_get_ctrl(udev);
        int slot_id = udev->slot_id;
        int ep_index;
        u32 trb_fields[4];
        struct xhci_virt_device *virt_dev = ctrl->devs[slot_id];
        struct xhci_ring *ep_ring;
        union xhci_trb *event;
        u32 remainder;

        debug("req=%u (%#x), type=%u (%#x), value=%u (%#x), index=%u\n",
                req->request, req->request,
                req->requesttype, req->requesttype,
                le16_to_cpu(req->value), le16_to_cpu(req->value),
                le16_to_cpu(req->index));

        ep_index = usb_pipe_ep_index(pipe);

        ep_ring = virt_dev->eps[ep_index].ring;

        /*
         * Check to see if the max packet size for the default control
         * endpoint changed during FS device enumeration
         */
        if (udev->speed == USB_SPEED_FULL) {
                ret = xhci_check_maxpacket(udev);
                if (ret < 0)
                        return ret;
        }

        xhci_inval_cache((uintptr_t)virt_dev->out_ctx->bytes,
                         virt_dev->out_ctx->size);

        struct xhci_ep_ctx *ep_ctx = NULL;
        ep_ctx = xhci_get_ep_ctx(ctrl, virt_dev->out_ctx, ep_index);

        /* 1 TRB for setup, 1 for status */
        num_trbs = 2;
        /*
         * Don't need to check if we need additional event data and normal TRBs,
         * since data in control transfers will never get bigger than 16MB
         * XXX: can we get a buffer that crosses 64KB boundaries?
         */

        if (length > 0)
                num_trbs++;
        /*
         * XXX: Calling routine prepare_ring() called in place of
         * prepare_trasfer() as there in 'Linux' since we are not
         * maintaining multiple TDs/transfer at the same time.
         */
        ret = prepare_ring(ctrl, ep_ring,
                                le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK);

        if (ret < 0)
                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 = &ep_ring->enqueue->generic;
        start_cycle = ep_ring->cycle_state;

        debug("start_trb %p, start_cycle %d\n", start_trb, start_cycle);

        /* Queue setup TRB - see section 6.4.1.2.1 */
        /* FIXME better way to translate setup_packet into two u32 fields? */
        field = 0;
        field |= TRB_IDT | TRB_TYPE(TRB_SETUP);
        if (start_cycle == 0)
                field |= 0x1;

        /* xHCI 1.0 6.4.1.2.1: Transfer Type field */
        if (ctrl->hci_version >= 0x100 || ctrl->quirks & XHCI_MTK_HOST) {
                if (length > 0) {
                        if (req->requesttype & USB_DIR_IN)
                                field |= TRB_TX_TYPE(TRB_DATA_IN);
                        else
                                field |= TRB_TX_TYPE(TRB_DATA_OUT);
                }
        }

        debug("req->requesttype = %d, req->request = %d, req->value = %d, req->index = %d, req->length = %d\n",
              req->requesttype, req->request, le16_to_cpu(req->value),
              le16_to_cpu(req->index), le16_to_cpu(req->length));

        trb_fields[0] = req->requesttype | req->request << 8 |
                                le16_to_cpu(req->value) << 16;
        trb_fields[1] = le16_to_cpu(req->index) |
                        le16_to_cpu(req->length) << 16;
        /* TRB_LEN | (TRB_INTR_TARGET) */
        trb_fields[2] = (TRB_LEN(8) | TRB_INTR_TARGET(0));
        /* Immediate data in pointer */
        trb_fields[3] = field;
        queue_trb(ctrl, ep_ring, true, trb_fields);

        /* Re-initializing field to zero */
        field = 0;
        /* If there's data, queue data TRBs */
        /* Only set interrupt on short packet for IN endpoints */
        if (usb_pipein(pipe))
                field = TRB_ISP | TRB_TYPE(TRB_DATA);
        else
                field = TRB_TYPE(TRB_DATA);

        remainder = xhci_td_remainder(ctrl, 0, length, length,
                                      usb_maxpacket(udev, pipe), true);
        length_field = TRB_LEN(length) | TRB_TD_SIZE(remainder) |
                       TRB_INTR_TARGET(0);
        debug("length_field = %d, length = %d,"
                "xhci_td_remainder(length) = %d , TRB_INTR_TARGET(0) = %d\n",
                length_field, TRB_LEN(length),
                TRB_TD_SIZE(remainder), 0);

        if (length > 0) {
                if (req->requesttype & USB_DIR_IN)
                        field |= TRB_DIR_IN;
                buf_64 = xhci_virt_to_bus(ctrl, buffer);

                trb_fields[0] = lower_32_bits(buf_64);
                trb_fields[1] = upper_32_bits(buf_64);
                trb_fields[2] = length_field;
                trb_fields[3] = field | ep_ring->cycle_state;

                xhci_flush_cache((uintptr_t)buffer, length);
                queue_trb(ctrl, ep_ring, true, trb_fields);
        }

        /*
         * Queue status TRB -
         * see Table 7 and sections 4.11.2.2 and 6.4.1.2.3
         */

        /* If the device sent data, the status stage is an OUT transfer */
        field = 0;
        if (length > 0 && req->requesttype & USB_DIR_IN)
                field = 0;
        else
                field = TRB_DIR_IN;

        trb_fields[0] = 0;
        trb_fields[1] = 0;
        trb_fields[2] = TRB_INTR_TARGET(0);
                /* Event on completion */
        trb_fields[3] = field | TRB_IOC |
                        TRB_TYPE(TRB_STATUS) | ep_ring->cycle_state;

        queue_trb(ctrl, ep_ring, false, trb_fields);

        giveback_first_trb(udev, ep_index, start_cycle, start_trb);

        event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
        if (!event)
                goto abort;
        field = le32_to_cpu(event->trans_event.flags);

        BUG_ON(TRB_TO_SLOT_ID(field) != slot_id);
        BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);

        record_transfer_result(udev, event, length);
        xhci_acknowledge_event(ctrl);

        /* Invalidate buffer to make it available to usb-core */
        if (length > 0)
                xhci_inval_cache((uintptr_t)buffer, length);

        if (GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len))
                        == COMP_SHORT_TX) {
                /* Short data stage, clear up additional status stage event */
                event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
                if (!event)
                        goto abort;
                BUG_ON(TRB_TO_SLOT_ID(field) != slot_id);
                BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);
                xhci_acknowledge_event(ctrl);
        }

        return (udev->status != USB_ST_NOT_PROC) ? 0 : -1;

abort:
        debug("XHCI control transfer timed out, aborting...\n");
        abort_td(udev, ep_index);
        udev->status = USB_ST_NAK_REC;
        udev->act_len = 0;
        return -ETIMEDOUT;
}