Linux 4.2.1

[linux/fpc-iii.git] / drivers / usb / host / whci / qset.c

/*
 * Wireless Host Controller (WHC) qset management.
 *
 * Copyright (C) 2007 Cambridge Silicon Radio Ltd.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/kernel.h>
#include <linux/dma-mapping.h>
#include <linux/slab.h>
#include <linux/uwb/umc.h>
#include <linux/usb.h>

#include "../../wusbcore/wusbhc.h"

#include "whcd.h"

struct whc_qset *qset_alloc(struct whc *whc, gfp_t mem_flags)
{
        struct whc_qset *qset;
        dma_addr_t dma;

        qset = dma_pool_alloc(whc->qset_pool, mem_flags, &dma);
        if (qset == NULL)
                return NULL;
        memset(qset, 0, sizeof(struct whc_qset));

        qset->qset_dma = dma;
        qset->whc = whc;

        INIT_LIST_HEAD(&qset->list_node);
        INIT_LIST_HEAD(&qset->stds);

        return qset;
}

/**
 * qset_fill_qh - fill the static endpoint state in a qset's QHead
 * @qset: the qset whose QH needs initializing with static endpoint
 *        state
 * @urb:  an urb for a transfer to this endpoint
 */
static void qset_fill_qh(struct whc *whc, struct whc_qset *qset, struct urb *urb)
{
        struct usb_device *usb_dev = urb->dev;
        struct wusb_dev *wusb_dev = usb_dev->wusb_dev;
        struct usb_wireless_ep_comp_descriptor *epcd;
        bool is_out;
        uint8_t phy_rate;

        is_out = usb_pipeout(urb->pipe);

        qset->max_packet = le16_to_cpu(urb->ep->desc.wMaxPacketSize);

        epcd = (struct usb_wireless_ep_comp_descriptor *)qset->ep->extra;
        if (epcd) {
                qset->max_seq = epcd->bMaxSequence;
                qset->max_burst = epcd->bMaxBurst;
        } else {
                qset->max_seq = 2;
                qset->max_burst = 1;
        }

        /*
         * Initial PHY rate is 53.3 Mbit/s for control endpoints or
         * the maximum supported by the device for other endpoints
         * (unless limited by the user).
         */
        if (usb_pipecontrol(urb->pipe))
                phy_rate = UWB_PHY_RATE_53;
        else {
                uint16_t phy_rates;

                phy_rates = le16_to_cpu(wusb_dev->wusb_cap_descr->wPHYRates);
                phy_rate = fls(phy_rates) - 1;
                if (phy_rate > whc->wusbhc.phy_rate)
                        phy_rate = whc->wusbhc.phy_rate;
        }

        qset->qh.info1 = cpu_to_le32(
                QH_INFO1_EP(usb_pipeendpoint(urb->pipe))
                | (is_out ? QH_INFO1_DIR_OUT : QH_INFO1_DIR_IN)
                | usb_pipe_to_qh_type(urb->pipe)
                | QH_INFO1_DEV_INFO_IDX(wusb_port_no_to_idx(usb_dev->portnum))
                | QH_INFO1_MAX_PKT_LEN(qset->max_packet)
                );
        qset->qh.info2 = cpu_to_le32(
                QH_INFO2_BURST(qset->max_burst)
                | QH_INFO2_DBP(0)
                | QH_INFO2_MAX_COUNT(3)
                | QH_INFO2_MAX_RETRY(3)
                | QH_INFO2_MAX_SEQ(qset->max_seq - 1)
                );
        /* FIXME: where can we obtain these Tx parameters from?  Why
         * doesn't the chip know what Tx power to use? It knows the Rx
         * strength and can presumably guess the Tx power required
         * from that? */
        qset->qh.info3 = cpu_to_le32(
                QH_INFO3_TX_RATE(phy_rate)
                | QH_INFO3_TX_PWR(0) /* 0 == max power */
                );

        qset->qh.cur_window = cpu_to_le32((1 << qset->max_burst) - 1);
}

/**
 * qset_clear - clear fields in a qset so it may be reinserted into a
 * schedule.
 *
 * The sequence number and current window are not cleared (see
 * qset_reset()).
 */
void qset_clear(struct whc *whc, struct whc_qset *qset)
{
        qset->td_start = qset->td_end = qset->ntds = 0;

        qset->qh.link = cpu_to_le64(QH_LINK_NTDS(8) | QH_LINK_T);
        qset->qh.status = qset->qh.status & QH_STATUS_SEQ_MASK;
        qset->qh.err_count = 0;
        qset->qh.scratch[0] = 0;
        qset->qh.scratch[1] = 0;
        qset->qh.scratch[2] = 0;

        memset(&qset->qh.overlay, 0, sizeof(qset->qh.overlay));

        init_completion(&qset->remove_complete);
}

/**
 * qset_reset - reset endpoint state in a qset.
 *
 * Clears the sequence number and current window.  This qset must not
 * be in the ASL or PZL.
 */
void qset_reset(struct whc *whc, struct whc_qset *qset)
{
        qset->reset = 0;

        qset->qh.status &= ~QH_STATUS_SEQ_MASK;
        qset->qh.cur_window = cpu_to_le32((1 << qset->max_burst) - 1);
}

/**
 * get_qset - get the qset for an async endpoint
 *
 * A new qset is created if one does not already exist.
 */
struct whc_qset *get_qset(struct whc *whc, struct urb *urb,
                                 gfp_t mem_flags)
{
        struct whc_qset *qset;

        qset = urb->ep->hcpriv;
        if (qset == NULL) {
                qset = qset_alloc(whc, mem_flags);
                if (qset == NULL)
                        return NULL;

                qset->ep = urb->ep;
                urb->ep->hcpriv = qset;
                qset_fill_qh(whc, qset, urb);
        }
        return qset;
}

void qset_remove_complete(struct whc *whc, struct whc_qset *qset)
{
        qset->remove = 0;
        list_del_init(&qset->list_node);
        complete(&qset->remove_complete);
}

/**
 * qset_add_qtds - add qTDs for an URB to a qset
 *
 * Returns true if the list (ASL/PZL) must be updated because (for a
 * WHCI 0.95 controller) an activated qTD was pointed to be iCur.
 */
enum whc_update qset_add_qtds(struct whc *whc, struct whc_qset *qset)
{
        struct whc_std *std;
        enum whc_update update = 0;

        list_for_each_entry(std, &qset->stds, list_node) {
                struct whc_qtd *qtd;
                uint32_t status;

                if (qset->ntds >= WHCI_QSET_TD_MAX
                    || (qset->pause_after_urb && std->urb != qset->pause_after_urb))
                        break;

                if (std->qtd)
                        continue; /* already has a qTD */

                qtd = std->qtd = &qset->qtd[qset->td_end];

                /* Fill in setup bytes for control transfers. */
                if (usb_pipecontrol(std->urb->pipe))
                        memcpy(qtd->setup, std->urb->setup_packet, 8);

                status = QTD_STS_ACTIVE | QTD_STS_LEN(std->len);

                if (whc_std_last(std) && usb_pipeout(std->urb->pipe))
                        status |= QTD_STS_LAST_PKT;

                /*
                 * For an IN transfer the iAlt field should be set so
                 * the h/w will automatically advance to the next
                 * transfer. However, if there are 8 or more TDs
                 * remaining in this transfer then iAlt cannot be set
                 * as it could point to somewhere in this transfer.
                 */
                if (std->ntds_remaining < WHCI_QSET_TD_MAX) {
                        int ialt;
                        ialt = (qset->td_end + std->ntds_remaining) % WHCI_QSET_TD_MAX;
                        status |= QTD_STS_IALT(ialt);
                } else if (usb_pipein(std->urb->pipe))
                        qset->pause_after_urb = std->urb;

                if (std->num_pointers)
                        qtd->options = cpu_to_le32(QTD_OPT_IOC);
                else
                        qtd->options = cpu_to_le32(QTD_OPT_IOC | QTD_OPT_SMALL);
                qtd->page_list_ptr = cpu_to_le64(std->dma_addr);

                qtd->status = cpu_to_le32(status);

                if (QH_STATUS_TO_ICUR(qset->qh.status) == qset->td_end)
                        update = WHC_UPDATE_UPDATED;

                if (++qset->td_end >= WHCI_QSET_TD_MAX)
                        qset->td_end = 0;
                qset->ntds++;
        }

        return update;
}

/**
 * qset_remove_qtd - remove the first qTD from a qset.
 *
 * The qTD might be still active (if it's part of a IN URB that
 * resulted in a short read) so ensure it's deactivated.
 */
static void qset_remove_qtd(struct whc *whc, struct whc_qset *qset)
{
        qset->qtd[qset->td_start].status = 0;

        if (++qset->td_start >= WHCI_QSET_TD_MAX)
                qset->td_start = 0;
        qset->ntds--;
}

static void qset_copy_bounce_to_sg(struct whc *whc, struct whc_std *std)
{
        struct scatterlist *sg;
        void *bounce;
        size_t remaining, offset;

        bounce = std->bounce_buf;
        remaining = std->len;

        sg = std->bounce_sg;
        offset = std->bounce_offset;

        while (remaining) {
                size_t len;

                len = min(sg->length - offset, remaining);
                memcpy(sg_virt(sg) + offset, bounce, len);

                bounce += len;
                remaining -= len;

                offset += len;
                if (offset >= sg->length) {
                        sg = sg_next(sg);
                        offset = 0;
                }
        }

}

/**
 * qset_free_std - remove an sTD and free it.
 * @whc: the WHCI host controller
 * @std: the sTD to remove and free.
 */
void qset_free_std(struct whc *whc, struct whc_std *std)
{
        list_del(&std->list_node);
        if (std->bounce_buf) {
                bool is_out = usb_pipeout(std->urb->pipe);
                dma_addr_t dma_addr;

                if (std->num_pointers)
                        dma_addr = le64_to_cpu(std->pl_virt[0].buf_ptr);
                else
                        dma_addr = std->dma_addr;

                dma_unmap_single(whc->wusbhc.dev, dma_addr,
                                 std->len, is_out ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
                if (!is_out)
                        qset_copy_bounce_to_sg(whc, std);
                kfree(std->bounce_buf);
        }
        if (std->pl_virt) {
                if (std->dma_addr)
                        dma_unmap_single(whc->wusbhc.dev, std->dma_addr,
                                         std->num_pointers * sizeof(struct whc_page_list_entry),
                                         DMA_TO_DEVICE);
                kfree(std->pl_virt);
                std->pl_virt = NULL;
        }
        kfree(std);
}

/**
 * qset_remove_qtds - remove an URB's qTDs (and sTDs).
 */
static void qset_remove_qtds(struct whc *whc, struct whc_qset *qset,
                             struct urb *urb)
{
        struct whc_std *std, *t;

        list_for_each_entry_safe(std, t, &qset->stds, list_node) {
                if (std->urb != urb)
                        break;
                if (std->qtd != NULL)
                        qset_remove_qtd(whc, qset);
                qset_free_std(whc, std);
        }
}

/**
 * qset_free_stds - free any remaining sTDs for an URB.
 */
static void qset_free_stds(struct whc_qset *qset, struct urb *urb)
{
        struct whc_std *std, *t;

        list_for_each_entry_safe(std, t, &qset->stds, list_node) {
                if (std->urb == urb)
                        qset_free_std(qset->whc, std);
        }
}

static int qset_fill_page_list(struct whc *whc, struct whc_std *std, gfp_t mem_flags)
{
        dma_addr_t dma_addr = std->dma_addr;
        dma_addr_t sp, ep;
        size_t pl_len;
        int p;

        /* Short buffers don't need a page list. */
        if (std->len <= WHCI_PAGE_SIZE) {
                std->num_pointers = 0;
                return 0;
        }

        sp = dma_addr & ~(WHCI_PAGE_SIZE-1);
        ep = dma_addr + std->len;
        std->num_pointers = DIV_ROUND_UP(ep - sp, WHCI_PAGE_SIZE);

        pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);
        std->pl_virt = kmalloc(pl_len, mem_flags);
        if (std->pl_virt == NULL)
                return -ENOMEM;
        std->dma_addr = dma_map_single(whc->wusbhc.dev, std->pl_virt, pl_len, DMA_TO_DEVICE);

        for (p = 0; p < std->num_pointers; p++) {
                std->pl_virt[p].buf_ptr = cpu_to_le64(dma_addr);
                dma_addr = (dma_addr + WHCI_PAGE_SIZE) & ~(WHCI_PAGE_SIZE-1);
        }

        return 0;
}

/**
 * urb_dequeue_work - executes asl/pzl update and gives back the urb to the system.
 */
static void urb_dequeue_work(struct work_struct *work)
{
        struct whc_urb *wurb = container_of(work, struct whc_urb, dequeue_work);
        struct whc_qset *qset = wurb->qset;
        struct whc *whc = qset->whc;
        unsigned long flags;

        if (wurb->is_async == true)
                asl_update(whc, WUSBCMD_ASYNC_UPDATED
                           | WUSBCMD_ASYNC_SYNCED_DB
                           | WUSBCMD_ASYNC_QSET_RM);
        else
                pzl_update(whc, WUSBCMD_PERIODIC_UPDATED
                           | WUSBCMD_PERIODIC_SYNCED_DB
                           | WUSBCMD_PERIODIC_QSET_RM);

        spin_lock_irqsave(&whc->lock, flags);
        qset_remove_urb(whc, qset, wurb->urb, wurb->status);
        spin_unlock_irqrestore(&whc->lock, flags);
}

static struct whc_std *qset_new_std(struct whc *whc, struct whc_qset *qset,
                                    struct urb *urb, gfp_t mem_flags)
{
        struct whc_std *std;

        std = kzalloc(sizeof(struct whc_std), mem_flags);
        if (std == NULL)
                return NULL;

        std->urb = urb;
        std->qtd = NULL;

        INIT_LIST_HEAD(&std->list_node);
        list_add_tail(&std->list_node, &qset->stds);

        return std;
}

static int qset_add_urb_sg(struct whc *whc, struct whc_qset *qset, struct urb *urb,
                           gfp_t mem_flags)
{
        size_t remaining;
        struct scatterlist *sg;
        int i;
        int ntds = 0;
        struct whc_std *std = NULL;
        struct whc_page_list_entry *new_pl_virt;
        dma_addr_t prev_end = 0;
        size_t pl_len;
        int p = 0;

        remaining = urb->transfer_buffer_length;

        for_each_sg(urb->sg, sg, urb->num_mapped_sgs, i) {
                dma_addr_t dma_addr;
                size_t dma_remaining;
                dma_addr_t sp, ep;
                int num_pointers;

                if (remaining == 0) {
                        break;
                }

                dma_addr = sg_dma_address(sg);
                dma_remaining = min_t(size_t, sg_dma_len(sg), remaining);

                while (dma_remaining) {
                        size_t dma_len;

                        /*
                         * We can use the previous std (if it exists) provided that:
                         * - the previous one ended on a page boundary.
                         * - the current one begins on a page boundary.
                         * - the previous one isn't full.
                         *
                         * If a new std is needed but the previous one
                         * was not a whole number of packets then this
                         * sg list cannot be mapped onto multiple
                         * qTDs.  Return an error and let the caller
                         * sort it out.
                         */
                        if (!std
                            || (prev_end & (WHCI_PAGE_SIZE-1))
                            || (dma_addr & (WHCI_PAGE_SIZE-1))
                            || std->len + WHCI_PAGE_SIZE > QTD_MAX_XFER_SIZE) {
                                if (std && std->len % qset->max_packet != 0)
                                        return -EINVAL;
                                std = qset_new_std(whc, qset, urb, mem_flags);
                                if (std == NULL) {
                                        return -ENOMEM;
                                }
                                ntds++;
                                p = 0;
                        }

                        dma_len = dma_remaining;

                        /*
                         * If the remainder of this element doesn't
                         * fit in a single qTD, limit the qTD to a
                         * whole number of packets.  This allows the
                         * remainder to go into the next qTD.
                         */
                        if (std->len + dma_len > QTD_MAX_XFER_SIZE) {
                                dma_len = (QTD_MAX_XFER_SIZE / qset->max_packet)
                                        * qset->max_packet - std->len;
                        }

                        std->len += dma_len;
                        std->ntds_remaining = -1; /* filled in later */

                        sp = dma_addr & ~(WHCI_PAGE_SIZE-1);
                        ep = dma_addr + dma_len;
                        num_pointers = DIV_ROUND_UP(ep - sp, WHCI_PAGE_SIZE);
                        std->num_pointers += num_pointers;

                        pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);

                        new_pl_virt = krealloc(std->pl_virt, pl_len, mem_flags);
                        if (new_pl_virt == NULL) {
                                kfree(std->pl_virt);
                                std->pl_virt = NULL;
                                return -ENOMEM;
                        }
                        std->pl_virt = new_pl_virt;

                        for (;p < std->num_pointers; p++) {
                                std->pl_virt[p].buf_ptr = cpu_to_le64(dma_addr);
                                dma_addr = (dma_addr + WHCI_PAGE_SIZE) & ~(WHCI_PAGE_SIZE-1);
                        }

                        prev_end = dma_addr = ep;
                        dma_remaining -= dma_len;
                        remaining -= dma_len;
                }
        }

        /* Now the number of stds is know, go back and fill in
           std->ntds_remaining. */
        list_for_each_entry(std, &qset->stds, list_node) {
                if (std->ntds_remaining == -1) {
                        pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);
                        std->ntds_remaining = ntds--;
                        std->dma_addr = dma_map_single(whc->wusbhc.dev, std->pl_virt,
                                                       pl_len, DMA_TO_DEVICE);
                }
        }
        return 0;
}

/**
 * qset_add_urb_sg_linearize - add an urb with sg list, copying the data
 *
 * If the URB contains an sg list whose elements cannot be directly
 * mapped to qTDs then the data must be transferred via bounce
 * buffers.
 */
static int qset_add_urb_sg_linearize(struct whc *whc, struct whc_qset *qset,
                                     struct urb *urb, gfp_t mem_flags)
{
        bool is_out = usb_pipeout(urb->pipe);
        size_t max_std_len;
        size_t remaining;
        int ntds = 0;
        struct whc_std *std = NULL;
        void *bounce = NULL;
        struct scatterlist *sg;
        int i;

        /* limit maximum bounce buffer to 16 * 3.5 KiB ~= 28 k */
        max_std_len = qset->max_burst * qset->max_packet;

        remaining = urb->transfer_buffer_length;

        for_each_sg(urb->sg, sg, urb->num_mapped_sgs, i) {
                size_t len;
                size_t sg_remaining;
                void *orig;

                if (remaining == 0) {
                        break;
                }

                sg_remaining = min_t(size_t, remaining, sg->length);
                orig = sg_virt(sg);

                while (sg_remaining) {
                        if (!std || std->len == max_std_len) {
                                std = qset_new_std(whc, qset, urb, mem_flags);
                                if (std == NULL)
                                        return -ENOMEM;
                                std->bounce_buf = kmalloc(max_std_len, mem_flags);
                                if (std->bounce_buf == NULL)
                                        return -ENOMEM;
                                std->bounce_sg = sg;
                                std->bounce_offset = orig - sg_virt(sg);
                                bounce = std->bounce_buf;
                                ntds++;
                        }

                        len = min(sg_remaining, max_std_len - std->len);

                        if (is_out)
                                memcpy(bounce, orig, len);

                        std->len += len;
                        std->ntds_remaining = -1; /* filled in later */

                        bounce += len;
                        orig += len;
                        sg_remaining -= len;
                        remaining -= len;
                }
        }

        /*
         * For each of the new sTDs, map the bounce buffers, create
         * page lists (if necessary), and fill in std->ntds_remaining.
         */
        list_for_each_entry(std, &qset->stds, list_node) {
                if (std->ntds_remaining != -1)
                        continue;

                std->dma_addr = dma_map_single(&whc->umc->dev, std->bounce_buf, std->len,
                                               is_out ? DMA_TO_DEVICE : DMA_FROM_DEVICE);

                if (qset_fill_page_list(whc, std, mem_flags) < 0)
                        return -ENOMEM;

                std->ntds_remaining = ntds--;
        }

        return 0;
}

/**
 * qset_add_urb - add an urb to the qset's queue.
 *
 * The URB is chopped into sTDs, one for each qTD that will required.
 * At least one qTD (and sTD) is required even if the transfer has no
 * data (e.g., for some control transfers).
 */
int qset_add_urb(struct whc *whc, struct whc_qset *qset, struct urb *urb,
        gfp_t mem_flags)
{
        struct whc_urb *wurb;
        int remaining = urb->transfer_buffer_length;
        u64 transfer_dma = urb->transfer_dma;
        int ntds_remaining;
        int ret;

        wurb = kzalloc(sizeof(struct whc_urb), mem_flags);
        if (wurb == NULL)
                goto err_no_mem;
        urb->hcpriv = wurb;
        wurb->qset = qset;
        wurb->urb = urb;
        INIT_WORK(&wurb->dequeue_work, urb_dequeue_work);

        if (urb->num_sgs) {
                ret = qset_add_urb_sg(whc, qset, urb, mem_flags);
                if (ret == -EINVAL) {
                        qset_free_stds(qset, urb);
                        ret = qset_add_urb_sg_linearize(whc, qset, urb, mem_flags);
                }
                if (ret < 0)
                        goto err_no_mem;
                return 0;
        }

        ntds_remaining = DIV_ROUND_UP(remaining, QTD_MAX_XFER_SIZE);
        if (ntds_remaining == 0)
                ntds_remaining = 1;

        while (ntds_remaining) {
                struct whc_std *std;
                size_t std_len;

                std_len = remaining;
                if (std_len > QTD_MAX_XFER_SIZE)
                        std_len = QTD_MAX_XFER_SIZE;

                std = qset_new_std(whc, qset, urb, mem_flags);
                if (std == NULL)
                        goto err_no_mem;

                std->dma_addr = transfer_dma;
                std->len = std_len;
                std->ntds_remaining = ntds_remaining;

                if (qset_fill_page_list(whc, std, mem_flags) < 0)
                        goto err_no_mem;

                ntds_remaining--;
                remaining -= std_len;
                transfer_dma += std_len;
        }

        return 0;

err_no_mem:
        qset_free_stds(qset, urb);
        return -ENOMEM;
}

/**
 * qset_remove_urb - remove an URB from the urb queue.
 *
 * The URB is returned to the USB subsystem.
 */
void qset_remove_urb(struct whc *whc, struct whc_qset *qset,
                            struct urb *urb, int status)
{
        struct wusbhc *wusbhc = &whc->wusbhc;
        struct whc_urb *wurb = urb->hcpriv;

        usb_hcd_unlink_urb_from_ep(&wusbhc->usb_hcd, urb);
        /* Drop the lock as urb->complete() may enqueue another urb. */
        spin_unlock(&whc->lock);
        wusbhc_giveback_urb(wusbhc, urb, status);
        spin_lock(&whc->lock);

        kfree(wurb);
}

/**
 * get_urb_status_from_qtd - get the completed urb status from qTD status
 * @urb:    completed urb
 * @status: qTD status
 */
static int get_urb_status_from_qtd(struct urb *urb, u32 status)
{
        if (status & QTD_STS_HALTED) {
                if (status & QTD_STS_DBE)
                        return usb_pipein(urb->pipe) ? -ENOSR : -ECOMM;
                else if (status & QTD_STS_BABBLE)
                        return -EOVERFLOW;
                else if (status & QTD_STS_RCE)
                        return -ETIME;
                return -EPIPE;
        }
        if (usb_pipein(urb->pipe)
            && (urb->transfer_flags & URB_SHORT_NOT_OK)
            && urb->actual_length < urb->transfer_buffer_length)
                return -EREMOTEIO;
        return 0;
}

/**
 * process_inactive_qtd - process an inactive (but not halted) qTD.
 *
 * Update the urb with the transfer bytes from the qTD, if the urb is
 * completely transferred or (in the case of an IN only) the LPF is
 * set, then the transfer is complete and the urb should be returned
 * to the system.
 */
void process_inactive_qtd(struct whc *whc, struct whc_qset *qset,
                                 struct whc_qtd *qtd)
{
        struct whc_std *std = list_first_entry(&qset->stds, struct whc_std, list_node);
        struct urb *urb = std->urb;
        uint32_t status;
        bool complete;

        status = le32_to_cpu(qtd->status);

        urb->actual_length += std->len - QTD_STS_TO_LEN(status);

        if (usb_pipein(urb->pipe) && (status & QTD_STS_LAST_PKT))
                complete = true;
        else
                complete = whc_std_last(std);

        qset_remove_qtd(whc, qset);
        qset_free_std(whc, std);

        /*
         * Transfers for this URB are complete?  Then return it to the
         * USB subsystem.
         */
        if (complete) {
                qset_remove_qtds(whc, qset, urb);
                qset_remove_urb(whc, qset, urb, get_urb_status_from_qtd(urb, status));

                /*
                 * If iAlt isn't valid then the hardware didn't
                 * advance iCur. Adjust the start and end pointers to
                 * match iCur.
                 */
                if (!(status & QTD_STS_IALT_VALID))
                        qset->td_start = qset->td_end
                                = QH_STATUS_TO_ICUR(le16_to_cpu(qset->qh.status));
                qset->pause_after_urb = NULL;
        }
}

/**
 * process_halted_qtd - process a qset with a halted qtd
 *
 * Remove all the qTDs for the failed URB and return the failed URB to
 * the USB subsystem.  Then remove all other qTDs so the qset can be
 * removed.
 *
 * FIXME: this is the point where rate adaptation can be done.  If a
 * transfer failed because it exceeded the maximum number of retries
 * then it could be reactivated with a slower rate without having to
 * remove the qset.
 */
void process_halted_qtd(struct whc *whc, struct whc_qset *qset,
                               struct whc_qtd *qtd)
{
        struct whc_std *std = list_first_entry(&qset->stds, struct whc_std, list_node);
        struct urb *urb = std->urb;
        int urb_status;

        urb_status = get_urb_status_from_qtd(urb, le32_to_cpu(qtd->status));

        qset_remove_qtds(whc, qset, urb);
        qset_remove_urb(whc, qset, urb, urb_status);

        list_for_each_entry(std, &qset->stds, list_node) {
                if (qset->ntds == 0)
                        break;
                qset_remove_qtd(whc, qset);
                std->qtd = NULL;
        }

        qset->remove = 1;
}

void qset_free(struct whc *whc, struct whc_qset *qset)
{
        dma_pool_free(whc->qset_pool, qset, qset->qset_dma);
}

/**
 * qset_delete - wait for a qset to be unused, then free it.
 */
void qset_delete(struct whc *whc, struct whc_qset *qset)
{
        wait_for_completion(&qset->remove_complete);
        qset_free(whc, qset);
}