// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2001-2004 by David Brownell
 * Copyright (c) 2003 Michal Sojka, for high-speed iso transfers
 */

/* this file is part of ehci-hcd.c */

/*-------------------------------------------------------------------------*/

/*
 * EHCI scheduled transaction support:  interrupt, iso, split iso
 * These are called "periodic" transactions in the EHCI spec.
 *
 * Note that for interrupt transfers, the QH/QTD manipulation is shared
 * with the "asynchronous" transaction support (control/bulk transfers).
 * The only real difference is in how interrupt transfers are scheduled.
 *
 * For ISO, we make an "iso_stream" head to serve the same role as a QH.
 * It keeps track of every ITD (or SITD) that's linked, and holds enough
 * pre-calculated schedule data to make appending to the queue be quick.
 */

static int ehci_get_frame(struct usb_hcd *hcd);

/*
 * periodic_next_shadow - return "next" pointer on shadow list
 * @periodic: host pointer to qh/itd/sitd
 * @tag: hardware tag for type of this record
 */
static union ehci_shadow *
periodic_next_shadow(struct ehci_hcd *ehci, union ehci_shadow *periodic,
                __hc32 tag)
{
        switch (hc32_to_cpu(ehci, tag)) {
        case Q_TYPE_QH:
                return &periodic->qh->qh_next;
        case Q_TYPE_FSTN:
                return &periodic->fstn->fstn_next;
        case Q_TYPE_ITD:
                return &periodic->itd->itd_next;
        /* case Q_TYPE_SITD: */
        default:
                return &periodic->sitd->sitd_next;
        }
}

static __hc32 *
shadow_next_periodic(struct ehci_hcd *ehci, union ehci_shadow *periodic,
                __hc32 tag)
{
        switch (hc32_to_cpu(ehci, tag)) {
        /* our ehci_shadow.qh is actually software part */
        case Q_TYPE_QH:
                return &periodic->qh->hw->hw_next;
        /* others are hw parts */
        default:
                return periodic->hw_next;
        }
}

/* caller must hold ehci->lock */
static void periodic_unlink(struct ehci_hcd *ehci, unsigned frame, void *ptr)
{
        union ehci_shadow       *prev_p = &ehci->pshadow[frame];
        __hc32                  *hw_p = &ehci->periodic[frame];
        union ehci_shadow       here = *prev_p;

        /* find predecessor of "ptr"; hw and shadow lists are in sync */
        while (here.ptr && here.ptr != ptr) {
                prev_p = periodic_next_shadow(ehci, prev_p,
                                Q_NEXT_TYPE(ehci, *hw_p));
                hw_p = shadow_next_periodic(ehci, &here,
                                Q_NEXT_TYPE(ehci, *hw_p));
                here = *prev_p;
        }
        /* an interrupt entry (at list end) could have been shared */
        if (!here.ptr)
                return;

        /* update shadow and hardware lists ... the old "next" pointers
         * from ptr may still be in use, the caller updates them.
         */
        *prev_p = *periodic_next_shadow(ehci, &here,
                        Q_NEXT_TYPE(ehci, *hw_p));

        if (!ehci->use_dummy_qh ||
            *shadow_next_periodic(ehci, &here, Q_NEXT_TYPE(ehci, *hw_p))
                        != EHCI_LIST_END(ehci))
                *hw_p = *shadow_next_periodic(ehci, &here,
                                Q_NEXT_TYPE(ehci, *hw_p));
        else
                *hw_p = cpu_to_hc32(ehci, ehci->dummy->qh_dma);
}

/*-------------------------------------------------------------------------*/

/* Bandwidth and TT management */

/* Find the TT data structure for this device; create it if necessary */
static struct ehci_tt *find_tt(struct usb_device *udev)
{
        struct usb_tt           *utt = udev->tt;
        struct ehci_tt          *tt, **tt_index, **ptt;
        unsigned                port;
        bool                    allocated_index = false;

        if (!utt)
                return NULL;            /* Not below a TT */

        /*
         * Find/create our data structure.
         * For hubs with a single TT, we get it directly.
         * For hubs with multiple TTs, there's an extra level of pointers.
         */
        tt_index = NULL;
        if (utt->multi) {
                tt_index = utt->hcpriv;
                if (!tt_index) {                /* Create the index array */
                        tt_index = kzalloc_objs(*tt_index, utt->hub->maxchild,
                                                GFP_ATOMIC);
                        if (!tt_index)
                                return ERR_PTR(-ENOMEM);
                        utt->hcpriv = tt_index;
                        allocated_index = true;
                }
                port = udev->ttport - 1;
                ptt = &tt_index[port];
        } else {
                port = 0;
                ptt = (struct ehci_tt **) &utt->hcpriv;
        }

        tt = *ptt;
        if (!tt) {                              /* Create the ehci_tt */
                struct ehci_hcd         *ehci =
                                hcd_to_ehci(bus_to_hcd(udev->bus));

                tt = kzalloc_obj(*tt, GFP_ATOMIC);
                if (!tt) {
                        if (allocated_index) {
                                utt->hcpriv = NULL;
                                kfree(tt_index);
                        }
                        return ERR_PTR(-ENOMEM);
                }
                list_add_tail(&tt->tt_list, &ehci->tt_list);
                INIT_LIST_HEAD(&tt->ps_list);
                tt->usb_tt = utt;
                tt->tt_port = port;
                *ptt = tt;
        }

        return tt;
}

/* Release the TT above udev, if it's not in use */
static void drop_tt(struct usb_device *udev)
{
        struct usb_tt           *utt = udev->tt;
        struct ehci_tt          *tt, **tt_index, **ptt;
        int                     cnt, i;

        if (!utt || !utt->hcpriv)
                return;         /* Not below a TT, or never allocated */

        cnt = 0;
        if (utt->multi) {
                tt_index = utt->hcpriv;
                ptt = &tt_index[udev->ttport - 1];

                /* How many entries are left in tt_index? */
                for (i = 0; i < utt->hub->maxchild; ++i)
                        cnt += !!tt_index[i];
        } else {
                tt_index = NULL;
                ptt = (struct ehci_tt **) &utt->hcpriv;
        }

        tt = *ptt;
        if (!tt || !list_empty(&tt->ps_list))
                return;         /* never allocated, or still in use */

        list_del(&tt->tt_list);
        *ptt = NULL;
        kfree(tt);
        if (cnt == 1) {
                utt->hcpriv = NULL;
                kfree(tt_index);
        }
}

static void bandwidth_dbg(struct ehci_hcd *ehci, int sign, char *type,
                struct ehci_per_sched *ps)
{
        dev_dbg(&ps->udev->dev,
                        "ep %02x: %s %s @ %u+%u (%u.%u+%u) [%u/%u us] mask %04x\n",
                        ps->ep->desc.bEndpointAddress,
                        (sign >= 0 ? "reserve" : "release"), type,
                        (ps->bw_phase << 3) + ps->phase_uf, ps->bw_uperiod,
                        ps->phase, ps->phase_uf, ps->period,
                        ps->usecs, ps->c_usecs, ps->cs_mask);
}

static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
                struct ehci_qh *qh, int sign)
{
        unsigned                start_uf;
        unsigned                i, j, m;
        int                     usecs = qh->ps.usecs;
        int                     c_usecs = qh->ps.c_usecs;
        int                     tt_usecs = qh->ps.tt_usecs;
        struct ehci_tt          *tt;

        if (qh->ps.phase == NO_FRAME)   /* Bandwidth wasn't reserved */
                return;
        start_uf = qh->ps.bw_phase << 3;

        bandwidth_dbg(ehci, sign, "intr", &qh->ps);

        if (sign < 0) {         /* Release bandwidth */
                usecs = -usecs;
                c_usecs = -c_usecs;
                tt_usecs = -tt_usecs;
        }

        /* Entire transaction (high speed) or start-split (full/low speed) */
        for (i = start_uf + qh->ps.phase_uf; i < EHCI_BANDWIDTH_SIZE;
                        i += qh->ps.bw_uperiod)
                ehci->bandwidth[i] += usecs;

        /* Complete-split (full/low speed) */
        if (qh->ps.c_usecs) {
                /* NOTE: adjustments needed for FSTN */
                for (i = start_uf; i < EHCI_BANDWIDTH_SIZE;
                                i += qh->ps.bw_uperiod) {
                        for ((j = 2, m = 1 << (j+8)); j < 8; (++j, m <<= 1)) {
                                if (qh->ps.cs_mask & m)
                                        ehci->bandwidth[i+j] += c_usecs;
                        }
                }
        }

        /* FS/LS bus bandwidth */
        if (tt_usecs) {
                /*
                 * find_tt() will not return any error here as we have
                 * already called find_tt() before calling this function
                 * and checked for any error return. The previous call
                 * would have created the data structure.
                 */
                tt = find_tt(qh->ps.udev);
                if (sign > 0)
                        list_add_tail(&qh->ps.ps_list, &tt->ps_list);
                else
                        list_del(&qh->ps.ps_list);

                for (i = start_uf >> 3; i < EHCI_BANDWIDTH_FRAMES;
                                i += qh->ps.bw_period)
                        tt->bandwidth[i] += tt_usecs;
        }
}

/*-------------------------------------------------------------------------*/

static void compute_tt_budget(u8 budget_table[EHCI_BANDWIDTH_SIZE],
                struct ehci_tt *tt)
{
        struct ehci_per_sched   *ps;
        unsigned                uframe, uf, x;
        u8                      *budget_line;

        if (!tt)
                return;
        memset(budget_table, 0, EHCI_BANDWIDTH_SIZE);

        /* Add up the contributions from all the endpoints using this TT */
        list_for_each_entry(ps, &tt->ps_list, ps_list) {
                for (uframe = ps->bw_phase << 3; uframe < EHCI_BANDWIDTH_SIZE;
                                uframe += ps->bw_uperiod) {
                        budget_line = &budget_table[uframe];
                        x = ps->tt_usecs;

                        /* propagate the time forward */
                        for (uf = ps->phase_uf; uf < 8; ++uf) {
                                x += budget_line[uf];

                                /* Each microframe lasts 125 us */
                                if (x <= 125) {
                                        budget_line[uf] = x;
                                        break;
                                }
                                budget_line[uf] = 125;
                                x -= 125;
                        }
                }
        }
}

static int __maybe_unused same_tt(struct usb_device *dev1,
                struct usb_device *dev2)
{
        if (!dev1->tt || !dev2->tt)
                return 0;
        if (dev1->tt != dev2->tt)
                return 0;
        if (dev1->tt->multi)
                return dev1->ttport == dev2->ttport;
        else
                return 1;
}

#ifdef CONFIG_USB_EHCI_TT_NEWSCHED

static const unsigned char
max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };

/* carryover low/fullspeed bandwidth that crosses uframe boundries */
static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])
{
        int i;

        for (i = 0; i < 7; i++) {
                if (max_tt_usecs[i] < tt_usecs[i]) {
                        tt_usecs[i+1] += tt_usecs[i] - max_tt_usecs[i];
                        tt_usecs[i] = max_tt_usecs[i];
                }
        }
}

/*
 * Return true if the device's tt's downstream bus is available for a
 * periodic transfer of the specified length (usecs), starting at the
 * specified frame/uframe.  Note that (as summarized in section 11.19
 * of the usb 2.0 spec) TTs can buffer multiple transactions for each
 * uframe.
 *
 * The uframe parameter is when the fullspeed/lowspeed transfer
 * should be executed in "B-frame" terms, which is the same as the
 * highspeed ssplit's uframe (which is in "H-frame" terms).  For example
 * a ssplit in "H-frame" 0 causes a transfer in "B-frame" 0.
 * See the EHCI spec sec 4.5 and fig 4.7.
 *
 * This checks if the full/lowspeed bus, at the specified starting uframe,
 * has the specified bandwidth available, according to rules listed
 * in USB 2.0 spec section 11.18.1 fig 11-60.
 *
 * This does not check if the transfer would exceed the max ssplit
 * limit of 16, specified in USB 2.0 spec section 11.18.4 requirement #4,
 * since proper scheduling limits ssplits to less than 16 per uframe.
 */
static int tt_available(
        struct ehci_hcd         *ehci,
        struct ehci_per_sched   *ps,
        struct ehci_tt          *tt,
        unsigned                frame,
        unsigned                uframe
)
{
        unsigned                period = ps->bw_period;
        unsigned                usecs = ps->tt_usecs;

        if ((period == 0) || (uframe >= 7))     /* error */
                return 0;

        for (frame &= period - 1; frame < EHCI_BANDWIDTH_FRAMES;
                        frame += period) {
                unsigned        i, uf;
                unsigned short  tt_usecs[8];

                if (tt->bandwidth[frame] + usecs > 900)
                        return 0;

                uf = frame << 3;
                for (i = 0; i < 8; (++i, ++uf))
                        tt_usecs[i] = ehci->tt_budget[uf];

                if (max_tt_usecs[uframe] <= tt_usecs[uframe])
                        return 0;

                /* special case for isoc transfers larger than 125us:
                 * the first and each subsequent fully used uframe
                 * must be empty, so as to not illegally delay
                 * already scheduled transactions
                 */
                if (usecs > 125) {
                        int ufs = (usecs / 125);

                        for (i = uframe; i < (uframe + ufs) && i < 8; i++)
                                if (tt_usecs[i] > 0)
                                        return 0;
                }

                tt_usecs[uframe] += usecs;

                carryover_tt_bandwidth(tt_usecs);

                /* fail if the carryover pushed bw past the last uframe's limit */
                if (max_tt_usecs[7] < tt_usecs[7])
                        return 0;
        }

        return 1;
}

#else

/* return true iff the device's transaction translator is available
 * for a periodic transfer starting at the specified frame, using
 * all the uframes in the mask.
 */
static int tt_no_collision(
        struct ehci_hcd         *ehci,
        unsigned                period,
        struct usb_device       *dev,
        unsigned                frame,
        u32                     uf_mask
)
{
        if (period == 0)        /* error */
                return 0;

        /* note bandwidth wastage:  split never follows csplit
         * (different dev or endpoint) until the next uframe.
         * calling convention doesn't make that distinction.
         */
        for (; frame < ehci->periodic_size; frame += period) {
                union ehci_shadow       here;
                __hc32                  type;
                struct ehci_qh_hw       *hw;

                here = ehci->pshadow[frame];
                type = Q_NEXT_TYPE(ehci, ehci->periodic[frame]);
                while (here.ptr) {
                        switch (hc32_to_cpu(ehci, type)) {
                        case Q_TYPE_ITD:
                                type = Q_NEXT_TYPE(ehci, here.itd->hw_next);
                                here = here.itd->itd_next;
                                continue;
                        case Q_TYPE_QH:
                                hw = here.qh->hw;
                                if (same_tt(dev, here.qh->ps.udev)) {
                                        u32             mask;

                                        mask = hc32_to_cpu(ehci,
                                                        hw->hw_info2);
                                        /* "knows" no gap is needed */
                                        mask |= mask >> 8;
                                        if (mask & uf_mask)
                                                break;
                                }
                                type = Q_NEXT_TYPE(ehci, hw->hw_next);
                                here = here.qh->qh_next;
                                continue;
                        case Q_TYPE_SITD:
                                if (same_tt(dev, here.sitd->urb->dev)) {
                                        u16             mask;

                                        mask = hc32_to_cpu(ehci, here.sitd
                                                                ->hw_uframe);
                                        /* FIXME assumes no gap for IN! */
                                        mask |= mask >> 8;
                                        if (mask & uf_mask)
                                                break;
                                }
                                type = Q_NEXT_TYPE(ehci, here.sitd->hw_next);
                                here = here.sitd->sitd_next;
                                continue;
                        /* case Q_TYPE_FSTN: */
                        default:
                                ehci_dbg(ehci,
                                        "periodic frame %d bogus type %d\n",
                                        frame, type);
                        }

                        /* collision or error */
                        return 0;
                }
        }

        /* no collision */
        return 1;
}

#endif /* CONFIG_USB_EHCI_TT_NEWSCHED */

/*-------------------------------------------------------------------------*/

static void enable_periodic(struct ehci_hcd *ehci)
{
        if (ehci->periodic_count++)
                goto out;

        /* Stop waiting to turn off the periodic schedule */
        ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_PERIODIC);

        /* Don't start the schedule until PSS is 0 */
        ehci_poll_PSS(ehci);
out:
        turn_on_io_watchdog(ehci);
}

static void disable_periodic(struct ehci_hcd *ehci)
{
        if (--ehci->periodic_count)
                return;

        /* Don't turn off the schedule until PSS is 1 */
        ehci_poll_PSS(ehci);
}

/*-------------------------------------------------------------------------*/

/* periodic schedule slots have iso tds (normal or split) first, then a
 * sparse tree for active interrupt transfers.
 *
 * this just links in a qh; caller guarantees uframe masks are set right.
 * no FSTN support (yet; ehci 0.96+)
 */
static void qh_link_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        unsigned        i;
        unsigned        period = qh->ps.period;

        dev_dbg(&qh->ps.udev->dev,
                "link qh%d-%04x/%p start %d [%d/%d us]\n",
                period, hc32_to_cpup(ehci, &qh->hw->hw_info2)
                        & (QH_CMASK | QH_SMASK),
                qh, qh->ps.phase, qh->ps.usecs, qh->ps.c_usecs);

        /* high bandwidth, or otherwise every microframe */
        if (period == 0)
                period = 1;

        for (i = qh->ps.phase; i < ehci->periodic_size; i += period) {
                union ehci_shadow       *prev = &ehci->pshadow[i];
                __hc32                  *hw_p = &ehci->periodic[i];
                union ehci_shadow       here = *prev;
                __hc32                  type = 0;

                /* skip the iso nodes at list head */
                while (here.ptr) {
                        type = Q_NEXT_TYPE(ehci, *hw_p);
                        if (type == cpu_to_hc32(ehci, Q_TYPE_QH))
                                break;
                        prev = periodic_next_shadow(ehci, prev, type);
                        hw_p = shadow_next_periodic(ehci, &here, type);
                        here = *prev;
                }

                /* sorting each branch by period (slow-->fast)
                 * enables sharing interior tree nodes
                 */
                while (here.ptr && qh != here.qh) {
                        if (qh->ps.period > here.qh->ps.period)
                                break;
                        prev = &here.qh->qh_next;
                        hw_p = &here.qh->hw->hw_next;
                        here = *prev;
                }
                /* link in this qh, unless some earlier pass did that */
                if (qh != here.qh) {
                        qh->qh_next = here;
                        if (here.qh)
                                qh->hw->hw_next = *hw_p;
                        wmb();
                        prev->qh = qh;
                        *hw_p = QH_NEXT(ehci, qh->qh_dma);
                }
        }
        qh->qh_state = QH_STATE_LINKED;
        qh->xacterrs = 0;
        qh->unlink_reason = 0;

        /* update per-qh bandwidth for debugfs */
        ehci_to_hcd(ehci)->self.bandwidth_allocated += qh->ps.bw_period
                ? ((qh->ps.usecs + qh->ps.c_usecs) / qh->ps.bw_period)
                : (qh->ps.usecs * 8);

        list_add(&qh->intr_node, &ehci->intr_qh_list);

        /* maybe enable periodic schedule processing */
        ++ehci->intr_count;
        enable_periodic(ehci);
}

static void qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        unsigned        i;
        unsigned        period;

        /*
         * If qh is for a low/full-speed device, simply unlinking it
         * could interfere with an ongoing split transaction.  To unlink
         * it safely would require setting the QH_INACTIVATE bit and
         * waiting at least one frame, as described in EHCI 4.12.2.5.
         *
         * We won't bother with any of this.  Instead, we assume that the
         * only reason for unlinking an interrupt QH while the current URB
         * is still active is to dequeue all the URBs (flush the whole
         * endpoint queue).
         *
         * If rebalancing the periodic schedule is ever implemented, this
         * approach will no longer be valid.
         */

        /* high bandwidth, or otherwise part of every microframe */
        period = qh->ps.period ? : 1;

        for (i = qh->ps.phase; i < ehci->periodic_size; i += period)
                periodic_unlink(ehci, i, qh);

        /* update per-qh bandwidth for debugfs */
        ehci_to_hcd(ehci)->self.bandwidth_allocated -= qh->ps.bw_period
                ? ((qh->ps.usecs + qh->ps.c_usecs) / qh->ps.bw_period)
                : (qh->ps.usecs * 8);

        dev_dbg(&qh->ps.udev->dev,
                "unlink qh%d-%04x/%p start %d [%d/%d us]\n",
                qh->ps.period,
                hc32_to_cpup(ehci, &qh->hw->hw_info2) & (QH_CMASK | QH_SMASK),
                qh, qh->ps.phase, qh->ps.usecs, qh->ps.c_usecs);

        /* qh->qh_next still "live" to HC */
        qh->qh_state = QH_STATE_UNLINK;
        qh->qh_next.ptr = NULL;

        if (ehci->qh_scan_next == qh)
                ehci->qh_scan_next = list_entry(qh->intr_node.next,
                                struct ehci_qh, intr_node);
        list_del(&qh->intr_node);
}

static void cancel_unlink_wait_intr(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        if (qh->qh_state != QH_STATE_LINKED ||
                        list_empty(&qh->unlink_node))
                return;

        list_del_init(&qh->unlink_node);

        /*
         * TODO: disable the event of EHCI_HRTIMER_START_UNLINK_INTR for
         * avoiding unnecessary CPU wakeup
         */
}

static void start_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        /* If the QH isn't linked then there's nothing we can do. */
        if (qh->qh_state != QH_STATE_LINKED)
                return;

        /* if the qh is waiting for unlink, cancel it now */
        cancel_unlink_wait_intr(ehci, qh);

        qh_unlink_periodic(ehci, qh);

        /* Make sure the unlinks are visible before starting the timer */
        wmb();

        /*
         * The EHCI spec doesn't say how long it takes the controller to
         * stop accessing an unlinked interrupt QH.  The timer delay is
         * 9 uframes; presumably that will be long enough.
         */
        qh->unlink_cycle = ehci->intr_unlink_cycle;

        /* New entries go at the end of the intr_unlink list */
        list_add_tail(&qh->unlink_node, &ehci->intr_unlink);

        if (ehci->intr_unlinking)
                ;       /* Avoid recursive calls */
        else if (ehci->rh_state < EHCI_RH_RUNNING)
                ehci_handle_intr_unlinks(ehci);
        else if (ehci->intr_unlink.next == &qh->unlink_node) {
                ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
                ++ehci->intr_unlink_cycle;
        }
}

/*
 * It is common only one intr URB is scheduled on one qh, and
 * given complete() is run in tasklet context, introduce a bit
 * delay to avoid unlink qh too early.
 */
static void start_unlink_intr_wait(struct ehci_hcd *ehci,
                                   struct ehci_qh *qh)
{
        qh->unlink_cycle = ehci->intr_unlink_wait_cycle;

        /* New entries go at the end of the intr_unlink_wait list */
        list_add_tail(&qh->unlink_node, &ehci->intr_unlink_wait);

        if (ehci->rh_state < EHCI_RH_RUNNING)
                ehci_handle_start_intr_unlinks(ehci);
        else if (ehci->intr_unlink_wait.next == &qh->unlink_node) {
                ehci_enable_event(ehci, EHCI_HRTIMER_START_UNLINK_INTR, true);
                ++ehci->intr_unlink_wait_cycle;
        }
}

static void end_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        struct ehci_qh_hw       *hw = qh->hw;
        int                     rc;

        qh->qh_state = QH_STATE_IDLE;
        hw->hw_next = EHCI_LIST_END(ehci);

        if (!list_empty(&qh->qtd_list))
                qh_completions(ehci, qh);

        /* reschedule QH iff another request is queued */
        if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING) {
                rc = qh_schedule(ehci, qh);
                if (rc == 0) {
                        qh_refresh(ehci, qh);
                        qh_link_periodic(ehci, qh);
                }

                /* An error here likely indicates handshake failure
                 * or no space left in the schedule.  Neither fault
                 * should happen often ...
                 *
                 * FIXME kill the now-dysfunctional queued urbs
                 */
                else {
                        ehci_err(ehci, "can't reschedule qh %p, err %d\n",
                                        qh, rc);
                }
        }

        /* maybe turn off periodic schedule */
        --ehci->intr_count;
        disable_periodic(ehci);
}

/*-------------------------------------------------------------------------*/

static int check_period(
        struct ehci_hcd *ehci,
        unsigned        frame,
        unsigned        uframe,
        unsigned        uperiod,
        unsigned        usecs
) {
        /* complete split running into next frame?
         * given FSTN support, we could sometimes check...
         */
        if (uframe >= 8)
                return 0;

        /* convert "usecs we need" to "max already claimed" */
        usecs = ehci->uframe_periodic_max - usecs;

        for (uframe += frame << 3; uframe < EHCI_BANDWIDTH_SIZE;
                        uframe += uperiod) {
                if (ehci->bandwidth[uframe] > usecs)
                        return 0;
        }

        /* success! */
        return 1;
}

static int check_intr_schedule(
        struct ehci_hcd         *ehci,
        unsigned                frame,
        unsigned                uframe,
        struct ehci_qh          *qh,
        unsigned                *c_maskp,
        struct ehci_tt          *tt
)
{
        int             retval = -ENOSPC;
        u8              mask = 0;

        if (qh->ps.c_usecs && uframe >= 6)      /* FSTN territory? */
                goto done;

        if (!check_period(ehci, frame, uframe, qh->ps.bw_uperiod, qh->ps.usecs))
                goto done;
        if (!qh->ps.c_usecs) {
                retval = 0;
                *c_maskp = 0;
                goto done;
        }

#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
        if (tt_available(ehci, &qh->ps, tt, frame, uframe)) {
                unsigned i;

                /* TODO : this may need FSTN for SSPLIT in uframe 5. */
                for (i = uframe+2; i < 8 && i <= uframe+4; i++)
                        if (!check_period(ehci, frame, i,
                                        qh->ps.bw_uperiod, qh->ps.c_usecs))
                                goto done;
                        else
                                mask |= 1 << i;

                retval = 0;

                *c_maskp = mask;
        }
#else
        /* Make sure this tt's buffer is also available for CSPLITs.
         * We pessimize a bit; probably the typical full speed case
         * doesn't need the second CSPLIT.
         *
         * NOTE:  both SPLIT and CSPLIT could be checked in just
         * one smart pass...
         */
        mask = 0x03 << (uframe + qh->gap_uf);
        *c_maskp = mask;

        mask |= 1 << uframe;
        if (tt_no_collision(ehci, qh->ps.bw_period, qh->ps.udev, frame, mask)) {
                if (!check_period(ehci, frame, uframe + qh->gap_uf + 1,
                                qh->ps.bw_uperiod, qh->ps.c_usecs))
                        goto done;
                if (!check_period(ehci, frame, uframe + qh->gap_uf,
                                qh->ps.bw_uperiod, qh->ps.c_usecs))
                        goto done;
                retval = 0;
        }
#endif
done:
        return retval;
}

/* "first fit" scheduling policy used the first time through,
 * or when the previous schedule slot can't be re-used.
 */
static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        int             status = 0;
        unsigned        uframe;
        unsigned        c_mask;
        struct ehci_qh_hw       *hw = qh->hw;
        struct ehci_tt          *tt;

        hw->hw_next = EHCI_LIST_END(ehci);

        /* reuse the previous schedule slots, if we can */
        if (qh->ps.phase != NO_FRAME) {
                ehci_dbg(ehci, "reused qh %p schedule\n", qh);
                return 0;
        }

        uframe = 0;
        c_mask = 0;
        tt = find_tt(qh->ps.udev);
        if (IS_ERR(tt)) {
                status = PTR_ERR(tt);
                goto done;
        }
        compute_tt_budget(ehci->tt_budget, tt);

        /* else scan the schedule to find a group of slots such that all
         * uframes have enough periodic bandwidth available.
         */
        /* "normal" case, uframing flexible except with splits */
        if (qh->ps.bw_period) {
                int             i;
                unsigned        frame;

                for (i = qh->ps.bw_period; i > 0; --i) {
                        frame = ++ehci->random_frame & (qh->ps.bw_period - 1);
                        for (uframe = 0; uframe < 8; uframe++) {
                                status = check_intr_schedule(ehci,
                                                frame, uframe, qh, &c_mask, tt);
                                if (status == 0)
                                        goto got_it;
                        }
                }

        /* qh->ps.bw_period == 0 means every uframe */
        } else {
                status = check_intr_schedule(ehci, 0, 0, qh, &c_mask, tt);
        }
        if (status)
                goto done;

 got_it:
        qh->ps.phase = (qh->ps.period ? ehci->random_frame &
                        (qh->ps.period - 1) : 0);
        qh->ps.bw_phase = qh->ps.phase & (qh->ps.bw_period - 1);
        qh->ps.phase_uf = uframe;
        qh->ps.cs_mask = qh->ps.period ?
                        (c_mask << 8) | (1 << uframe) :
                        QH_SMASK;

        /* reset S-frame and (maybe) C-frame masks */
        hw->hw_info2 &= cpu_to_hc32(ehci, ~(QH_CMASK | QH_SMASK));
        hw->hw_info2 |= cpu_to_hc32(ehci, qh->ps.cs_mask);
        reserve_release_intr_bandwidth(ehci, qh, 1);

done:
        return status;
}

static int intr_submit(
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        struct list_head        *qtd_list,
        gfp_t                   mem_flags
) {
        unsigned                epnum;
        unsigned long           flags;
        struct ehci_qh          *qh;
        int                     status;
        struct list_head        empty;

        /* get endpoint and transfer/schedule data */
        epnum = urb->ep->desc.bEndpointAddress;

        spin_lock_irqsave(&ehci->lock, flags);

        if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
                status = -ESHUTDOWN;
                goto done_not_linked;
        }
        status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
        if (unlikely(status))
                goto done_not_linked;

        /* get qh and force any scheduling errors */
        INIT_LIST_HEAD(&empty);
        qh = qh_append_tds(ehci, urb, &empty, epnum, &urb->ep->hcpriv);
        if (qh == NULL) {
                status = -ENOMEM;
                goto done;
        }
        if (qh->qh_state == QH_STATE_IDLE) {
                status = qh_schedule(ehci, qh);
                if (status)
                        goto done;
        }

        /* then queue the urb's tds to the qh */
        qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
        BUG_ON(qh == NULL);

        /* stuff into the periodic schedule */
        if (qh->qh_state == QH_STATE_IDLE) {
                qh_refresh(ehci, qh);
                qh_link_periodic(ehci, qh);
        } else {
                /* cancel unlink wait for the qh */
                cancel_unlink_wait_intr(ehci, qh);
        }

        /* ... update usbfs periodic stats */
        ehci_to_hcd(ehci)->self.bandwidth_int_reqs++;

done:
        if (unlikely(status))
                usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
done_not_linked:
        spin_unlock_irqrestore(&ehci->lock, flags);
        if (status)
                qtd_list_free(ehci, urb, qtd_list);

        return status;
}

static void scan_intr(struct ehci_hcd *ehci)
{
        struct ehci_qh          *qh;

        list_for_each_entry_safe(qh, ehci->qh_scan_next, &ehci->intr_qh_list,
                        intr_node) {

                /* clean any finished work for this qh */
                if (!list_empty(&qh->qtd_list)) {
                        int temp;

                        /*
                         * Unlinks could happen here; completion reporting
                         * drops the lock.  That's why ehci->qh_scan_next
                         * always holds the next qh to scan; if the next qh
                         * gets unlinked then ehci->qh_scan_next is adjusted
                         * in qh_unlink_periodic().
                         */
                        temp = qh_completions(ehci, qh);
                        if (unlikely(temp))
                                start_unlink_intr(ehci, qh);
                        else if (unlikely(list_empty(&qh->qtd_list) &&
                                        qh->qh_state == QH_STATE_LINKED))
                                start_unlink_intr_wait(ehci, qh);
                }
        }
}

/*-------------------------------------------------------------------------*/

/* ehci_iso_stream ops work with both ITD and SITD */

static struct ehci_iso_stream *
iso_stream_alloc(gfp_t mem_flags)
{
        struct ehci_iso_stream *stream;

        stream = kzalloc_obj(*stream, mem_flags);
        if (likely(stream != NULL)) {
                INIT_LIST_HEAD(&stream->td_list);
                INIT_LIST_HEAD(&stream->free_list);
                stream->next_uframe = NO_FRAME;
                stream->ps.phase = NO_FRAME;
        }
        return stream;
}

static void
iso_stream_init(
        struct ehci_hcd         *ehci,
        struct ehci_iso_stream  *stream,
        struct urb              *urb
)
{
        static const u8 smask_out[] = { 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f };

        struct usb_device       *dev = urb->dev;
        u32                     buf1;
        unsigned                epnum, maxp;
        int                     is_input;
        unsigned                tmp;

        /*
         * this might be a "high bandwidth" highspeed endpoint,
         * as encoded in the ep descriptor's wMaxPacket field
         */
        epnum = usb_pipeendpoint(urb->pipe);
        is_input = usb_pipein(urb->pipe) ? USB_DIR_IN : 0;
        maxp = usb_endpoint_maxp(&urb->ep->desc);
        buf1 = is_input ? 1 << 11 : 0;

        /* knows about ITD vs SITD */
        if (dev->speed == USB_SPEED_HIGH) {
                unsigned multi = usb_endpoint_maxp_mult(&urb->ep->desc);

                stream->highspeed = 1;

                buf1 |= maxp;
                maxp *= multi;

                stream->buf0 = cpu_to_hc32(ehci, (epnum << 8) | dev->devnum);
                stream->buf1 = cpu_to_hc32(ehci, buf1);
                stream->buf2 = cpu_to_hc32(ehci, multi);

                /* usbfs wants to report the average usecs per frame tied up
                 * when transfers on this endpoint are scheduled ...
                 */
                stream->ps.usecs = HS_USECS_ISO(maxp);

                /* period for bandwidth allocation */
                tmp = min_t(unsigned, EHCI_BANDWIDTH_SIZE,
                                1 << (urb->ep->desc.bInterval - 1));

                /* Allow urb->interval to override */
                stream->ps.bw_uperiod = min_t(unsigned, tmp, urb->interval);

                stream->uperiod = urb->interval;
                stream->ps.period = urb->interval >> 3;
                stream->bandwidth = stream->ps.usecs * 8 /
                                stream->ps.bw_uperiod;

        } else {
                u32             addr;
                int             think_time;
                int             hs_transfers;

                addr = dev->ttport << 24;
                if (!ehci_is_TDI(ehci)
                                || (dev->tt->hub !=
                                        ehci_to_hcd(ehci)->self.root_hub))
                        addr |= dev->tt->hub->devnum << 16;
                addr |= epnum << 8;
                addr |= dev->devnum;
                stream->ps.usecs = HS_USECS_ISO(maxp);
                think_time = dev->tt->think_time;
                stream->ps.tt_usecs = NS_TO_US(think_time + usb_calc_bus_time(
                                dev->speed, is_input, 1, maxp));
                hs_transfers = max(1u, (maxp + 187) / 188);
                if (is_input) {
                        u32     tmp;

                        addr |= 1 << 31;
                        stream->ps.c_usecs = stream->ps.usecs;
                        stream->ps.usecs = HS_USECS_ISO(1);
                        stream->ps.cs_mask = 1;

                        /* c-mask as specified in USB 2.0 11.18.4 3.c */
                        tmp = (1 << (hs_transfers + 2)) - 1;
                        stream->ps.cs_mask |= tmp << (8 + 2);
                } else
                        stream->ps.cs_mask = smask_out[hs_transfers - 1];

                /* period for bandwidth allocation */
                tmp = min_t(unsigned, EHCI_BANDWIDTH_FRAMES,
                                1 << (urb->ep->desc.bInterval - 1));

                /* Allow urb->interval to override */
                stream->ps.bw_period = min_t(unsigned, tmp, urb->interval);
                stream->ps.bw_uperiod = stream->ps.bw_period << 3;

                stream->ps.period = urb->interval;
                stream->uperiod = urb->interval << 3;
                stream->bandwidth = (stream->ps.usecs + stream->ps.c_usecs) /
                                stream->ps.bw_period;

                /* stream->splits gets created from cs_mask later */
                stream->address = cpu_to_hc32(ehci, addr);
        }

        stream->ps.udev = dev;
        stream->ps.ep = urb->ep;

        stream->bEndpointAddress = is_input | epnum;
        stream->maxp = maxp;
}

static struct ehci_iso_stream *
iso_stream_find(struct ehci_hcd *ehci, struct urb *urb)
{
        unsigned                epnum;
        struct ehci_iso_stream  *stream;
        struct usb_host_endpoint *ep;
        unsigned long           flags;

        epnum = usb_pipeendpoint (urb->pipe);
        if (usb_pipein(urb->pipe))
                ep = urb->dev->ep_in[epnum];
        else
                ep = urb->dev->ep_out[epnum];

        spin_lock_irqsave(&ehci->lock, flags);
        stream = ep->hcpriv;

        if (unlikely(stream == NULL)) {
                stream = iso_stream_alloc(GFP_ATOMIC);
                if (likely(stream != NULL)) {
                        ep->hcpriv = stream;
                        iso_stream_init(ehci, stream, urb);
                }

        /* if dev->ep [epnum] is a QH, hw is set */
        } else if (unlikely(stream->hw != NULL)) {
                ehci_dbg(ehci, "dev %s ep%d%s, not iso??\n",
                        urb->dev->devpath, epnum,
                        usb_pipein(urb->pipe) ? "in" : "out");
                stream = NULL;
        }

        spin_unlock_irqrestore(&ehci->lock, flags);
        return stream;
}

/*-------------------------------------------------------------------------*/

/* ehci_iso_sched ops can be ITD-only or SITD-only */

static struct ehci_iso_sched *
iso_sched_alloc(unsigned packets, gfp_t mem_flags)
{
        struct ehci_iso_sched   *iso_sched;

        iso_sched = kzalloc_flex(*iso_sched, packet, packets, mem_flags);
        if (likely(iso_sched != NULL))
                INIT_LIST_HEAD(&iso_sched->td_list);

        return iso_sched;
}

static inline void
itd_sched_init(
        struct ehci_hcd         *ehci,
        struct ehci_iso_sched   *iso_sched,
        struct ehci_iso_stream  *stream,
        struct urb              *urb
)
{
        unsigned        i;
        dma_addr_t      dma = urb->transfer_dma;

        /* how many uframes are needed for these transfers */
        iso_sched->span = urb->number_of_packets * stream->uperiod;

        /* figure out per-uframe itd fields that we'll need later
         * when we fit new itds into the schedule.
         */
        for (i = 0; i < urb->number_of_packets; i++) {
                struct ehci_iso_packet  *uframe = &iso_sched->packet[i];
                unsigned                length;
                dma_addr_t              buf;
                u32                     trans;

                length = urb->iso_frame_desc[i].length;
                buf = dma + urb->iso_frame_desc[i].offset;

                trans = EHCI_ISOC_ACTIVE;
                trans |= buf & 0x0fff;
                if (unlikely(((i + 1) == urb->number_of_packets))
                                && !(urb->transfer_flags & URB_NO_INTERRUPT))
                        trans |= EHCI_ITD_IOC;
                trans |= length << 16;
                uframe->transaction = cpu_to_hc32(ehci, trans);

                /* might need to cross a buffer page within a uframe */
                uframe->bufp = (buf & ~(u64)0x0fff);
                buf += length;
                if (unlikely((uframe->bufp != (buf & ~(u64)0x0fff))))
                        uframe->cross = 1;
        }
}

static void
iso_sched_free(
        struct ehci_iso_stream  *stream,
        struct ehci_iso_sched   *iso_sched
)
{
        if (!iso_sched)
                return;
        /* caller must hold ehci->lock! */
        list_splice(&iso_sched->td_list, &stream->free_list);
        kfree(iso_sched);
}

static int
itd_urb_transaction(
        struct ehci_iso_stream  *stream,
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        gfp_t                   mem_flags
)
{
        struct ehci_itd         *itd;
        dma_addr_t              itd_dma;
        int                     i;
        unsigned                num_itds;
        struct ehci_iso_sched   *sched;
        unsigned long           flags;

        sched = iso_sched_alloc(urb->number_of_packets, mem_flags);
        if (unlikely(sched == NULL))
                return -ENOMEM;

        itd_sched_init(ehci, sched, stream, urb);

        if (urb->interval < 8)
                num_itds = 1 + (sched->span + 7) / 8;
        else
                num_itds = urb->number_of_packets;

        /* allocate/init ITDs */
        spin_lock_irqsave(&ehci->lock, flags);
        for (i = 0; i < num_itds; i++) {

                /*
                 * Use iTDs from the free list, but not iTDs that may
                 * still be in use by the hardware.
                 */
                if (likely(!list_empty(&stream->free_list))) {
                        itd = list_first_entry(&stream->free_list,
                                        struct ehci_itd, itd_list);
                        if (itd->frame == ehci->now_frame)
                                goto alloc_itd;
                        list_del(&itd->itd_list);
                        itd_dma = itd->itd_dma;
                } else {
 alloc_itd:
                        spin_unlock_irqrestore(&ehci->lock, flags);
                        itd = dma_pool_alloc(ehci->itd_pool, mem_flags,
                                        &itd_dma);
                        spin_lock_irqsave(&ehci->lock, flags);
                        if (!itd) {
                                iso_sched_free(stream, sched);
                                spin_unlock_irqrestore(&ehci->lock, flags);
                                return -ENOMEM;
                        }
                }

                memset(itd, 0, sizeof(*itd));
                itd->itd_dma = itd_dma;
                itd->frame = NO_FRAME;
                list_add(&itd->itd_list, &sched->td_list);
        }
        spin_unlock_irqrestore(&ehci->lock, flags);

        /* temporarily store schedule info in hcpriv */
        urb->hcpriv = sched;
        urb->error_count = 0;
        return 0;
}

/*-------------------------------------------------------------------------*/

static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
                struct ehci_iso_stream *stream, int sign)
{
        unsigned                uframe;
        unsigned                i, j;
        unsigned                s_mask, c_mask, m;
        int                     usecs = stream->ps.usecs;
        int                     c_usecs = stream->ps.c_usecs;
        int                     tt_usecs = stream->ps.tt_usecs;
        struct ehci_tt          *tt;

        if (stream->ps.phase == NO_FRAME)       /* Bandwidth wasn't reserved */
                return;
        uframe = stream->ps.bw_phase << 3;

        bandwidth_dbg(ehci, sign, "iso", &stream->ps);

        if (sign < 0) {         /* Release bandwidth */
                usecs = -usecs;
                c_usecs = -c_usecs;
                tt_usecs = -tt_usecs;
        }

        if (!stream->splits) {          /* High speed */
                for (i = uframe + stream->ps.phase_uf; i < EHCI_BANDWIDTH_SIZE;
                                i += stream->ps.bw_uperiod)
                        ehci->bandwidth[i] += usecs;

        } else {                        /* Full speed */
                s_mask = stream->ps.cs_mask;
                c_mask = s_mask >> 8;

                /* NOTE: adjustment needed for frame overflow */
                for (i = uframe; i < EHCI_BANDWIDTH_SIZE;
                                i += stream->ps.bw_uperiod) {
                        for ((j = stream->ps.phase_uf, m = 1 << j); j < 8;
                                        (++j, m <<= 1)) {
                                if (s_mask & m)
                                        ehci->bandwidth[i+j] += usecs;
                                else if (c_mask & m)
                                        ehci->bandwidth[i+j] += c_usecs;
                        }
                }

                /*
                 * find_tt() will not return any error here as we have
                 * already called find_tt() before calling this function
                 * and checked for any error return. The previous call
                 * would have created the data structure.
                 */
                tt = find_tt(stream->ps.udev);
                if (sign > 0)
                        list_add_tail(&stream->ps.ps_list, &tt->ps_list);
                else
                        list_del(&stream->ps.ps_list);

                for (i = uframe >> 3; i < EHCI_BANDWIDTH_FRAMES;
                                i += stream->ps.bw_period)
                        tt->bandwidth[i] += tt_usecs;
        }
}

static inline int
itd_slot_ok(
        struct ehci_hcd         *ehci,
        struct ehci_iso_stream  *stream,
        unsigned                uframe
)
{
        unsigned                usecs;

        /* convert "usecs we need" to "max already claimed" */
        usecs = ehci->uframe_periodic_max - stream->ps.usecs;

        for (uframe &= stream->ps.bw_uperiod - 1; uframe < EHCI_BANDWIDTH_SIZE;
                        uframe += stream->ps.bw_uperiod) {
                if (ehci->bandwidth[uframe] > usecs)
                        return 0;
        }
        return 1;
}

static inline int
sitd_slot_ok(
        struct ehci_hcd         *ehci,
        struct ehci_iso_stream  *stream,
        unsigned                uframe,
        struct ehci_iso_sched   *sched,
        struct ehci_tt          *tt
)
{
        unsigned                mask, tmp;
        unsigned                frame, uf;

        mask = stream->ps.cs_mask << (uframe & 7);

        /* for OUT, don't wrap SSPLIT into H-microframe 7 */
        if (((stream->ps.cs_mask & 0xff) << (uframe & 7)) >= (1 << 7))
                return 0;

        /* for IN, don't wrap CSPLIT into the next frame */
        if (mask & ~0xffff)
                return 0;

        /* check bandwidth */
        uframe &= stream->ps.bw_uperiod - 1;
        frame = uframe >> 3;

#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
        /* The tt's fullspeed bus bandwidth must be available.
         * tt_available scheduling guarantees 10+% for control/bulk.
         */
        uf = uframe & 7;
        if (!tt_available(ehci, &stream->ps, tt, frame, uf))
                return 0;
#else
        /* tt must be idle for start(s), any gap, and csplit.
         * assume scheduling slop leaves 10+% for control/bulk.
         */
        if (!tt_no_collision(ehci, stream->ps.bw_period,
                        stream->ps.udev, frame, mask))
                return 0;
#endif

        do {
                unsigned        max_used;
                unsigned        i;

                /* check starts (OUT uses more than one) */
                uf = uframe;
                max_used = ehci->uframe_periodic_max - stream->ps.usecs;
                for (tmp = stream->ps.cs_mask & 0xff; tmp; tmp >>= 1, uf++) {
                        if (ehci->bandwidth[uf] > max_used)
                                return 0;
                }

                /* for IN, check CSPLIT */
                if (stream->ps.c_usecs) {
                        max_used = ehci->uframe_periodic_max -
                                        stream->ps.c_usecs;
                        uf = uframe & ~7;
                        tmp = 1 << (2+8);
                        for (i = (uframe & 7) + 2; i < 8; (++i, tmp <<= 1)) {
                                if ((stream->ps.cs_mask & tmp) == 0)
                                        continue;
                                if (ehci->bandwidth[uf+i] > max_used)
                                        return 0;
                        }
                }

                uframe += stream->ps.bw_uperiod;
        } while (uframe < EHCI_BANDWIDTH_SIZE);

        stream->ps.cs_mask <<= uframe & 7;
        stream->splits = cpu_to_hc32(ehci, stream->ps.cs_mask);
        return 1;
}

/*
 * This scheduler plans almost as far into the future as it has actual
 * periodic schedule slots.  (Affected by TUNE_FLS, which defaults to
 * "as small as possible" to be cache-friendlier.)  That limits the size
 * transfers you can stream reliably; avoid more than 64 msec per urb.
 * Also avoid queue depths of less than ehci's worst irq latency (affected
 * by the per-urb URB_NO_INTERRUPT hint, the log2_irq_thresh module parameter,
 * and other factors); or more than about 230 msec total (for portability,
 * given EHCI_TUNE_FLS and the slop).  Or, write a smarter scheduler!
 */

static int
iso_stream_schedule(
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        struct ehci_iso_stream  *stream
)
{
        u32                     now, base, next, start, period, span, now2;
        u32                     wrap = 0, skip = 0;
        int                     status = 0;
        unsigned                mod = ehci->periodic_size << 3;
        struct ehci_iso_sched   *sched = urb->hcpriv;
        bool                    empty = list_empty(&stream->td_list);
        bool                    new_stream = false;

        period = stream->uperiod;
        span = sched->span;
        if (!stream->highspeed)
                span <<= 3;

        /* Start a new isochronous stream? */
        if (unlikely(empty && !hcd_periodic_completion_in_progress(
                        ehci_to_hcd(ehci), urb->ep))) {

                /* Schedule the endpoint */
                if (stream->ps.phase == NO_FRAME) {
                        int             done = 0;
                        struct ehci_tt  *tt = find_tt(stream->ps.udev);

                        if (IS_ERR(tt)) {
                                status = PTR_ERR(tt);
                                goto fail;
                        }
                        compute_tt_budget(ehci->tt_budget, tt);

                        start = ((-(++ehci->random_frame)) << 3) & (period - 1);

                        /* find a uframe slot with enough bandwidth.
                         * Early uframes are more precious because full-speed
                         * iso IN transfers can't use late uframes,
                         * and therefore they should be allocated last.
                         */
                        next = start;
                        start += period;
                        do {
                                start--;
                                /* check schedule: enough space? */
                                if (stream->highspeed) {
                                        if (itd_slot_ok(ehci, stream, start))
                                                done = 1;
                                } else {
                                        if ((start % 8) >= 6)
                                                continue;
                                        if (sitd_slot_ok(ehci, stream, start,
                                                        sched, tt))
                                                done = 1;
                                }
                        } while (start > next && !done);

                        /* no room in the schedule */
                        if (!done) {
                                ehci_dbg(ehci, "iso sched full %p", urb);
                                status = -ENOSPC;
                                goto fail;
                        }
                        stream->ps.phase = (start >> 3) &
                                        (stream->ps.period - 1);
                        stream->ps.bw_phase = stream->ps.phase &
                                        (stream->ps.bw_period - 1);
                        stream->ps.phase_uf = start & 7;
                        reserve_release_iso_bandwidth(ehci, stream, 1);
                }

                /* New stream is already scheduled; use the upcoming slot */
                else {
                        start = (stream->ps.phase << 3) + stream->ps.phase_uf;
                }

                stream->next_uframe = start;
                new_stream = true;
        }

        now = ehci_read_frame_index(ehci) & (mod - 1);

        /* Take the isochronous scheduling threshold into account */
        if (ehci->i_thresh)
                next = now + ehci->i_thresh;    /* uframe cache */
        else
                next = (now + 2 + 7) & ~0x07;   /* full frame cache */

        /* If needed, initialize last_iso_frame so that this URB will be seen */
        if (ehci->isoc_count == 0)
                ehci->last_iso_frame = now >> 3;

        /*
         * Use ehci->last_iso_frame as the base.  There can't be any
         * TDs scheduled for earlier than that.
         */
        base = ehci->last_iso_frame << 3;
        next = (next - base) & (mod - 1);
        start = (stream->next_uframe - base) & (mod - 1);

        if (unlikely(new_stream))
                goto do_ASAP;

        /*
         * Typical case: reuse current schedule, stream may still be active.
         * Hopefully there are no gaps from the host falling behind
         * (irq delays etc).  If there are, the behavior depends on
         * whether URB_ISO_ASAP is set.
         */
        now2 = (now - base) & (mod - 1);

        /* Is the schedule about to wrap around? */
        if (unlikely(!empty && start < period)) {
                ehci_dbg(ehci, "request %p would overflow (%u-%u < %u mod %u)\n",
                                urb, stream->next_uframe, base, period, mod);
                status = -EFBIG;
                goto fail;
        }

        /* Is the next packet scheduled after the base time? */
        if (likely(!empty || start <= now2 + period)) {

                /* URB_ISO_ASAP: make sure that start >= next */
                if (unlikely(start < next &&
                                (urb->transfer_flags & URB_ISO_ASAP)))
                        goto do_ASAP;

                /* Otherwise use start, if it's not in the past */
                if (likely(start >= now2))
                        goto use_start;

        /* Otherwise we got an underrun while the queue was empty */
        } else {
                if (urb->transfer_flags & URB_ISO_ASAP)
                        goto do_ASAP;
                wrap = mod;
                now2 += mod;
        }

        /* How many uframes and packets do we need to skip? */
        skip = (now2 - start + period - 1) & -period;
        if (skip >= span) {             /* Entirely in the past? */
                ehci_dbg(ehci, "iso underrun %p (%u+%u < %u) [%u]\n",
                                urb, start + base, span - period, now2 + base,
                                base);

                /* Try to keep the last TD intact for scanning later */
                skip = span - period;

                /* Will it come before the current scan position? */
                if (empty) {
                        skip = span;    /* Skip the entire URB */
                        status = 1;     /* and give it back immediately */
                        iso_sched_free(stream, sched);
                        sched = NULL;
                }
        }
        urb->error_count = skip / period;
        if (sched)
                sched->first_packet = urb->error_count;
        goto use_start;

 do_ASAP:
        /* Use the first slot after "next" */
        start = next + ((start - next) & (period - 1));

 use_start:
        /* Tried to schedule too far into the future? */
        if (unlikely(start + span - period >= mod + wrap)) {
                ehci_dbg(ehci, "request %p would overflow (%u+%u >= %u)\n",
                                urb, start, span - period, mod + wrap);
                status = -EFBIG;
                goto fail;
        }

        start += base;
        stream->next_uframe = (start + skip) & (mod - 1);

        /* report high speed start in uframes; full speed, in frames */
        urb->start_frame = start & (mod - 1);
        if (!stream->highspeed)
                urb->start_frame >>= 3;
        return status;

 fail:
        iso_sched_free(stream, sched);
        urb->hcpriv = NULL;
        return status;
}

/*-------------------------------------------------------------------------*/

static inline void
itd_init(struct ehci_hcd *ehci, struct ehci_iso_stream *stream,
                struct ehci_itd *itd)
{
        int i;

        /* it's been recently zeroed */
        itd->hw_next = EHCI_LIST_END(ehci);
        itd->hw_bufp[0] = stream->buf0;
        itd->hw_bufp[1] = stream->buf1;
        itd->hw_bufp[2] = stream->buf2;

        for (i = 0; i < 8; i++)
                itd->index[i] = -1;

        /* All other fields are filled when scheduling */
}

static inline void
itd_patch(
        struct ehci_hcd         *ehci,
        struct ehci_itd         *itd,
        struct ehci_iso_sched   *iso_sched,
        unsigned                index,
        u16                     uframe
)
{
        struct ehci_iso_packet  *uf = &iso_sched->packet[index];
        unsigned                pg = itd->pg;

        /* BUG_ON(pg == 6 && uf->cross); */

        uframe &= 0x07;
        itd->index[uframe] = index;

        itd->hw_transaction[uframe] = uf->transaction;
        itd->hw_transaction[uframe] |= cpu_to_hc32(ehci, pg << 12);
        itd->hw_bufp[pg] |= cpu_to_hc32(ehci, uf->bufp & ~(u32)0);
        itd->hw_bufp_hi[pg] |= cpu_to_hc32(ehci, (u32)(uf->bufp >> 32));

        /* iso_frame_desc[].offset must be strictly increasing */
        if (unlikely(uf->cross)) {
                u64     bufp = uf->bufp + 4096;

                itd->pg = ++pg;
                itd->hw_bufp[pg] |= cpu_to_hc32(ehci, bufp & ~(u32)0);
                itd->hw_bufp_hi[pg] |= cpu_to_hc32(ehci, (u32)(bufp >> 32));
        }
}

static inline void
itd_link(struct ehci_hcd *ehci, unsigned frame, struct ehci_itd *itd)
{
        union ehci_shadow       *prev = &ehci->pshadow[frame];
        __hc32                  *hw_p = &ehci->periodic[frame];
        union ehci_shadow       here = *prev;
        __hc32                  type = 0;

        /* skip any iso nodes which might belong to previous microframes */
        while (here.ptr) {
                type = Q_NEXT_TYPE(ehci, *hw_p);
                if (type == cpu_to_hc32(ehci, Q_TYPE_QH))
                        break;
                prev = periodic_next_shadow(ehci, prev, type);
                hw_p = shadow_next_periodic(ehci, &here, type);
                here = *prev;
        }

        itd->itd_next = here;
        itd->hw_next = *hw_p;
        prev->itd = itd;
        itd->frame = frame;
        wmb();
        *hw_p = cpu_to_hc32(ehci, itd->itd_dma | Q_TYPE_ITD);
}

/* fit urb's itds into the selected schedule slot; activate as needed */
static void itd_link_urb(
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        unsigned                mod,
        struct ehci_iso_stream  *stream
)
{
        int                     packet;
        unsigned                next_uframe, uframe, frame;
        struct ehci_iso_sched   *iso_sched = urb->hcpriv;
        struct ehci_itd         *itd;

        next_uframe = stream->next_uframe & (mod - 1);

        if (unlikely(list_empty(&stream->td_list)))
                ehci_to_hcd(ehci)->self.bandwidth_allocated
                                += stream->bandwidth;

        if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
                if (ehci->amd_pll_fix == 1)
                        usb_amd_quirk_pll_disable();
        }

        ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs++;

        /* fill iTDs uframe by uframe */
        for (packet = iso_sched->first_packet, itd = NULL;
                        packet < urb->number_of_packets;) {
                if (itd == NULL) {
                        /* ASSERT:  we have all necessary itds */
                        /* BUG_ON(list_empty(&iso_sched->td_list)); */

                        /* ASSERT:  no itds for this endpoint in this uframe */

                        itd = list_entry(iso_sched->td_list.next,
                                        struct ehci_itd, itd_list);
                        list_move_tail(&itd->itd_list, &stream->td_list);
                        itd->stream = stream;
                        itd->urb = urb;
                        itd_init(ehci, stream, itd);
                }

                uframe = next_uframe & 0x07;
                frame = next_uframe >> 3;

                itd_patch(ehci, itd, iso_sched, packet, uframe);

                next_uframe += stream->uperiod;
                next_uframe &= mod - 1;
                packet++;

                /* link completed itds into the schedule */
                if (((next_uframe >> 3) != frame)
                                || packet == urb->number_of_packets) {
                        itd_link(ehci, frame & (ehci->periodic_size - 1), itd);
                        itd = NULL;
                }
        }
        stream->next_uframe = next_uframe;

        /* don't need that schedule data any more */
        iso_sched_free(stream, iso_sched);
        urb->hcpriv = stream;

        ++ehci->isoc_count;
        enable_periodic(ehci);
}

#define ISO_ERRS (EHCI_ISOC_BUF_ERR | EHCI_ISOC_BABBLE | EHCI_ISOC_XACTERR)

/* Process and recycle a completed ITD.  Return true iff its urb completed,
 * and hence its completion callback probably added things to the hardware
 * schedule.
 *
 * Note that we carefully avoid recycling this descriptor until after any
 * completion callback runs, so that it won't be reused quickly.  That is,
 * assuming (a) no more than two urbs per frame on this endpoint, and also
 * (b) only this endpoint's completions submit URBs.  It seems some silicon
 * corrupts things if you reuse completed descriptors very quickly...
 */
static bool itd_complete(struct ehci_hcd *ehci, struct ehci_itd *itd)
{
        struct urb                              *urb = itd->urb;
        struct usb_iso_packet_descriptor        *desc;
        u32                                     t;
        unsigned                                uframe;
        int                                     urb_index = -1;
        struct ehci_iso_stream                  *stream = itd->stream;
        bool                                    retval = false;

        /* for each uframe with a packet */
        for (uframe = 0; uframe < 8; uframe++) {
                if (likely(itd->index[uframe] == -1))
                        continue;
                urb_index = itd->index[uframe];
                desc = &urb->iso_frame_desc[urb_index];

                t = hc32_to_cpup(ehci, &itd->hw_transaction[uframe]);
                itd->hw_transaction[uframe] = 0;

                /* report transfer status */
                if (unlikely(t & ISO_ERRS)) {
                        urb->error_count++;
                        if (t & EHCI_ISOC_BUF_ERR)
                                desc->status = usb_pipein(urb->pipe)
                                        ? -ENOSR  /* hc couldn't read */
                                        : -ECOMM; /* hc couldn't write */
                        else if (t & EHCI_ISOC_BABBLE)
                                desc->status = -EOVERFLOW;
                        else /* (t & EHCI_ISOC_XACTERR) */
                                desc->status = -EPROTO;

                        /* HC need not update length with this error */
                        if (!(t & EHCI_ISOC_BABBLE)) {
                                desc->actual_length = EHCI_ITD_LENGTH(t);
                                urb->actual_length += desc->actual_length;
                        }
                } else if (likely((t & EHCI_ISOC_ACTIVE) == 0)) {
                        desc->status = 0;
                        desc->actual_length = EHCI_ITD_LENGTH(t);
                        urb->actual_length += desc->actual_length;
                } else {
                        /* URB was too late */
                        urb->error_count++;
                }
        }

        /* handle completion now? */
        if (likely((urb_index + 1) != urb->number_of_packets))
                goto done;

        /*
         * ASSERT: it's really the last itd for this urb
         * list_for_each_entry (itd, &stream->td_list, itd_list)
         *       BUG_ON(itd->urb == urb);
         */

        /* give urb back to the driver; completion often (re)submits */
        ehci_urb_done(ehci, urb, 0);
        retval = true;
        urb = NULL;

        --ehci->isoc_count;
        disable_periodic(ehci);

        ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
        if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
                if (ehci->amd_pll_fix == 1)
                        usb_amd_quirk_pll_enable();
        }

        if (unlikely(list_is_singular(&stream->td_list)))
                ehci_to_hcd(ehci)->self.bandwidth_allocated
                                -= stream->bandwidth;

done:
        itd->urb = NULL;

        /* Add to the end of the free list for later reuse */
        list_move_tail(&itd->itd_list, &stream->free_list);

        /* Recycle the iTDs when the pipeline is empty (ep no longer in use) */
        if (list_empty(&stream->td_list)) {
                list_splice_tail_init(&stream->free_list,
                                &ehci->cached_itd_list);
                start_free_itds(ehci);
        }

        return retval;
}

/*-------------------------------------------------------------------------*/

static int itd_submit(struct ehci_hcd *ehci, struct urb *urb,
        gfp_t mem_flags)
{
        int                     status = -EINVAL;
        unsigned long           flags;
        struct ehci_iso_stream  *stream;

        /* Get iso_stream head */
        stream = iso_stream_find(ehci, urb);
        if (unlikely(stream == NULL)) {
                ehci_dbg(ehci, "can't get iso stream\n");
                return -ENOMEM;
        }
        if (unlikely(urb->interval != stream->uperiod)) {
                ehci_dbg(ehci, "can't change iso interval %d --> %d\n",
                        stream->uperiod, urb->interval);
                goto done;
        }

#ifdef EHCI_URB_TRACE
        ehci_dbg(ehci,
                "%s %s urb %p ep%d%s len %d, %d pkts %d uframes [%p]\n",
                __func__, urb->dev->devpath, urb,
                usb_pipeendpoint(urb->pipe),
                usb_pipein(urb->pipe) ? "in" : "out",
                urb->transfer_buffer_length,
                urb->number_of_packets, urb->interval,
                stream);
#endif

        /* allocate ITDs w/o locking anything */
        status = itd_urb_transaction(stream, ehci, urb, mem_flags);
        if (unlikely(status < 0)) {
                ehci_dbg(ehci, "can't init itds\n");
                goto done;
        }

        /* schedule ... need to lock */
        spin_lock_irqsave(&ehci->lock, flags);
        if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
                status = -ESHUTDOWN;
                goto done_not_linked;
        }
        status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
        if (unlikely(status))
                goto done_not_linked;
        status = iso_stream_schedule(ehci, urb, stream);
        if (likely(status == 0)) {
                itd_link_urb(ehci, urb, ehci->periodic_size << 3, stream);
        } else if (status > 0) {
                status = 0;
                ehci_urb_done(ehci, urb, 0);
        } else {
                usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
        }
 done_not_linked:
        spin_unlock_irqrestore(&ehci->lock, flags);
 done:
        return status;
}

/*-------------------------------------------------------------------------*/

/*
 * "Split ISO TDs" ... used for USB 1.1 devices going through the
 * TTs in USB 2.0 hubs.  These need microframe scheduling.
 */

static inline void
sitd_sched_init(
        struct ehci_hcd         *ehci,
        struct ehci_iso_sched   *iso_sched,
        struct ehci_iso_stream  *stream,
        struct urb              *urb
)
{
        unsigned        i;
        dma_addr_t      dma = urb->transfer_dma;

        /* how many frames are needed for these transfers */
        iso_sched->span = urb->number_of_packets * stream->ps.period;

        /* figure out per-frame sitd fields that we'll need later
         * when we fit new sitds into the schedule.
         */
        for (i = 0; i < urb->number_of_packets; i++) {
                struct ehci_iso_packet  *packet = &iso_sched->packet[i];
                unsigned                length;
                dma_addr_t              buf;
                u32                     trans;

                length = urb->iso_frame_desc[i].length & 0x03ff;
                buf = dma + urb->iso_frame_desc[i].offset;

                trans = SITD_STS_ACTIVE;
                if (((i + 1) == urb->number_of_packets)
                                && !(urb->transfer_flags & URB_NO_INTERRUPT))
                        trans |= SITD_IOC;
                trans |= length << 16;
                packet->transaction = cpu_to_hc32(ehci, trans);

                /* might need to cross a buffer page within a td */
                packet->bufp = buf;
                packet->buf1 = (buf + length) & ~0x0fff;
                if (packet->buf1 != (buf & ~(u64)0x0fff))
                        packet->cross = 1;

                /* OUT uses multiple start-splits */
                if (stream->bEndpointAddress & USB_DIR_IN)
                        continue;
                length = (length + 187) / 188;
                if (length > 1) /* BEGIN vs ALL */
                        length |= 1 << 3;
                packet->buf1 |= length;
        }
}

static int
sitd_urb_transaction(
        struct ehci_iso_stream  *stream,
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        gfp_t                   mem_flags
)
{
        struct ehci_sitd        *sitd;
        dma_addr_t              sitd_dma;
        int                     i;
        struct ehci_iso_sched   *iso_sched;
        unsigned long           flags;

        iso_sched = iso_sched_alloc(urb->number_of_packets, mem_flags);
        if (iso_sched == NULL)
                return -ENOMEM;

        sitd_sched_init(ehci, iso_sched, stream, urb);

        /* allocate/init sITDs */
        spin_lock_irqsave(&ehci->lock, flags);
        for (i = 0; i < urb->number_of_packets; i++) {

                /* NOTE:  for now, we don't try to handle wraparound cases
                 * for IN (using sitd->hw_backpointer, like a FSTN), which
                 * means we never need two sitds for full speed packets.
                 */

                /*
                 * Use siTDs from the free list, but not siTDs that may
                 * still be in use by the hardware.
                 */
                if (likely(!list_empty(&stream->free_list))) {
                        sitd = list_first_entry(&stream->free_list,
                                         struct ehci_sitd, sitd_list);
                        if (sitd->frame == ehci->now_frame)
                                goto alloc_sitd;
                        list_del(&sitd->sitd_list);
                        sitd_dma = sitd->sitd_dma;
                } else {
 alloc_sitd:
                        spin_unlock_irqrestore(&ehci->lock, flags);
                        sitd = dma_pool_alloc(ehci->sitd_pool, mem_flags,
                                        &sitd_dma);
                        spin_lock_irqsave(&ehci->lock, flags);
                        if (!sitd) {
                                iso_sched_free(stream, iso_sched);
                                spin_unlock_irqrestore(&ehci->lock, flags);
                                return -ENOMEM;
                        }
                }

                memset(sitd, 0, sizeof(*sitd));
                sitd->sitd_dma = sitd_dma;
                sitd->frame = NO_FRAME;
                list_add(&sitd->sitd_list, &iso_sched->td_list);
        }

        /* temporarily store schedule info in hcpriv */
        urb->hcpriv = iso_sched;
        urb->error_count = 0;

        spin_unlock_irqrestore(&ehci->lock, flags);
        return 0;
}

/*-------------------------------------------------------------------------*/

static inline void
sitd_patch(
        struct ehci_hcd         *ehci,
        struct ehci_iso_stream  *stream,
        struct ehci_sitd        *sitd,
        struct ehci_iso_sched   *iso_sched,
        unsigned                index
)
{
        struct ehci_iso_packet  *uf = &iso_sched->packet[index];
        u64                     bufp;

        sitd->hw_next = EHCI_LIST_END(ehci);
        sitd->hw_fullspeed_ep = stream->address;
        sitd->hw_uframe = stream->splits;
        sitd->hw_results = uf->transaction;
        sitd->hw_backpointer = EHCI_LIST_END(ehci);

        bufp = uf->bufp;
        sitd->hw_buf[0] = cpu_to_hc32(ehci, bufp);
        sitd->hw_buf_hi[0] = cpu_to_hc32(ehci, bufp >> 32);

        sitd->hw_buf[1] = cpu_to_hc32(ehci, uf->buf1);
        if (uf->cross)
                bufp += 4096;
        sitd->hw_buf_hi[1] = cpu_to_hc32(ehci, bufp >> 32);
        sitd->index = index;
}

static inline void
sitd_link(struct ehci_hcd *ehci, unsigned frame, struct ehci_sitd *sitd)
{
        /* note: sitd ordering could matter (CSPLIT then SSPLIT) */
        sitd->sitd_next = ehci->pshadow[frame];
        sitd->hw_next = ehci->periodic[frame];
        ehci->pshadow[frame].sitd = sitd;
        sitd->frame = frame;
        wmb();
        ehci->periodic[frame] = cpu_to_hc32(ehci, sitd->sitd_dma | Q_TYPE_SITD);
}

/* fit urb's sitds into the selected schedule slot; activate as needed */
static void sitd_link_urb(
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        unsigned                mod,
        struct ehci_iso_stream  *stream
)
{
        int                     packet;
        unsigned                next_uframe;
        struct ehci_iso_sched   *sched = urb->hcpriv;
        struct ehci_sitd        *sitd;

        next_uframe = stream->next_uframe;

        if (list_empty(&stream->td_list))
                /* usbfs ignores TT bandwidth */
                ehci_to_hcd(ehci)->self.bandwidth_allocated
                                += stream->bandwidth;

        if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
                if (ehci->amd_pll_fix == 1)
                        usb_amd_quirk_pll_disable();
        }

        ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs++;

        /* fill sITDs frame by frame */
        for (packet = sched->first_packet, sitd = NULL;
                        packet < urb->number_of_packets;
                        packet++) {

                /* ASSERT:  we have all necessary sitds */
                BUG_ON(list_empty(&sched->td_list));

                /* ASSERT:  no itds for this endpoint in this frame */

                sitd = list_entry(sched->td_list.next,
                                struct ehci_sitd, sitd_list);
                list_move_tail(&sitd->sitd_list, &stream->td_list);
                sitd->stream = stream;
                sitd->urb = urb;

                sitd_patch(ehci, stream, sitd, sched, packet);
                sitd_link(ehci, (next_uframe >> 3) & (ehci->periodic_size - 1),
                                sitd);

                next_uframe += stream->uperiod;
        }
        stream->next_uframe = next_uframe & (mod - 1);

        /* don't need that schedule data any more */
        iso_sched_free(stream, sched);
        urb->hcpriv = stream;

        ++ehci->isoc_count;
        enable_periodic(ehci);
}

/*-------------------------------------------------------------------------*/

#define SITD_ERRS (SITD_STS_ERR | SITD_STS_DBE | SITD_STS_BABBLE \
                                | SITD_STS_XACT | SITD_STS_MMF)

/* Process and recycle a completed SITD.  Return true iff its urb completed,
 * and hence its completion callback probably added things to the hardware
 * schedule.
 *
 * Note that we carefully avoid recycling this descriptor until after any
 * completion callback runs, so that it won't be reused quickly.  That is,
 * assuming (a) no more than two urbs per frame on this endpoint, and also
 * (b) only this endpoint's completions submit URBs.  It seems some silicon
 * corrupts things if you reuse completed descriptors very quickly...
 */
static bool sitd_complete(struct ehci_hcd *ehci, struct ehci_sitd *sitd)
{
        struct urb                              *urb = sitd->urb;
        struct usb_iso_packet_descriptor        *desc;
        u32                                     t;
        int                                     urb_index;
        struct ehci_iso_stream                  *stream = sitd->stream;
        bool                                    retval = false;

        urb_index = sitd->index;
        desc = &urb->iso_frame_desc[urb_index];
        t = hc32_to_cpup(ehci, &sitd->hw_results);

        /* report transfer status */
        if (unlikely(t & SITD_ERRS)) {
                urb->error_count++;
                if (t & SITD_STS_DBE)
                        desc->status = usb_pipein(urb->pipe)
                                ? -ENOSR  /* hc couldn't read */
                                : -ECOMM; /* hc couldn't write */
                else if (t & SITD_STS_BABBLE)
                        desc->status = -EOVERFLOW;
                else /* XACT, MMF, etc */
                        desc->status = -EPROTO;
        } else if (unlikely(t & SITD_STS_ACTIVE)) {
                /* URB was too late */
                urb->error_count++;
        } else {
                desc->status = 0;
                desc->actual_length = desc->length - SITD_LENGTH(t);
                urb->actual_length += desc->actual_length;
        }

        /* handle completion now? */
        if ((urb_index + 1) != urb->number_of_packets)
                goto done;

        /*
         * ASSERT: it's really the last sitd for this urb
         * list_for_each_entry (sitd, &stream->td_list, sitd_list)
         *       BUG_ON(sitd->urb == urb);
         */

        /* give urb back to the driver; completion often (re)submits */
        ehci_urb_done(ehci, urb, 0);
        retval = true;
        urb = NULL;

        --ehci->isoc_count;
        disable_periodic(ehci);

        ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
        if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
                if (ehci->amd_pll_fix == 1)
                        usb_amd_quirk_pll_enable();
        }

        if (list_is_singular(&stream->td_list))
                ehci_to_hcd(ehci)->self.bandwidth_allocated
                                -= stream->bandwidth;

done:
        sitd->urb = NULL;

        /* Add to the end of the free list for later reuse */
        list_move_tail(&sitd->sitd_list, &stream->free_list);

        /* Recycle the siTDs when the pipeline is empty (ep no longer in use) */
        if (list_empty(&stream->td_list)) {
                list_splice_tail_init(&stream->free_list,
                                &ehci->cached_sitd_list);
                start_free_itds(ehci);
        }

        return retval;
}


static int sitd_submit(struct ehci_hcd *ehci, struct urb *urb,
        gfp_t mem_flags)
{
        int                     status = -EINVAL;
        unsigned long           flags;
        struct ehci_iso_stream  *stream;

        /* Get iso_stream head */
        stream = iso_stream_find(ehci, urb);
        if (stream == NULL) {
                ehci_dbg(ehci, "can't get iso stream\n");
                return -ENOMEM;
        }
        if (urb->interval != stream->ps.period) {
                ehci_dbg(ehci, "can't change iso interval %d --> %d\n",
                        stream->ps.period, urb->interval);
                goto done;
        }

#ifdef EHCI_URB_TRACE
        ehci_dbg(ehci,
                "submit %p dev%s ep%d%s-iso len %d\n",
                urb, urb->dev->devpath,
                usb_pipeendpoint(urb->pipe),
                usb_pipein(urb->pipe) ? "in" : "out",
                urb->transfer_buffer_length);
#endif

        /* allocate SITDs */
        status = sitd_urb_transaction(stream, ehci, urb, mem_flags);
        if (status < 0) {
                ehci_dbg(ehci, "can't init sitds\n");
                goto done;
        }

        /* schedule ... need to lock */
        spin_lock_irqsave(&ehci->lock, flags);
        if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
                status = -ESHUTDOWN;
                goto done_not_linked;
        }
        status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
        if (unlikely(status))
                goto done_not_linked;
        status = iso_stream_schedule(ehci, urb, stream);
        if (likely(status == 0)) {
                sitd_link_urb(ehci, urb, ehci->periodic_size << 3, stream);
        } else if (status > 0) {
                status = 0;
                ehci_urb_done(ehci, urb, 0);
        } else {
                usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
        }
 done_not_linked:
        spin_unlock_irqrestore(&ehci->lock, flags);
 done:
        return status;
}

/*-------------------------------------------------------------------------*/

static void scan_isoc(struct ehci_hcd *ehci)
{
        unsigned                uf, now_frame, frame;
        unsigned                fmask = ehci->periodic_size - 1;
        bool                    modified, live;
        union ehci_shadow       q, *q_p;
        __hc32                  type, *hw_p;

        /*
         * When running, scan from last scan point up to "now"
         * else clean up by scanning everything that's left.
         * Touches as few pages as possible:  cache-friendly.
         */
        if (ehci->rh_state >= EHCI_RH_RUNNING) {
                uf = ehci_read_frame_index(ehci);
                now_frame = (uf >> 3) & fmask;
                live = true;
        } else  {
                now_frame = (ehci->last_iso_frame - 1) & fmask;
                live = false;
        }
        ehci->now_frame = now_frame;

        frame = ehci->last_iso_frame;

restart:
        /* Scan each element in frame's queue for completions */
        q_p = &ehci->pshadow[frame];
        hw_p = &ehci->periodic[frame];
        q.ptr = q_p->ptr;
        type = Q_NEXT_TYPE(ehci, *hw_p);
        modified = false;

        while (q.ptr != NULL) {
                switch (hc32_to_cpu(ehci, type)) {
                case Q_TYPE_ITD:
                        /*
                         * If this ITD is still active, leave it for
                         * later processing ... check the next entry.
                         * No need to check for activity unless the
                         * frame is current.
                         */
                        if (frame == now_frame && live) {
                                rmb();
                                for (uf = 0; uf < 8; uf++) {
                                        if (q.itd->hw_transaction[uf] &
                                                        ITD_ACTIVE(ehci))
                                                break;
                                }
                                if (uf < 8) {
                                        q_p = &q.itd->itd_next;
                                        hw_p = &q.itd->hw_next;
                                        type = Q_NEXT_TYPE(ehci,
                                                        q.itd->hw_next);
                                        q = *q_p;
                                        break;
                                }
                        }

                        /*
                         * Take finished ITDs out of the schedule
                         * and process them:  recycle, maybe report
                         * URB completion.  HC won't cache the
                         * pointer for much longer, if at all.
                         */
                        *q_p = q.itd->itd_next;
                        if (!ehci->use_dummy_qh ||
                                        q.itd->hw_next != EHCI_LIST_END(ehci))
                                *hw_p = q.itd->hw_next;
                        else
                                *hw_p = cpu_to_hc32(ehci, ehci->dummy->qh_dma);
                        type = Q_NEXT_TYPE(ehci, q.itd->hw_next);
                        wmb();
                        modified = itd_complete(ehci, q.itd);
                        q = *q_p;
                        break;
                case Q_TYPE_SITD:
                        /*
                         * If this SITD is still active, leave it for
                         * later processing ... check the next entry.
                         * No need to check for activity unless the
                         * frame is current.
                         */
                        if (((frame == now_frame) ||
                                        (((frame + 1) & fmask) == now_frame))
                                && live
                                && (q.sitd->hw_results & SITD_ACTIVE(ehci))) {

                                q_p = &q.sitd->sitd_next;
                                hw_p = &q.sitd->hw_next;
                                type = Q_NEXT_TYPE(ehci, q.sitd->hw_next);
                                q = *q_p;
                                break;
                        }

                        /*
                         * Take finished SITDs out of the schedule
                         * and process them:  recycle, maybe report
                         * URB completion.
                         */
                        *q_p = q.sitd->sitd_next;
                        if (!ehci->use_dummy_qh ||
                                        q.sitd->hw_next != EHCI_LIST_END(ehci))
                                *hw_p = q.sitd->hw_next;
                        else
                                *hw_p = cpu_to_hc32(ehci, ehci->dummy->qh_dma);
                        type = Q_NEXT_TYPE(ehci, q.sitd->hw_next);
                        wmb();
                        modified = sitd_complete(ehci, q.sitd);
                        q = *q_p;
                        break;
                default:
                        ehci_dbg(ehci, "corrupt type %d frame %d shadow %p\n",
                                        type, frame, q.ptr);
                        /* BUG(); */
                        fallthrough;
                case Q_TYPE_QH:
                case Q_TYPE_FSTN:
                        /* End of the iTDs and siTDs */
                        q.ptr = NULL;
                        break;
                }

                /* Assume completion callbacks modify the queue */
                if (unlikely(modified && ehci->isoc_count > 0))
                        goto restart;
        }

        /* Stop when we have reached the current frame */
        if (frame == now_frame)
                return;

        /* The last frame may still have active siTDs */
        ehci->last_iso_frame = frame;
        frame = (frame + 1) & fmask;

        goto restart;
}