Committer: Michael Beasley <mike@snafu.setup>

[mikesnafu-overlay.git] / drivers / usb / host / ohci-q.c

/*
 * OHCI HCD (Host Controller Driver) for USB.
 *
 * (C) Copyright 1999 Roman Weissgaerber <weissg@vienna.at>
 * (C) Copyright 2000-2002 David Brownell <dbrownell@users.sourceforge.net>
 *
 * This file is licenced under the GPL.
 */

#include <linux/irq.h>

static void urb_free_priv (struct ohci_hcd *hc, urb_priv_t *urb_priv)
{
        int             last = urb_priv->length - 1;

        if (last >= 0) {
                int             i;
                struct td       *td;

                for (i = 0; i <= last; i++) {
                        td = urb_priv->td [i];
                        if (td)
                                td_free (hc, td);
                }
        }

        list_del (&urb_priv->pending);
        kfree (urb_priv);
}

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

/*
 * URB goes back to driver, and isn't reissued.
 * It's completely gone from HC data structures.
 * PRECONDITION:  ohci lock held, irqs blocked.
 */
static void
finish_urb(struct ohci_hcd *ohci, struct urb *urb, int status)
__releases(ohci->lock)
__acquires(ohci->lock)
{
        // ASSERT (urb->hcpriv != 0);

        urb_free_priv (ohci, urb->hcpriv);
        if (likely(status == -EINPROGRESS))
                status = 0;

        switch (usb_pipetype (urb->pipe)) {
        case PIPE_ISOCHRONOUS:
                ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs--;
                break;
        case PIPE_INTERRUPT:
                ohci_to_hcd(ohci)->self.bandwidth_int_reqs--;
                break;
        }

#ifdef OHCI_VERBOSE_DEBUG
        urb_print(urb, "RET", usb_pipeout (urb->pipe), status);
#endif

        /* urb->complete() can reenter this HCD */
        usb_hcd_unlink_urb_from_ep(ohci_to_hcd(ohci), urb);
        spin_unlock (&ohci->lock);
        usb_hcd_giveback_urb(ohci_to_hcd(ohci), urb, status);
        spin_lock (&ohci->lock);

        /* stop periodic dma if it's not needed */
        if (ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0
                        && ohci_to_hcd(ohci)->self.bandwidth_int_reqs == 0) {
                ohci->hc_control &= ~(OHCI_CTRL_PLE|OHCI_CTRL_IE);
                ohci_writel (ohci, ohci->hc_control, &ohci->regs->control);
        }
}


/*-------------------------------------------------------------------------*
 * ED handling functions
 *-------------------------------------------------------------------------*/

/* search for the right schedule branch to use for a periodic ed.
 * does some load balancing; returns the branch, or negative errno.
 */
static int balance (struct ohci_hcd *ohci, int interval, int load)
{
        int     i, branch = -ENOSPC;

        /* iso periods can be huge; iso tds specify frame numbers */
        if (interval > NUM_INTS)
                interval = NUM_INTS;

        /* search for the least loaded schedule branch of that period
         * that has enough bandwidth left unreserved.
         */
        for (i = 0; i < interval ; i++) {
                if (branch < 0 || ohci->load [branch] > ohci->load [i]) {
                        int     j;

                        /* usb 1.1 says 90% of one frame */
                        for (j = i; j < NUM_INTS; j += interval) {
                                if ((ohci->load [j] + load) > 900)
                                        break;
                        }
                        if (j < NUM_INTS)
                                continue;
                        branch = i;
                }
        }
        return branch;
}

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

/* both iso and interrupt requests have periods; this routine puts them
 * into the schedule tree in the apppropriate place.  most iso devices use
 * 1msec periods, but that's not required.
 */
static void periodic_link (struct ohci_hcd *ohci, struct ed *ed)
{
        unsigned        i;

        ohci_vdbg (ohci, "link %sed %p branch %d [%dus.], interval %d\n",
                (ed->hwINFO & cpu_to_hc32 (ohci, ED_ISO)) ? "iso " : "",
                ed, ed->branch, ed->load, ed->interval);

        for (i = ed->branch; i < NUM_INTS; i += ed->interval) {
                struct ed       **prev = &ohci->periodic [i];
                __hc32          *prev_p = &ohci->hcca->int_table [i];
                struct ed       *here = *prev;

                /* sorting each branch by period (slow before fast)
                 * lets us share the faster parts of the tree.
                 * (plus maybe: put interrupt eds before iso)
                 */
                while (here && ed != here) {
                        if (ed->interval > here->interval)
                                break;
                        prev = &here->ed_next;
                        prev_p = &here->hwNextED;
                        here = *prev;
                }
                if (ed != here) {
                        ed->ed_next = here;
                        if (here)
                                ed->hwNextED = *prev_p;
                        wmb ();
                        *prev = ed;
                        *prev_p = cpu_to_hc32(ohci, ed->dma);
                        wmb();
                }
                ohci->load [i] += ed->load;
        }
        ohci_to_hcd(ohci)->self.bandwidth_allocated += ed->load / ed->interval;
}

/* link an ed into one of the HC chains */

static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
{
        int     branch;

        if (ohci_to_hcd(ohci)->state == HC_STATE_QUIESCING)
                return -EAGAIN;

        ed->state = ED_OPER;
        ed->ed_prev = NULL;
        ed->ed_next = NULL;
        ed->hwNextED = 0;
        if (quirk_zfmicro(ohci)
                        && (ed->type == PIPE_INTERRUPT)
                        && !(ohci->eds_scheduled++))
                mod_timer(&ohci->unlink_watchdog, round_jiffies(jiffies + HZ));
        wmb ();

        /* we care about rm_list when setting CLE/BLE in case the HC was at
         * work on some TD when CLE/BLE was turned off, and isn't quiesced
         * yet.  finish_unlinks() restarts as needed, some upcoming INTR_SF.
         *
         * control and bulk EDs are doubly linked (ed_next, ed_prev), but
         * periodic ones are singly linked (ed_next). that's because the
         * periodic schedule encodes a tree like figure 3-5 in the ohci
         * spec:  each qh can have several "previous" nodes, and the tree
         * doesn't have unused/idle descriptors.
         */
        switch (ed->type) {
        case PIPE_CONTROL:
                if (ohci->ed_controltail == NULL) {
                        WARN_ON (ohci->hc_control & OHCI_CTRL_CLE);
                        ohci_writel (ohci, ed->dma,
                                        &ohci->regs->ed_controlhead);
                } else {
                        ohci->ed_controltail->ed_next = ed;
                        ohci->ed_controltail->hwNextED = cpu_to_hc32 (ohci,
                                                                ed->dma);
                }
                ed->ed_prev = ohci->ed_controltail;
                if (!ohci->ed_controltail && !ohci->ed_rm_list) {
                        wmb();
                        ohci->hc_control |= OHCI_CTRL_CLE;
                        ohci_writel (ohci, 0, &ohci->regs->ed_controlcurrent);
                        ohci_writel (ohci, ohci->hc_control,
                                        &ohci->regs->control);
                }
                ohci->ed_controltail = ed;
                break;

        case PIPE_BULK:
                if (ohci->ed_bulktail == NULL) {
                        WARN_ON (ohci->hc_control & OHCI_CTRL_BLE);
                        ohci_writel (ohci, ed->dma, &ohci->regs->ed_bulkhead);
                } else {
                        ohci->ed_bulktail->ed_next = ed;
                        ohci->ed_bulktail->hwNextED = cpu_to_hc32 (ohci,
                                                                ed->dma);
                }
                ed->ed_prev = ohci->ed_bulktail;
                if (!ohci->ed_bulktail && !ohci->ed_rm_list) {
                        wmb();
                        ohci->hc_control |= OHCI_CTRL_BLE;
                        ohci_writel (ohci, 0, &ohci->regs->ed_bulkcurrent);
                        ohci_writel (ohci, ohci->hc_control,
                                        &ohci->regs->control);
                }
                ohci->ed_bulktail = ed;
                break;

        // case PIPE_INTERRUPT:
        // case PIPE_ISOCHRONOUS:
        default:
                branch = balance (ohci, ed->interval, ed->load);
                if (branch < 0) {
                        ohci_dbg (ohci,
                                "ERR %d, interval %d msecs, load %d\n",
                                branch, ed->interval, ed->load);
                        // FIXME if there are TDs queued, fail them!
                        return branch;
                }
                ed->branch = branch;
                periodic_link (ohci, ed);
        }

        /* the HC may not see the schedule updates yet, but if it does
         * then they'll be properly ordered.
         */
        return 0;
}

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

/* scan the periodic table to find and unlink this ED */
static void periodic_unlink (struct ohci_hcd *ohci, struct ed *ed)
{
        int     i;

        for (i = ed->branch; i < NUM_INTS; i += ed->interval) {
                struct ed       *temp;
                struct ed       **prev = &ohci->periodic [i];
                __hc32          *prev_p = &ohci->hcca->int_table [i];

                while (*prev && (temp = *prev) != ed) {
                        prev_p = &temp->hwNextED;
                        prev = &temp->ed_next;
                }
                if (*prev) {
                        *prev_p = ed->hwNextED;
                        *prev = ed->ed_next;
                }
                ohci->load [i] -= ed->load;
        }
        ohci_to_hcd(ohci)->self.bandwidth_allocated -= ed->load / ed->interval;

        ohci_vdbg (ohci, "unlink %sed %p branch %d [%dus.], interval %d\n",
                (ed->hwINFO & cpu_to_hc32 (ohci, ED_ISO)) ? "iso " : "",
                ed, ed->branch, ed->load, ed->interval);
}

/* unlink an ed from one of the HC chains.
 * just the link to the ed is unlinked.
 * the link from the ed still points to another operational ed or 0
 * so the HC can eventually finish the processing of the unlinked ed
 * (assuming it already started that, which needn't be true).
 *
 * ED_UNLINK is a transient state: the HC may still see this ED, but soon
 * it won't.  ED_SKIP means the HC will finish its current transaction,
 * but won't start anything new.  The TD queue may still grow; device
 * drivers don't know about this HCD-internal state.
 *
 * When the HC can't see the ED, something changes ED_UNLINK to one of:
 *
 *  - ED_OPER: when there's any request queued, the ED gets rescheduled
 *    immediately.  HC should be working on them.
 *
 *  - ED_IDLE:  when there's no TD queue. there's no reason for the HC
 *    to care about this ED; safe to disable the endpoint.
 *
 * When finish_unlinks() runs later, after SOF interrupt, it will often
 * complete one or more URB unlinks before making that state change.
 */
static void ed_deschedule (struct ohci_hcd *ohci, struct ed *ed)
{
        ed->hwINFO |= cpu_to_hc32 (ohci, ED_SKIP);
        wmb ();
        ed->state = ED_UNLINK;

        /* To deschedule something from the control or bulk list, just
         * clear CLE/BLE and wait.  There's no safe way to scrub out list
         * head/current registers until later, and "later" isn't very
         * tightly specified.  Figure 6-5 and Section 6.4.2.2 show how
         * the HC is reading the ED queues (while we modify them).
         *
         * For now, ed_schedule() is "later".  It might be good paranoia
         * to scrub those registers in finish_unlinks(), in case of bugs
         * that make the HC try to use them.
         */
        switch (ed->type) {
        case PIPE_CONTROL:
                /* remove ED from the HC's list: */
                if (ed->ed_prev == NULL) {
                        if (!ed->hwNextED) {
                                ohci->hc_control &= ~OHCI_CTRL_CLE;
                                ohci_writel (ohci, ohci->hc_control,
                                                &ohci->regs->control);
                                // a ohci_readl() later syncs CLE with the HC
                        } else
                                ohci_writel (ohci,
                                        hc32_to_cpup (ohci, &ed->hwNextED),
                                        &ohci->regs->ed_controlhead);
                } else {
                        ed->ed_prev->ed_next = ed->ed_next;
                        ed->ed_prev->hwNextED = ed->hwNextED;
                }
                /* remove ED from the HCD's list: */
                if (ohci->ed_controltail == ed) {
                        ohci->ed_controltail = ed->ed_prev;
                        if (ohci->ed_controltail)
                                ohci->ed_controltail->ed_next = NULL;
                } else if (ed->ed_next) {
                        ed->ed_next->ed_prev = ed->ed_prev;
                }
                break;

        case PIPE_BULK:
                /* remove ED from the HC's list: */
                if (ed->ed_prev == NULL) {
                        if (!ed->hwNextED) {
                                ohci->hc_control &= ~OHCI_CTRL_BLE;
                                ohci_writel (ohci, ohci->hc_control,
                                                &ohci->regs->control);
                                // a ohci_readl() later syncs BLE with the HC
                        } else
                                ohci_writel (ohci,
                                        hc32_to_cpup (ohci, &ed->hwNextED),
                                        &ohci->regs->ed_bulkhead);
                } else {
                        ed->ed_prev->ed_next = ed->ed_next;
                        ed->ed_prev->hwNextED = ed->hwNextED;
                }
                /* remove ED from the HCD's list: */
                if (ohci->ed_bulktail == ed) {
                        ohci->ed_bulktail = ed->ed_prev;
                        if (ohci->ed_bulktail)
                                ohci->ed_bulktail->ed_next = NULL;
                } else if (ed->ed_next) {
                        ed->ed_next->ed_prev = ed->ed_prev;
                }
                break;

        // case PIPE_INTERRUPT:
        // case PIPE_ISOCHRONOUS:
        default:
                periodic_unlink (ohci, ed);
                break;
        }
}


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

/* get and maybe (re)init an endpoint. init _should_ be done only as part
 * of enumeration, usb_set_configuration() or usb_set_interface().
 */
static struct ed *ed_get (
        struct ohci_hcd         *ohci,
        struct usb_host_endpoint *ep,
        struct usb_device       *udev,
        unsigned int            pipe,
        int                     interval
) {
        struct ed               *ed;
        unsigned long           flags;

        spin_lock_irqsave (&ohci->lock, flags);

        if (!(ed = ep->hcpriv)) {
                struct td       *td;
                int             is_out;
                u32             info;

                ed = ed_alloc (ohci, GFP_ATOMIC);
                if (!ed) {
                        /* out of memory */
                        goto done;
                }

                /* dummy td; end of td list for ed */
                td = td_alloc (ohci, GFP_ATOMIC);
                if (!td) {
                        /* out of memory */
                        ed_free (ohci, ed);
                        ed = NULL;
                        goto done;
                }
                ed->dummy = td;
                ed->hwTailP = cpu_to_hc32 (ohci, td->td_dma);
                ed->hwHeadP = ed->hwTailP;      /* ED_C, ED_H zeroed */
                ed->state = ED_IDLE;

                is_out = !(ep->desc.bEndpointAddress & USB_DIR_IN);

                /* FIXME usbcore changes dev->devnum before SET_ADDRESS
                 * suceeds ... otherwise we wouldn't need "pipe".
                 */
                info = usb_pipedevice (pipe);
                ed->type = usb_pipetype(pipe);

                info |= (ep->desc.bEndpointAddress & ~USB_DIR_IN) << 7;
                info |= le16_to_cpu(ep->desc.wMaxPacketSize) << 16;
                if (udev->speed == USB_SPEED_LOW)
                        info |= ED_LOWSPEED;
                /* only control transfers store pids in tds */
                if (ed->type != PIPE_CONTROL) {
                        info |= is_out ? ED_OUT : ED_IN;
                        if (ed->type != PIPE_BULK) {
                                /* periodic transfers... */
                                if (ed->type == PIPE_ISOCHRONOUS)
                                        info |= ED_ISO;
                                else if (interval > 32) /* iso can be bigger */
                                        interval = 32;
                                ed->interval = interval;
                                ed->load = usb_calc_bus_time (
                                        udev->speed, !is_out,
                                        ed->type == PIPE_ISOCHRONOUS,
                                        le16_to_cpu(ep->desc.wMaxPacketSize))
                                                / 1000;
                        }
                }
                ed->hwINFO = cpu_to_hc32(ohci, info);

                ep->hcpriv = ed;
        }

done:
        spin_unlock_irqrestore (&ohci->lock, flags);
        return ed;
}

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

/* request unlinking of an endpoint from an operational HC.
 * put the ep on the rm_list
 * real work is done at the next start frame (SF) hardware interrupt
 * caller guarantees HCD is running, so hardware access is safe,
 * and that ed->state is ED_OPER
 */
static void start_ed_unlink (struct ohci_hcd *ohci, struct ed *ed)
{
        ed->hwINFO |= cpu_to_hc32 (ohci, ED_DEQUEUE);
        ed_deschedule (ohci, ed);

        /* rm_list is just singly linked, for simplicity */
        ed->ed_next = ohci->ed_rm_list;
        ed->ed_prev = NULL;
        ohci->ed_rm_list = ed;

        /* enable SOF interrupt */
        ohci_writel (ohci, OHCI_INTR_SF, &ohci->regs->intrstatus);
        ohci_writel (ohci, OHCI_INTR_SF, &ohci->regs->intrenable);
        // flush those writes, and get latest HCCA contents
        (void) ohci_readl (ohci, &ohci->regs->control);

        /* SF interrupt might get delayed; record the frame counter value that
         * indicates when the HC isn't looking at it, so concurrent unlinks
         * behave.  frame_no wraps every 2^16 msec, and changes right before
         * SF is triggered.
         */
        ed->tick = ohci_frame_no(ohci) + 1;

}

/*-------------------------------------------------------------------------*
 * TD handling functions
 *-------------------------------------------------------------------------*/

/* enqueue next TD for this URB (OHCI spec 5.2.8.2) */

static void
td_fill (struct ohci_hcd *ohci, u32 info,
        dma_addr_t data, int len,
        struct urb *urb, int index)
{
        struct td               *td, *td_pt;
        struct urb_priv         *urb_priv = urb->hcpriv;
        int                     is_iso = info & TD_ISO;
        int                     hash;

        // ASSERT (index < urb_priv->length);

        /* aim for only one interrupt per urb.  mostly applies to control
         * and iso; other urbs rarely need more than one TD per urb.
         * this way, only final tds (or ones with an error) cause IRQs.
         * at least immediately; use DI=6 in case any control request is
         * tempted to die part way through.  (and to force the hc to flush
         * its donelist soonish, even on unlink paths.)
         *
         * NOTE: could delay interrupts even for the last TD, and get fewer
         * interrupts ... increasing per-urb latency by sharing interrupts.
         * Drivers that queue bulk urbs may request that behavior.
         */
        if (index != (urb_priv->length - 1)
                        || (urb->transfer_flags & URB_NO_INTERRUPT))
                info |= TD_DI_SET (6);

        /* use this td as the next dummy */
        td_pt = urb_priv->td [index];

        /* fill the old dummy TD */
        td = urb_priv->td [index] = urb_priv->ed->dummy;
        urb_priv->ed->dummy = td_pt;

        td->ed = urb_priv->ed;
        td->next_dl_td = NULL;
        td->index = index;
        td->urb = urb;
        td->data_dma = data;
        if (!len)
                data = 0;

        td->hwINFO = cpu_to_hc32 (ohci, info);
        if (is_iso) {
                td->hwCBP = cpu_to_hc32 (ohci, data & 0xFFFFF000);
                *ohci_hwPSWp(ohci, td, 0) = cpu_to_hc16 (ohci,
                                                (data & 0x0FFF) | 0xE000);
                td->ed->last_iso = info & 0xffff;
        } else {
                td->hwCBP = cpu_to_hc32 (ohci, data);
        }
        if (data)
                td->hwBE = cpu_to_hc32 (ohci, data + len - 1);
        else
                td->hwBE = 0;
        td->hwNextTD = cpu_to_hc32 (ohci, td_pt->td_dma);

        /* append to queue */
        list_add_tail (&td->td_list, &td->ed->td_list);

        /* hash it for later reverse mapping */
        hash = TD_HASH_FUNC (td->td_dma);
        td->td_hash = ohci->td_hash [hash];
        ohci->td_hash [hash] = td;

        /* HC might read the TD (or cachelines) right away ... */
        wmb ();
        td->ed->hwTailP = td->hwNextTD;
}

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

/* Prepare all TDs of a transfer, and queue them onto the ED.
 * Caller guarantees HC is active.
 * Usually the ED is already on the schedule, so TDs might be
 * processed as soon as they're queued.
 */
static void td_submit_urb (
        struct ohci_hcd *ohci,
        struct urb      *urb
) {
        struct urb_priv *urb_priv = urb->hcpriv;
        dma_addr_t      data;
        int             data_len = urb->transfer_buffer_length;
        int             cnt = 0;
        u32             info = 0;
        int             is_out = usb_pipeout (urb->pipe);
        int             periodic = 0;

        /* OHCI handles the bulk/interrupt data toggles itself.  We just
         * use the device toggle bits for resetting, and rely on the fact
         * that resetting toggle is meaningless if the endpoint is active.
         */
        if (!usb_gettoggle (urb->dev, usb_pipeendpoint (urb->pipe), is_out)) {
                usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe),
                        is_out, 1);
                urb_priv->ed->hwHeadP &= ~cpu_to_hc32 (ohci, ED_C);
        }

        urb_priv->td_cnt = 0;
        list_add (&urb_priv->pending, &ohci->pending);

        if (data_len)
                data = urb->transfer_dma;
        else
                data = 0;

        /* NOTE:  TD_CC is set so we can tell which TDs the HC processed by
         * using TD_CC_GET, as well as by seeing them on the done list.
         * (CC = NotAccessed ... 0x0F, or 0x0E in PSWs for ISO.)
         */
        switch (urb_priv->ed->type) {

        /* Bulk and interrupt are identical except for where in the schedule
         * their EDs live.
         */
        case PIPE_INTERRUPT:
                /* ... and periodic urbs have extra accounting */
                periodic = ohci_to_hcd(ohci)->self.bandwidth_int_reqs++ == 0
                        && ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs == 0;
                /* FALLTHROUGH */
        case PIPE_BULK:
                info = is_out
                        ? TD_T_TOGGLE | TD_CC | TD_DP_OUT
                        : TD_T_TOGGLE | TD_CC | TD_DP_IN;
                /* TDs _could_ transfer up to 8K each */
                while (data_len > 4096) {
                        td_fill (ohci, info, data, 4096, urb, cnt);
                        data += 4096;
                        data_len -= 4096;
                        cnt++;
                }
                /* maybe avoid ED halt on final TD short read */
                if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
                        info |= TD_R;
                td_fill (ohci, info, data, data_len, urb, cnt);
                cnt++;
                if ((urb->transfer_flags & URB_ZERO_PACKET)
                                && cnt < urb_priv->length) {
                        td_fill (ohci, info, 0, 0, urb, cnt);
                        cnt++;
                }
                /* maybe kickstart bulk list */
                if (urb_priv->ed->type == PIPE_BULK) {
                        wmb ();
                        ohci_writel (ohci, OHCI_BLF, &ohci->regs->cmdstatus);
                }
                break;

        /* control manages DATA0/DATA1 toggle per-request; SETUP resets it,
         * any DATA phase works normally, and the STATUS ack is special.
         */
        case PIPE_CONTROL:
                info = TD_CC | TD_DP_SETUP | TD_T_DATA0;
                td_fill (ohci, info, urb->setup_dma, 8, urb, cnt++);
                if (data_len > 0) {
                        info = TD_CC | TD_R | TD_T_DATA1;
                        info |= is_out ? TD_DP_OUT : TD_DP_IN;
                        /* NOTE:  mishandles transfers >8K, some >4K */
                        td_fill (ohci, info, data, data_len, urb, cnt++);
                }
                info = (is_out || data_len == 0)
                        ? TD_CC | TD_DP_IN | TD_T_DATA1
                        : TD_CC | TD_DP_OUT | TD_T_DATA1;
                td_fill (ohci, info, data, 0, urb, cnt++);
                /* maybe kickstart control list */
                wmb ();
                ohci_writel (ohci, OHCI_CLF, &ohci->regs->cmdstatus);
                break;

        /* ISO has no retransmit, so no toggle; and it uses special TDs.
         * Each TD could handle multiple consecutive frames (interval 1);
         * we could often reduce the number of TDs here.
         */
        case PIPE_ISOCHRONOUS:
                for (cnt = 0; cnt < urb->number_of_packets; cnt++) {
                        int     frame = urb->start_frame;

                        // FIXME scheduling should handle frame counter
                        // roll-around ... exotic case (and OHCI has
                        // a 2^16 iso range, vs other HCs max of 2^10)
                        frame += cnt * urb->interval;
                        frame &= 0xffff;
                        td_fill (ohci, TD_CC | TD_ISO | frame,
                                data + urb->iso_frame_desc [cnt].offset,
                                urb->iso_frame_desc [cnt].length, urb, cnt);
                }
                periodic = ohci_to_hcd(ohci)->self.bandwidth_isoc_reqs++ == 0
                        && ohci_to_hcd(ohci)->self.bandwidth_int_reqs == 0;
                break;
        }

        /* start periodic dma if needed */
        if (periodic) {
                wmb ();
                ohci->hc_control |= OHCI_CTRL_PLE|OHCI_CTRL_IE;
                ohci_writel (ohci, ohci->hc_control, &ohci->regs->control);
        }

        // ASSERT (urb_priv->length == cnt);
}

/*-------------------------------------------------------------------------*
 * Done List handling functions
 *-------------------------------------------------------------------------*/

/* calculate transfer length/status and update the urb */
static int td_done(struct ohci_hcd *ohci, struct urb *urb, struct td *td)
{
        u32     tdINFO = hc32_to_cpup (ohci, &td->hwINFO);
        int     cc = 0;
        int     status = -EINPROGRESS;

        list_del (&td->td_list);

        /* ISO ... drivers see per-TD length/status */
        if (tdINFO & TD_ISO) {
                u16     tdPSW = ohci_hwPSW(ohci, td, 0);
                int     dlen = 0;

                /* NOTE:  assumes FC in tdINFO == 0, and that
                 * only the first of 0..MAXPSW psws is used.
                 */

                cc = (tdPSW >> 12) & 0xF;
                if (tdINFO & TD_CC)     /* hc didn't touch? */
                        return status;

                if (usb_pipeout (urb->pipe))
                        dlen = urb->iso_frame_desc [td->index].length;
                else {
                        /* short reads are always OK for ISO */
                        if (cc == TD_DATAUNDERRUN)
                                cc = TD_CC_NOERROR;
                        dlen = tdPSW & 0x3ff;
                }
                urb->actual_length += dlen;
                urb->iso_frame_desc [td->index].actual_length = dlen;
                urb->iso_frame_desc [td->index].status = cc_to_error [cc];

                if (cc != TD_CC_NOERROR)
                        ohci_vdbg (ohci,
                                "urb %p iso td %p (%d) len %d cc %d\n",
                                urb, td, 1 + td->index, dlen, cc);

        /* BULK, INT, CONTROL ... drivers see aggregate length/status,
         * except that "setup" bytes aren't counted and "short" transfers
         * might not be reported as errors.
         */
        } else {
                int     type = usb_pipetype (urb->pipe);
                u32     tdBE = hc32_to_cpup (ohci, &td->hwBE);

                cc = TD_CC_GET (tdINFO);

                /* update packet status if needed (short is normally ok) */
                if (cc == TD_DATAUNDERRUN
                                && !(urb->transfer_flags & URB_SHORT_NOT_OK))
                        cc = TD_CC_NOERROR;
                if (cc != TD_CC_NOERROR && cc < 0x0E)
                        status = cc_to_error[cc];

                /* count all non-empty packets except control SETUP packet */
                if ((type != PIPE_CONTROL || td->index != 0) && tdBE != 0) {
                        if (td->hwCBP == 0)
                                urb->actual_length += tdBE - td->data_dma + 1;
                        else
                                urb->actual_length +=
                                          hc32_to_cpup (ohci, &td->hwCBP)
                                        - td->data_dma;
                }

                if (cc != TD_CC_NOERROR && cc < 0x0E)
                        ohci_vdbg (ohci,
                                "urb %p td %p (%d) cc %d, len=%d/%d\n",
                                urb, td, 1 + td->index, cc,
                                urb->actual_length,
                                urb->transfer_buffer_length);
        }
        return status;
}

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

static void ed_halted(struct ohci_hcd *ohci, struct td *td, int cc)
{
        struct urb              *urb = td->urb;
        urb_priv_t              *urb_priv = urb->hcpriv;
        struct ed               *ed = td->ed;
        struct list_head        *tmp = td->td_list.next;
        __hc32                  toggle = ed->hwHeadP & cpu_to_hc32 (ohci, ED_C);

        /* clear ed halt; this is the td that caused it, but keep it inactive
         * until its urb->complete() has a chance to clean up.
         */
        ed->hwINFO |= cpu_to_hc32 (ohci, ED_SKIP);
        wmb ();
        ed->hwHeadP &= ~cpu_to_hc32 (ohci, ED_H);

        /* Get rid of all later tds from this urb.  We don't have
         * to be careful: no errors and nothing was transferred.
         * Also patch the ed so it looks as if those tds completed normally.
         */
        while (tmp != &ed->td_list) {
                struct td       *next;

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

                if (next->urb != urb)
                        break;

                /* NOTE: if multi-td control DATA segments get supported,
                 * this urb had one of them, this td wasn't the last td
                 * in that segment (TD_R clear), this ed halted because
                 * of a short read, _and_ URB_SHORT_NOT_OK is clear ...
                 * then we need to leave the control STATUS packet queued
                 * and clear ED_SKIP.
                 */

                list_del(&next->td_list);
                urb_priv->td_cnt++;
                ed->hwHeadP = next->hwNextTD | toggle;
        }

        /* help for troubleshooting:  report anything that
         * looks odd ... that doesn't include protocol stalls
         * (or maybe some other things)
         */
        switch (cc) {
        case TD_DATAUNDERRUN:
                if ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0)
                        break;
                /* fallthrough */
        case TD_CC_STALL:
                if (usb_pipecontrol (urb->pipe))
                        break;
                /* fallthrough */
        default:
                ohci_dbg (ohci,
                        "urb %p path %s ep%d%s %08x cc %d --> status %d\n",
                        urb, urb->dev->devpath,
                        usb_pipeendpoint (urb->pipe),
                        usb_pipein (urb->pipe) ? "in" : "out",
                        hc32_to_cpu (ohci, td->hwINFO),
                        cc, cc_to_error [cc]);
        }
}

/* replies to the request have to be on a FIFO basis so
 * we unreverse the hc-reversed done-list
 */
static struct td *dl_reverse_done_list (struct ohci_hcd *ohci)
{
        u32             td_dma;
        struct td       *td_rev = NULL;
        struct td       *td = NULL;

        td_dma = hc32_to_cpup (ohci, &ohci->hcca->done_head);
        ohci->hcca->done_head = 0;
        wmb();

        /* get TD from hc's singly linked list, and
         * prepend to ours.  ed->td_list changes later.
         */
        while (td_dma) {
                int             cc;

                td = dma_to_td (ohci, td_dma);
                if (!td) {
                        ohci_err (ohci, "bad entry %8x\n", td_dma);
                        break;
                }

                td->hwINFO |= cpu_to_hc32 (ohci, TD_DONE);
                cc = TD_CC_GET (hc32_to_cpup (ohci, &td->hwINFO));

                /* Non-iso endpoints can halt on error; un-halt,
                 * and dequeue any other TDs from this urb.
                 * No other TD could have caused the halt.
                 */
                if (cc != TD_CC_NOERROR
                                && (td->ed->hwHeadP & cpu_to_hc32 (ohci, ED_H)))
                        ed_halted(ohci, td, cc);

                td->next_dl_td = td_rev;
                td_rev = td;
                td_dma = hc32_to_cpup (ohci, &td->hwNextTD);
        }
        return td_rev;
}

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

/* there are some urbs/eds to unlink; called in_irq(), with HCD locked */
static void
finish_unlinks (struct ohci_hcd *ohci, u16 tick)
{
        struct ed       *ed, **last;

rescan_all:
        for (last = &ohci->ed_rm_list, ed = *last; ed != NULL; ed = *last) {
                struct list_head        *entry, *tmp;
                int                     completed, modified;
                __hc32                  *prev;

                /* only take off EDs that the HC isn't using, accounting for
                 * frame counter wraps and EDs with partially retired TDs
                 */
                if (likely (HC_IS_RUNNING(ohci_to_hcd(ohci)->state))) {
                        if (tick_before (tick, ed->tick)) {
skip_ed:
                                last = &ed->ed_next;
                                continue;
                        }

                        if (!list_empty (&ed->td_list)) {
                                struct td       *td;
                                u32             head;

                                td = list_entry (ed->td_list.next, struct td,
                                                        td_list);
                                head = hc32_to_cpu (ohci, ed->hwHeadP) &
                                                                TD_MASK;

                                /* INTR_WDH may need to clean up first */
                                if (td->td_dma != head) {
                                        if (ed == ohci->ed_to_check)
                                                ohci->ed_to_check = NULL;
                                        else
                                                goto skip_ed;
                                }
                        }
                }

                /* reentrancy:  if we drop the schedule lock, someone might
                 * have modified this list.  normally it's just prepending
                 * entries (which we'd ignore), but paranoia won't hurt.
                 */
                *last = ed->ed_next;
                ed->ed_next = NULL;
                modified = 0;

                /* unlink urbs as requested, but rescan the list after
                 * we call a completion since it might have unlinked
                 * another (earlier) urb
                 *
                 * When we get here, the HC doesn't see this ed.  But it
                 * must not be rescheduled until all completed URBs have
                 * been given back to the driver.
                 */
rescan_this:
                completed = 0;
                prev = &ed->hwHeadP;
                list_for_each_safe (entry, tmp, &ed->td_list) {
                        struct td       *td;
                        struct urb      *urb;
                        urb_priv_t      *urb_priv;
                        __hc32          savebits;

                        td = list_entry (entry, struct td, td_list);
                        urb = td->urb;
                        urb_priv = td->urb->hcpriv;

                        if (!urb->unlinked) {
                                prev = &td->hwNextTD;
                                continue;
                        }

                        /* patch pointer hc uses */
                        savebits = *prev & ~cpu_to_hc32 (ohci, TD_MASK);
                        *prev = td->hwNextTD | savebits;

                        /* HC may have partly processed this TD */
                        td_done (ohci, urb, td);
                        urb_priv->td_cnt++;

                        /* if URB is done, clean up */
                        if (urb_priv->td_cnt == urb_priv->length) {
                                modified = completed = 1;
                                finish_urb(ohci, urb, 0);
                        }
                }
                if (completed && !list_empty (&ed->td_list))
                        goto rescan_this;

                /* ED's now officially unlinked, hc doesn't see */
                ed->state = ED_IDLE;
                if (quirk_zfmicro(ohci) && ed->type == PIPE_INTERRUPT)
                        ohci->eds_scheduled--;
                ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
                ed->hwNextED = 0;
                wmb ();
                ed->hwINFO &= ~cpu_to_hc32 (ohci, ED_SKIP | ED_DEQUEUE);

                /* but if there's work queued, reschedule */
                if (!list_empty (&ed->td_list)) {
                        if (HC_IS_RUNNING(ohci_to_hcd(ohci)->state))
                                ed_schedule (ohci, ed);
                }

                if (modified)
                        goto rescan_all;
        }

        /* maybe reenable control and bulk lists */
        if (HC_IS_RUNNING(ohci_to_hcd(ohci)->state)
                        && ohci_to_hcd(ohci)->state != HC_STATE_QUIESCING
                        && !ohci->ed_rm_list) {
                u32     command = 0, control = 0;

                if (ohci->ed_controltail) {
                        command |= OHCI_CLF;
                        if (quirk_zfmicro(ohci))
                                mdelay(1);
                        if (!(ohci->hc_control & OHCI_CTRL_CLE)) {
                                control |= OHCI_CTRL_CLE;
                                ohci_writel (ohci, 0,
                                        &ohci->regs->ed_controlcurrent);
                        }
                }
                if (ohci->ed_bulktail) {
                        command |= OHCI_BLF;
                        if (quirk_zfmicro(ohci))
                                mdelay(1);
                        if (!(ohci->hc_control & OHCI_CTRL_BLE)) {
                                control |= OHCI_CTRL_BLE;
                                ohci_writel (ohci, 0,
                                        &ohci->regs->ed_bulkcurrent);
                        }
                }

                /* CLE/BLE to enable, CLF/BLF to (maybe) kickstart */
                if (control) {
                        ohci->hc_control |= control;
                        if (quirk_zfmicro(ohci))
                                mdelay(1);
                        ohci_writel (ohci, ohci->hc_control,
                                        &ohci->regs->control);
                }
                if (command) {
                        if (quirk_zfmicro(ohci))
                                mdelay(1);
                        ohci_writel (ohci, command, &ohci->regs->cmdstatus);
                }
        }
}



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

/*
 * Used to take back a TD from the host controller. This would normally be
 * called from within dl_done_list, however it may be called directly if the
 * HC no longer sees the TD and it has not appeared on the donelist (after
 * two frames).  This bug has been observed on ZF Micro systems.
 */
static void takeback_td(struct ohci_hcd *ohci, struct td *td)
{
        struct urb      *urb = td->urb;
        urb_priv_t      *urb_priv = urb->hcpriv;
        struct ed       *ed = td->ed;
        int             status;

        /* update URB's length and status from TD */
        status = td_done(ohci, urb, td);
        urb_priv->td_cnt++;

        /* If all this urb's TDs are done, call complete() */
        if (urb_priv->td_cnt == urb_priv->length)
                finish_urb(ohci, urb, status);

        /* clean schedule:  unlink EDs that are no longer busy */
        if (list_empty(&ed->td_list)) {
                if (ed->state == ED_OPER)
                        start_ed_unlink(ohci, ed);

        /* ... reenabling halted EDs only after fault cleanup */
        } else if ((ed->hwINFO & cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE))
                        == cpu_to_hc32(ohci, ED_SKIP)) {
                td = list_entry(ed->td_list.next, struct td, td_list);
                if (!(td->hwINFO & cpu_to_hc32(ohci, TD_DONE))) {
                        ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP);
                        /* ... hc may need waking-up */
                        switch (ed->type) {
                        case PIPE_CONTROL:
                                ohci_writel(ohci, OHCI_CLF,
                                                &ohci->regs->cmdstatus);
                                break;
                        case PIPE_BULK:
                                ohci_writel(ohci, OHCI_BLF,
                                                &ohci->regs->cmdstatus);
                                break;
                        }
                }
        }
}

/*
 * Process normal completions (error or success) and clean the schedules.
 *
 * This is the main path for handing urbs back to drivers.  The only other
 * normal path is finish_unlinks(), which unlinks URBs using ed_rm_list,
 * instead of scanning the (re-reversed) donelist as this does.  There's
 * an abnormal path too, handling a quirk in some Compaq silicon:  URBs
 * with TDs that appear to be orphaned are directly reclaimed.
 */
static void
dl_done_list (struct ohci_hcd *ohci)
{
        struct td       *td = dl_reverse_done_list (ohci);

        while (td) {
                struct td       *td_next = td->next_dl_td;
                takeback_td(ohci, td);
                td = td_next;
        }
}