Linux-2.6.12-rc2

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / usb / host / ehci-q.c

/*
 * Copyright (c) 2001-2002 by David Brownell
 * 
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

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

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

/*
 * EHCI hardware queue manipulation ... the core.  QH/QTD manipulation.
 *
 * Control, bulk, and interrupt traffic all use "qh" lists.  They list "qtd"
 * entries describing USB transactions, max 16-20kB/entry (with 4kB-aligned
 * buffers needed for the larger number).  We use one QH per endpoint, queue
 * multiple urbs (all three types) per endpoint.  URBs may need several qtds.
 *
 * ISO traffic uses "ISO TD" (itd, and sitd) records, and (along with
 * interrupts) needs careful scheduling.  Performance improvements can be
 * an ongoing challenge.  That's in "ehci-sched.c".
 * 
 * USB 1.1 devices are handled (a) by "companion" OHCI or UHCI root hubs,
 * or otherwise through transaction translators (TTs) in USB 2.0 hubs using
 * (b) special fields in qh entries or (c) split iso entries.  TTs will
 * buffer low/full speed data so the host collects it at high speed.
 */

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

/* fill a qtd, returning how much of the buffer we were able to queue up */

static int
qtd_fill (struct ehci_qtd *qtd, dma_addr_t buf, size_t len,
                int token, int maxpacket)
{
        int     i, count;
        u64     addr = buf;

        /* one buffer entry per 4K ... first might be short or unaligned */
        qtd->hw_buf [0] = cpu_to_le32 ((u32)addr);
        qtd->hw_buf_hi [0] = cpu_to_le32 ((u32)(addr >> 32));
        count = 0x1000 - (buf & 0x0fff);        /* rest of that page */
        if (likely (len < count))               /* ... iff needed */
                count = len;
        else {
                buf +=  0x1000;
                buf &= ~0x0fff;

                /* per-qtd limit: from 16K to 20K (best alignment) */
                for (i = 1; count < len && i < 5; i++) {
                        addr = buf;
                        qtd->hw_buf [i] = cpu_to_le32 ((u32)addr);
                        qtd->hw_buf_hi [i] = cpu_to_le32 ((u32)(addr >> 32));
                        buf += 0x1000;
                        if ((count + 0x1000) < len)
                                count += 0x1000;
                        else
                                count = len;
                }

                /* short packets may only terminate transfers */
                if (count != len)
                        count -= (count % maxpacket);
        }
        qtd->hw_token = cpu_to_le32 ((count << 16) | token);
        qtd->length = count;

        return count;
}

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

static inline void
qh_update (struct ehci_hcd *ehci, struct ehci_qh *qh, struct ehci_qtd *qtd)
{
        /* writes to an active overlay are unsafe */
        BUG_ON(qh->qh_state != QH_STATE_IDLE);

        qh->hw_qtd_next = QTD_NEXT (qtd->qtd_dma);
        qh->hw_alt_next = EHCI_LIST_END;

        /* Except for control endpoints, we make hardware maintain data
         * toggle (like OHCI) ... here (re)initialize the toggle in the QH,
         * and set the pseudo-toggle in udev. Only usb_clear_halt() will
         * ever clear it.
         */
        if (!(qh->hw_info1 & cpu_to_le32(1 << 14))) {
                unsigned        is_out, epnum;

                is_out = !(qtd->hw_token & cpu_to_le32(1 << 8));
                epnum = (le32_to_cpup(&qh->hw_info1) >> 8) & 0x0f;
                if (unlikely (!usb_gettoggle (qh->dev, epnum, is_out))) {
                        qh->hw_token &= ~__constant_cpu_to_le32 (QTD_TOGGLE);
                        usb_settoggle (qh->dev, epnum, is_out, 1);
                }
        }

        /* HC must see latest qtd and qh data before we clear ACTIVE+HALT */
        wmb ();
        qh->hw_token &= __constant_cpu_to_le32 (QTD_TOGGLE | QTD_STS_PING);
}

/* if it weren't for a common silicon quirk (writing the dummy into the qh
 * overlay, so qh->hw_token wrongly becomes inactive/halted), only fault
 * recovery (including urb dequeue) would need software changes to a QH...
 */
static void
qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        struct ehci_qtd *qtd;

        if (list_empty (&qh->qtd_list))
                qtd = qh->dummy;
        else {
                qtd = list_entry (qh->qtd_list.next,
                                struct ehci_qtd, qtd_list);
                /* first qtd may already be partially processed */
                if (cpu_to_le32 (qtd->qtd_dma) == qh->hw_current)
                        qtd = NULL;
        }

        if (qtd)
                qh_update (ehci, qh, qtd);
}

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

static void qtd_copy_status (
        struct ehci_hcd *ehci,
        struct urb *urb,
        size_t length,
        u32 token
)
{
        /* count IN/OUT bytes, not SETUP (even short packets) */
        if (likely (QTD_PID (token) != 2))
                urb->actual_length += length - QTD_LENGTH (token);

        /* don't modify error codes */
        if (unlikely (urb->status != -EINPROGRESS))
                return;

        /* force cleanup after short read; not always an error */
        if (unlikely (IS_SHORT_READ (token)))
                urb->status = -EREMOTEIO;

        /* serious "can't proceed" faults reported by the hardware */
        if (token & QTD_STS_HALT) {
                if (token & QTD_STS_BABBLE) {
                        /* FIXME "must" disable babbling device's port too */
                        urb->status = -EOVERFLOW;
                } else if (token & QTD_STS_MMF) {
                        /* fs/ls interrupt xfer missed the complete-split */
                        urb->status = -EPROTO;
                } else if (token & QTD_STS_DBE) {
                        urb->status = (QTD_PID (token) == 1) /* IN ? */
                                ? -ENOSR  /* hc couldn't read data */
                                : -ECOMM; /* hc couldn't write data */
                } else if (token & QTD_STS_XACT) {
                        /* timeout, bad crc, wrong PID, etc; retried */
                        if (QTD_CERR (token))
                                urb->status = -EPIPE;
                        else {
                                ehci_dbg (ehci, "devpath %s ep%d%s 3strikes\n",
                                        urb->dev->devpath,
                                        usb_pipeendpoint (urb->pipe),
                                        usb_pipein (urb->pipe) ? "in" : "out");
                                urb->status = -EPROTO;
                        }
                /* CERR nonzero + no errors + halt --> stall */
                } else if (QTD_CERR (token))
                        urb->status = -EPIPE;
                else    /* unknown */
                        urb->status = -EPROTO;

                ehci_vdbg (ehci,
                        "dev%d ep%d%s qtd token %08x --> status %d\n",
                        usb_pipedevice (urb->pipe),
                        usb_pipeendpoint (urb->pipe),
                        usb_pipein (urb->pipe) ? "in" : "out",
                        token, urb->status);

                /* if async CSPLIT failed, try cleaning out the TT buffer */
                if (urb->status != -EPIPE
                                && urb->dev->tt && !usb_pipeint (urb->pipe)
                                && ((token & QTD_STS_MMF) != 0
                                        || QTD_CERR(token) == 0)
                                && (!ehci_is_TDI(ehci)
                                        || urb->dev->tt->hub !=
                                           ehci_to_hcd(ehci)->self.root_hub)) {
#ifdef DEBUG
                        struct usb_device *tt = urb->dev->tt->hub;
                        dev_dbg (&tt->dev,
                                "clear tt buffer port %d, a%d ep%d t%08x\n",
                                urb->dev->ttport, urb->dev->devnum,
                                usb_pipeendpoint (urb->pipe), token);
#endif /* DEBUG */
                        usb_hub_tt_clear_buffer (urb->dev, urb->pipe);
                }
        }
}

static void
ehci_urb_done (struct ehci_hcd *ehci, struct urb *urb, struct pt_regs *regs)
__releases(ehci->lock)
__acquires(ehci->lock)
{
        if (likely (urb->hcpriv != NULL)) {
                struct ehci_qh  *qh = (struct ehci_qh *) urb->hcpriv;

                /* S-mask in a QH means it's an interrupt urb */
                if ((qh->hw_info2 & __constant_cpu_to_le32 (0x00ff)) != 0) {

                        /* ... update hc-wide periodic stats (for usbfs) */
                        ehci_to_hcd(ehci)->self.bandwidth_int_reqs--;
                }
                qh_put (qh);
        }

        spin_lock (&urb->lock);
        urb->hcpriv = NULL;
        switch (urb->status) {
        case -EINPROGRESS:              /* success */
                urb->status = 0;
        default:                        /* fault */
                COUNT (ehci->stats.complete);
                break;
        case -EREMOTEIO:                /* fault or normal */
                if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
                        urb->status = 0;
                COUNT (ehci->stats.complete);
                break;
        case -ECONNRESET:               /* canceled */
        case -ENOENT:
                COUNT (ehci->stats.unlink);
                break;
        }
        spin_unlock (&urb->lock);

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

        /* complete() can reenter this HCD */
        spin_unlock (&ehci->lock);
        usb_hcd_giveback_urb (ehci_to_hcd(ehci), urb, regs);
        spin_lock (&ehci->lock);
}

static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);
static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);

static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh);

/*
 * Process and free completed qtds for a qh, returning URBs to drivers.
 * Chases up to qh->hw_current.  Returns number of completions called,
 * indicating how much "real" work we did.
 */
#define HALT_BIT __constant_cpu_to_le32(QTD_STS_HALT)
static unsigned
qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh, struct pt_regs *regs)
{
        struct ehci_qtd         *last = NULL, *end = qh->dummy;
        struct list_head        *entry, *tmp;
        int                     stopped;
        unsigned                count = 0;
        int                     do_status = 0;
        u8                      state;

        if (unlikely (list_empty (&qh->qtd_list)))
                return count;

        /* completions (or tasks on other cpus) must never clobber HALT
         * till we've gone through and cleaned everything up, even when
         * they add urbs to this qh's queue or mark them for unlinking.
         *
         * NOTE:  unlinking expects to be done in queue order.
         */
        state = qh->qh_state;
        qh->qh_state = QH_STATE_COMPLETING;
        stopped = (state == QH_STATE_IDLE);

        /* remove de-activated QTDs from front of queue.
         * after faults (including short reads), cleanup this urb
         * then let the queue advance.
         * if queue is stopped, handles unlinks.
         */
        list_for_each_safe (entry, tmp, &qh->qtd_list) {
                struct ehci_qtd *qtd;
                struct urb      *urb;
                u32             token = 0;

                qtd = list_entry (entry, struct ehci_qtd, qtd_list);
                urb = qtd->urb;

                /* clean up any state from previous QTD ...*/
                if (last) {
                        if (likely (last->urb != urb)) {
                                ehci_urb_done (ehci, last->urb, regs);
                                count++;
                        }
                        ehci_qtd_free (ehci, last);
                        last = NULL;
                }

                /* ignore urbs submitted during completions we reported */
                if (qtd == end)
                        break;

                /* hardware copies qtd out of qh overlay */
                rmb ();
                token = le32_to_cpu (qtd->hw_token);

                /* always clean up qtds the hc de-activated */
                if ((token & QTD_STS_ACTIVE) == 0) {

                        if ((token & QTD_STS_HALT) != 0) {
                                stopped = 1;

                        /* magic dummy for some short reads; qh won't advance.
                         * that silicon quirk can kick in with this dummy too.
                         */
                        } else if (IS_SHORT_READ (token)
                                        && !(qtd->hw_alt_next & EHCI_LIST_END)) {
                                stopped = 1;
                                goto halt;
                        }

                /* stop scanning when we reach qtds the hc is using */
                } else if (likely (!stopped
                                && HC_IS_RUNNING (ehci_to_hcd(ehci)->state))) {
                        break;

                } else {
                        stopped = 1;

                        if (unlikely (!HC_IS_RUNNING (ehci_to_hcd(ehci)->state)))
                                urb->status = -ESHUTDOWN;

                        /* ignore active urbs unless some previous qtd
                         * for the urb faulted (including short read) or
                         * its urb was canceled.  we may patch qh or qtds.
                         */
                        if (likely (urb->status == -EINPROGRESS))
                                continue;
                        
                        /* issue status after short control reads */
                        if (unlikely (do_status != 0)
                                        && QTD_PID (token) == 0 /* OUT */) {
                                do_status = 0;
                                continue;
                        }

                        /* token in overlay may be most current */
                        if (state == QH_STATE_IDLE
                                        && cpu_to_le32 (qtd->qtd_dma)
                                                == qh->hw_current)
                                token = le32_to_cpu (qh->hw_token);

                        /* force halt for unlinked or blocked qh, so we'll
                         * patch the qh later and so that completions can't
                         * activate it while we "know" it's stopped.
                         */
                        if ((HALT_BIT & qh->hw_token) == 0) {
halt:
                                qh->hw_token |= HALT_BIT;
                                wmb ();
                        }
                }
 
                /* remove it from the queue */
                spin_lock (&urb->lock);
                qtd_copy_status (ehci, urb, qtd->length, token);
                do_status = (urb->status == -EREMOTEIO)
                                && usb_pipecontrol (urb->pipe);
                spin_unlock (&urb->lock);

                if (stopped && qtd->qtd_list.prev != &qh->qtd_list) {
                        last = list_entry (qtd->qtd_list.prev,
                                        struct ehci_qtd, qtd_list);
                        last->hw_next = qtd->hw_next;
                }
                list_del (&qtd->qtd_list);
                last = qtd;
        }

        /* last urb's completion might still need calling */
        if (likely (last != NULL)) {
                ehci_urb_done (ehci, last->urb, regs);
                count++;
                ehci_qtd_free (ehci, last);
        }

        /* restore original state; caller must unlink or relink */
        qh->qh_state = state;

        /* be sure the hardware's done with the qh before refreshing
         * it after fault cleanup, or recovering from silicon wrongly
         * overlaying the dummy qtd (which reduces DMA chatter).
         */
        if (stopped != 0 || qh->hw_qtd_next == EHCI_LIST_END) {
                switch (state) {
                case QH_STATE_IDLE:
                        qh_refresh(ehci, qh);
                        break;
                case QH_STATE_LINKED:
                        /* should be rare for periodic transfers,
                         * except maybe high bandwidth ...
                         */
                        if (qh->period) {
                                intr_deschedule (ehci, qh);
                                (void) qh_schedule (ehci, qh);
                        } else
                                unlink_async (ehci, qh);
                        break;
                /* otherwise, unlink already started */
                }
        }

        return count;
}

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

// high bandwidth multiplier, as encoded in highspeed endpoint descriptors
#define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
// ... and packet size, for any kind of endpoint descriptor
#define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)

/*
 * reverse of qh_urb_transaction:  free a list of TDs.
 * used for cleanup after errors, before HC sees an URB's TDs.
 */
static void qtd_list_free (
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        struct list_head        *qtd_list
) {
        struct list_head        *entry, *temp;

        list_for_each_safe (entry, temp, qtd_list) {
                struct ehci_qtd *qtd;

                qtd = list_entry (entry, struct ehci_qtd, qtd_list);
                list_del (&qtd->qtd_list);
                ehci_qtd_free (ehci, qtd);
        }
}

/*
 * create a list of filled qtds for this URB; won't link into qh.
 */
static struct list_head *
qh_urb_transaction (
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        struct list_head        *head,
        int                     flags
) {
        struct ehci_qtd         *qtd, *qtd_prev;
        dma_addr_t              buf;
        int                     len, maxpacket;
        int                     is_input;
        u32                     token;

        /*
         * URBs map to sequences of QTDs:  one logical transaction
         */
        qtd = ehci_qtd_alloc (ehci, flags);
        if (unlikely (!qtd))
                return NULL;
        list_add_tail (&qtd->qtd_list, head);
        qtd->urb = urb;

        token = QTD_STS_ACTIVE;
        token |= (EHCI_TUNE_CERR << 10);
        /* for split transactions, SplitXState initialized to zero */

        len = urb->transfer_buffer_length;
        is_input = usb_pipein (urb->pipe);
        if (usb_pipecontrol (urb->pipe)) {
                /* SETUP pid */
                qtd_fill (qtd, urb->setup_dma, sizeof (struct usb_ctrlrequest),
                        token | (2 /* "setup" */ << 8), 8);

                /* ... and always at least one more pid */
                token ^= QTD_TOGGLE;
                qtd_prev = qtd;
                qtd = ehci_qtd_alloc (ehci, flags);
                if (unlikely (!qtd))
                        goto cleanup;
                qtd->urb = urb;
                qtd_prev->hw_next = QTD_NEXT (qtd->qtd_dma);
                list_add_tail (&qtd->qtd_list, head);
        } 

        /*
         * data transfer stage:  buffer setup
         */
        if (likely (len > 0))
                buf = urb->transfer_dma;
        else
                buf = 0;

        /* for zero length DATA stages, STATUS is always IN */
        if (!buf || is_input)
                token |= (1 /* "in" */ << 8);
        /* else it's already initted to "out" pid (0 << 8) */

        maxpacket = max_packet(usb_maxpacket(urb->dev, urb->pipe, !is_input));

        /*
         * buffer gets wrapped in one or more qtds;
         * last one may be "short" (including zero len)
         * and may serve as a control status ack
         */
        for (;;) {
                int this_qtd_len;

                this_qtd_len = qtd_fill (qtd, buf, len, token, maxpacket);
                len -= this_qtd_len;
                buf += this_qtd_len;
                if (is_input)
                        qtd->hw_alt_next = ehci->async->hw_alt_next;

                /* qh makes control packets use qtd toggle; maybe switch it */
                if ((maxpacket & (this_qtd_len + (maxpacket - 1))) == 0)
                        token ^= QTD_TOGGLE;

                if (likely (len <= 0))
                        break;

                qtd_prev = qtd;
                qtd = ehci_qtd_alloc (ehci, flags);
                if (unlikely (!qtd))
                        goto cleanup;
                qtd->urb = urb;
                qtd_prev->hw_next = QTD_NEXT (qtd->qtd_dma);
                list_add_tail (&qtd->qtd_list, head);
        }

        /* unless the bulk/interrupt caller wants a chance to clean
         * up after short reads, hc should advance qh past this urb
         */
        if (likely ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0
                                || usb_pipecontrol (urb->pipe)))
                qtd->hw_alt_next = EHCI_LIST_END;

        /*
         * control requests may need a terminating data "status" ack;
         * bulk ones may need a terminating short packet (zero length).
         */
        if (likely (buf != 0)) {
                int     one_more = 0;

                if (usb_pipecontrol (urb->pipe)) {
                        one_more = 1;
                        token ^= 0x0100;        /* "in" <--> "out"  */
                        token |= QTD_TOGGLE;    /* force DATA1 */
                } else if (usb_pipebulk (urb->pipe)
                                && (urb->transfer_flags & URB_ZERO_PACKET)
                                && !(urb->transfer_buffer_length % maxpacket)) {
                        one_more = 1;
                }
                if (one_more) {
                        qtd_prev = qtd;
                        qtd = ehci_qtd_alloc (ehci, flags);
                        if (unlikely (!qtd))
                                goto cleanup;
                        qtd->urb = urb;
                        qtd_prev->hw_next = QTD_NEXT (qtd->qtd_dma);
                        list_add_tail (&qtd->qtd_list, head);

                        /* never any data in such packets */
                        qtd_fill (qtd, 0, 0, token, 0);
                }
        }

        /* by default, enable interrupt on urb completion */
        if (likely (!(urb->transfer_flags & URB_NO_INTERRUPT)))
                qtd->hw_token |= __constant_cpu_to_le32 (QTD_IOC);
        return head;

cleanup:
        qtd_list_free (ehci, urb, head);
        return NULL;
}

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

// Would be best to create all qh's from config descriptors,
// when each interface/altsetting is established.  Unlink
// any previous qh and cancel its urbs first; endpoints are
// implicitly reset then (data toggle too).
// That'd mean updating how usbcore talks to HCDs. (2.7?)


/*
 * Each QH holds a qtd list; a QH is used for everything except iso.
 *
 * For interrupt urbs, the scheduler must set the microframe scheduling
 * mask(s) each time the QH gets scheduled.  For highspeed, that's
 * just one microframe in the s-mask.  For split interrupt transactions
 * there are additional complications: c-mask, maybe FSTNs.
 */
static struct ehci_qh *
qh_make (
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        int                     flags
) {
        struct ehci_qh          *qh = ehci_qh_alloc (ehci, flags);
        u32                     info1 = 0, info2 = 0;
        int                     is_input, type;
        int                     maxp = 0;

        if (!qh)
                return qh;

        /*
         * init endpoint/device data for this QH
         */
        info1 |= usb_pipeendpoint (urb->pipe) << 8;
        info1 |= usb_pipedevice (urb->pipe) << 0;

        is_input = usb_pipein (urb->pipe);
        type = usb_pipetype (urb->pipe);
        maxp = usb_maxpacket (urb->dev, urb->pipe, !is_input);

        /* Compute interrupt scheduling parameters just once, and save.
         * - allowing for high bandwidth, how many nsec/uframe are used?
         * - split transactions need a second CSPLIT uframe; same question
         * - splits also need a schedule gap (for full/low speed I/O)
         * - qh has a polling interval
         *
         * For control/bulk requests, the HC or TT handles these.
         */
        if (type == PIPE_INTERRUPT) {
                qh->usecs = usb_calc_bus_time (USB_SPEED_HIGH, is_input, 0,
                                hb_mult (maxp) * max_packet (maxp));
                qh->start = NO_FRAME;

                if (urb->dev->speed == USB_SPEED_HIGH) {
                        qh->c_usecs = 0;
                        qh->gap_uf = 0;

                        qh->period = urb->interval >> 3;
                        if (qh->period == 0 && urb->interval != 1) {
                                /* NOTE interval 2 or 4 uframes could work.
                                 * But interval 1 scheduling is simpler, and
                                 * includes high bandwidth.
                                 */
                                dbg ("intr period %d uframes, NYET!",
                                                urb->interval);
                                goto done;
                        }
                } else {
                        /* gap is f(FS/LS transfer times) */
                        qh->gap_uf = 1 + usb_calc_bus_time (urb->dev->speed,
                                        is_input, 0, maxp) / (125 * 1000);

                        /* FIXME this just approximates SPLIT/CSPLIT times */
                        if (is_input) {         // SPLIT, gap, CSPLIT+DATA
                                qh->c_usecs = qh->usecs + HS_USECS (0);
                                qh->usecs = HS_USECS (1);
                        } else {                // SPLIT+DATA, gap, CSPLIT
                                qh->usecs += HS_USECS (1);
                                qh->c_usecs = HS_USECS (0);
                        }

                        qh->period = urb->interval;
                }
        }

        /* support for tt scheduling, and access to toggles */
        qh->dev = usb_get_dev (urb->dev);

        /* using TT? */
        switch (urb->dev->speed) {
        case USB_SPEED_LOW:
                info1 |= (1 << 12);     /* EPS "low" */
                /* FALL THROUGH */

        case USB_SPEED_FULL:
                /* EPS 0 means "full" */
                if (type != PIPE_INTERRUPT)
                        info1 |= (EHCI_TUNE_RL_TT << 28);
                if (type == PIPE_CONTROL) {
                        info1 |= (1 << 27);     /* for TT */
                        info1 |= 1 << 14;       /* toggle from qtd */
                }
                info1 |= maxp << 16;

                info2 |= (EHCI_TUNE_MULT_TT << 30);
                info2 |= urb->dev->ttport << 23;

                /* set the address of the TT; for TDI's integrated
                 * root hub tt, leave it zeroed.
                 */
                if (!ehci_is_TDI(ehci)
                                || urb->dev->tt->hub !=
                                        ehci_to_hcd(ehci)->self.root_hub)
                        info2 |= urb->dev->tt->hub->devnum << 16;

                /* NOTE:  if (PIPE_INTERRUPT) { scheduler sets c-mask } */

                break;

        case USB_SPEED_HIGH:            /* no TT involved */
                info1 |= (2 << 12);     /* EPS "high" */
                if (type == PIPE_CONTROL) {
                        info1 |= (EHCI_TUNE_RL_HS << 28);
                        info1 |= 64 << 16;      /* usb2 fixed maxpacket */
                        info1 |= 1 << 14;       /* toggle from qtd */
                        info2 |= (EHCI_TUNE_MULT_HS << 30);
                } else if (type == PIPE_BULK) {
                        info1 |= (EHCI_TUNE_RL_HS << 28);
                        info1 |= 512 << 16;     /* usb2 fixed maxpacket */
                        info2 |= (EHCI_TUNE_MULT_HS << 30);
                } else {                /* PIPE_INTERRUPT */
                        info1 |= max_packet (maxp) << 16;
                        info2 |= hb_mult (maxp) << 30;
                }
                break;
        default:
                dbg ("bogus dev %p speed %d", urb->dev, urb->dev->speed);
done:
                qh_put (qh);
                return NULL;
        }

        /* NOTE:  if (PIPE_INTERRUPT) { scheduler sets s-mask } */

        /* init as live, toggle clear, advance to dummy */
        qh->qh_state = QH_STATE_IDLE;
        qh->hw_info1 = cpu_to_le32 (info1);
        qh->hw_info2 = cpu_to_le32 (info2);
        usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe), !is_input, 1);
        qh_refresh (ehci, qh);
        return qh;
}

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

/* move qh (and its qtds) onto async queue; maybe enable queue.  */

static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        __le32          dma = QH_NEXT (qh->qh_dma);
        struct ehci_qh  *head;

        /* (re)start the async schedule? */
        head = ehci->async;
        timer_action_done (ehci, TIMER_ASYNC_OFF);
        if (!head->qh_next.qh) {
                u32     cmd = readl (&ehci->regs->command);

                if (!(cmd & CMD_ASE)) {
                        /* in case a clear of CMD_ASE didn't take yet */
                        (void) handshake (&ehci->regs->status, STS_ASS, 0, 150);
                        cmd |= CMD_ASE | CMD_RUN;
                        writel (cmd, &ehci->regs->command);
                        ehci_to_hcd(ehci)->state = HC_STATE_RUNNING;
                        /* posted write need not be known to HC yet ... */
                }
        }

        /* clear halt and/or toggle; and maybe recover from silicon quirk */
        if (qh->qh_state == QH_STATE_IDLE)
                qh_refresh (ehci, qh);

        /* splice right after start */
        qh->qh_next = head->qh_next;
        qh->hw_next = head->hw_next;
        wmb ();

        head->qh_next.qh = qh;
        head->hw_next = dma;

        qh->qh_state = QH_STATE_LINKED;
        /* qtd completions reported later by interrupt */
}

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

#define QH_ADDR_MASK    __constant_cpu_to_le32(0x7f)

/*
 * For control/bulk/interrupt, return QH with these TDs appended.
 * Allocates and initializes the QH if necessary.
 * Returns null if it can't allocate a QH it needs to.
 * If the QH has TDs (urbs) already, that's great.
 */
static struct ehci_qh *qh_append_tds (
        struct ehci_hcd         *ehci,
        struct urb              *urb,
        struct list_head        *qtd_list,
        int                     epnum,
        void                    **ptr
)
{
        struct ehci_qh          *qh = NULL;

        qh = (struct ehci_qh *) *ptr;
        if (unlikely (qh == NULL)) {
                /* can't sleep here, we have ehci->lock... */
                qh = qh_make (ehci, urb, GFP_ATOMIC);
                *ptr = qh;
        }
        if (likely (qh != NULL)) {
                struct ehci_qtd *qtd;

                if (unlikely (list_empty (qtd_list)))
                        qtd = NULL;
                else
                        qtd = list_entry (qtd_list->next, struct ehci_qtd,
                                        qtd_list);

                /* control qh may need patching ... */
                if (unlikely (epnum == 0)) {

                        /* usb_reset_device() briefly reverts to address 0 */
                        if (usb_pipedevice (urb->pipe) == 0)
                                qh->hw_info1 &= ~QH_ADDR_MASK;
                }

                /* just one way to queue requests: swap with the dummy qtd.
                 * only hc or qh_refresh() ever modify the overlay.
                 */
                if (likely (qtd != NULL)) {
                        struct ehci_qtd         *dummy;
                        dma_addr_t              dma;
                        __le32                  token;

                        /* to avoid racing the HC, use the dummy td instead of
                         * the first td of our list (becomes new dummy).  both
                         * tds stay deactivated until we're done, when the
                         * HC is allowed to fetch the old dummy (4.10.2).
                         */
                        token = qtd->hw_token;
                        qtd->hw_token = HALT_BIT;
                        wmb ();
                        dummy = qh->dummy;

                        dma = dummy->qtd_dma;
                        *dummy = *qtd;
                        dummy->qtd_dma = dma;

                        list_del (&qtd->qtd_list);
                        list_add (&dummy->qtd_list, qtd_list);
                        __list_splice (qtd_list, qh->qtd_list.prev);

                        ehci_qtd_init (qtd, qtd->qtd_dma);
                        qh->dummy = qtd;

                        /* hc must see the new dummy at list end */
                        dma = qtd->qtd_dma;
                        qtd = list_entry (qh->qtd_list.prev,
                                        struct ehci_qtd, qtd_list);
                        qtd->hw_next = QTD_NEXT (dma);

                        /* let the hc process these next qtds */
                        wmb ();
                        dummy->hw_token = token;

                        urb->hcpriv = qh_get (qh);
                }
        }
        return qh;
}

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

static int
submit_async (
        struct ehci_hcd         *ehci,
        struct usb_host_endpoint *ep,
        struct urb              *urb,
        struct list_head        *qtd_list,
        int                     mem_flags
) {
        struct ehci_qtd         *qtd;
        int                     epnum;
        unsigned long           flags;
        struct ehci_qh          *qh = NULL;

        qtd = list_entry (qtd_list->next, struct ehci_qtd, qtd_list);
        epnum = ep->desc.bEndpointAddress;

#ifdef EHCI_URB_TRACE
        ehci_dbg (ehci,
                "%s %s urb %p ep%d%s len %d, qtd %p [qh %p]\n",
                __FUNCTION__, urb->dev->devpath, urb,
                epnum & 0x0f, (epnum & USB_DIR_IN) ? "in" : "out",
                urb->transfer_buffer_length,
                qtd, ep->hcpriv);
#endif

        spin_lock_irqsave (&ehci->lock, flags);
        qh = qh_append_tds (ehci, urb, qtd_list, epnum, &ep->hcpriv);

        /* Control/bulk operations through TTs don't need scheduling,
         * the HC and TT handle it when the TT has a buffer ready.
         */
        if (likely (qh != NULL)) {
                if (likely (qh->qh_state == QH_STATE_IDLE))
                        qh_link_async (ehci, qh_get (qh));
        }
        spin_unlock_irqrestore (&ehci->lock, flags);
        if (unlikely (qh == NULL)) {
                qtd_list_free (ehci, urb, qtd_list);
                return -ENOMEM;
        }
        return 0;
}

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

/* the async qh for the qtds being reclaimed are now unlinked from the HC */

static void end_unlink_async (struct ehci_hcd *ehci, struct pt_regs *regs)
{
        struct ehci_qh          *qh = ehci->reclaim;
        struct ehci_qh          *next;

        timer_action_done (ehci, TIMER_IAA_WATCHDOG);

        // qh->hw_next = cpu_to_le32 (qh->qh_dma);
        qh->qh_state = QH_STATE_IDLE;
        qh->qh_next.qh = NULL;
        qh_put (qh);                    // refcount from reclaim 

        /* other unlink(s) may be pending (in QH_STATE_UNLINK_WAIT) */
        next = qh->reclaim;
        ehci->reclaim = next;
        ehci->reclaim_ready = 0;
        qh->reclaim = NULL;

        qh_completions (ehci, qh, regs);

        if (!list_empty (&qh->qtd_list)
                        && HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
                qh_link_async (ehci, qh);
        else {
                qh_put (qh);            // refcount from async list

                /* it's not free to turn the async schedule on/off; leave it
                 * active but idle for a while once it empties.
                 */
                if (HC_IS_RUNNING (ehci_to_hcd(ehci)->state)
                                && ehci->async->qh_next.qh == NULL)
                        timer_action (ehci, TIMER_ASYNC_OFF);
        }

        if (next) {
                ehci->reclaim = NULL;
                start_unlink_async (ehci, next);
        }
}

/* makes sure the async qh will become idle */
/* caller must own ehci->lock */

static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
{
        int             cmd = readl (&ehci->regs->command);
        struct ehci_qh  *prev;

#ifdef DEBUG
        assert_spin_locked(&ehci->lock);
        if (ehci->reclaim
                        || (qh->qh_state != QH_STATE_LINKED
                                && qh->qh_state != QH_STATE_UNLINK_WAIT)
                        )
                BUG ();
#endif

        /* stop async schedule right now? */
        if (unlikely (qh == ehci->async)) {
                /* can't get here without STS_ASS set */
                if (ehci_to_hcd(ehci)->state != HC_STATE_HALT) {
                        writel (cmd & ~CMD_ASE, &ehci->regs->command);
                        wmb ();
                        // handshake later, if we need to
                }
                timer_action_done (ehci, TIMER_ASYNC_OFF);
                return;
        } 

        qh->qh_state = QH_STATE_UNLINK;
        ehci->reclaim = qh = qh_get (qh);

        prev = ehci->async;
        while (prev->qh_next.qh != qh)
                prev = prev->qh_next.qh;

        prev->hw_next = qh->hw_next;
        prev->qh_next = qh->qh_next;
        wmb ();

        if (unlikely (ehci_to_hcd(ehci)->state == HC_STATE_HALT)) {
                /* if (unlikely (qh->reclaim != 0))
                 *      this will recurse, probably not much
                 */
                end_unlink_async (ehci, NULL);
                return;
        }

        ehci->reclaim_ready = 0;
        cmd |= CMD_IAAD;
        writel (cmd, &ehci->regs->command);
        (void) readl (&ehci->regs->command);
        timer_action (ehci, TIMER_IAA_WATCHDOG);
}

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

static void
scan_async (struct ehci_hcd *ehci, struct pt_regs *regs)
{
        struct ehci_qh          *qh;
        enum ehci_timer_action  action = TIMER_IO_WATCHDOG;

        if (!++(ehci->stamp))
                ehci->stamp++;
        timer_action_done (ehci, TIMER_ASYNC_SHRINK);
rescan:
        qh = ehci->async->qh_next.qh;
        if (likely (qh != NULL)) {
                do {
                        /* clean any finished work for this qh */
                        if (!list_empty (&qh->qtd_list)
                                        && qh->stamp != ehci->stamp) {
                                int temp;

                                /* unlinks could happen here; completion
                                 * reporting drops the lock.  rescan using
                                 * the latest schedule, but don't rescan
                                 * qhs we already finished (no looping).
                                 */
                                qh = qh_get (qh);
                                qh->stamp = ehci->stamp;
                                temp = qh_completions (ehci, qh, regs);
                                qh_put (qh);
                                if (temp != 0) {
                                        goto rescan;
                                }
                        }

                        /* unlink idle entries, reducing HC PCI usage as well
                         * as HCD schedule-scanning costs.  delay for any qh
                         * we just scanned, there's a not-unusual case that it
                         * doesn't stay idle for long.
                         * (plus, avoids some kind of re-activation race.)
                         */
                        if (list_empty (&qh->qtd_list)) {
                                if (qh->stamp == ehci->stamp)
                                        action = TIMER_ASYNC_SHRINK;
                                else if (!ehci->reclaim
                                            && qh->qh_state == QH_STATE_LINKED)
                                        start_unlink_async (ehci, qh);
                        }

                        qh = qh->qh_next.qh;
                } while (qh);
        }
        if (action == TIMER_ASYNC_SHRINK)
                timer_action (ehci, TIMER_ASYNC_SHRINK);
}