dirty fix to merging

1 files changed, 1321 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
new file mode 100644
index 00000000..9e11e38a
--- /dev/null
+++ b/drivers/usb/host/ehci-q.c
@@ -0,0 +1,1321 @@
+/*
+ * Copyright (C) 2001-2004 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_hcd *ehci, 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_hc32(ehci, (u32)addr);
+	qtd->hw_buf_hi[0] = cpu_to_hc32(ehci, (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_hc32(ehci, (u32)addr);
+			qtd->hw_buf_hi[i] = cpu_to_hc32(ehci,
+					(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_hc32(ehci, (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)
+{
+	struct ehci_qh_hw *hw = qh->hw;
+
+	/* writes to an active overlay are unsafe */
+	BUG_ON(qh->qh_state != QH_STATE_IDLE);
+
+	hw->hw_qtd_next = QTD_NEXT(ehci, qtd->qtd_dma);
+	hw->hw_alt_next = EHCI_LIST_END(ehci);
+
+	/* 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 (!(hw->hw_info1 & cpu_to_hc32(ehci, 1 << 14))) {
+		unsigned	is_out, epnum;
+
+		is_out = qh->is_out;
+		epnum = (hc32_to_cpup(ehci, &hw->hw_info1) >> 8) & 0x0f;
+		if (unlikely (!usb_gettoggle (qh->dev, epnum, is_out))) {
+			hw->hw_token &= ~cpu_to_hc32(ehci, QTD_TOGGLE);
+			usb_settoggle (qh->dev, epnum, is_out, 1);
+		}
+	}
+
+	hw->hw_token &= cpu_to_hc32(ehci, 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_hc32(ehci, qtd->qtd_dma) == qh->hw->hw_current)
+			qtd = NULL;
+	}
+
+	if (qtd)
+		qh_update (ehci, qh, qtd);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void qh_link_async(struct ehci_hcd *ehci, struct ehci_qh *qh);
+
+static void ehci_clear_tt_buffer_complete(struct usb_hcd *hcd,
+		struct usb_host_endpoint *ep)
+{
+	struct ehci_hcd		*ehci = hcd_to_ehci(hcd);
+	struct ehci_qh		*qh = ep->hcpriv;
+	unsigned long		flags;
+
+	spin_lock_irqsave(&ehci->lock, flags);
+	qh->clearing_tt = 0;
+	if (qh->qh_state == QH_STATE_IDLE && !list_empty(&qh->qtd_list)
+			&& ehci->rh_state == EHCI_RH_RUNNING)
+		qh_link_async(ehci, qh);
+	spin_unlock_irqrestore(&ehci->lock, flags);
+}
+
+static void ehci_clear_tt_buffer(struct ehci_hcd *ehci, struct ehci_qh *qh,
+		struct urb *urb, u32 token)
+{
+
+	/* If an async split transaction gets an error or is unlinked,
+	 * the TT buffer may be left in an indeterminate state.  We
+	 * have to clear the TT buffer.
+	 *
+	 * Note: this routine is never called for Isochronous transfers.
+	 */
+	if (urb->dev->tt && !usb_pipeint(urb->pipe) && !qh->clearing_tt) {
+#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 */
+		if (!ehci_is_TDI(ehci)
+				|| urb->dev->tt->hub !=
+				   ehci_to_hcd(ehci)->self.root_hub) {
+			if (usb_hub_clear_tt_buffer(urb) == 0)
+				qh->clearing_tt = 1;
+		} else {
+
+			/* REVISIT ARC-derived cores don't clear the root
+			 * hub TT buffer in this way...
+			 */
+		}
+	}
+}
+
+static int qtd_copy_status (
+	struct ehci_hcd *ehci,
+	struct urb *urb,
+	size_t length,
+	u32 token
+)
+{
+	int	status = -EINPROGRESS;
+
+	/* 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->unlinked))
+		return status;
+
+	/* force cleanup after short read; not always an error */
+	if (unlikely (IS_SHORT_READ (token)))
+		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 */
+			status = -EOVERFLOW;
+		/* CERR nonzero + halt --> stall */
+		} else if (QTD_CERR(token)) {
+			status = -EPIPE;
+
+		/* In theory, more than one of the following bits can be set
+		 * since they are sticky and the transaction is retried.
+		 * Which to test first is rather arbitrary.
+		 */
+		} else if (token & QTD_STS_MMF) {
+			/* fs/ls interrupt xfer missed the complete-split */
+			status = -EPROTO;
+		} else if (token & QTD_STS_DBE) {
+			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 */
+			ehci_dbg(ehci, "devpath %s ep%d%s 3strikes\n",
+				urb->dev->devpath,
+				usb_pipeendpoint(urb->pipe),
+				usb_pipein(urb->pipe) ? "in" : "out");
+			status = -EPROTO;
+		} else {	/* unknown */
+			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, status);
+	}
+
+	return status;
+}
+
+static void
+ehci_urb_done(struct ehci_hcd *ehci, struct urb *urb, int status)
+__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->hw_info2 & cpu_to_hc32(ehci, QH_SMASK)) != 0) {
+
+			/* ... update hc-wide periodic stats (for usbfs) */
+			ehci_to_hcd(ehci)->self.bandwidth_int_reqs--;
+		}
+		qh_put (qh);
+	}
+
+	if (unlikely(urb->unlinked)) {
+		COUNT(ehci->stats.unlink);
+	} else {
+		/* report non-error and short read status as zero */
+		if (status == -EINPROGRESS || status == -EREMOTEIO)
+			status = 0;
+		COUNT(ehci->stats.complete);
+	}
+
+#ifdef EHCI_URB_TRACE
+	ehci_dbg (ehci,
+		"%s %s urb %p ep%d%s status %d len %d/%d\n",
+		__func__, urb->dev->devpath, urb,
+		usb_pipeendpoint (urb->pipe),
+		usb_pipein (urb->pipe) ? "in" : "out",
+		status,
+		urb->actual_length, urb->transfer_buffer_length);
+#endif
+	/*{CharlesTu, 2008.12.26, for test mode */
+#ifdef CONFIG_USB_EHCI_EHSET
+	if (likely(urb->transfer_flags == URB_HCD_DRIVER_TEST))
+	return;
+#endif
+	/*CharlesTu}*/
+	/* complete() can reenter this HCD */
+	usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
+	spin_unlock (&ehci->lock);
+	usb_hcd_giveback_urb(ehci_to_hcd(ehci), urb, status);
+	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 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.
+ */
+static unsigned
+qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
+{
+	struct ehci_qtd		*last, *end = qh->dummy;
+	struct list_head	*entry, *tmp;
+	int			last_status;
+	int			stopped;
+	unsigned		count = 0;
+	u8			state;
+	struct ehci_qh_hw	*hw = qh->hw;
+
+	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.
+	 *
+	 * It's a bug for qh->qh_state to be anything other than
+	 * QH_STATE_IDLE, unless our caller is scan_async() or
+	 * scan_periodic().
+	 */
+	state = qh->qh_state;
+	qh->qh_state = QH_STATE_COMPLETING;
+	stopped = (state == QH_STATE_IDLE);
+
+ rescan:
+	last = NULL;
+	last_status = -EINPROGRESS;
+	qh->needs_rescan = 0;
+
+	/* 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, last_status);
+				count++;
+				last_status = -EINPROGRESS;
+			}
+			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 = hc32_to_cpu(ehci, qtd->hw_token);
+
+		/* always clean up qtds the hc de-activated */
+ retry_xacterr:
+		if ((token & QTD_STS_ACTIVE) == 0) {
+
+			/* Report Data Buffer Error: non-fatal but useful */
+			if (token & QTD_STS_DBE)
+				ehci_dbg(ehci,
+					"detected DataBufferErr for urb %p ep%d%s len %d, qtd %p [qh %p]\n",
+					urb,
+					usb_endpoint_num(&urb->ep->desc),
+					usb_endpoint_dir_in(&urb->ep->desc) ? "in" : "out",
+					urb->transfer_buffer_length,
+					qtd,
+					qh);
+
+			/* on STALL, error, and short reads this urb must
+			 * complete and all its qtds must be recycled.
+			 */
+			if ((token & QTD_STS_HALT) != 0) {
+
+				/* retry transaction errors until we
+				 * reach the software xacterr limit
+				 */
+				if ((token & QTD_STS_XACT) &&
+						QTD_CERR(token) == 0 &&
+						++qh->xacterrs < QH_XACTERR_MAX &&
+						!urb->unlinked) {
+					ehci_dbg(ehci,
+	"detected XactErr len %zu/%zu retry %d\n",
+	qtd->length - QTD_LENGTH(token), qtd->length, qh->xacterrs);
+
+					/* reset the token in the qtd and the
+					 * qh overlay (which still contains
+					 * the qtd) so that we pick up from
+					 * where we left off
+					 */
+					token &= ~QTD_STS_HALT;
+					token |= QTD_STS_ACTIVE |
+							(EHCI_TUNE_CERR << 10);
+					qtd->hw_token = cpu_to_hc32(ehci,
+							token);
+					wmb();
+					hw->hw_token = cpu_to_hc32(ehci,
+							token);
+					goto retry_xacterr;
+				}
+				stopped = 1;
+
+			/* magic dummy for some short reads; qh won't advance.
+			 * that silicon quirk can kick in with this dummy too.
+			 *
+			 * other short reads won't stop the queue, including
+			 * control transfers (status stage handles that) or
+			 * most other single-qtd reads ... the queue stops if
+			 * URB_SHORT_NOT_OK was set so the driver submitting
+			 * the urbs could clean it up.
+			 */
+			} else if (IS_SHORT_READ (token)
+					&& !(qtd->hw_alt_next
+						& EHCI_LIST_END(ehci))) {
+				stopped = 1;
+			}
+
+		/* stop scanning when we reach qtds the hc is using */
+		} else if (likely (!stopped
+				&& ehci->rh_state == EHCI_RH_RUNNING)) {
+			break;
+
+		/* scan the whole queue for unlinks whenever it stops */
+		} else {
+			stopped = 1;
+
+			/* cancel everything if we halt, suspend, etc */
+			if (ehci->rh_state != EHCI_RH_RUNNING)
+				last_status = -ESHUTDOWN;
+
+			/* this qtd is active; skip it unless a previous qtd
+			 * for its urb faulted, or its urb was canceled.
+			 */
+			else if (last_status == -EINPROGRESS && !urb->unlinked)
+				continue;
+
+			/* qh unlinked; token in overlay may be most current */
+			if (state == QH_STATE_IDLE
+					&& cpu_to_hc32(ehci, qtd->qtd_dma)
+						== hw->hw_current) {
+				token = hc32_to_cpu(ehci, hw->hw_token);
+
+				/* An unlink may leave an incomplete
+				 * async transaction in the TT buffer.
+				 * We have to clear it.
+				 */
+				ehci_clear_tt_buffer(ehci, qh, urb, token);
+			}
+		}
+
+		/* unless we already know the urb's status, collect qtd status
+		 * and update count of bytes transferred.  in common short read
+		 * cases with only one data qtd (including control transfers),
+		 * queue processing won't halt.  but with two or more qtds (for
+		 * example, with a 32 KB transfer), when the first qtd gets a
+		 * short read the second must be removed by hand.
+		 */
+		if (last_status == -EINPROGRESS) {
+			last_status = qtd_copy_status(ehci, urb,
+					qtd->length, token);
+			if (last_status == -EREMOTEIO
+					&& (qtd->hw_alt_next
+						& EHCI_LIST_END(ehci)))
+				last_status = -EINPROGRESS;
+
+			/* As part of low/full-speed endpoint-halt processing
+			 * we must clear the TT buffer (11.17.5).
+			 */
+			if (unlikely(last_status != -EINPROGRESS &&
+					last_status != -EREMOTEIO)) {
+				/* The TT's in some hubs malfunction when they
+				 * receive this request following a STALL (they
+				 * stop sending isochronous packets).  Since a
+				 * STALL can't leave the TT buffer in a busy
+				 * state (if you believe Figures 11-48 - 11-51
+				 * in the USB 2.0 spec), we won't clear the TT
+				 * buffer in this case.  Strictly speaking this
+				 * is a violation of the spec.
+				 */
+				if (last_status != -EPIPE)
+					ehci_clear_tt_buffer(ehci, qh, urb,
+							token);
+			}
+		}
+
+		/* if we're removing something not at the queue head,
+		 * patch the hardware queue pointer.
+		 */
+		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;
+		}
+
+		/* remove qtd; it's recycled after possible urb completion */
+		list_del (&qtd->qtd_list);
+		last = qtd;
+
+		/* reinit the xacterr counter for the next qtd */
+		qh->xacterrs = 0;
+	}
+
+	/* last urb's completion might still need calling */
+	if (likely (last != NULL)) {
+		ehci_urb_done(ehci, last->urb, last_status);
+		count++;
+		ehci_qtd_free (ehci, last);
+	}
+
+	/* Do we need to rescan for URBs dequeued during a giveback? */
+	if (unlikely(qh->needs_rescan)) {
+		/* If the QH is already unlinked, do the rescan now. */
+		if (state == QH_STATE_IDLE)
+			goto rescan;
+
+		/* Otherwise we have to wait until the QH is fully unlinked.
+		 * Our caller will start an unlink if qh->needs_rescan is
+		 * set.  But if an unlink has already started, nothing needs
+		 * to be done.
+		 */
+		if (state != QH_STATE_LINKED)
+			qh->needs_rescan = 0;
+	}
+
+	/* 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 || hw->hw_qtd_next == EHCI_LIST_END(ehci)) {
+		switch (state) {
+		case QH_STATE_IDLE:
+			qh_refresh(ehci, qh);
+			break;
+		case QH_STATE_LINKED:
+			/* We won't refresh a QH that's linked (after the HC
+			 * stopped the queue).  That avoids a race:
+			 *  - HC reads first part of QH;
+			 *  - CPU updates that first part and the token;
+			 *  - HC reads rest of that QH, including token
+			 * Result:  HC gets an inconsistent image, and then
+			 * DMAs to/from the wrong memory (corrupting it).
+			 *
+			 * That should be rare for interrupt transfers,
+			 * except maybe high bandwidth ...
+			 */
+
+			/* Tell the caller to start an unlink */
+			qh->needs_rescan = 1;
+			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,
+	gfp_t			flags
+) {
+	struct ehci_qtd		*qtd, *qtd_prev;
+	dma_addr_t		buf;
+	int			len, this_sg_len, maxpacket;
+	int			is_input;
+	u32			token;
+	int			i;
+	struct scatterlist	*sg;
+
+	/*
+	 * 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(ehci, 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(ehci, qtd->qtd_dma);
+		list_add_tail (&qtd->qtd_list, head);
+
+		/* for zero length DATA stages, STATUS is always IN */
+		if (len == 0)
+			token |= (1 /* "in" */ << 8);
+	}
+
+	/*
+	 * data transfer stage:  buffer setup
+	 */
+	i = urb->num_mapped_sgs;
+	if (len > 0 && i > 0) {
+		sg = urb->sg;
+		buf = sg_dma_address(sg);
+
+		/* urb->transfer_buffer_length may be smaller than the
+		 * size of the scatterlist (or vice versa)
+		 */
+		this_sg_len = min_t(int, sg_dma_len(sg), len);
+	} else {
+		sg = NULL;
+		buf = urb->transfer_dma;
+		this_sg_len = len;
+	}
+
+	if (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(ehci, qtd, buf, this_sg_len, token,
+				maxpacket);
+		this_sg_len -= this_qtd_len;
+		len -= this_qtd_len;
+		buf += this_qtd_len;
+
+		/*
+		 * short reads advance to a "magic" dummy instead of the next
+		 * qtd ... that forces the queue to stop, for manual cleanup.
+		 * (this will usually be overridden later.)
+		 */
+		if (is_input)
+			qtd->hw_alt_next = ehci->async->hw->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(this_sg_len <= 0)) {
+			if (--i <= 0 || len <= 0)
+				break;
+			sg = sg_next(sg);
+			buf = sg_dma_address(sg);
+			this_sg_len = min_t(int, sg_dma_len(sg), len);
+		}
+
+		qtd_prev = qtd;
+		qtd = ehci_qtd_alloc (ehci, flags);
+		if (unlikely (!qtd))
+			goto cleanup;
+		qtd->urb = urb;
+		qtd_prev->hw_next = QTD_NEXT(ehci, qtd->qtd_dma);
+		list_add_tail (&qtd->qtd_list, head);
+	}
+
+	/*
+	 * unless the caller requires manual cleanup after short reads,
+	 * have the alt_next mechanism keep the queue running after the
+	 * last data qtd (the only one, for control and most other cases).
+	 */
+	if (likely ((urb->transfer_flags & URB_SHORT_NOT_OK) == 0
+				|| usb_pipecontrol (urb->pipe)))
+		qtd->hw_alt_next = EHCI_LIST_END(ehci);
+
+	/*
+	 * control requests may need a terminating data "status" ack;
+	 * other OUT ones may need a terminating short packet
+	 * (zero length).
+	 */
+	if (likely (urb->transfer_buffer_length != 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_pipeout(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(ehci, qtd->qtd_dma);
+			list_add_tail (&qtd->qtd_list, head);
+
+			/* never any data in such packets */
+			qtd_fill(ehci, qtd, 0, 0, token, 0);
+		}
+	}
+
+	/* by default, enable interrupt on urb completion */
+	if (likely (!(urb->transfer_flags & URB_NO_INTERRUPT)))
+		qtd->hw_token |= cpu_to_hc32(ehci, 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,
+	gfp_t			flags
+) {
+	struct ehci_qh		*qh = ehci_qh_alloc (ehci, flags);
+	u32			info1 = 0, info2 = 0;
+	int			is_input, type;
+	int			maxp = 0;
+	struct usb_tt		*tt = urb->dev->tt;
+	struct ehci_qh_hw	*hw;
+
+	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);
+
+	/* 1024 byte maxpacket is a hardware ceiling.  High bandwidth
+	 * acts like up to 3KB, but is built from smaller packets.
+	 */
+	if (max_packet(maxp) > 1024) {
+		ehci_dbg(ehci, "bogus qh maxpacket %d\n", max_packet(maxp));
+		goto done;
+	}
+
+	/* 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 = NS_TO_US(usb_calc_bus_time(USB_SPEED_HIGH,
+				is_input, 0,
+				hb_mult(maxp) * max_packet(maxp)));
+		qh->start = NO_FRAME;
+		qh->stamp = ehci->periodic_stamp;
+
+		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.
+				 */
+				urb->interval = 1;
+			} else if (qh->period > ehci->periodic_size) {
+				qh->period = ehci->periodic_size;
+				urb->interval = qh->period << 3;
+			}
+		} else {
+			int		think_time;
+
+			/* 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);
+			}
+
+			think_time = tt ? tt->think_time : 0;
+			qh->tt_usecs = NS_TO_US (think_time +
+					usb_calc_bus_time (urb->dev->speed,
+					is_input, 0, max_packet (maxp)));
+			qh->period = urb->interval;
+			if (qh->period > ehci->periodic_size) {
+				qh->period = ehci->periodic_size;
+				urb->interval = qh->period;
+			}
+		}
+	}
+
+	/* support for tt scheduling, and access to toggles */
+	qh->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);
+
+		/* Some Freescale processors have an erratum in which the
+		 * port number in the queue head was 0..N-1 instead of 1..N.
+		 */
+		if (ehci_has_fsl_portno_bug(ehci))
+			info2 |= (urb->dev->ttport-1) << 23;
+		else
+			info2 |= urb->dev->ttport << 23;
+
+		/* set the address of the TT; for TDI's integrated
+		 * root hub tt, leave it zeroed.
+		 */
+		if (tt && tt->hub != ehci_to_hcd(ehci)->self.root_hub)
+			info2 |= 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);
+			/* The USB spec says that high speed bulk endpoints
+			 * always use 512 byte maxpacket.  But some device
+			 * vendors decided to ignore that, and MSFT is happy
+			 * to help them do so.  So now people expect to use
+			 * such nonconformant devices with Linux too; sigh.
+			 */
+			info1 |= max_packet(maxp) << 16;
+			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;
+	hw = qh->hw;
+	hw->hw_info1 = cpu_to_hc32(ehci, info1);
+	hw->hw_info2 = cpu_to_hc32(ehci, info2);
+	qh->is_out = !is_input;
+	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)
+{
+	__hc32		dma = QH_NEXT(ehci, qh->qh_dma);
+	struct ehci_qh	*head;
+
+	/* Don't link a QH if there's a Clear-TT-Buffer pending */
+	if (unlikely(qh->clearing_tt))
+		return;
+
+	WARN_ON(qh->qh_state != QH_STATE_IDLE);
+
+	/* (re)start the async schedule? */
+	head = ehci->async;
+	timer_action_done (ehci, TIMER_ASYNC_OFF);
+	if (!head->qh_next.qh) {
+		u32	cmd = ehci_readl(ehci, &ehci->regs->command);
+
+		if (!(cmd & CMD_ASE)) {
+			/* in case a clear of CMD_ASE didn't take yet */
+			(void)handshake(ehci, &ehci->regs->status,
+					STS_ASS, 0, 150);
+			cmd |= CMD_ASE;
+			ehci_writel(ehci, cmd, &ehci->regs->command);
+			/* posted write need not be known to HC yet ... */
+		}
+	}
+
+	/* clear halt and/or toggle; and maybe recover from silicon quirk */
+	qh_refresh(ehci, qh);
+
+	/* splice right after start */
+	qh->qh_next = head->qh_next;
+	qh->hw->hw_next = head->hw->hw_next;
+	wmb ();
+
+	head->qh_next.qh = qh;
+	head->hw->hw_next = dma;
+
+	qh_get(qh);
+	qh->xacterrs = 0;
+	qh->qh_state = QH_STATE_LINKED;
+	/* qtd completions reported later by interrupt */
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * 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;
+	__hc32			qh_addr_mask = cpu_to_hc32(ehci, 0x7f);
+
+	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->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;
+			__hc32			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(ehci);
+
+			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_tail(qtd_list, &qh->qtd_list);
+
+			ehci_qtd_init(ehci, 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(ehci, 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 urb		*urb,
+	struct list_head	*qtd_list,
+	gfp_t			mem_flags
+) {
+	int			epnum;
+	unsigned long		flags;
+	struct ehci_qh		*qh = NULL;
+	int			rc;
+
+	epnum = urb->ep->desc.bEndpointAddress;
+
+#ifdef EHCI_URB_TRACE
+	{
+		struct ehci_qtd *qtd;
+		qtd = list_entry(qtd_list->next, struct ehci_qtd, qtd_list);
+		ehci_dbg(ehci,
+			 "%s %s urb %p ep%d%s len %d, qtd %p [qh %p]\n",
+			 __func__, urb->dev->devpath, urb,
+			 epnum & 0x0f, (epnum & USB_DIR_IN) ? "in" : "out",
+			 urb->transfer_buffer_length,
+			 qtd, urb->ep->hcpriv);
+	}
+#endif
+
+	spin_lock_irqsave (&ehci->lock, flags);
+	if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
+		rc = -ESHUTDOWN;
+		goto done;
+	}
+	rc = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
+	if (unlikely(rc))
+		goto done;
+
+	qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
+	if (unlikely(qh == NULL)) {
+		usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
+		rc = -ENOMEM;
+		goto done;
+	}
+
+	/* 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->qh_state == QH_STATE_IDLE))
+		qh_link_async(ehci, qh);
+ done:
+	spin_unlock_irqrestore (&ehci->lock, flags);
+	if (unlikely (qh == NULL))
+		qtd_list_free (ehci, urb, qtd_list);
+	return rc;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* the async qh for the qtds being reclaimed are now unlinked from the HC */
+
+static void end_unlink_async (struct ehci_hcd *ehci)
+{
+	struct ehci_qh		*qh = ehci->reclaim;
+	struct ehci_qh		*next;
+
+	iaa_watchdog_done(ehci);
+
+	// qh->hw_next = cpu_to_hc32(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;
+	qh->reclaim = NULL;
+
+	qh_completions (ehci, qh);
+
+	if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING) {
+		qh_link_async (ehci, qh);
+	} else {
+		/* it's not free to turn the async schedule on/off; leave it
+		 * active but idle for a while once it empties.
+		 */
+		if (ehci->rh_state == EHCI_RH_RUNNING
+				&& ehci->async->qh_next.qh == NULL)
+			timer_action (ehci, TIMER_ASYNC_OFF);
+	}
+	qh_put(qh);			/* refcount from async list */
+
+	if (next) {
+		ehci->reclaim = NULL;
+		start_unlink_async (ehci, next);
+	}
+
+	if (ehci->has_synopsys_hc_bug)
+		ehci_writel(ehci, (u32) ehci->async->qh_dma,
+			    &ehci->regs->async_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 = ehci_readl(ehci, &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->rh_state != EHCI_RH_HALTED
+				&& !ehci->reclaim) {
+			/* ... and CMD_IAAD clear */
+			ehci_writel(ehci, 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->hw_next = qh->hw->hw_next;
+	prev->qh_next = qh->qh_next;
+	if (ehci->qh_scan_next == qh)
+		ehci->qh_scan_next = qh->qh_next.qh;
+	wmb ();
+
+	/* If the controller isn't running, we don't have to wait for it */
+	if (unlikely(ehci->rh_state != EHCI_RH_RUNNING)) {
+		/* if (unlikely (qh->reclaim != 0))
+		 *	this will recurse, probably not much
+		 */
+		end_unlink_async (ehci);
+		return;
+	}
+
+	cmd |= CMD_IAAD;
+	ehci_writel(ehci, cmd, &ehci->regs->command);
+	(void)ehci_readl(ehci, &ehci->regs->command);
+	iaa_watchdog_start(ehci);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void scan_async (struct ehci_hcd *ehci)
+{
+	bool			stopped;
+	struct ehci_qh		*qh;
+	enum ehci_timer_action	action = TIMER_IO_WATCHDOG;
+
+	timer_action_done (ehci, TIMER_ASYNC_SHRINK);
+	stopped = (ehci->rh_state != EHCI_RH_RUNNING);
+
+	ehci->qh_scan_next = ehci->async->qh_next.qh;
+	while (ehci->qh_scan_next) {
+		qh = ehci->qh_scan_next;
+		ehci->qh_scan_next = qh->qh_next.qh;
+ rescan:
+		/* 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 start_unlink_async().
+			 */
+			qh = qh_get(qh);
+			temp = qh_completions(ehci, qh);
+			if (qh->needs_rescan)
+				unlink_async(ehci, qh);
+			qh->unlink_time = jiffies + EHCI_SHRINK_JIFFIES;
+			qh_put(qh);
+			if (temp != 0)
+				goto rescan;
+		}
+
+		/* unlink idle entries, reducing DMA 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)
+				&& qh->qh_state == QH_STATE_LINKED) {
+			if (!ehci->reclaim && (stopped ||
+					time_after_eq(jiffies, qh->unlink_time)))
+				start_unlink_async(ehci, qh);
+			else
+				action = TIMER_ASYNC_SHRINK;
+		}
+	}
+	if (action == TIMER_ASYNC_SHRINK)
+		timer_action (ehci, TIMER_ASYNC_SHRINK);
+}