zte's code,first commit

Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/drivers/usb/host/ehci-sched.c b/ap/os/linux/linux-3.4.x/drivers/usb/host/ehci-sched.c
new file mode 100644
index 0000000..34655d0
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/drivers/usb/host/ehci-sched.c
@@ -0,0 +1,2501 @@
+/*
+ * Copyright (c) 2001-2004 by David Brownell
+ * Copyright (c) 2003 Michal Sojka, for high-speed iso transfers
+ *
+ * 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 scheduled transaction support:  interrupt, iso, split iso
+ * These are called "periodic" transactions in the EHCI spec.
+ *
+ * Note that for interrupt transfers, the QH/QTD manipulation is shared
+ * with the "asynchronous" transaction support (control/bulk transfers).
+ * The only real difference is in how interrupt transfers are scheduled.
+ *
+ * For ISO, we make an "iso_stream" head to serve the same role as a QH.
+ * It keeps track of every ITD (or SITD) that's linked, and holds enough
+ * pre-calculated schedule data to make appending to the queue be quick.
+ */
+
+static int ehci_get_frame (struct usb_hcd *hcd);
+
+#ifdef CONFIG_PCI
+
+static unsigned ehci_read_frame_index(struct ehci_hcd *ehci)
+{
+	unsigned uf;
+
+	/*
+	 * The MosChip MCS9990 controller updates its microframe counter
+	 * a little before the frame counter, and occasionally we will read
+	 * the invalid intermediate value.  Avoid problems by checking the
+	 * microframe number (the low-order 3 bits); if they are 0 then
+	 * re-read the register to get the correct value.
+	 */
+	uf = ehci_readl(ehci, &ehci->regs->frame_index);
+	if (unlikely(ehci->frame_index_bug && ((uf & 7) == 0)))
+		uf = ehci_readl(ehci, &ehci->regs->frame_index);
+	return uf;
+}
+
+#endif
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * periodic_next_shadow - return "next" pointer on shadow list
+ * @periodic: host pointer to qh/itd/sitd
+ * @tag: hardware tag for type of this record
+ */
+static union ehci_shadow *
+periodic_next_shadow(struct ehci_hcd *ehci, union ehci_shadow *periodic,
+		__hc32 tag)
+{
+	switch (hc32_to_cpu(ehci, tag)) {
+	case Q_TYPE_QH:
+		return &periodic->qh->qh_next;
+	case Q_TYPE_FSTN:
+		return &periodic->fstn->fstn_next;
+	case Q_TYPE_ITD:
+		return &periodic->itd->itd_next;
+	// case Q_TYPE_SITD:
+	default:
+		return &periodic->sitd->sitd_next;
+	}
+}
+
+static __hc32 *
+shadow_next_periodic(struct ehci_hcd *ehci, union ehci_shadow *periodic,
+		__hc32 tag)
+{
+	switch (hc32_to_cpu(ehci, tag)) {
+	/* our ehci_shadow.qh is actually software part */
+	case Q_TYPE_QH:
+		return &periodic->qh->hw->hw_next;
+	/* others are hw parts */
+	default:
+		return periodic->hw_next;
+	}
+}
+
+/* caller must hold ehci->lock */
+static void periodic_unlink (struct ehci_hcd *ehci, unsigned frame, void *ptr)
+{
+	union ehci_shadow	*prev_p = &ehci->pshadow[frame];
+	__hc32			*hw_p = &ehci->periodic[frame];
+	union ehci_shadow	here = *prev_p;
+
+	/* find predecessor of "ptr"; hw and shadow lists are in sync */
+	while (here.ptr && here.ptr != ptr) {
+		prev_p = periodic_next_shadow(ehci, prev_p,
+				Q_NEXT_TYPE(ehci, *hw_p));
+		hw_p = shadow_next_periodic(ehci, &here,
+				Q_NEXT_TYPE(ehci, *hw_p));
+		here = *prev_p;
+	}
+	/* an interrupt entry (at list end) could have been shared */
+	if (!here.ptr)
+		return;
+
+	/* update shadow and hardware lists ... the old "next" pointers
+	 * from ptr may still be in use, the caller updates them.
+	 */
+	*prev_p = *periodic_next_shadow(ehci, &here,
+			Q_NEXT_TYPE(ehci, *hw_p));
+
+	if (!ehci->use_dummy_qh ||
+	    *shadow_next_periodic(ehci, &here, Q_NEXT_TYPE(ehci, *hw_p))
+			!= EHCI_LIST_END(ehci))
+		*hw_p = *shadow_next_periodic(ehci, &here,
+				Q_NEXT_TYPE(ehci, *hw_p));
+	else
+		*hw_p = ehci->dummy->qh_dma;
+}
+
+/* how many of the uframe's 125 usecs are allocated? */
+static unsigned short
+periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe)
+{
+	__hc32			*hw_p = &ehci->periodic [frame];
+	union ehci_shadow	*q = &ehci->pshadow [frame];
+	unsigned		usecs = 0;
+	struct ehci_qh_hw	*hw;
+
+	while (q->ptr) {
+		switch (hc32_to_cpu(ehci, Q_NEXT_TYPE(ehci, *hw_p))) {
+		case Q_TYPE_QH:
+			hw = q->qh->hw;
+			/* is it in the S-mask? */
+			if (hw->hw_info2 & cpu_to_hc32(ehci, 1 << uframe))
+				usecs += q->qh->usecs;
+			/* ... or C-mask? */
+			if (hw->hw_info2 & cpu_to_hc32(ehci,
+					1 << (8 + uframe)))
+				usecs += q->qh->c_usecs;
+			hw_p = &hw->hw_next;
+			q = &q->qh->qh_next;
+			break;
+		// case Q_TYPE_FSTN:
+		default:
+			/* for "save place" FSTNs, count the relevant INTR
+			 * bandwidth from the previous frame
+			 */
+			if (q->fstn->hw_prev != EHCI_LIST_END(ehci)) {
+				ehci_dbg (ehci, "ignoring FSTN cost ...\n");
+			}
+			hw_p = &q->fstn->hw_next;
+			q = &q->fstn->fstn_next;
+			break;
+		case Q_TYPE_ITD:
+			if (q->itd->hw_transaction[uframe])
+				usecs += q->itd->stream->usecs;
+			hw_p = &q->itd->hw_next;
+			q = &q->itd->itd_next;
+			break;
+		case Q_TYPE_SITD:
+			/* is it in the S-mask?  (count SPLIT, DATA) */
+			if (q->sitd->hw_uframe & cpu_to_hc32(ehci,
+					1 << uframe)) {
+				if (q->sitd->hw_fullspeed_ep &
+						cpu_to_hc32(ehci, 1<<31))
+					usecs += q->sitd->stream->usecs;
+				else	/* worst case for OUT start-split */
+					usecs += HS_USECS_ISO (188);
+			}
+
+			/* ... C-mask?  (count CSPLIT, DATA) */
+			if (q->sitd->hw_uframe &
+					cpu_to_hc32(ehci, 1 << (8 + uframe))) {
+				/* worst case for IN complete-split */
+				usecs += q->sitd->stream->c_usecs;
+			}
+
+			hw_p = &q->sitd->hw_next;
+			q = &q->sitd->sitd_next;
+			break;
+		}
+	}
+#ifdef	DEBUG
+	if (usecs > ehci->uframe_periodic_max)
+		ehci_err (ehci, "uframe %d sched overrun: %d usecs\n",
+			frame * 8 + uframe, usecs);
+#endif
+	return usecs;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static int same_tt (struct usb_device *dev1, struct usb_device *dev2)
+{
+	if (!dev1->tt || !dev2->tt)
+		return 0;
+	if (dev1->tt != dev2->tt)
+		return 0;
+	if (dev1->tt->multi)
+		return dev1->ttport == dev2->ttport;
+	else
+		return 1;
+}
+
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+
+/* Which uframe does the low/fullspeed transfer start in?
+ *
+ * The parameter is the mask of ssplits in "H-frame" terms
+ * and this returns the transfer start uframe in "B-frame" terms,
+ * which allows both to match, e.g. a ssplit in "H-frame" uframe 0
+ * will cause a transfer in "B-frame" uframe 0.  "B-frames" lag
+ * "H-frames" by 1 uframe.  See the EHCI spec sec 4.5 and figure 4.7.
+ */
+static inline unsigned char tt_start_uframe(struct ehci_hcd *ehci, __hc32 mask)
+{
+	unsigned char smask = QH_SMASK & hc32_to_cpu(ehci, mask);
+	if (!smask) {
+		ehci_err(ehci, "invalid empty smask!\n");
+		/* uframe 7 can't have bw so this will indicate failure */
+		return 7;
+	}
+	return ffs(smask) - 1;
+}
+
+static const unsigned char
+max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
+
+/* carryover low/fullspeed bandwidth that crosses uframe boundries */
+static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])
+{
+	int i;
+	for (i=0; i<7; i++) {
+		if (max_tt_usecs[i] < tt_usecs[i]) {
+			tt_usecs[i+1] += tt_usecs[i] - max_tt_usecs[i];
+			tt_usecs[i] = max_tt_usecs[i];
+		}
+	}
+}
+
+/* How many of the tt's periodic downstream 1000 usecs are allocated?
+ *
+ * While this measures the bandwidth in terms of usecs/uframe,
+ * the low/fullspeed bus has no notion of uframes, so any particular
+ * low/fullspeed transfer can "carry over" from one uframe to the next,
+ * since the TT just performs downstream transfers in sequence.
+ *
+ * For example two separate 100 usec transfers can start in the same uframe,
+ * and the second one would "carry over" 75 usecs into the next uframe.
+ */
+static void
+periodic_tt_usecs (
+	struct ehci_hcd *ehci,
+	struct usb_device *dev,
+	unsigned frame,
+	unsigned short tt_usecs[8]
+)
+{
+	__hc32			*hw_p = &ehci->periodic [frame];
+	union ehci_shadow	*q = &ehci->pshadow [frame];
+	unsigned char		uf;
+
+	memset(tt_usecs, 0, 16);
+
+	while (q->ptr) {
+		switch (hc32_to_cpu(ehci, Q_NEXT_TYPE(ehci, *hw_p))) {
+		case Q_TYPE_ITD:
+			hw_p = &q->itd->hw_next;
+			q = &q->itd->itd_next;
+			continue;
+		case Q_TYPE_QH:
+			if (same_tt(dev, q->qh->dev)) {
+				uf = tt_start_uframe(ehci, q->qh->hw->hw_info2);
+				tt_usecs[uf] += q->qh->tt_usecs;
+			}
+			hw_p = &q->qh->hw->hw_next;
+			q = &q->qh->qh_next;
+			continue;
+		case Q_TYPE_SITD:
+			if (same_tt(dev, q->sitd->urb->dev)) {
+				uf = tt_start_uframe(ehci, q->sitd->hw_uframe);
+				tt_usecs[uf] += q->sitd->stream->tt_usecs;
+			}
+			hw_p = &q->sitd->hw_next;
+			q = &q->sitd->sitd_next;
+			continue;
+		// case Q_TYPE_FSTN:
+		default:
+			ehci_dbg(ehci, "ignoring periodic frame %d FSTN\n",
+					frame);
+			hw_p = &q->fstn->hw_next;
+			q = &q->fstn->fstn_next;
+		}
+	}
+
+	carryover_tt_bandwidth(tt_usecs);
+
+	if (max_tt_usecs[7] < tt_usecs[7])
+		ehci_err(ehci, "frame %d tt sched overrun: %d usecs\n",
+			frame, tt_usecs[7] - max_tt_usecs[7]);
+}
+
+/*
+ * Return true if the device's tt's downstream bus is available for a
+ * periodic transfer of the specified length (usecs), starting at the
+ * specified frame/uframe.  Note that (as summarized in section 11.19
+ * of the usb 2.0 spec) TTs can buffer multiple transactions for each
+ * uframe.
+ *
+ * The uframe parameter is when the fullspeed/lowspeed transfer
+ * should be executed in "B-frame" terms, which is the same as the
+ * highspeed ssplit's uframe (which is in "H-frame" terms).  For example
+ * a ssplit in "H-frame" 0 causes a transfer in "B-frame" 0.
+ * See the EHCI spec sec 4.5 and fig 4.7.
+ *
+ * This checks if the full/lowspeed bus, at the specified starting uframe,
+ * has the specified bandwidth available, according to rules listed
+ * in USB 2.0 spec section 11.18.1 fig 11-60.
+ *
+ * This does not check if the transfer would exceed the max ssplit
+ * limit of 16, specified in USB 2.0 spec section 11.18.4 requirement #4,
+ * since proper scheduling limits ssplits to less than 16 per uframe.
+ */
+static int tt_available (
+	struct ehci_hcd		*ehci,
+	unsigned		period,
+	struct usb_device	*dev,
+	unsigned		frame,
+	unsigned		uframe,
+	u16			usecs
+)
+{
+	if ((period == 0) || (uframe >= 7))	/* error */
+		return 0;
+
+	for (; frame < ehci->periodic_size; frame += period) {
+		unsigned short tt_usecs[8];
+
+		periodic_tt_usecs (ehci, dev, frame, tt_usecs);
+
+		ehci_vdbg(ehci, "tt frame %d check %d usecs start uframe %d in"
+			" schedule %d/%d/%d/%d/%d/%d/%d/%d\n",
+			frame, usecs, uframe,
+			tt_usecs[0], tt_usecs[1], tt_usecs[2], tt_usecs[3],
+			tt_usecs[4], tt_usecs[5], tt_usecs[6], tt_usecs[7]);
+
+		if (max_tt_usecs[uframe] <= tt_usecs[uframe]) {
+			ehci_vdbg(ehci, "frame %d uframe %d fully scheduled\n",
+				frame, uframe);
+			return 0;
+		}
+
+		/* special case for isoc transfers larger than 125us:
+		 * the first and each subsequent fully used uframe
+		 * must be empty, so as to not illegally delay
+		 * already scheduled transactions
+		 */
+		if (125 < usecs) {
+			int ufs = (usecs / 125);
+			int i;
+			for (i = uframe; i < (uframe + ufs) && i < 8; i++)
+				if (0 < tt_usecs[i]) {
+					ehci_vdbg(ehci,
+						"multi-uframe xfer can't fit "
+						"in frame %d uframe %d\n",
+						frame, i);
+					return 0;
+				}
+		}
+
+		tt_usecs[uframe] += usecs;
+
+		carryover_tt_bandwidth(tt_usecs);
+
+		/* fail if the carryover pushed bw past the last uframe's limit */
+		if (max_tt_usecs[7] < tt_usecs[7]) {
+			ehci_vdbg(ehci,
+				"tt unavailable usecs %d frame %d uframe %d\n",
+				usecs, frame, uframe);
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
+#else
+
+/* return true iff the device's transaction translator is available
+ * for a periodic transfer starting at the specified frame, using
+ * all the uframes in the mask.
+ */
+static int tt_no_collision (
+	struct ehci_hcd		*ehci,
+	unsigned		period,
+	struct usb_device	*dev,
+	unsigned		frame,
+	u32			uf_mask
+)
+{
+	if (period == 0)	/* error */
+		return 0;
+
+	/* note bandwidth wastage:  split never follows csplit
+	 * (different dev or endpoint) until the next uframe.
+	 * calling convention doesn't make that distinction.
+	 */
+	for (; frame < ehci->periodic_size; frame += period) {
+		union ehci_shadow	here;
+		__hc32			type;
+		struct ehci_qh_hw	*hw;
+
+		here = ehci->pshadow [frame];
+		type = Q_NEXT_TYPE(ehci, ehci->periodic [frame]);
+		while (here.ptr) {
+			switch (hc32_to_cpu(ehci, type)) {
+			case Q_TYPE_ITD:
+				type = Q_NEXT_TYPE(ehci, here.itd->hw_next);
+				here = here.itd->itd_next;
+				continue;
+			case Q_TYPE_QH:
+				hw = here.qh->hw;
+				if (same_tt (dev, here.qh->dev)) {
+					u32		mask;
+
+					mask = hc32_to_cpu(ehci,
+							hw->hw_info2);
+					/* "knows" no gap is needed */
+					mask |= mask >> 8;
+					if (mask & uf_mask)
+						break;
+				}
+				type = Q_NEXT_TYPE(ehci, hw->hw_next);
+				here = here.qh->qh_next;
+				continue;
+			case Q_TYPE_SITD:
+				if (same_tt (dev, here.sitd->urb->dev)) {
+					u16		mask;
+
+					mask = hc32_to_cpu(ehci, here.sitd
+								->hw_uframe);
+					/* FIXME assumes no gap for IN! */
+					mask |= mask >> 8;
+					if (mask & uf_mask)
+						break;
+				}
+				type = Q_NEXT_TYPE(ehci, here.sitd->hw_next);
+				here = here.sitd->sitd_next;
+				continue;
+			// case Q_TYPE_FSTN:
+			default:
+				ehci_dbg (ehci,
+					"periodic frame %d bogus type %d\n",
+					frame, type);
+			}
+
+			/* collision or error */
+			return 0;
+		}
+	}
+
+	/* no collision */
+	return 1;
+}
+
+#endif /* CONFIG_USB_EHCI_TT_NEWSCHED */
+
+/*-------------------------------------------------------------------------*/
+
+static int enable_periodic (struct ehci_hcd *ehci)
+{
+	u32	cmd;
+	int	status;
+
+	if (ehci->periodic_sched++)
+		return 0;
+
+	/* did clearing PSE did take effect yet?
+	 * takes effect only at frame boundaries...
+	 */
+	status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
+					     STS_PSS, 0, 9 * 125);
+	if (status) {
+		usb_hc_died(ehci_to_hcd(ehci));
+		return status;
+	}
+
+	cmd = ehci_readl(ehci, &ehci->regs->command) | CMD_PSE;
+	ehci_writel(ehci, cmd, &ehci->regs->command);
+	/* posted write ... PSS happens later */
+
+	/* make sure ehci_work scans these */
+	ehci->next_uframe = ehci_read_frame_index(ehci)
+		% (ehci->periodic_size << 3);
+	if (unlikely(ehci->broken_periodic))
+		ehci->last_periodic_enable = ktime_get_real();
+	return 0;
+}
+
+static int disable_periodic (struct ehci_hcd *ehci)
+{
+	u32	cmd;
+	int	status;
+
+	if (--ehci->periodic_sched)
+		return 0;
+
+	if (unlikely(ehci->broken_periodic)) {
+		/* delay experimentally determined */
+		ktime_t safe = ktime_add_us(ehci->last_periodic_enable, 1000);
+		ktime_t now = ktime_get_real();
+		s64 delay = ktime_us_delta(safe, now);
+
+		if (unlikely(delay > 0))
+			udelay(delay);
+	}
+
+	/* did setting PSE not take effect yet?
+	 * takes effect only at frame boundaries...
+	 */
+	status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
+					     STS_PSS, STS_PSS, 9 * 125);
+	if (status) {
+		usb_hc_died(ehci_to_hcd(ehci));
+		return status;
+	}
+
+	cmd = ehci_readl(ehci, &ehci->regs->command) & ~CMD_PSE;
+	ehci_writel(ehci, cmd, &ehci->regs->command);
+	/* posted write ... */
+
+	free_cached_lists(ehci);
+
+	ehci->next_uframe = -1;
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* periodic schedule slots have iso tds (normal or split) first, then a
+ * sparse tree for active interrupt transfers.
+ *
+ * this just links in a qh; caller guarantees uframe masks are set right.
+ * no FSTN support (yet; ehci 0.96+)
+ */
+static int qh_link_periodic (struct ehci_hcd *ehci, struct ehci_qh *qh)
+{
+	unsigned	i;
+	unsigned	period = qh->period;
+
+	dev_dbg (&qh->dev->dev,
+		"link qh%d-%04x/%p start %d [%d/%d us]\n",
+		period, hc32_to_cpup(ehci, &qh->hw->hw_info2)
+			& (QH_CMASK | QH_SMASK),
+		qh, qh->start, qh->usecs, qh->c_usecs);
+
+	/* high bandwidth, or otherwise every microframe */
+	if (period == 0)
+		period = 1;
+
+	for (i = qh->start; i < ehci->periodic_size; i += period) {
+		union ehci_shadow	*prev = &ehci->pshadow[i];
+		__hc32			*hw_p = &ehci->periodic[i];
+		union ehci_shadow	here = *prev;
+		__hc32			type = 0;
+
+		/* skip the iso nodes at list head */
+		while (here.ptr) {
+			type = Q_NEXT_TYPE(ehci, *hw_p);
+			if (type == cpu_to_hc32(ehci, Q_TYPE_QH))
+				break;
+			prev = periodic_next_shadow(ehci, prev, type);
+			hw_p = shadow_next_periodic(ehci, &here, type);
+			here = *prev;
+		}
+
+		/* sorting each branch by period (slow-->fast)
+		 * enables sharing interior tree nodes
+		 */
+		while (here.ptr && qh != here.qh) {
+			if (qh->period > here.qh->period)
+				break;
+			prev = &here.qh->qh_next;
+			hw_p = &here.qh->hw->hw_next;
+			here = *prev;
+		}
+		/* link in this qh, unless some earlier pass did that */
+		if (qh != here.qh) {
+			qh->qh_next = here;
+			if (here.qh)
+				qh->hw->hw_next = *hw_p;
+			wmb ();
+			prev->qh = qh;
+			*hw_p = QH_NEXT (ehci, qh->qh_dma);
+		}
+	}
+	qh->qh_state = QH_STATE_LINKED;
+	qh->xacterrs = 0;
+	qh_get (qh);
+
+	/* update per-qh bandwidth for usbfs */
+	ehci_to_hcd(ehci)->self.bandwidth_allocated += qh->period
+		? ((qh->usecs + qh->c_usecs) / qh->period)
+		: (qh->usecs * 8);
+
+	/* maybe enable periodic schedule processing */
+	return enable_periodic(ehci);
+}
+
+static int qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
+{
+	unsigned	i;
+	unsigned	period;
+
+	// FIXME:
+	// IF this isn't high speed
+	//   and this qh is active in the current uframe
+	//   (and overlay token SplitXstate is false?)
+	// THEN
+	//   qh->hw_info1 |= cpu_to_hc32(1 << 7 /* "ignore" */);
+
+	/* high bandwidth, or otherwise part of every microframe */
+	if ((period = qh->period) == 0)
+		period = 1;
+
+	for (i = qh->start; i < ehci->periodic_size; i += period)
+		periodic_unlink (ehci, i, qh);
+
+	/* update per-qh bandwidth for usbfs */
+	ehci_to_hcd(ehci)->self.bandwidth_allocated -= qh->period
+		? ((qh->usecs + qh->c_usecs) / qh->period)
+		: (qh->usecs * 8);
+
+	dev_dbg (&qh->dev->dev,
+		"unlink qh%d-%04x/%p start %d [%d/%d us]\n",
+		qh->period,
+		hc32_to_cpup(ehci, &qh->hw->hw_info2) & (QH_CMASK | QH_SMASK),
+		qh, qh->start, qh->usecs, qh->c_usecs);
+
+	/* qh->qh_next still "live" to HC */
+	qh->qh_state = QH_STATE_UNLINK;
+	qh->qh_next.ptr = NULL;
+	qh_put (qh);
+
+	/* maybe turn off periodic schedule */
+	return disable_periodic(ehci);
+}
+
+static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
+{
+	unsigned		wait;
+	struct ehci_qh_hw	*hw = qh->hw;
+	int			rc;
+
+	/* If the QH isn't linked then there's nothing we can do
+	 * unless we were called during a giveback, in which case
+	 * qh_completions() has to deal with it.
+	 */
+	if (qh->qh_state != QH_STATE_LINKED) {
+		if (qh->qh_state == QH_STATE_COMPLETING)
+			qh->needs_rescan = 1;
+		return;
+	}
+
+	qh_unlink_periodic (ehci, qh);
+
+	/* simple/paranoid:  always delay, expecting the HC needs to read
+	 * qh->hw_next or finish a writeback after SPLIT/CSPLIT ... and
+	 * expect khubd to clean up after any CSPLITs we won't issue.
+	 * active high speed queues may need bigger delays...
+	 */
+	if (list_empty (&qh->qtd_list)
+			|| (cpu_to_hc32(ehci, QH_CMASK)
+					& hw->hw_info2) != 0)
+		wait = 2;
+	else
+		wait = 55;	/* worst case: 3 * 1024 */
+
+	udelay (wait);
+	qh->qh_state = QH_STATE_IDLE;
+	hw->hw_next = EHCI_LIST_END(ehci);
+	wmb ();
+
+	qh_completions(ehci, qh);
+
+	/* reschedule QH iff another request is queued */
+	if (!list_empty(&qh->qtd_list) &&
+			ehci->rh_state == EHCI_RH_RUNNING) {
+		rc = qh_schedule(ehci, qh);
+
+		/* An error here likely indicates handshake failure
+		 * or no space left in the schedule.  Neither fault
+		 * should happen often ...
+		 *
+		 * FIXME kill the now-dysfunctional queued urbs
+		 */
+		if (rc != 0)
+			ehci_err(ehci, "can't reschedule qh %p, err %d\n",
+					qh, rc);
+	}
+}
+
+/*-------------------------------------------------------------------------*/
+
+static int check_period (
+	struct ehci_hcd *ehci,
+	unsigned	frame,
+	unsigned	uframe,
+	unsigned	period,
+	unsigned	usecs
+) {
+	int		claimed;
+
+	/* complete split running into next frame?
+	 * given FSTN support, we could sometimes check...
+	 */
+	if (uframe >= 8)
+		return 0;
+
+	/* convert "usecs we need" to "max already claimed" */
+	usecs = ehci->uframe_periodic_max - usecs;
+
+	/* we "know" 2 and 4 uframe intervals were rejected; so
+	 * for period 0, check _every_ microframe in the schedule.
+	 */
+	if (unlikely (period == 0)) {
+		do {
+			for (uframe = 0; uframe < 7; uframe++) {
+				claimed = periodic_usecs (ehci, frame, uframe);
+				if (claimed > usecs)
+					return 0;
+			}
+		} while ((frame += 1) < ehci->periodic_size);
+
+	/* just check the specified uframe, at that period */
+	} else {
+		do {
+			claimed = periodic_usecs (ehci, frame, uframe);
+			if (claimed > usecs)
+				return 0;
+		} while ((frame += period) < ehci->periodic_size);
+	}
+
+	// success!
+	return 1;
+}
+
+static int check_intr_schedule (
+	struct ehci_hcd		*ehci,
+	unsigned		frame,
+	unsigned		uframe,
+	const struct ehci_qh	*qh,
+	__hc32			*c_maskp
+)
+{
+	int		retval = -ENOSPC;
+	u8		mask = 0;
+
+	if (qh->c_usecs && uframe >= 6)		/* FSTN territory? */
+		goto done;
+
+	if (!check_period (ehci, frame, uframe, qh->period, qh->usecs))
+		goto done;
+	if (!qh->c_usecs) {
+		retval = 0;
+		*c_maskp = 0;
+		goto done;
+	}
+
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+	if (tt_available (ehci, qh->period, qh->dev, frame, uframe,
+				qh->tt_usecs)) {
+		unsigned i;
+
+		/* TODO : this may need FSTN for SSPLIT in uframe 5. */
+		for (i=uframe+1; i<8 && i<uframe+4; i++)
+			if (!check_period (ehci, frame, i,
+						qh->period, qh->c_usecs))
+				goto done;
+			else
+				mask |= 1 << i;
+
+		retval = 0;
+
+		*c_maskp = cpu_to_hc32(ehci, mask << 8);
+	}
+#else
+	/* Make sure this tt's buffer is also available for CSPLITs.
+	 * We pessimize a bit; probably the typical full speed case
+	 * doesn't need the second CSPLIT.
+	 *
+	 * NOTE:  both SPLIT and CSPLIT could be checked in just
+	 * one smart pass...
+	 */
+	mask = 0x03 << (uframe + qh->gap_uf);
+	*c_maskp = cpu_to_hc32(ehci, mask << 8);
+
+	mask |= 1 << uframe;
+	if (tt_no_collision (ehci, qh->period, qh->dev, frame, mask)) {
+		if (!check_period (ehci, frame, uframe + qh->gap_uf + 1,
+					qh->period, qh->c_usecs))
+			goto done;
+		if (!check_period (ehci, frame, uframe + qh->gap_uf,
+					qh->period, qh->c_usecs))
+			goto done;
+		retval = 0;
+	}
+#endif
+done:
+	return retval;
+}
+
+/* "first fit" scheduling policy used the first time through,
+ * or when the previous schedule slot can't be re-used.
+ */
+static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh)
+{
+	int		status;
+	unsigned	uframe;
+	__hc32		c_mask;
+	unsigned	frame;		/* 0..(qh->period - 1), or NO_FRAME */
+	struct ehci_qh_hw	*hw = qh->hw;
+
+	qh_refresh(ehci, qh);
+	hw->hw_next = EHCI_LIST_END(ehci);
+	frame = qh->start;
+
+	/* reuse the previous schedule slots, if we can */
+	if (frame < qh->period) {
+		uframe = ffs(hc32_to_cpup(ehci, &hw->hw_info2) & QH_SMASK);
+		status = check_intr_schedule (ehci, frame, --uframe,
+				qh, &c_mask);
+	} else {
+		uframe = 0;
+		c_mask = 0;
+		status = -ENOSPC;
+	}
+
+	/* else scan the schedule to find a group of slots such that all
+	 * uframes have enough periodic bandwidth available.
+	 */
+	if (status) {
+		/* "normal" case, uframing flexible except with splits */
+		if (qh->period) {
+			int		i;
+
+			for (i = qh->period; status && i > 0; --i) {
+				frame = ++ehci->random_frame % qh->period;
+				for (uframe = 0; uframe < 8; uframe++) {
+					status = check_intr_schedule (ehci,
+							frame, uframe, qh,
+							&c_mask);
+					if (status == 0)
+						break;
+				}
+			}
+
+		/* qh->period == 0 means every uframe */
+		} else {
+			frame = 0;
+			status = check_intr_schedule (ehci, 0, 0, qh, &c_mask);
+		}
+		if (status)
+			goto done;
+		qh->start = frame;
+
+		/* reset S-frame and (maybe) C-frame masks */
+		hw->hw_info2 &= cpu_to_hc32(ehci, ~(QH_CMASK | QH_SMASK));
+		hw->hw_info2 |= qh->period
+			? cpu_to_hc32(ehci, 1 << uframe)
+			: cpu_to_hc32(ehci, QH_SMASK);
+		hw->hw_info2 |= c_mask;
+	} else
+		ehci_dbg (ehci, "reused qh %p schedule\n", qh);
+
+	/* stuff into the periodic schedule */
+	status = qh_link_periodic (ehci, qh);
+done:
+	return status;
+}
+
+static int intr_submit (
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	struct list_head	*qtd_list,
+	gfp_t			mem_flags
+) {
+	unsigned		epnum;
+	unsigned long		flags;
+	struct ehci_qh		*qh;
+	int			status;
+	struct list_head	empty;
+
+	/* get endpoint and transfer/schedule data */
+	epnum = urb->ep->desc.bEndpointAddress;
+
+	spin_lock_irqsave (&ehci->lock, flags);
+
+	if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
+		status = -ESHUTDOWN;
+		goto done_not_linked;
+	}
+	status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
+	if (unlikely(status))
+		goto done_not_linked;
+
+	/* get qh and force any scheduling errors */
+	INIT_LIST_HEAD (&empty);
+	qh = qh_append_tds(ehci, urb, &empty, epnum, &urb->ep->hcpriv);
+	if (qh == NULL) {
+		status = -ENOMEM;
+		goto done;
+	}
+	if (qh->qh_state == QH_STATE_IDLE) {
+		if ((status = qh_schedule (ehci, qh)) != 0)
+			goto done;
+	}
+
+	/* then queue the urb's tds to the qh */
+	qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
+	BUG_ON (qh == NULL);
+
+	/* ... update usbfs periodic stats */
+	ehci_to_hcd(ehci)->self.bandwidth_int_reqs++;
+
+done:
+	if (unlikely(status))
+		usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
+done_not_linked:
+	spin_unlock_irqrestore (&ehci->lock, flags);
+	if (status)
+		qtd_list_free (ehci, urb, qtd_list);
+
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* ehci_iso_stream ops work with both ITD and SITD */
+
+static struct ehci_iso_stream *
+iso_stream_alloc (gfp_t mem_flags)
+{
+	struct ehci_iso_stream *stream;
+
+	stream = kzalloc(sizeof *stream, mem_flags);
+	if (likely (stream != NULL)) {
+		INIT_LIST_HEAD(&stream->td_list);
+		INIT_LIST_HEAD(&stream->free_list);
+		stream->next_uframe = -1;
+		stream->refcount = 1;
+	}
+	return stream;
+}
+
+static void
+iso_stream_init (
+	struct ehci_hcd		*ehci,
+	struct ehci_iso_stream	*stream,
+	struct usb_device	*dev,
+	int			pipe,
+	unsigned		interval
+)
+{
+	static const u8 smask_out [] = { 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f };
+
+	u32			buf1;
+	unsigned		epnum, maxp;
+	int			is_input;
+	long			bandwidth;
+
+	/*
+	 * this might be a "high bandwidth" highspeed endpoint,
+	 * as encoded in the ep descriptor's wMaxPacket field
+	 */
+	epnum = usb_pipeendpoint (pipe);
+	is_input = usb_pipein (pipe) ? USB_DIR_IN : 0;
+	maxp = usb_maxpacket(dev, pipe, !is_input);
+	if (is_input) {
+		buf1 = (1 << 11);
+	} else {
+		buf1 = 0;
+	}
+
+	/* knows about ITD vs SITD */
+	if (dev->speed == USB_SPEED_HIGH) {
+		unsigned multi = hb_mult(maxp);
+
+		stream->highspeed = 1;
+
+		maxp = max_packet(maxp);
+		buf1 |= maxp;
+		maxp *= multi;
+
+		stream->buf0 = cpu_to_hc32(ehci, (epnum << 8) | dev->devnum);
+		stream->buf1 = cpu_to_hc32(ehci, buf1);
+		stream->buf2 = cpu_to_hc32(ehci, multi);
+
+		/* usbfs wants to report the average usecs per frame tied up
+		 * when transfers on this endpoint are scheduled ...
+		 */
+		stream->usecs = HS_USECS_ISO (maxp);
+		bandwidth = stream->usecs * 8;
+		bandwidth /= interval;
+
+	} else {
+		u32		addr;
+		int		think_time;
+		int		hs_transfers;
+
+		addr = dev->ttport << 24;
+		if (!ehci_is_TDI(ehci)
+				|| (dev->tt->hub !=
+					ehci_to_hcd(ehci)->self.root_hub))
+			addr |= dev->tt->hub->devnum << 16;
+		addr |= epnum << 8;
+		addr |= dev->devnum;
+		stream->usecs = HS_USECS_ISO (maxp);
+		think_time = dev->tt ? dev->tt->think_time : 0;
+		stream->tt_usecs = NS_TO_US (think_time + usb_calc_bus_time (
+				dev->speed, is_input, 1, maxp));
+		hs_transfers = max (1u, (maxp + 187) / 188);
+		if (is_input) {
+			u32	tmp;
+
+			addr |= 1 << 31;
+			stream->c_usecs = stream->usecs;
+			stream->usecs = HS_USECS_ISO (1);
+			stream->raw_mask = 1;
+
+			/* c-mask as specified in USB 2.0 11.18.4 3.c */
+			tmp = (1 << (hs_transfers + 2)) - 1;
+			stream->raw_mask |= tmp << (8 + 2);
+		} else
+			stream->raw_mask = smask_out [hs_transfers - 1];
+		bandwidth = stream->usecs + stream->c_usecs;
+		bandwidth /= interval << 3;
+
+		/* stream->splits gets created from raw_mask later */
+		stream->address = cpu_to_hc32(ehci, addr);
+	}
+	stream->bandwidth = bandwidth;
+
+	stream->udev = dev;
+
+	stream->bEndpointAddress = is_input | epnum;
+	stream->interval = interval;
+	stream->maxp = maxp;
+}
+
+static void
+iso_stream_put(struct ehci_hcd *ehci, struct ehci_iso_stream *stream)
+{
+	stream->refcount--;
+
+	/* free whenever just a dev->ep reference remains.
+	 * not like a QH -- no persistent state (toggle, halt)
+	 */
+	if (stream->refcount == 1) {
+		// BUG_ON (!list_empty(&stream->td_list));
+
+		while (!list_empty (&stream->free_list)) {
+			struct list_head	*entry;
+
+			entry = stream->free_list.next;
+			list_del (entry);
+
+			/* knows about ITD vs SITD */
+			if (stream->highspeed) {
+				struct ehci_itd		*itd;
+
+				itd = list_entry (entry, struct ehci_itd,
+						itd_list);
+				dma_pool_free (ehci->itd_pool, itd,
+						itd->itd_dma);
+			} else {
+				struct ehci_sitd	*sitd;
+
+				sitd = list_entry (entry, struct ehci_sitd,
+						sitd_list);
+				dma_pool_free (ehci->sitd_pool, sitd,
+						sitd->sitd_dma);
+			}
+		}
+
+		stream->bEndpointAddress &= 0x0f;
+		if (stream->ep)
+			stream->ep->hcpriv = NULL;
+
+		kfree(stream);
+	}
+}
+
+static inline struct ehci_iso_stream *
+iso_stream_get (struct ehci_iso_stream *stream)
+{
+	if (likely (stream != NULL))
+		stream->refcount++;
+	return stream;
+}
+
+static struct ehci_iso_stream *
+iso_stream_find (struct ehci_hcd *ehci, struct urb *urb)
+{
+	unsigned		epnum;
+	struct ehci_iso_stream	*stream;
+	struct usb_host_endpoint *ep;
+	unsigned long		flags;
+
+	epnum = usb_pipeendpoint (urb->pipe);
+	if (usb_pipein(urb->pipe))
+		ep = urb->dev->ep_in[epnum];
+	else
+		ep = urb->dev->ep_out[epnum];
+
+	spin_lock_irqsave (&ehci->lock, flags);
+	stream = ep->hcpriv;
+
+	if (unlikely (stream == NULL)) {
+		stream = iso_stream_alloc(GFP_ATOMIC);
+		if (likely (stream != NULL)) {
+			/* dev->ep owns the initial refcount */
+			ep->hcpriv = stream;
+			stream->ep = ep;
+			iso_stream_init(ehci, stream, urb->dev, urb->pipe,
+					urb->interval);
+		}
+
+	/* if dev->ep [epnum] is a QH, hw is set */
+	} else if (unlikely (stream->hw != NULL)) {
+		ehci_dbg (ehci, "dev %s ep%d%s, not iso??\n",
+			urb->dev->devpath, epnum,
+			usb_pipein(urb->pipe) ? "in" : "out");
+		stream = NULL;
+	}
+
+	/* caller guarantees an eventual matching iso_stream_put */
+	stream = iso_stream_get (stream);
+
+	spin_unlock_irqrestore (&ehci->lock, flags);
+	return stream;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* ehci_iso_sched ops can be ITD-only or SITD-only */
+
+static struct ehci_iso_sched *
+iso_sched_alloc (unsigned packets, gfp_t mem_flags)
+{
+	struct ehci_iso_sched	*iso_sched;
+	int			size = sizeof *iso_sched;
+
+	size += packets * sizeof (struct ehci_iso_packet);
+	iso_sched = kzalloc(size, mem_flags);
+	if (likely (iso_sched != NULL)) {
+		INIT_LIST_HEAD (&iso_sched->td_list);
+	}
+	return iso_sched;
+}
+
+static inline void
+itd_sched_init(
+	struct ehci_hcd		*ehci,
+	struct ehci_iso_sched	*iso_sched,
+	struct ehci_iso_stream	*stream,
+	struct urb		*urb
+)
+{
+	unsigned	i;
+	dma_addr_t	dma = urb->transfer_dma;
+
+	/* how many uframes are needed for these transfers */
+	iso_sched->span = urb->number_of_packets * stream->interval;
+
+	/* figure out per-uframe itd fields that we'll need later
+	 * when we fit new itds into the schedule.
+	 */
+	for (i = 0; i < urb->number_of_packets; i++) {
+		struct ehci_iso_packet	*uframe = &iso_sched->packet [i];
+		unsigned		length;
+		dma_addr_t		buf;
+		u32			trans;
+
+		length = urb->iso_frame_desc [i].length;
+		buf = dma + urb->iso_frame_desc [i].offset;
+
+		trans = EHCI_ISOC_ACTIVE;
+		trans |= buf & 0x0fff;
+		if (unlikely (((i + 1) == urb->number_of_packets))
+				&& !(urb->transfer_flags & URB_NO_INTERRUPT))
+			trans |= EHCI_ITD_IOC;
+		trans |= length << 16;
+		uframe->transaction = cpu_to_hc32(ehci, trans);
+
+		/* might need to cross a buffer page within a uframe */
+		uframe->bufp = (buf & ~(u64)0x0fff);
+		buf += length;
+		if (unlikely ((uframe->bufp != (buf & ~(u64)0x0fff))))
+			uframe->cross = 1;
+	}
+}
+
+static void
+iso_sched_free (
+	struct ehci_iso_stream	*stream,
+	struct ehci_iso_sched	*iso_sched
+)
+{
+	if (!iso_sched)
+		return;
+	// caller must hold ehci->lock!
+	list_splice (&iso_sched->td_list, &stream->free_list);
+	kfree (iso_sched);
+}
+
+static int
+itd_urb_transaction (
+	struct ehci_iso_stream	*stream,
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	gfp_t			mem_flags
+)
+{
+	struct ehci_itd		*itd;
+	dma_addr_t		itd_dma;
+	int			i;
+	unsigned		num_itds;
+	struct ehci_iso_sched	*sched;
+	unsigned long		flags;
+
+	sched = iso_sched_alloc (urb->number_of_packets, mem_flags);
+	if (unlikely (sched == NULL))
+		return -ENOMEM;
+
+	itd_sched_init(ehci, sched, stream, urb);
+
+	if (urb->interval < 8)
+		num_itds = 1 + (sched->span + 7) / 8;
+	else
+		num_itds = urb->number_of_packets;
+
+	/* allocate/init ITDs */
+	spin_lock_irqsave (&ehci->lock, flags);
+	for (i = 0; i < num_itds; i++) {
+
+		/* free_list.next might be cache-hot ... but maybe
+		 * the HC caches it too. avoid that issue for now.
+		 */
+
+		/* prefer previously-allocated itds */
+		if (likely (!list_empty(&stream->free_list))) {
+			itd = list_entry (stream->free_list.prev,
+					struct ehci_itd, itd_list);
+			list_del (&itd->itd_list);
+			itd_dma = itd->itd_dma;
+		} else {
+			spin_unlock_irqrestore (&ehci->lock, flags);
+			itd = dma_pool_alloc (ehci->itd_pool, mem_flags,
+					&itd_dma);
+			spin_lock_irqsave (&ehci->lock, flags);
+			if (!itd) {
+				iso_sched_free(stream, sched);
+				spin_unlock_irqrestore(&ehci->lock, flags);
+				return -ENOMEM;
+			}
+		}
+
+		memset (itd, 0, sizeof *itd);
+		itd->itd_dma = itd_dma;
+		list_add (&itd->itd_list, &sched->td_list);
+	}
+	spin_unlock_irqrestore (&ehci->lock, flags);
+
+	/* temporarily store schedule info in hcpriv */
+	urb->hcpriv = sched;
+	urb->error_count = 0;
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static inline int
+itd_slot_ok (
+	struct ehci_hcd		*ehci,
+	u32			mod,
+	u32			uframe,
+	u8			usecs,
+	u32			period
+)
+{
+	uframe %= period;
+	do {
+		/* can't commit more than uframe_periodic_max usec */
+		if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7)
+				> (ehci->uframe_periodic_max - usecs))
+			return 0;
+
+		/* we know urb->interval is 2^N uframes */
+		uframe += period;
+	} while (uframe < mod);
+	return 1;
+}
+
+static inline int
+sitd_slot_ok (
+	struct ehci_hcd		*ehci,
+	u32			mod,
+	struct ehci_iso_stream	*stream,
+	u32			uframe,
+	struct ehci_iso_sched	*sched,
+	u32			period_uframes
+)
+{
+	u32			mask, tmp;
+	u32			frame, uf;
+
+	mask = stream->raw_mask << (uframe & 7);
+
+	/* for IN, don't wrap CSPLIT into the next frame */
+	if (mask & ~0xffff)
+		return 0;
+
+	/* this multi-pass logic is simple, but performance may
+	 * suffer when the schedule data isn't cached.
+	 */
+
+	/* check bandwidth */
+	uframe %= period_uframes;
+	do {
+		u32		max_used;
+
+		frame = uframe >> 3;
+		uf = uframe & 7;
+
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+		/* The tt's fullspeed bus bandwidth must be available.
+		 * tt_available scheduling guarantees 10+% for control/bulk.
+		 */
+		if (!tt_available (ehci, period_uframes << 3,
+				stream->udev, frame, uf, stream->tt_usecs))
+			return 0;
+#else
+		/* tt must be idle for start(s), any gap, and csplit.
+		 * assume scheduling slop leaves 10+% for control/bulk.
+		 */
+		if (!tt_no_collision (ehci, period_uframes << 3,
+				stream->udev, frame, mask))
+			return 0;
+#endif
+
+		/* check starts (OUT uses more than one) */
+		max_used = ehci->uframe_periodic_max - stream->usecs;
+		for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) {
+			if (periodic_usecs (ehci, frame, uf) > max_used)
+				return 0;
+		}
+
+		/* for IN, check CSPLIT */
+		if (stream->c_usecs) {
+			uf = uframe & 7;
+			max_used = ehci->uframe_periodic_max - stream->c_usecs;
+			do {
+				tmp = 1 << uf;
+				tmp <<= 8;
+				if ((stream->raw_mask & tmp) == 0)
+					continue;
+				if (periodic_usecs (ehci, frame, uf)
+						> max_used)
+					return 0;
+			} while (++uf < 8);
+		}
+
+		/* we know urb->interval is 2^N uframes */
+		uframe += period_uframes;
+	} while (uframe < mod);
+
+	stream->splits = cpu_to_hc32(ehci, stream->raw_mask << (uframe & 7));
+	return 1;
+}
+
+/*
+ * This scheduler plans almost as far into the future as it has actual
+ * periodic schedule slots.  (Affected by TUNE_FLS, which defaults to
+ * "as small as possible" to be cache-friendlier.)  That limits the size
+ * transfers you can stream reliably; avoid more than 64 msec per urb.
+ * Also avoid queue depths of less than ehci's worst irq latency (affected
+ * by the per-urb URB_NO_INTERRUPT hint, the log2_irq_thresh module parameter,
+ * and other factors); or more than about 230 msec total (for portability,
+ * given EHCI_TUNE_FLS and the slop).  Or, write a smarter scheduler!
+ */
+
+#define SCHEDULE_SLOP	80	/* microframes */
+
+static int
+iso_stream_schedule (
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	struct ehci_iso_stream	*stream
+)
+{
+	u32			now, next, start, period, span;
+	int			status;
+	unsigned		mod = ehci->periodic_size << 3;
+	struct ehci_iso_sched	*sched = urb->hcpriv;
+
+	period = urb->interval;
+	span = sched->span;
+	if (!stream->highspeed) {
+		period <<= 3;
+		span <<= 3;
+	}
+
+	if (span > mod - SCHEDULE_SLOP) {
+		ehci_dbg (ehci, "iso request %p too long\n", urb);
+		status = -EFBIG;
+		goto fail;
+	}
+
+	now = ehci_read_frame_index(ehci) & (mod - 1);
+
+	/* Typical case: reuse current schedule, stream is still active.
+	 * Hopefully there are no gaps from the host falling behind
+	 * (irq delays etc), but if there are we'll take the next
+	 * slot in the schedule, implicitly assuming URB_ISO_ASAP.
+	 */
+	if (likely (!list_empty (&stream->td_list))) {
+		u32	excess;
+
+		/* For high speed devices, allow scheduling within the
+		 * isochronous scheduling threshold.  For full speed devices
+		 * and Intel PCI-based controllers, don't (work around for
+		 * Intel ICH9 bug).
+		 */
+		if (!stream->highspeed && ehci->fs_i_thresh)
+			next = now + ehci->i_thresh;
+		else
+			next = now;
+
+		/* Fell behind (by up to twice the slop amount)?
+		 * We decide based on the time of the last currently-scheduled
+		 * slot, not the time of the next available slot.
+		 */
+		excess = (stream->next_uframe - period - next) & (mod - 1);
+		if (excess >= mod - 2 * SCHEDULE_SLOP)
+			start = next + excess - mod + period *
+					DIV_ROUND_UP(mod - excess, period);
+		else
+			start = next + excess + period;
+		if (start - now >= mod) {
+			ehci_dbg(ehci, "request %p would overflow (%d+%d >= %d)\n",
+					urb, start - now - period, period,
+					mod);
+			status = -EFBIG;
+			goto fail;
+		}
+	}
+
+	/* need to schedule; when's the next (u)frame we could start?
+	 * this is bigger than ehci->i_thresh allows; scheduling itself
+	 * isn't free, the slop should handle reasonably slow cpus.  it
+	 * can also help high bandwidth if the dma and irq loads don't
+	 * jump until after the queue is primed.
+	 */
+	else {
+		int done = 0;
+		start = SCHEDULE_SLOP + (now & ~0x07);
+
+		/* NOTE:  assumes URB_ISO_ASAP, to limit complexity/bugs */
+
+		/* find a uframe slot with enough bandwidth.
+		 * Early uframes are more precious because full-speed
+		 * iso IN transfers can't use late uframes,
+		 * and therefore they should be allocated last.
+		 */
+		next = start;
+		start += period;
+		do {
+			start--;
+			/* check schedule: enough space? */
+			if (stream->highspeed) {
+				if (itd_slot_ok(ehci, mod, start,
+						stream->usecs, period))
+					done = 1;
+			} else {
+				if ((start % 8) >= 6)
+					continue;
+				if (sitd_slot_ok(ehci, mod, stream,
+						start, sched, period))
+					done = 1;
+			}
+		} while (start > next && !done);
+
+		/* no room in the schedule */
+		if (!done) {
+			ehci_dbg(ehci, "iso resched full %p (now %d max %d)\n",
+				urb, now, now + mod);
+			status = -ENOSPC;
+			goto fail;
+		}
+	}
+
+	/* Tried to schedule too far into the future? */
+	if (unlikely(start - now + span - period
+				>= mod - 2 * SCHEDULE_SLOP)) {
+		ehci_dbg(ehci, "request %p would overflow (%d+%d >= %d)\n",
+				urb, start - now, span - period,
+				mod - 2 * SCHEDULE_SLOP);
+		status = -EFBIG;
+		goto fail;
+	}
+
+	stream->next_uframe = start & (mod - 1);
+
+	/* report high speed start in uframes; full speed, in frames */
+	urb->start_frame = stream->next_uframe;
+	if (!stream->highspeed)
+		urb->start_frame >>= 3;
+	return 0;
+
+ fail:
+	iso_sched_free(stream, sched);
+	urb->hcpriv = NULL;
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static inline void
+itd_init(struct ehci_hcd *ehci, struct ehci_iso_stream *stream,
+		struct ehci_itd *itd)
+{
+	int i;
+
+	/* it's been recently zeroed */
+	itd->hw_next = EHCI_LIST_END(ehci);
+	itd->hw_bufp [0] = stream->buf0;
+	itd->hw_bufp [1] = stream->buf1;
+	itd->hw_bufp [2] = stream->buf2;
+
+	for (i = 0; i < 8; i++)
+		itd->index[i] = -1;
+
+	/* All other fields are filled when scheduling */
+}
+
+static inline void
+itd_patch(
+	struct ehci_hcd		*ehci,
+	struct ehci_itd		*itd,
+	struct ehci_iso_sched	*iso_sched,
+	unsigned		index,
+	u16			uframe
+)
+{
+	struct ehci_iso_packet	*uf = &iso_sched->packet [index];
+	unsigned		pg = itd->pg;
+
+	// BUG_ON (pg == 6 && uf->cross);
+
+	uframe &= 0x07;
+	itd->index [uframe] = index;
+
+	itd->hw_transaction[uframe] = uf->transaction;
+	itd->hw_transaction[uframe] |= cpu_to_hc32(ehci, pg << 12);
+	itd->hw_bufp[pg] |= cpu_to_hc32(ehci, uf->bufp & ~(u32)0);
+	itd->hw_bufp_hi[pg] |= cpu_to_hc32(ehci, (u32)(uf->bufp >> 32));
+
+	/* iso_frame_desc[].offset must be strictly increasing */
+	if (unlikely (uf->cross)) {
+		u64	bufp = uf->bufp + 4096;
+
+		itd->pg = ++pg;
+		itd->hw_bufp[pg] |= cpu_to_hc32(ehci, bufp & ~(u32)0);
+		itd->hw_bufp_hi[pg] |= cpu_to_hc32(ehci, (u32)(bufp >> 32));
+	}
+}
+
+static inline void
+itd_link (struct ehci_hcd *ehci, unsigned frame, struct ehci_itd *itd)
+{
+	union ehci_shadow	*prev = &ehci->pshadow[frame];
+	__hc32			*hw_p = &ehci->periodic[frame];
+	union ehci_shadow	here = *prev;
+	__hc32			type = 0;
+
+	/* skip any iso nodes which might belong to previous microframes */
+	while (here.ptr) {
+		type = Q_NEXT_TYPE(ehci, *hw_p);
+		if (type == cpu_to_hc32(ehci, Q_TYPE_QH))
+			break;
+		prev = periodic_next_shadow(ehci, prev, type);
+		hw_p = shadow_next_periodic(ehci, &here, type);
+		here = *prev;
+	}
+
+	itd->itd_next = here;
+	itd->hw_next = *hw_p;
+	prev->itd = itd;
+	itd->frame = frame;
+	wmb ();
+	*hw_p = cpu_to_hc32(ehci, itd->itd_dma | Q_TYPE_ITD);
+}
+
+/* fit urb's itds into the selected schedule slot; activate as needed */
+static int
+itd_link_urb (
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	unsigned		mod,
+	struct ehci_iso_stream	*stream
+)
+{
+	int			packet;
+	unsigned		next_uframe, uframe, frame;
+	struct ehci_iso_sched	*iso_sched = urb->hcpriv;
+	struct ehci_itd		*itd;
+
+	next_uframe = stream->next_uframe & (mod - 1);
+
+	if (unlikely (list_empty(&stream->td_list))) {
+		ehci_to_hcd(ehci)->self.bandwidth_allocated
+				+= stream->bandwidth;
+		ehci_vdbg (ehci,
+			"schedule devp %s ep%d%s-iso period %d start %d.%d\n",
+			urb->dev->devpath, stream->bEndpointAddress & 0x0f,
+			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out",
+			urb->interval,
+			next_uframe >> 3, next_uframe & 0x7);
+	}
+
+	if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
+		if (ehci->amd_pll_fix == 1)
+			usb_amd_quirk_pll_disable();
+	}
+
+	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs++;
+
+	/* fill iTDs uframe by uframe */
+	for (packet = 0, itd = NULL; packet < urb->number_of_packets; ) {
+		if (itd == NULL) {
+			/* ASSERT:  we have all necessary itds */
+			// BUG_ON (list_empty (&iso_sched->td_list));
+
+			/* ASSERT:  no itds for this endpoint in this uframe */
+
+			itd = list_entry (iso_sched->td_list.next,
+					struct ehci_itd, itd_list);
+			list_move_tail (&itd->itd_list, &stream->td_list);
+			itd->stream = iso_stream_get (stream);
+			itd->urb = urb;
+			itd_init (ehci, stream, itd);
+		}
+
+		uframe = next_uframe & 0x07;
+		frame = next_uframe >> 3;
+
+		itd_patch(ehci, itd, iso_sched, packet, uframe);
+
+		next_uframe += stream->interval;
+		next_uframe &= mod - 1;
+		packet++;
+
+		/* link completed itds into the schedule */
+		if (((next_uframe >> 3) != frame)
+				|| packet == urb->number_of_packets) {
+			itd_link(ehci, frame & (ehci->periodic_size - 1), itd);
+			itd = NULL;
+		}
+	}
+	stream->next_uframe = next_uframe;
+
+	/* don't need that schedule data any more */
+	iso_sched_free (stream, iso_sched);
+	urb->hcpriv = stream;
+
+	timer_action (ehci, TIMER_IO_WATCHDOG);
+	return enable_periodic(ehci);
+}
+
+#define	ISO_ERRS (EHCI_ISOC_BUF_ERR | EHCI_ISOC_BABBLE | EHCI_ISOC_XACTERR)
+
+/* Process and recycle a completed ITD.  Return true iff its urb completed,
+ * and hence its completion callback probably added things to the hardware
+ * schedule.
+ *
+ * Note that we carefully avoid recycling this descriptor until after any
+ * completion callback runs, so that it won't be reused quickly.  That is,
+ * assuming (a) no more than two urbs per frame on this endpoint, and also
+ * (b) only this endpoint's completions submit URBs.  It seems some silicon
+ * corrupts things if you reuse completed descriptors very quickly...
+ */
+static unsigned
+itd_complete (
+	struct ehci_hcd	*ehci,
+	struct ehci_itd	*itd
+) {
+	struct urb				*urb = itd->urb;
+	struct usb_iso_packet_descriptor	*desc;
+	u32					t;
+	unsigned				uframe;
+	int					urb_index = -1;
+	struct ehci_iso_stream			*stream = itd->stream;
+	struct usb_device			*dev;
+	unsigned				retval = false;
+
+	/* for each uframe with a packet */
+	for (uframe = 0; uframe < 8; uframe++) {
+		if (likely (itd->index[uframe] == -1))
+			continue;
+		urb_index = itd->index[uframe];
+		desc = &urb->iso_frame_desc [urb_index];
+
+		t = hc32_to_cpup(ehci, &itd->hw_transaction [uframe]);
+		itd->hw_transaction [uframe] = 0;
+
+		/* report transfer status */
+		if (unlikely (t & ISO_ERRS)) {
+			urb->error_count++;
+			if (t & EHCI_ISOC_BUF_ERR)
+				desc->status = usb_pipein (urb->pipe)
+					? -ENOSR  /* hc couldn't read */
+					: -ECOMM; /* hc couldn't write */
+			else if (t & EHCI_ISOC_BABBLE)
+				desc->status = -EOVERFLOW;
+			else /* (t & EHCI_ISOC_XACTERR) */
+				desc->status = -EPROTO;
+
+			/* HC need not update length with this error */
+			if (!(t & EHCI_ISOC_BABBLE)) {
+				desc->actual_length = EHCI_ITD_LENGTH(t);
+				urb->actual_length += desc->actual_length;
+			}
+		} else if (likely ((t & EHCI_ISOC_ACTIVE) == 0)) {
+			desc->status = 0;
+			desc->actual_length = EHCI_ITD_LENGTH(t);
+			urb->actual_length += desc->actual_length;
+		} else {
+			/* URB was too late */
+			desc->status = -EXDEV;
+		}
+	}
+
+	/* handle completion now? */
+	if (likely ((urb_index + 1) != urb->number_of_packets))
+		goto done;
+
+	/* ASSERT: it's really the last itd for this urb
+	list_for_each_entry (itd, &stream->td_list, itd_list)
+		BUG_ON (itd->urb == urb);
+	 */
+
+	/* give urb back to the driver; completion often (re)submits */
+	dev = urb->dev;
+	ehci_urb_done(ehci, urb, 0);
+	retval = true;
+	urb = NULL;
+	(void) disable_periodic(ehci);
+	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
+
+	if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
+		if (ehci->amd_pll_fix == 1)
+			usb_amd_quirk_pll_enable();
+	}
+
+	if (unlikely(list_is_singular(&stream->td_list))) {
+		ehci_to_hcd(ehci)->self.bandwidth_allocated
+				-= stream->bandwidth;
+		ehci_vdbg (ehci,
+			"deschedule devp %s ep%d%s-iso\n",
+			dev->devpath, stream->bEndpointAddress & 0x0f,
+			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out");
+	}
+	iso_stream_put (ehci, stream);
+
+done:
+	itd->urb = NULL;
+	if (ehci->clock_frame != itd->frame || itd->index[7] != -1) {
+		/* OK to recycle this ITD now. */
+		itd->stream = NULL;
+		list_move(&itd->itd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	} else {
+		/* HW might remember this ITD, so we can't recycle it yet.
+		 * Move it to a safe place until a new frame starts.
+		 */
+		list_move(&itd->itd_list, &ehci->cached_itd_list);
+		if (stream->refcount == 2) {
+			/* If iso_stream_put() were called here, stream
+			 * would be freed.  Instead, just prevent reuse.
+			 */
+			stream->ep->hcpriv = NULL;
+			stream->ep = NULL;
+		}
+	}
+	return retval;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static int itd_submit (struct ehci_hcd *ehci, struct urb *urb,
+	gfp_t mem_flags)
+{
+	int			status = -EINVAL;
+	unsigned long		flags;
+	struct ehci_iso_stream	*stream;
+
+	/* Get iso_stream head */
+	stream = iso_stream_find (ehci, urb);
+	if (unlikely (stream == NULL)) {
+		ehci_dbg (ehci, "can't get iso stream\n");
+		return -ENOMEM;
+	}
+	if (unlikely (urb->interval != stream->interval)) {
+		ehci_dbg (ehci, "can't change iso interval %d --> %d\n",
+			stream->interval, urb->interval);
+		goto done;
+	}
+
+#ifdef EHCI_URB_TRACE
+	ehci_dbg (ehci,
+		"%s %s urb %p ep%d%s len %d, %d pkts %d uframes [%p]\n",
+		__func__, urb->dev->devpath, urb,
+		usb_pipeendpoint (urb->pipe),
+		usb_pipein (urb->pipe) ? "in" : "out",
+		urb->transfer_buffer_length,
+		urb->number_of_packets, urb->interval,
+		stream);
+#endif
+
+	/* allocate ITDs w/o locking anything */
+	status = itd_urb_transaction (stream, ehci, urb, mem_flags);
+	if (unlikely (status < 0)) {
+		ehci_dbg (ehci, "can't init itds\n");
+		goto done;
+	}
+
+	/* schedule ... need to lock */
+	spin_lock_irqsave (&ehci->lock, flags);
+	if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
+		status = -ESHUTDOWN;
+		goto done_not_linked;
+	}
+	status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
+	if (unlikely(status))
+		goto done_not_linked;
+	status = iso_stream_schedule(ehci, urb, stream);
+	if (likely (status == 0))
+		itd_link_urb (ehci, urb, ehci->periodic_size << 3, stream);
+	else
+		usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
+done_not_linked:
+	spin_unlock_irqrestore (&ehci->lock, flags);
+
+done:
+	if (unlikely (status < 0))
+		iso_stream_put (ehci, stream);
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * "Split ISO TDs" ... used for USB 1.1 devices going through the
+ * TTs in USB 2.0 hubs.  These need microframe scheduling.
+ */
+
+static inline void
+sitd_sched_init(
+	struct ehci_hcd		*ehci,
+	struct ehci_iso_sched	*iso_sched,
+	struct ehci_iso_stream	*stream,
+	struct urb		*urb
+)
+{
+	unsigned	i;
+	dma_addr_t	dma = urb->transfer_dma;
+
+	/* how many frames are needed for these transfers */
+	iso_sched->span = urb->number_of_packets * stream->interval;
+
+	/* figure out per-frame sitd fields that we'll need later
+	 * when we fit new sitds into the schedule.
+	 */
+	for (i = 0; i < urb->number_of_packets; i++) {
+		struct ehci_iso_packet	*packet = &iso_sched->packet [i];
+		unsigned		length;
+		dma_addr_t		buf;
+		u32			trans;
+
+		length = urb->iso_frame_desc [i].length & 0x03ff;
+		buf = dma + urb->iso_frame_desc [i].offset;
+
+		trans = SITD_STS_ACTIVE;
+		if (((i + 1) == urb->number_of_packets)
+				&& !(urb->transfer_flags & URB_NO_INTERRUPT))
+			trans |= SITD_IOC;
+		trans |= length << 16;
+		packet->transaction = cpu_to_hc32(ehci, trans);
+
+		/* might need to cross a buffer page within a td */
+		packet->bufp = buf;
+		packet->buf1 = (buf + length) & ~0x0fff;
+		if (packet->buf1 != (buf & ~(u64)0x0fff))
+			packet->cross = 1;
+
+		/* OUT uses multiple start-splits */
+		if (stream->bEndpointAddress & USB_DIR_IN)
+			continue;
+		length = (length + 187) / 188;
+		if (length > 1) /* BEGIN vs ALL */
+			length |= 1 << 3;
+		packet->buf1 |= length;
+	}
+}
+
+static int
+sitd_urb_transaction (
+	struct ehci_iso_stream	*stream,
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	gfp_t			mem_flags
+)
+{
+	struct ehci_sitd	*sitd;
+	dma_addr_t		sitd_dma;
+	int			i;
+	struct ehci_iso_sched	*iso_sched;
+	unsigned long		flags;
+
+	iso_sched = iso_sched_alloc (urb->number_of_packets, mem_flags);
+	if (iso_sched == NULL)
+		return -ENOMEM;
+
+	sitd_sched_init(ehci, iso_sched, stream, urb);
+
+	/* allocate/init sITDs */
+	spin_lock_irqsave (&ehci->lock, flags);
+	for (i = 0; i < urb->number_of_packets; i++) {
+
+		/* NOTE:  for now, we don't try to handle wraparound cases
+		 * for IN (using sitd->hw_backpointer, like a FSTN), which
+		 * means we never need two sitds for full speed packets.
+		 */
+
+		/* free_list.next might be cache-hot ... but maybe
+		 * the HC caches it too. avoid that issue for now.
+		 */
+
+		/* prefer previously-allocated sitds */
+		if (!list_empty(&stream->free_list)) {
+			sitd = list_entry (stream->free_list.prev,
+					 struct ehci_sitd, sitd_list);
+			list_del (&sitd->sitd_list);
+			sitd_dma = sitd->sitd_dma;
+		} else {
+			spin_unlock_irqrestore (&ehci->lock, flags);
+			sitd = dma_pool_alloc (ehci->sitd_pool, mem_flags,
+					&sitd_dma);
+			spin_lock_irqsave (&ehci->lock, flags);
+			if (!sitd) {
+				iso_sched_free(stream, iso_sched);
+				spin_unlock_irqrestore(&ehci->lock, flags);
+				return -ENOMEM;
+			}
+		}
+
+		memset (sitd, 0, sizeof *sitd);
+		sitd->sitd_dma = sitd_dma;
+		list_add (&sitd->sitd_list, &iso_sched->td_list);
+	}
+
+	/* temporarily store schedule info in hcpriv */
+	urb->hcpriv = iso_sched;
+	urb->error_count = 0;
+
+	spin_unlock_irqrestore (&ehci->lock, flags);
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static inline void
+sitd_patch(
+	struct ehci_hcd		*ehci,
+	struct ehci_iso_stream	*stream,
+	struct ehci_sitd	*sitd,
+	struct ehci_iso_sched	*iso_sched,
+	unsigned		index
+)
+{
+	struct ehci_iso_packet	*uf = &iso_sched->packet [index];
+	u64			bufp = uf->bufp;
+
+	sitd->hw_next = EHCI_LIST_END(ehci);
+	sitd->hw_fullspeed_ep = stream->address;
+	sitd->hw_uframe = stream->splits;
+	sitd->hw_results = uf->transaction;
+	sitd->hw_backpointer = EHCI_LIST_END(ehci);
+
+	bufp = uf->bufp;
+	sitd->hw_buf[0] = cpu_to_hc32(ehci, bufp);
+	sitd->hw_buf_hi[0] = cpu_to_hc32(ehci, bufp >> 32);
+
+	sitd->hw_buf[1] = cpu_to_hc32(ehci, uf->buf1);
+	if (uf->cross)
+		bufp += 4096;
+	sitd->hw_buf_hi[1] = cpu_to_hc32(ehci, bufp >> 32);
+	sitd->index = index;
+}
+
+static inline void
+sitd_link (struct ehci_hcd *ehci, unsigned frame, struct ehci_sitd *sitd)
+{
+	/* note: sitd ordering could matter (CSPLIT then SSPLIT) */
+	sitd->sitd_next = ehci->pshadow [frame];
+	sitd->hw_next = ehci->periodic [frame];
+	ehci->pshadow [frame].sitd = sitd;
+	sitd->frame = frame;
+	wmb ();
+	ehci->periodic[frame] = cpu_to_hc32(ehci, sitd->sitd_dma | Q_TYPE_SITD);
+}
+
+/* fit urb's sitds into the selected schedule slot; activate as needed */
+static int
+sitd_link_urb (
+	struct ehci_hcd		*ehci,
+	struct urb		*urb,
+	unsigned		mod,
+	struct ehci_iso_stream	*stream
+)
+{
+	int			packet;
+	unsigned		next_uframe;
+	struct ehci_iso_sched	*sched = urb->hcpriv;
+	struct ehci_sitd	*sitd;
+
+	next_uframe = stream->next_uframe;
+
+	if (list_empty(&stream->td_list)) {
+		/* usbfs ignores TT bandwidth */
+		ehci_to_hcd(ehci)->self.bandwidth_allocated
+				+= stream->bandwidth;
+		ehci_vdbg (ehci,
+			"sched devp %s ep%d%s-iso [%d] %dms/%04x\n",
+			urb->dev->devpath, stream->bEndpointAddress & 0x0f,
+			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out",
+			(next_uframe >> 3) & (ehci->periodic_size - 1),
+			stream->interval, hc32_to_cpu(ehci, stream->splits));
+	}
+
+	if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
+		if (ehci->amd_pll_fix == 1)
+			usb_amd_quirk_pll_disable();
+	}
+
+	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs++;
+
+	/* fill sITDs frame by frame */
+	for (packet = 0, sitd = NULL;
+			packet < urb->number_of_packets;
+			packet++) {
+
+		/* ASSERT:  we have all necessary sitds */
+		BUG_ON (list_empty (&sched->td_list));
+
+		/* ASSERT:  no itds for this endpoint in this frame */
+
+		sitd = list_entry (sched->td_list.next,
+				struct ehci_sitd, sitd_list);
+		list_move_tail (&sitd->sitd_list, &stream->td_list);
+		sitd->stream = iso_stream_get (stream);
+		sitd->urb = urb;
+
+		sitd_patch(ehci, stream, sitd, sched, packet);
+		sitd_link(ehci, (next_uframe >> 3) & (ehci->periodic_size - 1),
+				sitd);
+
+		next_uframe += stream->interval << 3;
+	}
+	stream->next_uframe = next_uframe & (mod - 1);
+
+	/* don't need that schedule data any more */
+	iso_sched_free (stream, sched);
+	urb->hcpriv = stream;
+
+	timer_action (ehci, TIMER_IO_WATCHDOG);
+	return enable_periodic(ehci);
+}
+
+/*-------------------------------------------------------------------------*/
+
+#define	SITD_ERRS (SITD_STS_ERR | SITD_STS_DBE | SITD_STS_BABBLE \
+				| SITD_STS_XACT | SITD_STS_MMF)
+
+/* Process and recycle a completed SITD.  Return true iff its urb completed,
+ * and hence its completion callback probably added things to the hardware
+ * schedule.
+ *
+ * Note that we carefully avoid recycling this descriptor until after any
+ * completion callback runs, so that it won't be reused quickly.  That is,
+ * assuming (a) no more than two urbs per frame on this endpoint, and also
+ * (b) only this endpoint's completions submit URBs.  It seems some silicon
+ * corrupts things if you reuse completed descriptors very quickly...
+ */
+static unsigned
+sitd_complete (
+	struct ehci_hcd		*ehci,
+	struct ehci_sitd	*sitd
+) {
+	struct urb				*urb = sitd->urb;
+	struct usb_iso_packet_descriptor	*desc;
+	u32					t;
+	int					urb_index = -1;
+	struct ehci_iso_stream			*stream = sitd->stream;
+	struct usb_device			*dev;
+	unsigned				retval = false;
+
+	urb_index = sitd->index;
+	desc = &urb->iso_frame_desc [urb_index];
+	t = hc32_to_cpup(ehci, &sitd->hw_results);
+
+	/* report transfer status */
+	if (t & SITD_ERRS) {
+		urb->error_count++;
+		if (t & SITD_STS_DBE)
+			desc->status = usb_pipein (urb->pipe)
+				? -ENOSR  /* hc couldn't read */
+				: -ECOMM; /* hc couldn't write */
+		else if (t & SITD_STS_BABBLE)
+			desc->status = -EOVERFLOW;
+		else /* XACT, MMF, etc */
+			desc->status = -EPROTO;
+	} else {
+		desc->status = 0;
+		desc->actual_length = desc->length - SITD_LENGTH(t);
+		urb->actual_length += desc->actual_length;
+	}
+
+	/* handle completion now? */
+	if ((urb_index + 1) != urb->number_of_packets)
+		goto done;
+
+	/* ASSERT: it's really the last sitd for this urb
+	list_for_each_entry (sitd, &stream->td_list, sitd_list)
+		BUG_ON (sitd->urb == urb);
+	 */
+
+	/* give urb back to the driver; completion often (re)submits */
+	dev = urb->dev;
+	ehci_urb_done(ehci, urb, 0);
+	retval = true;
+	urb = NULL;
+	(void) disable_periodic(ehci);
+	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
+
+	if (ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs == 0) {
+		if (ehci->amd_pll_fix == 1)
+			usb_amd_quirk_pll_enable();
+	}
+
+	if (list_is_singular(&stream->td_list)) {
+		ehci_to_hcd(ehci)->self.bandwidth_allocated
+				-= stream->bandwidth;
+		ehci_vdbg (ehci,
+			"deschedule devp %s ep%d%s-iso\n",
+			dev->devpath, stream->bEndpointAddress & 0x0f,
+			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out");
+	}
+	iso_stream_put (ehci, stream);
+
+done:
+	sitd->urb = NULL;
+	if (ehci->clock_frame != sitd->frame) {
+		/* OK to recycle this SITD now. */
+		sitd->stream = NULL;
+		list_move(&sitd->sitd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	} else {
+		/* HW might remember this SITD, so we can't recycle it yet.
+		 * Move it to a safe place until a new frame starts.
+		 */
+		list_move(&sitd->sitd_list, &ehci->cached_sitd_list);
+		if (stream->refcount == 2) {
+			/* If iso_stream_put() were called here, stream
+			 * would be freed.  Instead, just prevent reuse.
+			 */
+			stream->ep->hcpriv = NULL;
+			stream->ep = NULL;
+		}
+	}
+	return retval;
+}
+
+
+static int sitd_submit (struct ehci_hcd *ehci, struct urb *urb,
+	gfp_t mem_flags)
+{
+	int			status = -EINVAL;
+	unsigned long		flags;
+	struct ehci_iso_stream	*stream;
+
+	/* Get iso_stream head */
+	stream = iso_stream_find (ehci, urb);
+	if (stream == NULL) {
+		ehci_dbg (ehci, "can't get iso stream\n");
+		return -ENOMEM;
+	}
+	if (urb->interval != stream->interval) {
+		ehci_dbg (ehci, "can't change iso interval %d --> %d\n",
+			stream->interval, urb->interval);
+		goto done;
+	}
+
+#ifdef EHCI_URB_TRACE
+	ehci_dbg (ehci,
+		"submit %p dev%s ep%d%s-iso len %d\n",
+		urb, urb->dev->devpath,
+		usb_pipeendpoint (urb->pipe),
+		usb_pipein (urb->pipe) ? "in" : "out",
+		urb->transfer_buffer_length);
+#endif
+
+	/* allocate SITDs */
+	status = sitd_urb_transaction (stream, ehci, urb, mem_flags);
+	if (status < 0) {
+		ehci_dbg (ehci, "can't init sitds\n");
+		goto done;
+	}
+
+	/* schedule ... need to lock */
+	spin_lock_irqsave (&ehci->lock, flags);
+	if (unlikely(!HCD_HW_ACCESSIBLE(ehci_to_hcd(ehci)))) {
+		status = -ESHUTDOWN;
+		goto done_not_linked;
+	}
+	status = usb_hcd_link_urb_to_ep(ehci_to_hcd(ehci), urb);
+	if (unlikely(status))
+		goto done_not_linked;
+	status = iso_stream_schedule(ehci, urb, stream);
+	if (status == 0)
+		sitd_link_urb (ehci, urb, ehci->periodic_size << 3, stream);
+	else
+		usb_hcd_unlink_urb_from_ep(ehci_to_hcd(ehci), urb);
+done_not_linked:
+	spin_unlock_irqrestore (&ehci->lock, flags);
+
+done:
+	if (status < 0)
+		iso_stream_put (ehci, stream);
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void free_cached_lists(struct ehci_hcd *ehci)
+{
+	struct ehci_itd *itd, *n;
+	struct ehci_sitd *sitd, *sn;
+
+	list_for_each_entry_safe(itd, n, &ehci->cached_itd_list, itd_list) {
+		struct ehci_iso_stream	*stream = itd->stream;
+		itd->stream = NULL;
+		list_move(&itd->itd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	}
+
+	list_for_each_entry_safe(sitd, sn, &ehci->cached_sitd_list, sitd_list) {
+		struct ehci_iso_stream	*stream = sitd->stream;
+		sitd->stream = NULL;
+		list_move(&sitd->sitd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	}
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void
+scan_periodic (struct ehci_hcd *ehci)
+{
+	unsigned	now_uframe, frame, clock, clock_frame, mod;
+	unsigned	modified;
+
+	mod = ehci->periodic_size << 3;
+
+	/*
+	 * When running, scan from last scan point up to "now"
+	 * else clean up by scanning everything that's left.
+	 * Touches as few pages as possible:  cache-friendly.
+	 */
+	now_uframe = ehci->next_uframe;
+	if (ehci->rh_state == EHCI_RH_RUNNING) {
+		clock = ehci_read_frame_index(ehci);
+		clock_frame = (clock >> 3) & (ehci->periodic_size - 1);
+	} else  {
+		clock = now_uframe + mod - 1;
+		clock_frame = -1;
+	}
+	if (ehci->clock_frame != clock_frame) {
+		free_cached_lists(ehci);
+		ehci->clock_frame = clock_frame;
+	}
+	clock &= mod - 1;
+	clock_frame = clock >> 3;
+	++ehci->periodic_stamp;
+
+	for (;;) {
+		union ehci_shadow	q, *q_p;
+		__hc32			type, *hw_p;
+		unsigned		incomplete = false;
+
+		frame = now_uframe >> 3;
+
+restart:
+		/* scan each element in frame's queue for completions */
+		q_p = &ehci->pshadow [frame];
+		hw_p = &ehci->periodic [frame];
+		q.ptr = q_p->ptr;
+		type = Q_NEXT_TYPE(ehci, *hw_p);
+		modified = 0;
+
+		while (q.ptr != NULL) {
+			unsigned		uf;
+			union ehci_shadow	temp;
+			int			live;
+
+			live = (ehci->rh_state == EHCI_RH_RUNNING);
+			switch (hc32_to_cpu(ehci, type)) {
+			case Q_TYPE_QH:
+				/* handle any completions */
+				temp.qh = qh_get (q.qh);
+				type = Q_NEXT_TYPE(ehci, q.qh->hw->hw_next);
+				q = q.qh->qh_next;
+				if (temp.qh->stamp != ehci->periodic_stamp) {
+					modified = qh_completions(ehci, temp.qh);
+					if (!modified)
+						temp.qh->stamp = ehci->periodic_stamp;
+					if (unlikely(list_empty(&temp.qh->qtd_list) ||
+							temp.qh->needs_rescan))
+						intr_deschedule(ehci, temp.qh);
+				}
+				qh_put (temp.qh);
+				break;
+			case Q_TYPE_FSTN:
+				/* for "save place" FSTNs, look at QH entries
+				 * in the previous frame for completions.
+				 */
+				if (q.fstn->hw_prev != EHCI_LIST_END(ehci)) {
+					dbg ("ignoring completions from FSTNs");
+				}
+				type = Q_NEXT_TYPE(ehci, q.fstn->hw_next);
+				q = q.fstn->fstn_next;
+				break;
+			case Q_TYPE_ITD:
+				/* If this ITD is still active, leave it for
+				 * later processing ... check the next entry.
+				 * No need to check for activity unless the
+				 * frame is current.
+				 */
+				if (frame == clock_frame && live) {
+					rmb();
+					for (uf = 0; uf < 8; uf++) {
+						if (q.itd->hw_transaction[uf] &
+							    ITD_ACTIVE(ehci))
+							break;
+					}
+					if (uf < 8) {
+						incomplete = true;
+						q_p = &q.itd->itd_next;
+						hw_p = &q.itd->hw_next;
+						type = Q_NEXT_TYPE(ehci,
+							q.itd->hw_next);
+						q = *q_p;
+						break;
+					}
+				}
+
+				/* Take finished ITDs out of the schedule
+				 * and process them:  recycle, maybe report
+				 * URB completion.  HC won't cache the
+				 * pointer for much longer, if at all.
+				 */
+				*q_p = q.itd->itd_next;
+				if (!ehci->use_dummy_qh ||
+				    q.itd->hw_next != EHCI_LIST_END(ehci))
+					*hw_p = q.itd->hw_next;
+				else
+					*hw_p = ehci->dummy->qh_dma;
+				type = Q_NEXT_TYPE(ehci, q.itd->hw_next);
+				wmb();
+				modified = itd_complete (ehci, q.itd);
+				q = *q_p;
+				break;
+			case Q_TYPE_SITD:
+				/* If this SITD is still active, leave it for
+				 * later processing ... check the next entry.
+				 * No need to check for activity unless the
+				 * frame is current.
+				 */
+				if (((frame == clock_frame) ||
+				     (((frame + 1) & (ehci->periodic_size - 1))
+				      == clock_frame))
+				    && live
+				    && (q.sitd->hw_results &
+					SITD_ACTIVE(ehci))) {
+
+					incomplete = true;
+					q_p = &q.sitd->sitd_next;
+					hw_p = &q.sitd->hw_next;
+					type = Q_NEXT_TYPE(ehci,
+							q.sitd->hw_next);
+					q = *q_p;
+					break;
+				}
+
+				/* Take finished SITDs out of the schedule
+				 * and process them:  recycle, maybe report
+				 * URB completion.
+				 */
+				*q_p = q.sitd->sitd_next;
+				if (!ehci->use_dummy_qh ||
+				    q.sitd->hw_next != EHCI_LIST_END(ehci))
+					*hw_p = q.sitd->hw_next;
+				else
+					*hw_p = ehci->dummy->qh_dma;
+				type = Q_NEXT_TYPE(ehci, q.sitd->hw_next);
+				wmb();
+				modified = sitd_complete (ehci, q.sitd);
+				q = *q_p;
+				break;
+			default:
+				dbg ("corrupt type %d frame %d shadow %p",
+					type, frame, q.ptr);
+				// BUG ();
+				q.ptr = NULL;
+			}
+
+			/* assume completion callbacks modify the queue */
+			if (unlikely (modified)) {
+				if (likely(ehci->periodic_sched > 0))
+					goto restart;
+				/* short-circuit this scan */
+				now_uframe = clock;
+				break;
+			}
+		}
+
+		/* If we can tell we caught up to the hardware, stop now.
+		 * We can't advance our scan without collecting the ISO
+		 * transfers that are still pending in this frame.
+		 */
+		if (incomplete && ehci->rh_state == EHCI_RH_RUNNING) {
+			ehci->next_uframe = now_uframe;
+			break;
+		}
+
+		// FIXME:  this assumes we won't get lapped when
+		// latencies climb; that should be rare, but...
+		// detect it, and just go all the way around.
+		// FLR might help detect this case, so long as latencies
+		// don't exceed periodic_size msec (default 1.024 sec).
+
+		// FIXME:  likewise assumes HC doesn't halt mid-scan
+
+		if (now_uframe == clock) {
+			unsigned	now;
+
+			if (ehci->rh_state != EHCI_RH_RUNNING
+					|| ehci->periodic_sched == 0)
+				break;
+			ehci->next_uframe = now_uframe;
+			now = ehci_read_frame_index(ehci) & (mod - 1);
+			if (now_uframe == now)
+				break;
+
+			/* rescan the rest of this frame, then ... */
+			clock = now;
+			clock_frame = clock >> 3;
+			if (ehci->clock_frame != clock_frame) {
+				free_cached_lists(ehci);
+				ehci->clock_frame = clock_frame;
+				++ehci->periodic_stamp;
+			}
+		} else {
+			now_uframe++;
+			now_uframe &= mod - 1;
+		}
+	}
+}