USB: xhci: URB cancellation support.

Add URB cancellation support to the xHCI host controller driver.  This
currently supports cancellation for endpoints that do not have streams
enabled.

An URB is represented by a number of Transaction Request Buffers (TRBs),
that are chained together to make one (or more) Transaction Descriptors
(TDs) on an endpoint ring.  The ring is comprised of contiguous segments,
linked together with Link TRBs (which may or may not be chained into a TD).

To cancel an URB, we must stop the endpoint ring, make the hardware skip
over the TDs in the URB (either by turning them into No-op TDs, or by
moving the hardware's ring dequeue pointer past the last TRB in the last
TD), and then restart the ring.

There are times when we must drop the xHCI lock during this process, like
when we need to complete cancelled URBs.  We must ensure that additional
URBs can be marked as cancelled, and that new URBs can be enqueued (since
the URB completion handlers can do either).  The new endpoint ring
variables cancels_pending and state (which can only be modified while
holding the xHCI lock) ensure that future cancellation and enqueueing do
not interrupt any pending cancellation code.

To facilitate cancellation, we must keep track of the starting ring
segment, first TRB, and last TRB for each URB.  We also need to keep track
of the list of TDs that have been marked as cancelled, separate from the
list of TDs that are queued for this endpoint.  The new variables and
cancellation list are stored in the xhci_td structure.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 545 insertions, 42 deletions

diff --git a/drivers/usb/host/xhci-hcd.c b/drivers/usb/host/xhci-hcd.c
index e5fbdcd..36e440c 100644
--- a/drivers/usb/host/xhci-hcd.c
+++ b/drivers/usb/host/xhci-hcd.c
@@ -613,12 +613,70 @@ exit:
 	return ret;
 }
 
-/* Remove from hardware lists
- * completions normally happen asynchronously
+/*
+ * Remove the URB's TD from the endpoint ring.  This may cause the HC to stop
+ * USB transfers, potentially stopping in the middle of a TRB buffer.  The HC
+ * should pick up where it left off in the TD, unless a Set Transfer Ring
+ * Dequeue Pointer is issued.
+ *
+ * The TRBs that make up the buffers for the canceled URB will be "removed" from
+ * the ring.  Since the ring is a contiguous structure, they can't be physically
+ * removed.  Instead, there are two options:
+ *
+ *  1) If the HC is in the middle of processing the URB to be canceled, we
+ *     simply move the ring's dequeue pointer past those TRBs using the Set
+ *     Transfer Ring Dequeue Pointer command.  This will be the common case,
+ *     when drivers timeout on the last submitted URB and attempt to cancel.
+ *
+ *  2) If the HC is in the middle of a different TD, we turn the TRBs into a
+ *     series of 1-TRB transfer no-op TDs.  (No-ops shouldn't be chained.)  The
+ *     HC will need to invalidate the any TRBs it has cached after the stop
+ *     endpoint command, as noted in the xHCI 0.95 errata.
+ *
+ *  3) The TD may have completed by the time the Stop Endpoint Command
+ *     completes, so software needs to handle that case too.
+ *
+ * This function should protect against the TD enqueueing code ringing the
+ * doorbell while this code is waiting for a Stop Endpoint command to complete.
+ * It also needs to account for multiple cancellations on happening at the same
+ * time for the same endpoint.
+ *
+ * Note that this function can be called in any context, or so says
+ * usb_hcd_unlink_urb()
  */
 int xhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 {
-	return -ENOSYS;
+	unsigned long flags;
+	int ret;
+	struct xhci_hcd *xhci;
+	struct xhci_td *td;
+	unsigned int ep_index;
+	struct xhci_ring *ep_ring;
+
+	xhci = hcd_to_xhci(hcd);
+	spin_lock_irqsave(&xhci->lock, flags);
+	/* Make sure the URB hasn't completed or been unlinked already */
+	ret = usb_hcd_check_unlink_urb(hcd, urb, status);
+	if (ret || !urb->hcpriv)
+		goto done;
+
+	xhci_dbg(xhci, "Cancel URB 0x%x\n", (unsigned int) urb);
+	ep_index = xhci_get_endpoint_index(&urb->ep->desc);
+	ep_ring = xhci->devs[urb->dev->slot_id]->ep_rings[ep_index];
+	td = (struct xhci_td *) urb->hcpriv;
+
+	ep_ring->cancels_pending++;
+	list_add_tail(&td->cancelled_td_list, &ep_ring->cancelled_td_list);
+	/* Queue a stop endpoint command, but only if this is
+	 * the first cancellation to be handled.
+	 */
+	if (ep_ring->cancels_pending == 1) {
+		queue_stop_endpoint(xhci, urb->dev->slot_id, ep_index);
+		ring_cmd_db(xhci);
+	}
+done:
+	spin_unlock_irqrestore(&xhci->lock, flags);
+	return ret;
 }
 
 /* Drop an endpoint from a new bandwidth configuration for this device.
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 617db9c..e81d10a 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -142,6 +142,7 @@ static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
 		return 0;
 
 	INIT_LIST_HEAD(&ring->td_list);
+	INIT_LIST_HEAD(&ring->cancelled_td_list);
 	if (num_segs == 0)
 		return ring;
 
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index c948288..f967a6d 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -112,6 +112,23 @@ static inline int last_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
 		return (trb->link.control & TRB_TYPE_BITMASK) == TRB_TYPE(TRB_LINK);
 }
 
+/* Updates trb to point to the next TRB in the ring, and updates seg if the next
+ * TRB is in a new segment.  This does not skip over link TRBs, and it does not
+ * effect the ring dequeue or enqueue pointers.
+ */
+static void next_trb(struct xhci_hcd *xhci,
+		struct xhci_ring *ring,
+		struct xhci_segment **seg,
+		union xhci_trb **trb)
+{
+	if (last_trb(xhci, ring, *seg, *trb)) {
+		*seg = (*seg)->next;
+		*trb = ((*seg)->trbs);
+	} else {
+		*trb = (*trb)++;
+	}
+}
+
 /*
  * See Cycle bit rules. SW is the consumer for the event ring only.
  * Don't make a ring full of link TRBs.  That would be dumb and this would loop.
@@ -250,6 +267,344 @@ void ring_cmd_db(struct xhci_hcd *xhci)
 	xhci_readl(xhci, &xhci->dba->doorbell[0]);
 }
 
+static void ring_ep_doorbell(struct xhci_hcd *xhci,
+		unsigned int slot_id,
+		unsigned int ep_index)
+{
+	struct xhci_ring *ep_ring;
+	u32 field;
+	__u32 __iomem *db_addr = &xhci->dba->doorbell[slot_id];
+
+	ep_ring = xhci->devs[slot_id]->ep_rings[ep_index];
+	/* Don't ring the doorbell for this endpoint if there are pending
+	 * cancellations because the we don't want to interrupt processing.
+	 */
+	if (!ep_ring->cancels_pending && !(ep_ring->state & SET_DEQ_PENDING)) {
+		field = xhci_readl(xhci, db_addr) & DB_MASK;
+		xhci_writel(xhci, field | EPI_TO_DB(ep_index), db_addr);
+		/* Flush PCI posted writes - FIXME Matthew Wilcox says this
+		 * isn't time-critical and we shouldn't make the CPU wait for
+		 * the flush.
+		 */
+		xhci_readl(xhci, db_addr);
+	}
+}
+
+/*
+ * Find the segment that trb is in.  Start searching in start_seg.
+ * If we must move past a segment that has a link TRB with a toggle cycle state
+ * bit set, then we will toggle the value pointed at by cycle_state.
+ */
+static struct xhci_segment *find_trb_seg(
+		struct xhci_segment *start_seg,
+		union xhci_trb	*trb, int *cycle_state)
+{
+	struct xhci_segment *cur_seg = start_seg;
+	struct xhci_generic_trb *generic_trb;
+
+	while (cur_seg->trbs > trb ||
+			&cur_seg->trbs[TRBS_PER_SEGMENT - 1] < trb) {
+		generic_trb = &cur_seg->trbs[TRBS_PER_SEGMENT - 1].generic;
+		if (TRB_TYPE(generic_trb->field[3]) == TRB_LINK &&
+				(generic_trb->field[3] & LINK_TOGGLE))
+			*cycle_state = ~(*cycle_state) & 0x1;
+		cur_seg = cur_seg->next;
+		if (cur_seg == start_seg)
+			/* Looped over the entire list.  Oops! */
+			return 0;
+	}
+	return cur_seg;
+}
+
+struct dequeue_state {
+	struct xhci_segment *new_deq_seg;
+	union xhci_trb *new_deq_ptr;
+	int new_cycle_state;
+};
+
+/*
+ * Move the xHC's endpoint ring dequeue pointer past cur_td.
+ * Record the new state of the xHC's endpoint ring dequeue segment,
+ * dequeue pointer, and new consumer cycle state in state.
+ * Update our internal representation of the ring's dequeue pointer.
+ *
+ * We do this in three jumps:
+ *  - First we update our new ring state to be the same as when the xHC stopped.
+ *  - Then we traverse the ring to find the segment that contains
+ *    the last TRB in the TD.  We toggle the xHC's new cycle state when we pass
+ *    any link TRBs with the toggle cycle bit set.
+ *  - Finally we move the dequeue state one TRB further, toggling the cycle bit
+ *    if we've moved it past a link TRB with the toggle cycle bit set.
+ */
+static void find_new_dequeue_state(struct xhci_hcd *xhci,
+		unsigned int slot_id, unsigned int ep_index,
+		struct xhci_td *cur_td, struct dequeue_state *state)
+{
+	struct xhci_virt_device *dev = xhci->devs[slot_id];
+	struct xhci_ring *ep_ring = dev->ep_rings[ep_index];
+	struct xhci_generic_trb *trb;
+
+	state->new_cycle_state = 0;
+	state->new_deq_seg = find_trb_seg(cur_td->start_seg,
+			ep_ring->stopped_trb,
+			&state->new_cycle_state);
+	if (!state->new_deq_seg)
+		BUG();
+	/* Dig out the cycle state saved by the xHC during the stop ep cmd */
+	state->new_cycle_state = 0x1 & dev->out_ctx->ep[ep_index].deq[0];
+
+	state->new_deq_ptr = cur_td->last_trb;
+	state->new_deq_seg = find_trb_seg(state->new_deq_seg,
+			state->new_deq_ptr,
+			&state->new_cycle_state);
+	if (!state->new_deq_seg)
+		BUG();
+
+	trb = &state->new_deq_ptr->generic;
+	if (TRB_TYPE(trb->field[3]) == TRB_LINK &&
+				(trb->field[3] & LINK_TOGGLE))
+		state->new_cycle_state = ~(state->new_cycle_state) & 0x1;
+	next_trb(xhci, ep_ring, &state->new_deq_seg, &state->new_deq_ptr);
+
+	/* Don't update the ring cycle state for the producer (us). */
+	ep_ring->dequeue = state->new_deq_ptr;
+	ep_ring->deq_seg = state->new_deq_seg;
+}
+
+void td_to_noop(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
+		struct xhci_td *cur_td)
+{
+	struct xhci_segment *cur_seg;
+	union xhci_trb *cur_trb;
+
+	for (cur_seg = cur_td->start_seg, cur_trb = cur_td->first_trb;
+			true;
+			next_trb(xhci, ep_ring, &cur_seg, &cur_trb)) {
+		if ((cur_trb->generic.field[3] & TRB_TYPE_BITMASK) ==
+				TRB_TYPE(TRB_LINK)) {
+			/* Unchain any chained Link TRBs, but
+			 * leave the pointers intact.
+			 */
+			cur_trb->generic.field[3] &= ~TRB_CHAIN;
+			xhci_dbg(xhci, "Cancel (unchain) link TRB\n");
+			xhci_dbg(xhci, "Address = 0x%x (0x%x dma); "
+					"in seg 0x%x (0x%x dma)\n",
+					(unsigned int) cur_trb,
+					trb_virt_to_dma(cur_seg, cur_trb),
+					(unsigned int) cur_seg,
+					cur_seg->dma);
+		} else {
+			cur_trb->generic.field[0] = 0;
+			cur_trb->generic.field[1] = 0;
+			cur_trb->generic.field[2] = 0;
+			/* Preserve only the cycle bit of this TRB */
+			cur_trb->generic.field[3] &= TRB_CYCLE;
+			cur_trb->generic.field[3] |= TRB_TYPE(TRB_TR_NOOP);
+			xhci_dbg(xhci, "Cancel TRB 0x%x (0x%x dma) "
+					"in seg 0x%x (0x%x dma)\n",
+					(unsigned int) cur_trb,
+					trb_virt_to_dma(cur_seg, cur_trb),
+					(unsigned int) cur_seg,
+					cur_seg->dma);
+		}
+		if (cur_trb == cur_td->last_trb)
+			break;
+	}
+}
+
+static int queue_set_tr_deq(struct xhci_hcd *xhci, int slot_id,
+		unsigned int ep_index, struct xhci_segment *deq_seg,
+		union xhci_trb *deq_ptr, u32 cycle_state);
+
+/*
+ * When we get a command completion for a Stop Endpoint Command, we need to
+ * unlink any cancelled TDs from the ring.  There are two ways to do that:
+ *
+ *  1. If the HW was in the middle of processing the TD that needs to be
+ *     cancelled, then we must move the ring's dequeue pointer past the last TRB
+ *     in the TD with a Set Dequeue Pointer Command.
+ *  2. Otherwise, we turn all the TRBs in the TD into No-op TRBs (with the chain
+ *     bit cleared) so that the HW will skip over them.
+ */
+static void handle_stopped_endpoint(struct xhci_hcd *xhci,
+		union xhci_trb *trb)
+{
+	unsigned int slot_id;
+	unsigned int ep_index;
+	struct xhci_ring *ep_ring;
+	struct list_head *entry;
+	struct xhci_td *cur_td = 0;
+	struct xhci_td *last_unlinked_td;
+
+	struct dequeue_state deq_state;
+#ifdef CONFIG_USB_HCD_STAT
+	ktime_t stop_time = ktime_get();
+#endif
+
+	memset(&deq_state, 0, sizeof(deq_state));
+	slot_id = TRB_TO_SLOT_ID(trb->generic.field[3]);
+	ep_index = TRB_TO_EP_INDEX(trb->generic.field[3]);
+	ep_ring = xhci->devs[slot_id]->ep_rings[ep_index];
+
+	if (list_empty(&ep_ring->cancelled_td_list))
+		return;
+
+	/* Fix up the ep ring first, so HW stops executing cancelled TDs.
+	 * We have the xHCI lock, so nothing can modify this list until we drop
+	 * it.  We're also in the event handler, so we can't get re-interrupted
+	 * if another Stop Endpoint command completes
+	 */
+	list_for_each(entry, &ep_ring->cancelled_td_list) {
+		cur_td = list_entry(entry, struct xhci_td, cancelled_td_list);
+		xhci_dbg(xhci, "Cancelling TD starting at 0x%x, 0x%x (dma).\n",
+				(unsigned int) cur_td->first_trb,
+				trb_virt_to_dma(cur_td->start_seg, cur_td->first_trb));
+		/*
+		 * If we stopped on the TD we need to cancel, then we have to
+		 * move the xHC endpoint ring dequeue pointer past this TD.
+		 */
+		if (cur_td == ep_ring->stopped_td)
+			find_new_dequeue_state(xhci, slot_id, ep_index, cur_td,
+					&deq_state);
+		else
+			td_to_noop(xhci, ep_ring, cur_td);
+		/*
+		 * The event handler won't see a completion for this TD anymore,
+		 * so remove it from the endpoint ring's TD list.  Keep it in
+		 * the cancelled TD list for URB completion later.
+		 */
+		list_del(&cur_td->td_list);
+		ep_ring->cancels_pending--;
+	}
+	last_unlinked_td = cur_td;
+
+	/* If necessary, queue a Set Transfer Ring Dequeue Pointer command */
+	if (deq_state.new_deq_ptr && deq_state.new_deq_seg) {
+		xhci_dbg(xhci, "Set TR Deq Ptr cmd, new deq seg = 0x%x (0x%x dma), "
+				"new deq ptr = 0x%x (0x%x dma), new cycle = %u\n",
+				(unsigned int) deq_state.new_deq_seg,
+				deq_state.new_deq_seg->dma,
+				(unsigned int) deq_state.new_deq_ptr,
+				trb_virt_to_dma(deq_state.new_deq_seg, deq_state.new_deq_ptr),
+				deq_state.new_cycle_state);
+		queue_set_tr_deq(xhci, slot_id, ep_index,
+				deq_state.new_deq_seg,
+				deq_state.new_deq_ptr,
+				(u32) deq_state.new_cycle_state);
+		/* Stop the TD queueing code from ringing the doorbell until
+		 * this command completes.  The HC won't set the dequeue pointer
+		 * if the ring is running, and ringing the doorbell starts the
+		 * ring running.
+		 */
+		ep_ring->state |= SET_DEQ_PENDING;
+		ring_cmd_db(xhci);
+	} else {
+		/* Otherwise just ring the doorbell to restart the ring */
+		ring_ep_doorbell(xhci, slot_id, ep_index);
+	}
+
+	/*
+	 * Drop the lock and complete the URBs in the cancelled TD list.
+	 * New TDs to be cancelled might be added to the end of the list before
+	 * we can complete all the URBs for the TDs we already unlinked.
+	 * So stop when we've completed the URB for the last TD we unlinked.
+	 */
+	do {
+		cur_td = list_entry(ep_ring->cancelled_td_list.next,
+				struct xhci_td, cancelled_td_list);
+		list_del(&cur_td->cancelled_td_list);
+
+		/* Clean up the cancelled URB */
+#ifdef CONFIG_USB_HCD_STAT
+		hcd_stat_update(xhci->tp_stat, cur_td->urb->actual_length,
+				ktime_sub(stop_time, cur_td->start_time));
+#endif
+		cur_td->urb->hcpriv = NULL;
+		usb_hcd_unlink_urb_from_ep(xhci_to_hcd(xhci), cur_td->urb);
+
+		xhci_dbg(xhci, "Giveback cancelled URB 0x%x\n",
+				(unsigned int) cur_td->urb);
+		spin_unlock(&xhci->lock);
+		/* Doesn't matter what we pass for status, since the core will
+		 * just overwrite it (because the URB has been unlinked).
+		 */
+		usb_hcd_giveback_urb(xhci_to_hcd(xhci), cur_td->urb, 0);
+		kfree(cur_td);
+
+		spin_lock(&xhci->lock);
+	} while (cur_td != last_unlinked_td);
+
+	/* Return to the event handler with xhci->lock re-acquired */
+}
+
+/*
+ * When we get a completion for a Set Transfer Ring Dequeue Pointer command,
+ * we need to clear the set deq pending flag in the endpoint ring state, so that
+ * the TD queueing code can ring the doorbell again.  We also need to ring the
+ * endpoint doorbell to restart the ring, but only if there aren't more
+ * cancellations pending.
+ */
+static void handle_set_deq_completion(struct xhci_hcd *xhci,
+		struct xhci_event_cmd *event,
+		union xhci_trb *trb)
+{
+	unsigned int slot_id;
+	unsigned int ep_index;
+	struct xhci_ring *ep_ring;
+	struct xhci_virt_device *dev;
+
+	slot_id = TRB_TO_SLOT_ID(trb->generic.field[3]);
+	ep_index = TRB_TO_EP_INDEX(trb->generic.field[3]);
+	dev = xhci->devs[slot_id];
+	ep_ring = dev->ep_rings[ep_index];
+
+	if (GET_COMP_CODE(event->status) != COMP_SUCCESS) {
+		unsigned int ep_state;
+		unsigned int slot_state;
+
+		switch (GET_COMP_CODE(event->status)) {
+		case COMP_TRB_ERR:
+			xhci_warn(xhci, "WARN Set TR Deq Ptr cmd invalid because "
+					"of stream ID configuration\n");
+			break;
+		case COMP_CTX_STATE:
+			xhci_warn(xhci, "WARN Set TR Deq Ptr cmd failed due "
+					"to incorrect slot or ep state.\n");
+			ep_state = dev->out_ctx->ep[ep_index].ep_info;
+			ep_state &= EP_STATE_MASK;
+			slot_state = dev->out_ctx->slot.dev_state;
+			slot_state = GET_SLOT_STATE(slot_state);
+			xhci_dbg(xhci, "Slot state = %u, EP state = %u\n",
+					slot_state, ep_state);
+			break;
+		case COMP_EBADSLT:
+			xhci_warn(xhci, "WARN Set TR Deq Ptr cmd failed because "
+					"slot %u was not enabled.\n", slot_id);
+			break;
+		default:
+			xhci_warn(xhci, "WARN Set TR Deq Ptr cmd with unknown "
+					"completion code of %u.\n",
+					GET_COMP_CODE(event->status));
+			break;
+		}
+		/* OK what do we do now?  The endpoint state is hosed, and we
+		 * should never get to this point if the synchronization between
+		 * queueing, and endpoint state are correct.  This might happen
+		 * if the device gets disconnected after we've finished
+		 * cancelling URBs, which might not be an error...
+		 */
+	} else {
+		xhci_dbg(xhci, "Successful Set TR Deq Ptr cmd, deq[0] = 0x%x, "
+				"deq[1] = 0x%x.\n",
+				dev->out_ctx->ep[ep_index].deq[0],
+				dev->out_ctx->ep[ep_index].deq[1]);
+	}
+
+	ep_ring->state &= ~SET_DEQ_PENDING;
+	ring_ep_doorbell(xhci, slot_id, ep_index);
+}
+
+
 static void handle_cmd_completion(struct xhci_hcd *xhci,
 		struct xhci_event_cmd *event)
 {
@@ -290,6 +645,12 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
 		xhci->devs[slot_id]->cmd_status = GET_COMP_CODE(event->status);
 		complete(&xhci->addr_dev);
 		break;
+	case TRB_TYPE(TRB_STOP_RING):
+		handle_stopped_endpoint(xhci, xhci->cmd_ring->dequeue);
+		break;
+	case TRB_TYPE(TRB_SET_DEQ):
+		handle_set_deq_completion(xhci, event, xhci->cmd_ring->dequeue);
+		break;
 	case TRB_TYPE(TRB_CMD_NOOP):
 		++xhci->noops_handled;
 		break;
@@ -346,11 +707,9 @@ static struct xhci_segment *trb_in_td(
 	cur_seg = start_seg;
 
 	do {
-		/*
-		 * Last TRB is a link TRB (unless we start inserting links in
-		 * the middle, FIXME if you do)
-		 */
-		end_seg_dma = trb_virt_to_dma(cur_seg, &start_seg->trbs[TRBS_PER_SEGMENT - 2]);
+		/* We may get an event for a Link TRB in the middle of a TD */
+		end_seg_dma = trb_virt_to_dma(cur_seg,
+				&start_seg->trbs[TRBS_PER_SEGMENT - 1]);
 		/* If the end TRB isn't in this segment, this is set to 0 */
 		end_trb_dma = trb_virt_to_dma(cur_seg, end_trb);
 
@@ -396,7 +755,7 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 	dma_addr_t event_dma;
 	struct xhci_segment *event_seg;
 	union xhci_trb *event_trb;
-	struct urb *urb;
+	struct urb *urb = 0;
 	int status = -EINPROGRESS;
 
 	xdev = xhci->devs[TRB_TO_SLOT_ID(event->flags)];
@@ -457,6 +816,12 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 	case COMP_SUCCESS:
 	case COMP_SHORT_TX:
 		break;
+	case COMP_STOP:
+		xhci_dbg(xhci, "Stopped on Transfer TRB\n");
+		break;
+	case COMP_STOP_INVAL:
+		xhci_dbg(xhci, "Stopped on No-op or Link TRB\n");
+		break;
 	case COMP_STALL:
 		xhci_warn(xhci, "WARN: Stalled endpoint\n");
 		status = -EPIPE;
@@ -510,11 +875,15 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		if (event_trb != ep_ring->dequeue) {
 			/* The event was for the status stage */
 			if (event_trb == td->last_trb) {
-				td->urb->actual_length = td->urb->transfer_buffer_length;
+				td->urb->actual_length =
+					td->urb->transfer_buffer_length;
 			} else {
-			/* The event was for the data stage */
-				td->urb->actual_length = td->urb->transfer_buffer_length -
-					TRB_LEN(event->transfer_len);
+			/* Maybe the event was for the data stage? */
+				if (GET_COMP_CODE(event->transfer_len) != COMP_STOP_INVAL)
+					/* We didn't stop on a link TRB in the middle */
+					td->urb->actual_length =
+						td->urb->transfer_buffer_length -
+						TRB_LEN(event->transfer_len);
 			}
 		}
 	} else {
@@ -573,29 +942,55 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 				status = 0;
 			}
 		} else {
-			/* Slow path - walk the list, starting from the first
-			 * TRB to get the actual length transferred
+			/* Slow path - walk the list, starting from the dequeue
+			 * pointer, to get the actual length transferred.
 			 */
+			union xhci_trb *cur_trb;
+			struct xhci_segment *cur_seg;
+
 			td->urb->actual_length = 0;
-			while (ep_ring->dequeue != event_trb) {
-				td->urb->actual_length += TRB_LEN(ep_ring->dequeue->generic.field[2]);
-				inc_deq(xhci, ep_ring, false);
+			for (cur_trb = ep_ring->dequeue, cur_seg = ep_ring->deq_seg;
+					cur_trb != event_trb;
+					next_trb(xhci, ep_ring, &cur_seg, &cur_trb)) {
+				if (TRB_TYPE(cur_trb->generic.field[3]) != TRB_TR_NOOP &&
+						TRB_TYPE(cur_trb->generic.field[3]) != TRB_LINK)
+					td->urb->actual_length +=
+						TRB_LEN(cur_trb->generic.field[2]);
 			}
-			td->urb->actual_length += TRB_LEN(ep_ring->dequeue->generic.field[2]) -
-				TRB_LEN(event->transfer_len);
-
+			/* If the ring didn't stop on a Link or No-op TRB, add
+			 * in the actual bytes transferred from the Normal TRB
+			 */
+			if (GET_COMP_CODE(event->transfer_len) != COMP_STOP_INVAL)
+				td->urb->actual_length +=
+					TRB_LEN(cur_trb->generic.field[2]) -
+					TRB_LEN(event->transfer_len);
 		}
 	}
-	/* Update ring dequeue pointer */
-	while (ep_ring->dequeue != td->last_trb)
+	/* The Endpoint Stop Command completion will take care of
+	 * any stopped TDs.  A stopped TD may be restarted, so don't update the
+	 * ring dequeue pointer or take this TD off any lists yet.
+	 */
+	if (GET_COMP_CODE(event->transfer_len) == COMP_STOP_INVAL ||
+			GET_COMP_CODE(event->transfer_len) == COMP_STOP) {
+		ep_ring->stopped_td = td;
+		ep_ring->stopped_trb = event_trb;
+	} else {
+		/* Update ring dequeue pointer */
+		while (ep_ring->dequeue != td->last_trb)
+			inc_deq(xhci, ep_ring, false);
 		inc_deq(xhci, ep_ring, false);
-	inc_deq(xhci, ep_ring, false);
 
-	/* Clean up the endpoint's TD list */
-	urb = td->urb;
-	list_del(&td->td_list);
-	kfree(td);
-	urb->hcpriv = NULL;
+		/* Clean up the endpoint's TD list */
+		urb = td->urb;
+		list_del(&td->td_list);
+		/* Was this TD slated to be cancelled but completed anyway? */
+		if (!list_empty(&td->cancelled_td_list)) {
+			list_del(&td->cancelled_td_list);
+			ep_ring->cancels_pending--;
+		}
+		kfree(td);
+		urb->hcpriv = NULL;
+	}
 cleanup:
 	inc_deq(xhci, xhci->event_ring, true);
 	set_hc_event_deq(xhci);
@@ -744,6 +1139,7 @@ int xhci_prepare_transfer(struct xhci_hcd *xhci,
 	if (!*td)
 		return -ENOMEM;
 	INIT_LIST_HEAD(&(*td)->td_list);
+	INIT_LIST_HEAD(&(*td)->cancelled_td_list);
 
 	ret = usb_hcd_link_urb_to_ep(xhci_to_hcd(xhci), urb);
 	if (unlikely(ret)) {
@@ -755,6 +1151,8 @@ int xhci_prepare_transfer(struct xhci_hcd *xhci,
 	urb->hcpriv = (void *) (*td);
 	/* Add this TD to the tail of the endpoint ring's TD list */
 	list_add_tail(&(*td)->td_list, &xdev->ep_rings[ep_index]->td_list);
+	(*td)->start_seg = xdev->ep_rings[ep_index]->enq_seg;
+	(*td)->first_trb = xdev->ep_rings[ep_index]->enqueue;
 
 	return 0;
 }
@@ -823,19 +1221,13 @@ void giveback_first_trb(struct xhci_hcd *xhci, int slot_id,
 		unsigned int ep_index, int start_cycle,
 		struct xhci_generic_trb *start_trb, struct xhci_td *td)
 {
-	u32 field;
-
 	/*
 	 * Pass all the TRBs to the hardware at once and make sure this write
 	 * isn't reordered.
 	 */
 	wmb();
 	start_trb->field[3] |= start_cycle;
-	field = xhci_readl(xhci, &xhci->dba->doorbell[slot_id]) & DB_MASK;
-	xhci_writel(xhci, field | EPI_TO_DB(ep_index),
-			&xhci->dba->doorbell[slot_id]);
-	/* Flush PCI posted writes */
-	xhci_readl(xhci, &xhci->dba->doorbell[slot_id]);
+	ring_ep_doorbell(xhci, slot_id, ep_index);
 }
 
 int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
@@ -1221,3 +1613,36 @@ int queue_configure_endpoint(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr, u32 s
 	return queue_command(xhci, in_ctx_ptr, 0, 0,
 			TRB_TYPE(TRB_CONFIG_EP) | SLOT_ID_FOR_TRB(slot_id));
 }
+
+int queue_stop_endpoint(struct xhci_hcd *xhci, int slot_id,
+		unsigned int ep_index)
+{
+	u32 trb_slot_id = SLOT_ID_FOR_TRB(slot_id);
+	u32 trb_ep_index = EP_ID_FOR_TRB(ep_index);
+	u32 type = TRB_TYPE(TRB_STOP_RING);
+
+	return queue_command(xhci, 0, 0, 0,
+			trb_slot_id | trb_ep_index | type);
+}
+
+/* Set Transfer Ring Dequeue Pointer command.
+ * This should not be used for endpoints that have streams enabled.
+ */
+static int queue_set_tr_deq(struct xhci_hcd *xhci, int slot_id,
+		unsigned int ep_index, struct xhci_segment *deq_seg,
+		union xhci_trb *deq_ptr, u32 cycle_state)
+{
+	dma_addr_t addr;
+	u32 trb_slot_id = SLOT_ID_FOR_TRB(slot_id);
+	u32 trb_ep_index = EP_ID_FOR_TRB(ep_index);
+	u32 type = TRB_TYPE(TRB_SET_DEQ);
+
+	addr = trb_virt_to_dma(deq_seg, deq_ptr);
+	if (addr == 0)
+		xhci_warn(xhci, "WARN Cannot submit Set TR Deq Ptr\n");
+		xhci_warn(xhci, "WARN deq seg = 0x%x, deq pt = 0x%x\n",
+				(unsigned int) deq_seg,
+				(unsigned int) deq_ptr);
+	return queue_command(xhci, (u32) addr | cycle_state, 0, 0,
+			trb_slot_id | trb_ep_index | type);
+}
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 06e0761..7b71034 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -514,6 +514,7 @@ struct xhci_slot_ctx {
 /* bits 8:26 reserved */
 /* Slot state */
 #define SLOT_STATE	(0x1f << 27)
+#define GET_SLOT_STATE(p)	(((p) & (0x1f << 27)) >> 27)
 
 
 /**
@@ -765,6 +766,11 @@ struct xhci_event_cmd {
 #define TRB_TO_SLOT_ID(p)	(((p) & (0xff<<24)) >> 24)
 #define SLOT_ID_FOR_TRB(p)	(((p) & 0xff) << 24)
 
+/* Stop Endpoint TRB - ep_index to endpoint ID for this TRB */
+#define TRB_TO_EP_INDEX(p)		((((p) & (0x1f << 16)) >> 16) - 1)
+#define	EP_ID_FOR_TRB(p)		((((p) + 1) & 0x1f) << 16)
+
+
 /* Port Status Change Event TRB fields */
 /* Port ID - bits 31:24 */
 #define GET_PORT_ID(p)		(((p) & (0xff << 24)) >> 24)
@@ -893,12 +899,6 @@ union xhci_trb {
 #define TRB_MAX_BUFF_SHIFT		16
 #define TRB_MAX_BUFF_SIZE	(1 << TRB_MAX_BUFF_SHIFT)
 
-struct xhci_td {
-	struct list_head	td_list;
-	struct urb		*urb;
-	union xhci_trb		*last_trb;
-};
-
 struct xhci_segment {
 	union xhci_trb		*trbs;
 	/* private to HCD */
@@ -906,6 +906,15 @@ struct xhci_segment {
 	dma_addr_t		dma;
 } __attribute__ ((packed));
 
+struct xhci_td {
+	struct list_head	td_list;
+	struct list_head	cancelled_td_list;
+	struct urb		*urb;
+	struct xhci_segment	*start_seg;
+	union xhci_trb		*first_trb;
+	union xhci_trb		*last_trb;
+};
+
 struct xhci_ring {
 	struct xhci_segment	*first_seg;
 	union  xhci_trb		*enqueue;
@@ -915,6 +924,14 @@ struct xhci_ring {
 	struct xhci_segment	*deq_seg;
 	unsigned int		deq_updates;
 	struct list_head	td_list;
+	/* ----  Related to URB cancellation ---- */
+	struct list_head	cancelled_td_list;
+	unsigned int		cancels_pending;
+	unsigned int		state;
+#define SET_DEQ_PENDING		(1 << 0)
+	/* The TRB that was last reported in a stopped endpoint ring */
+	union xhci_trb		*stopped_trb;
+	struct xhci_td		*stopped_td;
 	/*
 	 * Write the cycle state into the TRB cycle field to give ownership of
 	 * the TRB to the host controller (if we are the producer), or to check
@@ -1119,6 +1136,8 @@ void handle_event(struct xhci_hcd *xhci);
 void set_hc_event_deq(struct xhci_hcd *xhci);
 int queue_slot_control(struct xhci_hcd *xhci, u32 trb_type, u32 slot_id);
 int queue_address_device(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr, u32 slot_id);
+int queue_stop_endpoint(struct xhci_hcd *xhci, int slot_id,
+		unsigned int ep_index);
 int queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags, struct urb *urb, int slot_id, unsigned int ep_index);
 int queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags, struct urb *urb, int slot_id, unsigned int ep_index);
 int queue_configure_endpoint(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr, u32 slot_id);