USB: xHCI: Missed Service Error Event process

This patch adds mechanism to process Missed Service Error Event.
Sometimes the xHC is unable to process the isoc TDs in time, it will
generate Missed Service Error Event. In this case some TDs on the ring are
not processed and missed. When encounter a Missed Servce Error Event, set
the skip flag of the ep, and process the missed TDs until reach the next
processed TD, then clear the skip flag.
Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci-mem.c

@@ -1124,6 +1124,7 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
 		virt_dev->num_rings_cached--;
 		xhci_reinit_cached_ring(xhci, virt_dev->eps[ep_index].new_ring);
 	}
+	virt_dev->eps[ep_index].skip = false;
 	ep_ring = virt_dev->eps[ep_index].new_ring;
 	ep_ctx->deq = ep_ring->first_seg->dma | ep_ring->cycle_state;
 

drivers/usb/host/xhci-ring.c

@@ -1675,6 +1675,16 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 					"still with TDs queued?\n",
 				TRB_TO_SLOT_ID(event->flags), ep_index);
 		goto cleanup;
+	case COMP_MISSED_INT:
+		/*
+		 * When encounter missed service error, one or more isoc tds
+		 * may be missed by xHC.
+		 * Set skip flag of the ep_ring; Complete the missed tds as
+		 * short transfer when process the ep_ring next time.
+		 */
+		ep->skip = true;
+		xhci_dbg(xhci, "Miss service interval error, set skip flag\n");
+		goto cleanup;
 	default:
 		if (xhci_is_vendor_info_code(xhci, trb_comp_code)) {
 			status = 0;
@@ -1685,47 +1695,85 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		goto cleanup;
 	}
 
-	/* This TRB should be in the TD at the head of this ring's TD list */
+	do {
+		/* This TRB should be in the TD at the head of this ring's
+		 * TD list.
+		 */
 		if (list_empty(&ep_ring->td_list)) {
-		xhci_warn(xhci, "WARN Event TRB for slot %d ep %d with no TDs queued?\n",
+			xhci_warn(xhci, "WARN Event TRB for slot %d ep %d "
+					"with no TDs queued?\n",
 				  TRB_TO_SLOT_ID(event->flags), ep_index);
 			xhci_dbg(xhci, "Event TRB with TRB type ID %u\n",
 			  (unsigned int) (event->flags & TRB_TYPE_BITMASK)>>10);
 			xhci_print_trb_offsets(xhci, (union xhci_trb *) event);
+			if (ep->skip) {
+				ep->skip = false;
+				xhci_dbg(xhci, "td_list is empty while skip "
+						"flag set. Clear skip flag.\n");
+			}
+			ret = 0;
 			goto cleanup;
 		}
-	td = list_entry(ep_ring->td_list.next, struct xhci_td, td_list);
 
+		td = list_entry(ep_ring->td_list.next, struct xhci_td, td_list);
 		/* Is this a TRB in the currently executing TD? */
 		event_seg = trb_in_td(ep_ring->deq_seg, ep_ring->dequeue,
 				td->last_trb, event_dma);
-	if (!event_seg) {
+		if (event_seg && ep->skip) {
+			xhci_dbg(xhci, "Found td. Clear skip flag.\n");
+			ep->skip = false;
+		}
+		if (!event_seg &&
+		   (!ep->skip || !usb_endpoint_xfer_isoc(&td->urb->ep->desc))) {
 			/* HC is busted, give up! */
-		xhci_err(xhci, "ERROR Transfer event TRB DMA ptr not part of current TD\n");
+			xhci_err(xhci, "ERROR Transfer event TRB DMA ptr not "
+					"part of current TD\n");
 			return -ESHUTDOWN;
 		}
-	event_trb = &event_seg->trbs[(event_dma - event_seg->dma) / sizeof(*event_trb)];
 
-	/* Now update the urb's actual_length and give back to the core */
-	/* Was this a control transfer? */
+		if (event_seg) {
+			event_trb = &event_seg->trbs[(event_dma -
+					 event_seg->dma) / sizeof(*event_trb)];
+			/*
+			 * No-op TRB should not trigger interrupts.
+			 * If event_trb is a no-op TRB, it means the
+			 * corresponding TD has been cancelled. Just ignore
+			 * the TD.
+			 */
+			if ((event_trb->generic.field[3] & TRB_TYPE_BITMASK)
+					 == TRB_TYPE(TRB_TR_NOOP)) {
+				xhci_dbg(xhci, "event_trb is a no-op TRB. "
+						"Skip it\n");
+				goto cleanup;
+			}
+		}
+
+		/* Now update the urb's actual_length and give back to
+		 * the core
+		 */
 		if (usb_endpoint_xfer_control(&td->urb->ep->desc))
 			ret = process_ctrl_td(xhci, td, event_trb, event, ep,
 						 &status);
 		else
-		ret = process_bulk_intr_td(xhci, td, event_trb, event, ep,
-					&status);
+			ret = process_bulk_intr_td(xhci, td, event_trb, event,
+						 ep, &status);
 
 cleanup:
+		/*
+		 * Do not update event ring dequeue pointer if ep->skip is set.
+		 * Will roll back to continue process missed tds.
+		 */
+		if (trb_comp_code == COMP_MISSED_INT || !ep->skip) {
 			inc_deq(xhci, xhci->event_ring, true);
 			xhci_set_hc_event_deq(xhci);
+		}
 
-	/* FIXME for multi-TD URBs (who have buffers bigger than 64MB) */
 		if (ret) {
 			urb = td->urb;
-		/* Leave the TD around for the reset endpoint function to use
-		 * (but only if it's not a control endpoint, since we already
-		 * queued the Set TR dequeue pointer command for stalled
-		 * control endpoints).
+			/* Leave the TD around for the reset endpoint function
+			 * to use(but only if it's not a control endpoint,
+			 * since we already queued the Set TR dequeue pointer
+			 * command for stalled control endpoints).
 			 */
 			if (usb_endpoint_xfer_control(&urb->ep->desc) ||
 				(trb_comp_code != COMP_STALL &&
@@ -1733,12 +1781,22 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 				kfree(td);
 
 			usb_hcd_unlink_urb_from_ep(xhci_to_hcd(xhci), urb);
-		xhci_dbg(xhci, "Giveback URB %p, len = %d, status = %d\n",
+			xhci_dbg(xhci, "Giveback URB %p, len = %d, "
+					"status = %d\n",
 					urb, urb->actual_length, status);
 			spin_unlock(&xhci->lock);
 			usb_hcd_giveback_urb(xhci_to_hcd(xhci), urb, status);
 			spin_lock(&xhci->lock);
 		}
+
+	/*
+	 * If ep->skip is set, it means there are missed tds on the
+	 * endpoint ring need to take care of.
+	 * Process them as short transfer until reach the td pointed by
+	 * the event.
+	 */
+	} while (ep->skip && trb_comp_code != COMP_MISSED_INT);
+
 	return 0;
 }
 

drivers/usb/host/xhci.h

@@ -720,6 +720,14 @@ struct xhci_virt_ep {
 	struct timer_list	stop_cmd_timer;
 	int			stop_cmds_pending;
 	struct xhci_hcd		*xhci;
+	/*
+	 * Sometimes the xHC can not process isochronous endpoint ring quickly
+	 * enough, and it will miss some isoc tds on the ring and generate
+	 * a Missed Service Error Event.
+	 * Set skip flag when receive a Missed Service Error Event and
+	 * process the missed tds on the endpoint ring.
+	 */
+	bool			skip;
 };
 
 struct xhci_virt_device {