[PATCH 3/4] usb: xhci: Reset halted endpoint if trb is noop

[Mathias Nyman <mathias.nyman@linux.intel.com>]

From: Lu Baolu <baolu.lu@linux.intel.com>

When a URB is cancled, xhci driver turns the untransferred trbs
into no-ops.  If an endpoint stalls on a no-op trb that belongs
to the cancelled URB, the event handler won't reset the endpoint.
Hence, it will stay halted.

Link: http://marc.info/?l=linux-usb&m=149582598330127&w=2

Cc: <stable@vger.kernel.org>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci-ring.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 48ae15af..82c746e 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2580,15 +2580,21 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 				(struct xhci_generic_trb *) ep_trb);
 
 		/*
-		 * No-op TRB should not trigger interrupts.
-		 * If ep_trb is a no-op TRB, it means the
-		 * corresponding TD has been cancelled. Just ignore
-		 * the TD.
+		 * No-op TRB could trigger interrupts in a case where
+		 * a URB was killed and a STALL_ERROR happens right
+		 * after the endpoint ring stopped. Reset the halted
+		 * endpoint. Otherwise, the endpoint remains stalled
+		 * indefinitely.
 		 */
 		if (trb_is_noop(ep_trb)) {
-			xhci_dbg(xhci,
-				 "ep_trb is a no-op TRB. Skip it for slot %u ep %u\n",
-				 slot_id, ep_index);
+			if (trb_comp_code == COMP_STALL_ERROR ||
+			    xhci_requires_manual_halt_cleanup(xhci, ep_ctx,
+							      trb_comp_code))
+				xhci_cleanup_halted_endpoint(xhci, slot_id,
+							     ep_index,
+							     ep_ring->stream_id,
+							     td, ep_trb,
+							     EP_HARD_RESET);
 			goto cleanup;
 		}
 
-- 
2.7.4