xhci: Don't warn on empty ring for suspended devices.

When a device attached to the roothub is suspended, the endpoint rings
are stopped.  The host may generate a completion event with the
completion code set to 'Stopped' or 'Stopped Invalid' when the ring is
halted.  The current xHCI code prints a warning in that case, which can
be really annoying if the USB device is coming into and out of suspend.

Remove the unnecessary warning.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Stephen Hemminger <stephen@networkplumber.org>

drivers/usb/host/xhci-ring.c

@@ -2463,14 +2463,21 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		 * 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",
+			/*
+			 * A stopped endpoint may generate an extra completion
+			 * event if the device was suspended.  Don't print
+			 * warnings.
+			 */
+			if (!(trb_comp_code == COMP_STOP ||
+						trb_comp_code == COMP_STOP_INVAL)) {
+				xhci_warn(xhci, "WARN Event TRB for slot %d ep %d with no TDs queued?\n",
 						TRB_TO_SLOT_ID(le32_to_cpu(event->flags)),
 						ep_index);
 				xhci_dbg(xhci, "Event TRB with TRB type ID %u\n",
 						(le32_to_cpu(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 "