Intel xhci: Ignore spurious successful event.

The xHCI host controller in the Panther Point chipset sometimes produces
spurious events on the event ring.  If it receives a short packet, it
first puts a Transfer Event with a short transfer completion code on the
event ring.  Then it puts a Transfer Event with a successful completion
code on the ring for the same TD.  The xHCI driver correctly processes the
short transfer completion code, gives the URB back to the driver, and then
prints a warning in dmesg about the spurious event.  These warning
messages really fill up dmesg when an HD webcam is plugged into xHCI.

This spurious successful event behavior isn't technically disallowed by
the xHCI specification, so make the xHCI driver just ignore the spurious
completion event.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d1498c03c4c..56f6c584c65 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2061,6 +2061,16 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		if (!event_seg) {
 			if (!ep->skip ||
 			    !usb_endpoint_xfer_isoc(&td->urb->ep->desc)) {
+				/* Some host controllers give a spurious
+				 * successful event after a short transfer.
+				 * Ignore it.
+				 */
+				if ((xhci->quirks & XHCI_SPURIOUS_SUCCESS) && 
+						ep_ring->last_td_was_short) {
+					ep_ring->last_td_was_short = false;
+					ret = 0;
+					goto cleanup;
+				}
 				/* HC is busted, give up! */
 				xhci_err(xhci,
 					"ERROR Transfer event TRB DMA ptr not "
@@ -2071,6 +2081,10 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 			ret = skip_isoc_td(xhci, td, event, ep, &status);
 			goto cleanup;
 		}
+		if (trb_comp_code == COMP_SHORT_TX)
+			ep_ring->last_td_was_short = true;
+		else
+			ep_ring->last_td_was_short = false;
 
 		if (ep->skip) {
 			xhci_dbg(xhci, "Found td. Clear skip flag.\n");