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>

drivers/usb/host/xhci-pci.c

@@ -118,6 +118,10 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
 	/* AMD PLL quirk */
 	if (pdev->vendor == PCI_VENDOR_ID_AMD && usb_amd_find_chipset_info())
 		xhci->quirks |= XHCI_AMD_PLL_FIX;
+	if (pdev->vendor == PCI_VENDOR_ID_INTEL &&
+			pdev->device == PCI_DEVICE_ID_INTEL_PANTHERPOINT_XHCI) {
+		xhci->quirks |= XHCI_SPURIOUS_SUCCESS;
+	}
 
 	/* Make sure the HC is halted. */
 	retval = xhci_halt(xhci);

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");

drivers/usb/host/xhci.h

@@ -1123,6 +1123,7 @@ struct xhci_ring {
 	 */
 	u32			cycle_state;
 	unsigned int		stream_id;
+	bool			last_td_was_short;
 };
 
 struct xhci_erst_entry {
@@ -1290,6 +1291,7 @@ struct xhci_hcd {
 #define XHCI_RESET_EP_QUIRK	(1 << 1)
 #define XHCI_NEC_HOST		(1 << 2)
 #define XHCI_AMD_PLL_FIX	(1 << 3)
+#define XHCI_SPURIOUS_SUCCESS	(1 << 4)
 	/* There are two roothubs to keep track of bus suspend info for */
 	struct xhci_bus_state   bus_state[2];
 	/* Is each xHCI roothub port a USB 3.0, USB 2.0, or USB 1.1 port? */