xhci: handle transfer events without TRB pointer

Most transfer events have a TRB pointer indicating which TRB caused
the event.
In the case of streams, transfer events such as
USB Transaction error may have its TRB pointer set to zero.

driver won't know which stream or what TRB on that stream caused
the error, but it can issue a soft reset to recover the transfer.
A soft reset will clear the host side halt of the endpoint without
clearing Data toggle or sequence number, and let the transfer
continue from where it halted.

see xhci section 4.12 streams and 4.6.8.2 soft retry.

USB Transaction errors with a zero TRB pointer are seen with
UAS usb devices.
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-ring.c

@@ -2317,13 +2317,33 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 	ep_ring = xhci_dma_to_transfer_ring(ep, ep_trb_dma);
 	ep_ctx = xhci_get_ep_ctx(xhci, xdev->out_ctx, ep_index);
 
-	if (!ep_ring || GET_EP_CTX_STATE(ep_ctx) == EP_STATE_DISABLED) {
+	if (GET_EP_CTX_STATE(ep_ctx) == EP_STATE_DISABLED) {
 		xhci_err(xhci,
-			 "ERROR Transfer event for disabled endpoint slot %u ep %u or incorrect stream ring\n",
+			 "ERROR Transfer event for disabled endpoint slot %u ep %u\n",
 			  slot_id, ep_index);
 		goto err_out;
 	}
 
+	/* Some transfer events don't always point to a trb, see xhci 4.17.4 */
+	if (!ep_ring) {
+		switch (trb_comp_code) {
+		case COMP_STALL_ERROR:
+		case COMP_USB_TRANSACTION_ERROR:
+		case COMP_INVALID_STREAM_TYPE_ERROR:
+		case COMP_INVALID_STREAM_ID_ERROR:
+			xhci_cleanup_halted_endpoint(xhci, slot_id, ep_index, 0,
+						     NULL, NULL, EP_SOFT_RESET);
+			goto cleanup;
+		case COMP_RING_UNDERRUN:
+		case COMP_RING_OVERRUN:
+			goto cleanup;
+		default:
+			xhci_err(xhci, "ERROR Transfer event for unknown stream ring slot %u ep %u\n",
+				 slot_id, ep_index);
+			goto err_out;
+		}
+	}
+
 	/* Count current td numbers if ep->skip is set */
 	if (ep->skip) {
 		list_for_each(tmp, &ep_ring->td_list)