[PATCH] xhci: No XHCI_TRUST_TX_LENGTH check in the absence of matching TD

[eli.billauer@gmail.com]

From: Eli Billauer <eli.billauer@gmail.com>

When an IN transfer ends with a short packet, the xHCI controller is
required to submit an event TRB with Completion Code COMP_SHORT_PACKET
against the data TRB that was in effect when the short packet arrived, as
well as any event TRBs it submits on behalf of this transfer.

Alas, some controllers (e.g. Renesas) mark the subsequent events TRBs (if
any) with COMP_SUCCESS. As these subsequent event TRBs are useless, they
are ignored on the basis that they have no matching TD queued (it was
dequeued in response to the first COMP_SHORT_PACKET event TRB).

Accordingly, the quirk handling and kernel log warning is moved to after
the TD match check, in particular in order to avoid unnecessary warnings
messages.

Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9741cdeea9d7..96680eb71a45 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2376,14 +2376,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 	 * transfer type
 	 */
 	case COMP_SUCCESS:
-		if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
-			break;
-		if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
-			trb_comp_code = COMP_SHORT_PACKET;
-		else
-			xhci_warn_ratelimited(xhci,
-					      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
-					      slot_id, ep_index);
 	case COMP_SHORT_PACKET:
 		break;
 	/* Completion codes for endpoint stopped state */
@@ -2586,6 +2578,17 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 			skip_isoc_td(xhci, td, event, ep, &status);
 			goto cleanup;
 		}
+
+		if ((trb_comp_code == COMP_SUCCESS) &&
+		    (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0)) {
+			if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
+				trb_comp_code = COMP_SHORT_PACKET;
+			else
+				xhci_warn_ratelimited(xhci,
+						      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
+						      slot_id, ep_index);
+		}
+
 		if (trb_comp_code == COMP_SHORT_PACKET)
 			ep_ring->last_td_was_short = true;
 		else
-- 
2.17.1