linux-kernel - [PATCH 1/5] usb: xhci: Complete 'error mid TD' transfers when handling Missed Service

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Message-ID: <20250210083827.2de46507@foxbook>
Date: Mon, 10 Feb 2025 08:38:27 +0100
From: Michal Pecio <michal.pecio@...il.com>
To: Mathias Nyman <mathias.nyman@...el.com>, Greg Kroah-Hartman 
 <gregkh@...uxfoundation.org>
Cc: Niklas Neronin <niklas.neronin@...ux.intel.com>,
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] usb: xhci: Complete 'error mid TD' transfers when
 handling Missed Service

Missed Service Error after an error mid TD means that the failed TD has
already been passed by the xHC without acknowledgment of the final TRB,
a known hardware bug. So don't wait any more and give back the TD.

Reproduced on NEC uPD720200 under conditions of ludicrously bad USB link
quality, confirmed to behave as expected using dynamic debug.

Signed-off-by: Michal Pecio <michal.pecio@...il.com>
---
 drivers/usb/host/xhci-ring.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 965bffce301e..af6c4c4cbe1c 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2789,7 +2789,7 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		xhci_dbg(xhci,
 			 "Miss service interval error for slot %u ep %u, set skip flag\n",
 			 slot_id, ep_index);
-		return 0;
+		break;
 	case COMP_NO_PING_RESPONSE_ERROR:
 		ep->skip = true;
 		xhci_dbg(xhci,
@@ -2837,6 +2837,10 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		xhci_dequeue_td(xhci, td, ep_ring, td->status);
 	}
 
+	/* Missed TDs will be skipped on the next event */
+	if (trb_comp_code == COMP_MISSED_SERVICE_ERROR)
+		return 0;
+
 	if (list_empty(&ep_ring->td_list)) {
 		/*
 		 * Don't print wanings if ring is empty due to a stopped endpoint generating an
-- 
2.48.1