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Message-ID: <69eccfa6-5ca0-44d7-b6a8-2152260106e2@linux.intel.com>
Date: Wed, 5 Feb 2025 17:17:31 +0200
From: Mathias Nyman <mathias.nyman@...ux.intel.com>
To: Kuangyi Chiang <ki.chiang65@...il.com>, mathias.nyman@...el.com,
gregkh@...uxfoundation.org
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH v4 1/1] xhci: Correctly handle last TRB of isoc TD on
Etron xHCI host
On 5.2.2025 16.17, Mathias Nyman wrote:
> On 5.2.2025 7.37, Kuangyi Chiang wrote:
>> Unplugging a USB3.0 webcam while streaming results in errors like this:
>>
>> [ 132.646387] xhci_hcd 0000:03:00.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 18 comp_code 13
>> [ 132.646446] xhci_hcd 0000:03:00.0: Looking for event-dma 000000002fdf8630 trb-start 000000002fdf8640 trb-end 000000002fdf8650 seg-start 000000002fdf8000 seg-end 000000002fdf8ff0
>> [ 132.646560] xhci_hcd 0000:03:00.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 18 comp_code 13
>> [ 132.646568] xhci_hcd 0000:03:00.0: Looking for event-dma 000000002fdf8660 trb-start 000000002fdf8670 trb-end 000000002fdf8670 seg-start 000000002fdf8000 seg-end 000000002fdf8ff0
>>
>> If an error is detected while processing the last TRB of an isoc TD,
>> the Etron xHC generates two transfer events for the TRB where the
>> error was detected. The first event can be any sort of error (like
>> USB Transaction or Babble Detected, etc), and the final event is
>> Success.
>>
>> The xHCI driver will handle the TD after the first event and remove it
>> from its internal list, and then print an "Transfer event TRB DMA ptr
>> not part of current TD" error message after the final event.
>>
>> Commit 5372c65e1311 ("xhci: process isoc TD properly when there was a
>> transaction error mid TD.") is designed to address isoc transaction
>> errors, but unfortunately it doesn't account for this scenario.
>>
>> To work around this by reusing the logic that handles isoc transaction
>> errors, but continuing to wait for the final event when this condition
>> occurs. Sometimes we see the Stopped event after an error mid TD, this
>> is a normal event for a pending TD and we can think of it as the final
>> event we are waiting for.
>
> Not giving back the TD when we get an event for the last TRB in the
> TD sounds risky. With this change we assume all old and future ETRON hosts
> will trigger this additional spurious success event.
>
> I think we could handle this more like the XHCI_SPURIOUS_SUCCESS case seen
> with short transfers, and just silence the error message.
>
> Are there any other issues besides the error message seen?
>
Would something like this work: (untested, compiles)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 965bffce301e..81d45ddebace 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2644,6 +2644,22 @@ static int handle_transferless_tx_event(struct xhci_hcd *xhci, struct xhci_virt_
return 0;
}
+static bool xhci_spurious_success_tx_event(struct xhci_hcd *xhci,
+ struct xhci_ring *ring)
+{
+ switch(ring->last_td_comp_code) {
+ case COMP_SHORT_PACKET:
+ return xhci->quirks & XHCI_SPURIOUS_SUCCESS;
+ case COMP_USB_TRANSACTION_ERROR:
+ case COMP_BABBLE_DETECTED_ERROR:
+ case COMP_ISOCH_BUFFER_OVERRUN:
+ return xhci->quirks & XHCI_ETRON_HOST &&
+ ring->type == TYPE_ISOC;
+ default:
+ return false;
+ }
+}
+
/*
* If this function returns an error condition, it means it got a Transfer
* event with a corrupted Slot ID, Endpoint ID, or TRB DMA address.
@@ -2697,8 +2713,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
case COMP_SUCCESS:
if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0) {
trb_comp_code = COMP_SHORT_PACKET;
- xhci_dbg(xhci, "Successful completion on short TX for slot %u ep %u with last td short %d\n",
- slot_id, ep_index, ep_ring->last_td_was_short);
+ xhci_dbg(xhci, "Successful completion on short TX for slot %u ep %u with last td comp code %d\n",
+ slot_id, ep_index, ep_ring->last_td_comp_code);
}
break;
case COMP_SHORT_PACKET:
@@ -2846,7 +2862,7 @@ static int handle_tx_event(struct xhci_hcd *xhci,
*/
if (trb_comp_code != COMP_STOPPED &&
trb_comp_code != COMP_STOPPED_LENGTH_INVALID &&
- !ep_ring->last_td_was_short) {
+ !xhci_spurious_success_tx_event(xhci, ep_ring)) {
xhci_warn(xhci, "Event TRB for slot %u ep %u with no TDs queued\n",
slot_id, ep_index);
}
@@ -2890,11 +2906,10 @@ static int handle_tx_event(struct xhci_hcd *xhci,
/*
* Some hosts give a spurious success event after a short
- * transfer. Ignore it.
+ * transfer or error on last TRB. Ignore it.
*/
- if ((xhci->quirks & XHCI_SPURIOUS_SUCCESS) &&
- ep_ring->last_td_was_short) {
- ep_ring->last_td_was_short = false;
+ if (xhci_spurious_success_tx_event(xhci, ep_ring)) {
+ ep_ring->last_td_comp_code = trb_comp_code;
return 0;
}
@@ -2922,10 +2937,7 @@ static int handle_tx_event(struct xhci_hcd *xhci,
*/
} while (ep->skip);
- if (trb_comp_code == COMP_SHORT_PACKET)
- ep_ring->last_td_was_short = true;
- else
- ep_ring->last_td_was_short = false;
+ ep_ring->last_td_comp_code = trb_comp_code;
ep_trb = &ep_seg->trbs[(ep_trb_dma - ep_seg->dma) / sizeof(*ep_trb)];
trace_xhci_handle_transfer(ep_ring, (struct xhci_generic_trb *) ep_trb, ep_trb_dma);
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 779b01dee068..acc8d3c7a199 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1371,7 +1371,7 @@ struct xhci_ring {
unsigned int num_trbs_free; /* used only by xhci DbC */
unsigned int bounce_buf_len;
enum xhci_ring_type type;
- bool last_td_was_short;
+ u32 last_td_comp_code;
struct radix_tree_root *trb_address_map;
};
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