A trb_in_td() call is used to determine if a completion event matches one of the TRBs of the currently executing TD. This function is given ep_ring->deq_seg and ep_ring->dequeue as the starting point to search, but these have been observed to be out of sync with td->start_seg and td->first_trb of the current TD under some circumstances when the EP is being stopped. Consequently, spurious completion events have been observed to become erroneously associated with an unrelated pending TD. Since the ring is being searched for the specific purpose of finding a match with current TD, always start from current TD's first TRB. Signed-off-by: Michal Pecio <michal.pecio@xxxxxxxxx> --- Questions: Is this a good idea? Is it useful? Or am I missing something? Should a diagnostic be emitted when these pointers don't match? Or when they don't match AND something else is also wrong? And yes, I am observing unexpected completion events when stopping an isochronous endpoint on NEC uPD720200. They used to retire the current TD and "TRB not in TD" appeared when its true completion arrived, now they correctly give "TRB not in TD" right away. I consider it progress, though the origin of spurious completions is still unknown. drivers/usb/host/xhci-ring.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 9673354d70d5..d9be5023abe6 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -2809,7 +2809,7 @@ static int handle_tx_event(struct xhci_hcd *xhci, td_num--; /* Is this a TRB in the currently executing TD? */ - ep_seg = trb_in_td(xhci, ep_ring->deq_seg, ep_ring->dequeue, + ep_seg = trb_in_td(xhci, td->start_seg, td->first_trb, td->last_trb, ep_trb_dma, false); /* @@ -2877,9 +2877,8 @@ static int handle_tx_event(struct xhci_hcd *xhci, "part of current TD ep_index %d " "comp_code %u\n", ep_index, trb_comp_code); - trb_in_td(xhci, ep_ring->deq_seg, - ep_ring->dequeue, td->last_trb, - ep_trb_dma, true); + trb_in_td(xhci, td->start_seg, td->first_trb, + td->last_trb, ep_trb_dma, true); return -ESHUTDOWN; } } -- 2.43.0
