Hi,
> During the aborting of a command, the software receives a command
> completion event for the command ring stopped, with the TRB pointing
> to the next TRB after the aborted command.
>
> If the command we abort is located just before the Link TRB in the
> command ring, then during the 'command ring stopped' completion event,
> the xHC gives the Link TRB in the event's cmd DMA, which causes a
> mismatch in handling command completion event.
>
> To handle this situation, an additional check has been added to ignore
> the mismatch error and continue the operation.
Thanks, I remember having some issues with command aborts, but I blamed
them on my own bugs, although I never found what the problem was. I may
take a look at it later, but I'm currently busy with other things.
No comment about validity of this patch for now, but a few remarks:
>+static bool is_dma_link_trb(struct xhci_ring *ring, dma_addr_t dma)
>+{
>+ struct xhci_segment *seg;
>+ union xhci_trb *trb;
>+ dma_addr_t trb_dma;
>+ int i;
>+
>+ seg = ring->first_seg;
>+ do {
>+ for (i = 0; i < TRBS_PER_SEGMENT; i++) {
>+ trb = &seg->trbs[i];
>+ trb_dma = seg->dma + (i * sizeof(union xhci_trb));
>+
>+ if (trb_is_link(trb) && trb_dma == dma)
>+ return true;
>+ }
You don't need to iterate the array. Something like this should work:
do {
if (in_range(dma, seg->dma, TRB_SEGMENT_SIZE)) {
/* found the TRB, check if it's link */
trb = &seg->trbs[(dma - seg->dma) / sizeof(*trb)];
return trb_is_link(trb);
}
// try next seg, while (blah blah), return false
We should probably have a helper for (ring, dma)->trb lookups, but
for stable it may be sensible to do it without excess complication.
>+ if ((!cmd_dequeue_dma || cmd_dma != (u64)cmd_dequeue_dma) &&
>+ !(cmd_comp_code == COMP_COMMAND_RING_STOPPED &&
>+ is_dma_link_trb(xhci->cmd_ring, cmd_dma))) {
This if statement is quite complex now. I would be tempted to write
it this way instead:
/* original comment */
if (cmd_dma != dequeue_dma) {
/* your new comment */
if (! (RING_STOPPED && is_link)) {
warn();
return;
}
}
Regards,
Michal
