Re: [PATCH 1/1] usb: xhci: fix checking ep busy for CFC

[Lu, Baolu]

On 10/28/2015 09:27 PM, Mathias Nyman wrote:
> On 28.10.2015 03:36, Lu Baolu wrote:
> > Function ep_ring_is_processing() checks the dequeue pointer
> > in endpoint context to know whether an endpoint is busy with
> > processing TRBs. This is not correct since dequeue pointer
> > field in an endpoint context is only valid when the endpoint
> > is in Halted or Stopped states. This buggy code causes audio
> > noise when playing sound with USB headset connected to host
> > controllers which support CFC (one of xhci 1.1 features).
> >
> > This patch should exist in stable kernel since v4.3.
> >
> > Reported-and-tested-by: YD Tseng <yd_tseng@xxxxxxxxxxxxxx>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/usb/host/xhci-ring.c | 5 +----
> >   1 file changed, 1 insertion(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> > index fa83625..2b50d45 100644
> > --- a/drivers/usb/host/xhci-ring.c
> > +++ b/drivers/usb/host/xhci-ring.c
> > @@ -3903,7 +3903,6 @@ static int ep_ring_is_processing(struct 
> > xhci_hcd *xhci,
> >       struct xhci_ring *ep_ring;
> >       struct xhci_ep_ctx *ep_ctx;
> >       struct xhci_virt_ep *xep;
> > -    dma_addr_t hw_deq;
> >
> >       xdev = xhci->devs[slot_id];
> >       xep = &xhci->devs[slot_id]->eps[ep_index];
> > @@ -3913,9 +3912,7 @@ static int ep_ring_is_processing(struct 
> > xhci_hcd *xhci,
> >       if ((le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK) != 
> > EP_STATE_RUNNING)
> >           return 0;
> >
> > -    hw_deq = le64_to_cpu(ep_ctx->deq) & ~EP_CTX_CYCLE_MASK;
> > -    return (hw_deq !=
> > -        xhci_trb_virt_to_dma(ep_ring->enq_seg, ep_ring->enqueue));
> > +    return !list_empty(&ep_ring->td_list);
> >   }
>
> Would it make sense to remove the ep_ring_is_processing() function 
> completely?
>
> It is only called in one place, and the main use is checking 
> list_empty(&ep_ring->td_list).
> This could be checked directly in xhci_queue_isoc_tx_prepare()

Fair enough. I will make this change and send out the v2.

> -Mathias

Thanks,
Baolu

> --
> To unsubscribe from this list: send the line "unsubscribe 
> linux-kernel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/