Hi Bin, I've just checked that the issue is still present in 4.13.10. 2017-04-27 13:20 GMT+03:00 Matwey V. Kornilov <matwey@xxxxxxxxxx>: > This commit changes the order of actions undertaken in > musb_advance_schedule() in order to overcome issue with broken > isochronous transfer [1]. > > There is no harm to split musb_giveback into two pieces. The first > unlinks finished urb, the second givebacks it. The issue here that > givebacking may be quite time-consuming due to urb->complete() call. > As it happens in case of pwc-driven web cameras. It may take about 0.5 > ms to call __musb_giveback() that calls urb->callback() internally. > Under specific circumstances setting MUSB_RXCSR_H_REQPKT in subsequent > musb_start_urb() for the next urb will be too late to produce physical > IN packet. Since auto req is not used by this module the exchange > would be as the following: > > [ ] 7.220456 d= 0.000997 [182 + 3.667] [ 3] IN : 4.5 > [ T ] 7.220459 d= 0.000003 [182 + 7.000] [800] DATA0: [skipped] > [ ] 7.222456 d= 0.001997 [184 + 3.667] [ 3] IN : 4.5 > [ ] 7.222459 d= 0.000003 [184 + 7.000] [ 3] DATA0: 00 00 > > It is known that missed IN in isochronous mode makes some > perepherial broken. For instance, pwc-driven or uvc-driven > web cameras. > In order to workaround this issue we postpone calling > urb->callback() after setting MUSB_RXCSR_H_REQPKT for the > next urb if there is the next urb pending in queue. > > [1] https://www.spinics.net/lists/linux-usb/msg145747.html > > Fixes: f551e1352983 ("Revert "usb: musb: musb_host: Enable HCD_BH flag to handle urb return in bottom half"") > Signed-off-by: Matwey V. Kornilov <matwey@xxxxxxxxxx> > --- > drivers/usb/musb/musb_host.c | 54 +++++++++++++++++++++++++++++++++++++------- > 1 file changed, 46 insertions(+), 8 deletions(-) > > diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c > index ac3a4952abb4..b590c2555dab 100644 > --- a/drivers/usb/musb/musb_host.c > +++ b/drivers/usb/musb/musb_host.c > @@ -299,19 +299,24 @@ musb_start_urb(struct musb *musb, int is_in, struct musb_qh *qh) > } > } > > -/* Context: caller owns controller lock, IRQs are blocked */ > -static void musb_giveback(struct musb *musb, struct urb *urb, int status) > +static void __musb_giveback(struct musb *musb, struct urb *urb, int status) > __releases(musb->lock) > __acquires(musb->lock) > { > - trace_musb_urb_gb(musb, urb); > - > - usb_hcd_unlink_urb_from_ep(musb->hcd, urb); > spin_unlock(&musb->lock); > usb_hcd_giveback_urb(musb->hcd, urb, status); > spin_lock(&musb->lock); > } > > +/* Context: caller owns controller lock, IRQs are blocked */ > +static void musb_giveback(struct musb *musb, struct urb *urb, int status) > +{ > + trace_musb_urb_gb(musb, urb); > + > + usb_hcd_unlink_urb_from_ep(musb->hcd, urb); > + __musb_giveback(musb, urb, status); > +} > + > /* For bulk/interrupt endpoints only */ > static inline void musb_save_toggle(struct musb_qh *qh, int is_in, > struct urb *urb) > @@ -346,6 +351,7 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb, > struct musb_hw_ep *ep = qh->hw_ep; > int ready = qh->is_ready; > int status; > + int postponed_giveback = 0; > > status = (urb->status == -EINPROGRESS) ? 0 : urb->status; > > @@ -361,9 +367,35 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb, > break; > } > > - qh->is_ready = 0; > - musb_giveback(musb, urb, status); > - qh->is_ready = ready; > + usb_hcd_unlink_urb_from_ep(musb->hcd, urb); > + > + /* It may take about 0.5 ms to call __musb_giveback() that > + * calls urb->callback() internally. Under specific circumstances > + * setting MUSB_RXCSR_H_REQPKT in subsequent musb_start_urb() for the > + * next urb will be too late to produce physical IN packet. Since > + * auto req is not used by this module the exchange would be as the > + * following: > + * > + * [ ] 7.220456 d= 0.000997 [182 + 3.667] [ 3] IN : 4.5 > + * [ T ] 7.220459 d= 0.000003 [182 + 7.000] [800] DATA0: [skipped] > + * [ ] 7.222456 d= 0.001997 [184 + 3.667] [ 3] IN : 4.5 > + * [ ] 7.222459 d= 0.000003 [184 + 7.000] [ 3] DATA0: 00 00 > + * > + * It is known that missed IN in isochronous mode makes some > + * perepherial broken. For instance, pwc-driven or uvc-driven > + * web cameras. > + * In order to workaround this issue we postpone calling > + * urb->callback() after setting MUSB_RXCSR_H_REQPKT for the > + * next urb if there is the next urb pending in queue. > + */ > + if (is_in && qh->type == USB_ENDPOINT_XFER_ISOC > + && !list_empty(&qh->hep->urb_list)) { > + postponed_giveback = 1; > + } else { > + qh->is_ready = 0; > + __musb_giveback(musb, urb, status); > + qh->is_ready = ready; > + } > > /* reclaim resources (and bandwidth) ASAP; deschedule it, and > * invalidate qh as soon as list_empty(&hep->urb_list) > @@ -428,6 +460,12 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb, > hw_ep->epnum, is_in ? 'R' : 'T', next_urb(qh)); > musb_start_urb(musb, is_in, qh); > } > + > + if (postponed_giveback) { > + qh->is_ready = 0; > + __musb_giveback(musb, urb, status); > + qh->is_ready = ready; > + } > } > > static u16 musb_h_flush_rxfifo(struct musb_hw_ep *hw_ep, u16 csr) > -- > 2.12.0 > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119234, Moscow, Universitetsky pr-k 13, +7 (495) 9392382 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
