Re: [PATCH v2 2/2] usb: dwc2: fix isoc split in transfer with no data

[wlf]

Dear Doug,


å 2018å05æ02æ 13:02, Doug Anderson åé:
> Hi,
>
> On Tue, May 1, 2018 at 8:04 PM, William Wu <william.wu@xxxxxxxxxxxxxx> wrote:
> > If isoc split in transfer with no data (the length of DATA0
> > packet is zero), we can't simply return immediately. Because
> > the DATA0 can be the first transaction or the second transaction
> > for the isoc split in transaction. If the DATA0 packet with no
> > data is in the first transaction, we can return immediately.
> > But if the DATA0 packet with no data is in the second transaction
> > of isoc split in transaction sequence, we need to increase the
> > qtd->isoc_frame_index and giveback urb to device driver if needed,
> > otherwise, the MDATA packet will be lost.
> >
> > A typical test case is that connect the dwc2 controller with an
> > usb hs Hub (GL852G-12), and plug an usb fs audio device (Plantronics
> > headset) into the downstream port of Hub. Then use the usb mic
> > to record, we can find noise when playback.
> >
> > In the case, the isoc split in transaction sequence like this:
> >
> > - SSPLIT IN transaction
> > - CSPLIT IN transaction
> >    - MDATA packet (176 bytes)
> > - CSPLIT IN transaction
> >    - DATA0 packet (0 byte)
> >
> > This patch use both the length of DATA0 and qtd->isoc_split_offset
> > to check if the DATA0 is in the second transaction.
> >
> > Signed-off-by: William Wu <william.wu@xxxxxxxxxxxxxx>
> > ---
> > Changes in v2:
> > - Modify the commit message
> >
> >   drivers/usb/dwc2/hcd_intr.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
> > index 5e2378f..479f628 100644
> > --- a/drivers/usb/dwc2/hcd_intr.c
> > +++ b/drivers/usb/dwc2/hcd_intr.c
> > @@ -930,7 +930,7 @@ static int dwc2_xfercomp_isoc_split_in(struct dwc2_hsotg *hsotg,
> >          frame_desc = &qtd->urb->iso_descs[qtd->isoc_frame_index];
> >          len = dwc2_get_actual_xfer_length(hsotg, chan, chnum, qtd,
> >                                            DWC2_HC_XFER_COMPLETE, NULL);
> > -       if (!len) {
> > +       if (!len && !qtd->isoc_split_offset) {
> >                  qtd->complete_split = 0;
> >                  qtd->isoc_split_offset = 0;
> >                  return 0;
> I don't think my USB-fu is strong enough to do a real review of this
> patch, but one small nitpick is that you can remove
> "qtd->isoc_split_offset = 0" in the if test now.  AKA:
>
> if (!len && !qtd->isoc_split_offset) {
>    qtd->complete_split = 0;
>    return 0;
> }
Yes, good idea! I will fix it in next patch. Thank you!
> ...since you only enter the "if" test now when isoc_split_offset is
> already 0...  Hopefully John Youn will have some time to comment on
> this patch with more real USB knowledge...
>
>
> -Doug
Best regards,
ÂÂÂÂ wulf
>