On Tue, Jan 28, 2020 at 5:23 AM Felipe Balbi <balbi@xxxxxxxxxx> wrote: > > > Hi, > > John Stultz <john.stultz@xxxxxxxxxx> writes: > > > From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xxxxxxxxxx> > > > > The current code in dwc3_gadget_ep_reclaim_completed_trb() will > > check for IOC/LST bit in the event->status and returns if > > IOC/LST bit is set. This logic doesn't work if multiple TRBs > > are queued per request and the IOC/LST bit is set on the last > > TRB of that request. > > > > Consider an example where a queued request has multiple queued > > TRBs and IOC/LST bit is set only for the last TRB. In this case, > > the core generates XferComplete/XferInProgress events only for > > the last TRB (since IOC/LST are set only for the last TRB). As > > per the logic in dwc3_gadget_ep_reclaim_completed_trb() > > event->status is checked for IOC/LST bit and returns on the > > first TRB. This leaves the remaining TRBs left unhandled. > > > > Similarly, if the gadget function enqueues an unaligned request > > with sglist already in it, it should fail the same way, since we > > will append another TRB to something that already uses more than > > one TRB. > > > > To aviod this, this patch changes the code to check for IOC/LST > > bits in TRB->ctrl instead. > > > > At a practical level, this patch resolves USB transfer stalls seen > > with adb on dwc3 based HiKey960 after functionfs gadget added > > scatter-gather support around v4.20. > > > > Cc: Felipe Balbi <balbi@xxxxxxxxxx> > > Cc: Yang Fei <fei.yang@xxxxxxxxx> > > Cc: Thinh Nguyen <thinhn@xxxxxxxxxxxx> > > Cc: Tejas Joglekar <tejas.joglekar@xxxxxxxxxxxx> > > Cc: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx> > > Cc: Jack Pham <jackp@xxxxxxxxxxxxxx> > > Cc: Todd Kjos <tkjos@xxxxxxxxxx> > > Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > > Cc: Linux USB List <linux-usb@xxxxxxxxxxxxxxx> > > Cc: stable <stable@xxxxxxxxxxxxxxx> > > Tested-by: Tejas Joglekar <tejas.joglekar@xxxxxxxxxxxx> > > Reviewed-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx> > > Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xxxxxxxxxx> > > [jstultz: forward ported to mainline, reworded commit log, reworked > > to only check trb->ctrl as suggested by Felipe] > > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> > > --- > > v2: > > * Rework to only check trb->ctrl as suggested by Felipe > > * Reword the commit message to include more of Felipe's assessment > > --- > > drivers/usb/dwc3/gadget.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c > > index 154f3f3e8cff..9a085eee1ae3 100644 > > --- a/drivers/usb/dwc3/gadget.c > > +++ b/drivers/usb/dwc3/gadget.c > > @@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep, > > if (event->status & DEPEVT_STATUS_SHORT && !chain) > > return 1; > > > > - if (event->status & DEPEVT_STATUS_IOC) > > + if ((trb->ctrl & DWC3_TRB_CTRL_IOC) || > > + (trb->ctrl & DWC3_TRB_CTRL_LST)) > > why the LST bit here? It wasn't there before. In fact, we never set LST > in dwc3 anymore :-) So, it was in the patch before, just on separate lines: https://lore.kernel.org/lkml/20200122222645.38805-2-john.stultz@xxxxxxxxxx/ - if (event->status & DEPEVT_STATUS_IOC) + if ((event->status & DEPEVT_STATUS_IOC) && + (trb->ctrl & DWC3_TRB_CTRL_IOC)) + return 1; + + if ((event->status & DEPEVT_STATUS_LST) && + (trb->ctrl & DWC3_TRB_CTRL_LST)) return 1; So I just merged the two checks into one line. But I'm ok to drop the CTRL_LST check if that really isn't used. Let me know and I'll rework and resend. thanks -john
