Re: [PATCH] usb: dwc3: Check for IOC/LST bit in both event->status and TRB->ctrl fields

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On Tue, Jul 23, 2019 at 1:27 PM John Stultz <john.stultz@xxxxxxxxxx> wrote:
>
> From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xxxxxxxxxx>
>
> The present 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 makes the remaining
> TRBs left unhandled.
> To aviod this, changed the code to check for IOC/LST bits in both
> event->status & TRB->ctrl. This patch does the same.
>
> At a practical level, this patch resolves USB transfer stalls seen
> with adb on dwc3 based Android devices after functionfs gadget
> added scatter-gather support around v4.20.
>
> Cc: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> Cc: Fei Yang <fei.yang@xxxxxxxxx>
> Cc: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
> Cc: Tejas Joglekar <tejas.joglekar@xxxxxxxxxxxx>
> Cc: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
> 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, added note to commit log]
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
> Just wanted to send this out so we're all looking at the same thing.
> Not sure if its correct, but it seems to solve the adb stalls I've
> been seeing for awhile.

Felipe: Any thoughts on this patch?

thanks
-john



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