linux-kernel - Re: [PATCH] usb: dwc3: gadget: don't dequeue requests on already disabled endpoints

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Message-ID: <20200329190244.GK27849@pengutronix.de>
Date:   Sun, 29 Mar 2020 21:02:44 +0200
From:   Michael Grzeschik <mgr@...gutronix.de>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     lars@...afoo.de, alexandru.Ardelean@...log.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, bigeasy@...utronix.de,
        m.olbrich@...gutronix.de, kernel@...gutronix.de
Subject: Re: [PATCH] usb: dwc3: gadget: don't dequeue requests on already
 disabled endpoints

On Sat, Mar 28, 2020 at 10:27:49AM +0200, Felipe Balbi wrote:
> 
> Hi,
> 
> Michael Grzeschik <m.grzeschik@...gutronix.de> writes:
> > dwc3_gadget_ep_disable gets called before the last request gets
> > dequeued.
> >
> > In __dwc3_gadget_ep_disable all started, pending and cancelled
> > lists for this endpoint will call dwc3_gadget_giveback in
> > dwc3_remove_requests.
> >
> > After that no list containing the afterwards dequed request,
> > therefor it is not necessary to run the dequeue routine.
> >
> > Signed-off-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
> > ---
> > @Lars-Peter Clausen:
> >
> > This patch addresses the case that not queued requests get dequeued.
> > The only case that this happens seems on disabling the gadget.
> >
> >  drivers/usb/dwc3/gadget.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 9a6f741d1db0dc..5d4fa8d6c93e49 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -1609,6 +1609,9 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
> >  
> >  	trace_dwc3_ep_dequeue(req);
> >  
> > +	if (!(dep->flags & DWC3_EP_ENABLED))
> > +		return 0;
> 
> which driver is trying to call dequeue after the endpoint is disabled?
> Got some tracepoints of the problem happening?

I see the case when using uvc-gadget.

Look into uvc_v4l2_release in uvc_v4l2.c:

uvc_function_disconnect
   composite_disconnect
      reset_config
         uvc_function_disable->usb_ep_disable

uvcg_video_enable
   usb_ep_dequeue
      dwc3_gadget_ep_dequeue

Regards,
Michael

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