From: Michael Grzeschik <mgr@pengutronix.de>
To: Felipe Balbi <balbi@kernel.org>
Cc: lars@metafoo.de, alexandru.Ardelean@analog.com,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
gregkh@linuxfoundation.org, bigeasy@linutronix.de,
m.olbrich@pengutronix.de, kernel@pengutronix.de
Subject: Re: [PATCH] usb: dwc3: gadget: don't dequeue requests on already disabled endpoints
Date: Mon, 30 Mar 2020 10:25:48 +0200 [thread overview]
Message-ID: <20200330082548.GL27849@pengutronix.de> (raw)
In-Reply-To: <87sghq2tum.fsf@kernel.org>
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On Mon, Mar 30, 2020 at 10:18:57AM +0300, Felipe Balbi wrote:
>
> Hi,
>
> Michael Grzeschik <mgr@pengutronix.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@pengutronix.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
>
> Oh, I see what you mean. We get a disconnect, which disables the
> endpoints, which forces all requests to be dequeued. Now I remember why
> this exists: we giveback the requests from disconnect because not all
> gadget drivers will call usb_ep_dequeue() if simply told about the
> disconnect. Then UDC drivers have to be a little more careful and make
> sure that all requests are givenback.
>
> In any case, why is it a problem to call usb_ep_dequeue()? Is it only
> because of that dev_err()? We could just remove that message,
> really.
In my case, it is not a problem removing the dev_err. The ep_dequeue
will only be called once for each request at the stream end. I don't
know about the case Lars has mentioned.
If we have to search all lists for the request every n times while in
traffic, only to find out that it was not enqueued, I think it would be
worth it to keep the dev_err and let these cases trigger so we have an
option to find and avoid/fix these.
> Eventually, I want to move more of this logic into UDC core so
> udc drivers can be simplified. For that work, though, first we would
> have to add a "generic" struct usb_ep_hw implementation and manage list
> of requests as part of UDC core as well.
I don't know about the cases you plan to abstract but it sounds
like a good idea to get some gadget logic out of the drivers.
Thanks,
Michael
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next prev parent reply other threads:[~2020-03-30 8:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 14:45 [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully Alexandru Ardelean
2019-11-12 14:41 ` Michael Olbrich
2020-01-16 11:12 ` Ardelean, Alexandru
2020-01-16 13:05 ` Felipe Balbi
2020-01-16 13:24 ` [PATCH][RESEND] " Alexandru Ardelean
2020-01-30 12:02 ` Felipe Balbi
2020-03-10 13:22 ` Ardelean, Alexandru
2020-03-10 13:45 ` Lars-Peter Clausen
2020-03-10 14:07 ` Lars-Peter Clausen
2020-03-27 8:43 ` [PATCH] usb: dwc3: gadget: don't dequeue requests on already disabled endpoints Michael Grzeschik
2020-03-27 8:53 ` Sergei Shtylyov
2020-03-27 11:15 ` Andy Shevchenko
2020-03-27 9:14 ` Lars-Peter Clausen
2020-03-27 10:43 ` Michael Grzeschik
2020-03-27 10:55 ` Lars-Peter Clausen
2020-03-28 8:27 ` Felipe Balbi
2020-03-29 19:02 ` Michael Grzeschik
2020-03-30 7:18 ` Felipe Balbi
2020-03-30 8:25 ` Michael Grzeschik [this message]
2020-03-30 10:06 ` Felipe Balbi
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