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Date:   Tue, 6 Dec 2022 00:55:00 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Ricardo Ribalda <ribalda@chromium.org>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        Yunke Cao <yunkec@chromium.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: Re: [PATCH v3] media: uvcvideo: Recover stalled ElGato devices
Message-ID: <Y452xN7BzTdYIEIM@pendragon.ideasonboard.com>
References: <20220920-resend-elgato-v3-0-57668054127f@chromium.org>
 <Y45zApHY34WocyeM@pendragon.ideasonboard.com>
 <CANiDSCvtUmGzxOZLPXP5bxg5HRDGkn_=8tGx8qqa6R_ssJUpww@mail.gmail.com>
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Hi Ricardo,

On Mon, Dec 05, 2022 at 11:45:43PM +0100, Ricardo Ribalda wrote:
> On Mon, 5 Dec 2022 at 23:39, Laurent Pinchart wrote:
> > On Mon, Dec 05, 2022 at 01:53:01PM +0100, Ricardo Ribalda wrote:
> > > Elgato Cam Link 4k can be in a stalled state if the resolution of
> > > the external source has changed while the firmware initializes.
> > > Once in this state, the device is useless until it receives a
> > > USB reset. It has even been observed that the stalled state will
> > > continue even after unplugging the device.
> >
> > Why, ô, why :'-(
> >
> > > lsusb -v
> > >
> > > Bus 002 Device 002: ID 0fd9:0066 Elgato Systems GmbH Cam Link 4K
> > > Device Descriptor:
> > >   bLength                18
> > >   bDescriptorType         1
> > >   bcdUSB               3.00
> > >   bDeviceClass          239 Miscellaneous Device
> > >   bDeviceSubClass         2
> > >   bDeviceProtocol         1 Interface Association
> > >   bMaxPacketSize0         9
> > >   idVendor           0x0fd9 Elgato Systems GmbH
> > >   idProduct          0x0066
> > >   bcdDevice            0.00
> > >   iManufacturer           1 Elgato
> > >   iProduct                2 Cam Link 4K
> > >   iSerial                 4 0005AC52FE000
> > >   bNumConfigurations      1
> > >
> > > Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > > Recover stalled ElGato devices
> > >
> > > Just a resend of this hw fix.
> > >
> > > To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > To: Mauro Carvalho Chehab <mchehab@kernel.org>
> > > Cc: linux-media@vger.kernel.org
> > > Cc: linux-kernel@vger.kernel.org
> > > Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> > > Cc: Yunke Cao <yunkec@chromium.org>
> > > ---
> > > Changes in v3:
> > > - Add Reviewed-by: Sergey
> > > - Improve identation (Thanks Sergey!)
> > > - Link to v2: https://lore.kernel.org/r/20220920-resend-elgato-v2-0-06b48b3b486a@chromium.org
> > >
> > > Changes in v2:
> > > - Remove info from lsusb
> > > - Link to v1: https://lore.kernel.org/r/20220920-resend-elgato-v1-0-8672a2380e3d@chromium.org
> > > ---
> > >  drivers/media/usb/uvc/uvc_video.c | 23 +++++++++++++++++++----
> > >  1 file changed, 19 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > index 170a008f4006..a8323cf0e9f9 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -129,12 +129,13 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
> > >       return -EPIPE;
> > >  }
> > >
> > > +static const struct usb_device_id elgato_cam_link_4k = {
> > > +     USB_DEVICE(0x0fd9, 0x0066)
> > > +};
> > > +
> > >  static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
> > >       struct uvc_streaming_control *ctrl)
> > >  {
> > > -     static const struct usb_device_id elgato_cam_link_4k = {
> > > -             USB_DEVICE(0x0fd9, 0x0066)
> > > -     };
> > >       struct uvc_format *format = NULL;
> > >       struct uvc_frame *frame = NULL;
> > >       unsigned int i;
> > > @@ -297,7 +298,7 @@ static int uvc_get_video_ctrl(struct uvc_streaming *stream,
> > >               dev_err(&stream->intf->dev,
> > >                       "Failed to query (%u) UVC %s control : %d (exp. %u).\n",
> > >                       query, probe ? "probe" : "commit", ret, size);
> > > -             ret = -EIO;
> > > +             ret = (ret == -EPROTO) ? -EPROTO : -EIO;
> >
> > This will change the error returned by VIDIOC_S_FMT and VIDIOC_TRY_FMT,
> > but I don't think that will cause issues.
> >
> > >               goto out;
> > >       }
> > >
> > > @@ -2121,6 +2122,20 @@ int uvc_video_init(struct uvc_streaming *stream)
> > >        * request on the probe control, as required by the UVC specification.
> > >        */
> > >       ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR);
> > > +
> > > +     /*
> > > +      * Elgato Cam Link 4k can be in a stalled state if the resolution of
> > > +      * the external source has changed while the firmware initializes.
> > > +      * Once in this state, the device is useless until it receives a
> > > +      * USB reset. It has even been observed that the stalled state will
> > > +      * continue even after unplugging the device.
> > > +      */
> > > +     if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) &&
> > > +         (ret == -EPROTO)) {
> >
> > I'd swap the tests, as the second one is cheaper. You also don't need
> > the inner parentheses.
> >
> > > +             usb_reset_device(stream->dev->udev);
> > > +             dev_err(&stream->intf->dev, "Restarting Elgato Cam Link 4K\n");
> >
> > I would also swap those two lines, if an error occurs when resetting the
> > device, it's good to have the "restarting" message printed first.
> >
> > If I understand this correctly, probe will still fail, and the user will
> > have to unplug and replug the device to fix this, right ? If so I'd
> > expand the error message, maybe something along those lines:
> 
> I kind of recall that it was not needed to replug the device. Will
> test on real hardware to confirm.

How does it get reprobed then ? By unloading and reloading the driver
(or unbinding and rebinding the device through sysfs) ?

> >                 dev_err(&stream->intf->dev, "Elgato Cam Link 4K firmware crash detected\n");
> >                 dev_err(&stream->intf->dev, "Resetting the device, unplug and replug to recover\n");
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > > +     }
> > > +
> > >       if (ret < 0)
> > >               return ret;
> > >
> > >
> > > ---
> > > base-commit: 521a547ced6477c54b4b0cc206000406c221b4d6
> > > change-id: 20220920-resend-elgato-a845482bdd02

-- 
Regards,

Laurent Pinchart