On Tue, 17 Jan 2023 at 15:18, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Ricardo,
>
> On Tue, Jan 17, 2023 at 03:08:07PM +0100, Ricardo Ribalda wrote:
> > On Sun, 15 Jan 2023 at 22:17, Laurent Pinchart wrote:
> > >
> > > From: Ai Chao <aichao@xxxxxxxxxx>
> > >
> > > The Alcor Corp. Slave camera (1b17:6684 and 2017:0011) returns a wrong
> > > dwMaxPayloadTransferSize value for compressed formats. Valid values are
> > > typically up to 3072 bytes per interval (for high-speed, high-bandwidth
> > > devices), and those faulty devices request 2752512 bytes per interval.
> > > This is a firmware issue, but the manufacturer cannot provide a fixed
> > > firmware.
> > >
> > > Fix this by checking the dwMaxPayloadTransferSize field, and hardcoding
> > > a value of 1024 if it exceeds 3072 for compressed formats transferred
> > > over isochronous endpoints. While at it, document the other quirk that
> > > handles a bandwidth issue for uncompressed formats.
> > >
> > > Signed-off-by: Ai Chao <aichao@xxxxxxxxxx>
> > > ---
> > > I have dropped the Reviewed-by tags as the patch has changed
> > > significantly.
> > >
> > > Ricardo, do you know if the 3072 bytes limit is fine with super-speed
> > > devices, or does it need to be increased ?
> > Tried with a couple of super-speed:
> >
> > If I print: ctrl->dwMaxPayloadTransferSize
> >
> > [ 237.269972] drivers/media/usb/uvc/uvc_video.c:239 bw 3072
> > [ 175.761041] drivers/media/usb/uvc/uvc_video.c:239 bw 3060
> >
> > Format YUYV stall when I cap the dwMaxPayloadTransferSize to 1024, but
> > works fine with MJPEG and even NV12
> >
> > How does it sound to cap dwMaxPayloadTransferSize to 3072 for
> > superspeed and 1024 for high speed?
>
> Won't you still run out of bandwidth when using multiple cameras
> concurrently ? Is it the interval that is shorter with SS, or the
> maximum bytes per interval that is larger ?
>From UVC:
In the context of the USB Video Class, a Payload Transfer is a unit of
data transfer common to bulk and isochronous endpoints. Each Payload
Transfer includes a Payload Header followed by Payload Data. For
isochronous endpoints, a Payload Transfer is contained in the data
transmitted during a single (micro) frame: up to 1023 bytes for a
fullspeed endpoint; up to 1024 bytes for a high-speed endpoint; and up
to
3072 bytes for a high-speed/high-bandwidth endpoint. For bulk
endpoints, a Payload Transfer is contained in the data transmitted in a
single bulk transfer (which may consist of multiple bulk data
transactions).
What are the chances of having multiple broken cameras on the single
device VS having a single broken camera?
Actually, now that I think about this, maybe we should go back to the
previous version where we quirk based on vid:pid, hoping that this bug
is just one of.
Maybe we can use this logic to something like
if payloadTransfer > standard:
print(Blame vendor, contact mailing list)
:)
>
> > > ---
> > > drivers/media/usb/uvc/uvc_video.c | 31 +++++++++++++++++++++++++++++++
> > > 1 file changed, 31 insertions(+)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > index d4b023d4de7c..c6351d3b24cf 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -200,6 +200,20 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
> > > if ((ctrl->dwMaxPayloadTransferSize & 0xffff0000) == 0xffff0000)
> > > ctrl->dwMaxPayloadTransferSize &= ~0xffff0000;
> > >
> > > + /*
> > > + * Many devices report an incorrect dwMaxPayloadTransferSize value. The
> > > + * most common issue is devices requesting the maximum possible USB
> > > + * bandwidth (3072 bytes per interval for high-speed, high-bandwidth
> > > + * isochronous endpoints) while they actually require less, preventing
> > > + * multiple cameras from being used at the same time due to bandwidth
> > > + * overallocation.
> > > + *
> > > + * For those devices, replace the dwMaxPayloadTransferSize value based
> > > + * on an estimation calculated from the frame format and size. This is
> > > + * only possible for uncompressed formats, as not enough information is
> > > + * available to reliably estimate the bandwidth requirements for
> > > + * compressed formats.
> > > + */
> > > if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) &&
> > > stream->dev->quirks & UVC_QUIRK_FIX_BANDWIDTH &&
> > > stream->intf->num_altsetting > 1) {
> > > @@ -236,6 +250,23 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
> > >
> > > ctrl->dwMaxPayloadTransferSize = bandwidth;
> > > }
> > > +
> > > + /*
> > > + * Another issue is with devices that report a transfer size that
> > > + * greatly exceeds the maximum supported by any existing USB version
> > > + * for isochronous transfers. For instance, the "Slave camera" devices
> > > + * from Alcor Corp. (2017:0011 and 1b17:66B8) request 2752512 bytes per
> > > + * interval.
> > > + *
> > > + * For uncompressed formats, this can be addressed by the FIX_BANDWIDTH
> > > + * quirk, but for compressed format we can't meaningfully estimate the
> > > + * required bandwidth. Just hardcode it to 1024 bytes per interval,
> > > + * which should be large enough for compressed formats.
> > > + */
> > > + if ((format->flags & UVC_FMT_FLAG_COMPRESSED) &&
> > > + ctrl->dwMaxPayloadTransferSize > 3072 &&
> > > + stream->intf->num_altsetting > 1)
> > > + ctrl->dwMaxPayloadTransferSize = 1024;
> > > }
> > >
> > > static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
>
> --
> Regards,
>
> Laurent Pinchart
--
Ricardo Ribalda
