Hi Ricardo,
Thank you for the patch.
On Wed, Aug 18, 2021 at 10:35:02PM +0200, Ricardo Ribalda wrote:
> The hardware timestamping code has the assumption than the device_sof
> and the host_sof run at the same frequency (1 KHz).
>
> Unfortunately, this is not the case for all the hardware. Add a quirk to
> support such hardware.
>
> Note on how to identify such hardware:
> When running with "yavta -c /dev/videoX" Look for periodic jumps of the
> fps. Eg:
>
> 30 (6) [-] none 30 614400 B 21.245557 21.395214 34.133 fps ts mono/SoE
> 31 (7) [-] none 31 614400 B 21.275327 21.427246 33.591 fps ts mono/SoE
> 32 (0) [-] none 32 614400 B 21.304739 21.459256 34.000 fps ts mono/SoE
> 33 (1) [-] none 33 614400 B 21.334324 21.495274 33.801 fps ts mono/SoE
> 34 (2) [-] none 34 614400 B 21.529237 21.527297 5.130 fps ts mono/SoE
> 35 (3) [-] none 35 614400 B 21.649416 21.559306 8.321 fps ts mono/SoE
> 36 (4) [-] none 36 614400 B 21.678789 21.595320 34.045 fps ts mono/SoE
> ...
> 99 (3) [-] none 99 614400 B 23.542226 23.696352 33.541 fps ts mono/SoE
> 100 (4) [-] none 100 614400 B 23.571578 23.728404 34.069 fps ts mono/SoE
> 101 (5) [-] none 101 614400 B 23.601425 23.760420 33.504 fps ts mono/SoE
> 102 (6) [-] none 102 614400 B 23.798324 23.796428 5.079 fps ts mono/SoE
> 103 (7) [-] none 103 614400 B 23.916271 23.828450 8.478 fps ts mono/SoE
> 104 (0) [-] none 104 614400 B 23.945720 23.860479 33.957 fps ts mono/SoE
>
> They happen because the delta_sof calculated at
> uvc_video_clock_host_sof(), wraps periodically, as both clocks drift.
That looks plain wrong. First of all, the whole purpose of the SOF clock
is to have a shared clock between the host and the device. It makes no
sense for a device to have a free-running "SOF" clock. Given the log
above, the issue occurs so quickly that it doesn't seem to be a mere
drift of a free running clock. Could you investigate this more carefully
?
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> v2: Fix typo in frequency
>
> drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> drivers/media/usb/uvc/uvc_video.c | 11 +++++++++--
> drivers/media/usb/uvc/uvcvideo.h | 2 ++
> 3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 9a791d8ef200..d1e6cba10b15 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2771,6 +2771,15 @@ static const struct usb_device_id uvc_ids[] = {
> .bInterfaceSubClass = 1,
> .bInterfaceProtocol = 0,
> .driver_info = UVC_INFO_QUIRK(UVC_QUIRK_RESTORE_CTRLS_ON_INIT) },
> + /* Logitech HD Pro Webcam C922 */
> + { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
> + | USB_DEVICE_ID_MATCH_INT_INFO,
> + .idVendor = 0x046d,
> + .idProduct = 0x085c,
> + .bInterfaceClass = USB_CLASS_VIDEO,
> + .bInterfaceSubClass = 1,
> + .bInterfaceProtocol = 0,
> + .driver_info = UVC_INFO_QUIRK(UVC_QUIRK_INVALID_DEVICE_SOF) },
> /* Chicony CNF7129 (Asus EEE 100HE) */
> { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
> | USB_DEVICE_ID_MATCH_INT_INFO,
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 6d0e474671a2..760ab015cf9c 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -518,13 +518,20 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> /* To limit the amount of data, drop SCRs with an SOF identical to the
> * previous one.
> */
> - dev_sof = get_unaligned_le16(&data[header_size - 2]);
> + if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> + dev_sof = usb_get_current_frame_number(stream->dev->udev);
> + else
> + dev_sof = get_unaligned_le16(&data[header_size - 2]);
> +
> if (dev_sof == stream->clock.last_sof)
> return;
>
> stream->clock.last_sof = dev_sof;
>
> - host_sof = usb_get_current_frame_number(stream->dev->udev);
> + if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
> + host_sof = dev_sof;
> + else
> + host_sof = usb_get_current_frame_number(stream->dev->udev);
> time = uvc_video_get_time();
>
> /* The UVC specification allows device implementations that can't obtain
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index cce5e38133cd..89d909661915 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -209,6 +209,8 @@
> #define UVC_QUIRK_RESTORE_CTRLS_ON_INIT 0x00000400
> #define UVC_QUIRK_FORCE_Y8 0x00000800
> #define UVC_QUIRK_FORCE_BPP 0x00001000
> +#define UVC_QUIRK_INVALID_DEVICE_SOF 0x00002000
> +
>
> /* Format flags */
> #define UVC_FMT_FLAG_COMPRESSED 0x00000001
--
Regards,
Laurent Pinchart
