lkml.org 
[lkml]   [2023]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH v5 2/5] media: uvcvideo: Quirk for invalid dev_sof in Logitech C922
    Logitech C922 internal SOF does not increases at a stable rate of 1kHz.
    This causes that the device_sof and the host_sof run at different rates,
    breaking the clock domain conversion algorithm. 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

    Instead of disabling completely the hardware timestamping for such
    hardware we take the assumption that the packet handling jitter is
    under 2ms and use the host_sof as dev_sof.

    We can think of the UVC hardware clock as a system with a coarse clock
    (the SOF) and a fine clock (the PTS). The coarse clock can be replaced
    with a clock on the same frequency, if the jitter of such clock is
    smaller than its sampling rate. That way we can save some of the
    precision of the fine clock.

    To probe this point we have run three experiments on the Logitech C922.
    On that experiment we run the camera at 33fps and we analyse the
    difference in msec between a frame and its predecessor. If we display
    the histogram of that value, a thinner histogram will mean a better
    meassurement. The results for:
    - original hw timestamp: https://ibb.co/D1HJJ4x
    - pure software timestamp: https://ibb.co/QC9MgVK
    - modified hw timestamp: https://ibb.co/8s9dBdk

    This bug in the camera firmware has been confirmed by the vendor.

    lsusb -v

    Bus 001 Device 044: ID 046d:085c Logitech, Inc. C922 Pro Stream Webcam
    Device Descriptor:
    bLength 18
    bDescriptorType 1
    bcdUSB 2.00
    bDeviceClass 239 Miscellaneous Device
    bDeviceSubClass 2
    bDeviceProtocol 1 Interface Association
    bMaxPacketSize0 64
    idVendor 0x046d Logitech, Inc.
    idProduct 0x085c C922 Pro Stream Webcam
    bcdDevice 0.16
    iManufacturer 0
    iProduct 2 C922 Pro Stream Webcam
    iSerial 1 80B912DF
    bNumConfigurations 1

    Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
    ---
    drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
    drivers/media/usb/uvc/uvc_video.c | 8 +++++++-
    drivers/media/usb/uvc/uvcvideo.h | 1 +
    3 files changed, 17 insertions(+), 1 deletion(-)

    diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
    index c1e3c1fab976..eae88d0f420e 100644
    --- a/drivers/media/usb/uvc/uvc_driver.c
    +++ b/drivers/media/usb/uvc/uvc_driver.c
    @@ -2569,6 +2569,15 @@ 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 488c58bc9919..f4470f6df45c 100644
    --- a/drivers/media/usb/uvc/uvc_video.c
    +++ b/drivers/media/usb/uvc/uvc_video.c
    @@ -541,7 +541,13 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,

    stream->clock.last_sof = dev_sof;

    - host_sof = usb_get_current_frame_number(stream->dev->udev);
    + /*
    + * On some devices, like the Logitech C922, the device SOF does not run
    + * at a stable rate of 1kHz. For those devices use the host SOF instead.
    + */
    + if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
    + dev_sof = usb_get_current_frame_number(stream->dev->udev);
    +
    time = uvc_video_get_time();

    /*
    diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
    index 22656755a801..699c33bc24ed 100644
    --- a/drivers/media/usb/uvc/uvcvideo.h
    +++ b/drivers/media/usb/uvc/uvcvideo.h
    @@ -73,6 +73,7 @@
    #define UVC_QUIRK_FORCE_Y8 0x00000800
    #define UVC_QUIRK_FORCE_BPP 0x00001000
    #define UVC_QUIRK_WAKE_AUTOSUSPEND 0x00002000
    +#define UVC_QUIRK_INVALID_DEVICE_SOF 0x00004000

    /* Format flags */
    #define UVC_FMT_FLAG_COMPRESSED 0x00000001
    --
    2.39.0.314.g84b9a713c41-goog-b4-0.11.0-dev-696ae

    \
     
     \ /
      Last update: 2023-03-26 23:39    [W:4.335 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site