diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index bb3ee942e570..d2e61be35bf6 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -494,6 +494,13 @@ static int uvc_commit_video(struct uvc_streaming *stream, * Clocks and timestamps */ +/* + * The accuracy of the hardware timestamping depends on having enough data to + * interpolate between the different clock domains. This value is sof cycles, + * this is, milliseconds. + */ +#define UVC_MIN_HW_TIMESTAMP_DIFF 100 + static inline ktime_t uvc_video_get_time(void) { if (uvc_clock_param == CLOCK_MONOTONIC) @@ -843,13 +850,13 @@ void uvc_video_clock_update(struct uvc_streaming *stream, * buffer, but RAM is expensive these days, specially the infinitely * big. * - * The value of 1/4th of a second was determined by running Android's - * CTS on different devices. + * The value of UVC_MIN_HW_TIMESTAMP_DIFF was determined by running + * Android's CTS on different devices. * - * dev_sof runs at 1KHz, and we have a fixed point precision of - * 16 bits. + * y1 and y2 are dev_sof with a fixed point precision of 16 bits. */ - if (clock->size != clock->count && (y2 - y1) < ((1000 / 4) << 16)) + if (clock->size != clock->count && + (y2 - y1) < (UVC_MIN_HW_TIMESTAMP_DIFF << 16)) goto done; y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2