diff options
| -rw-r--r-- | drivers/media/usb/uvc/uvc_video.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index d6ca383f643e..af25b9f1b53f 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -768,10 +768,10 @@ void uvc_video_clock_update(struct uvc_streaming *stream, spin_lock_irqsave(&clock->lock, flags); - if (clock->count < clock->size) + if (clock->count < 2) goto done; - first = &clock->samples[clock->head]; + first = &clock->samples[(clock->head - clock->count + clock->size) % clock->size]; last = &clock->samples[(clock->head - 1 + clock->size) % clock->size]; /* First step, PTS to SOF conversion. */ @@ -786,6 +786,18 @@ void uvc_video_clock_update(struct uvc_streaming *stream, if (y2 < y1) y2 += 2048 << 16; + /* + * Have at least 1/4 of a second of timestamps before we + * try to do any calculation. Otherwise we do not have enough + * precision. This value was determined by running Android CTS + * on different devices. + * + * dev_sof runs at 1KHz, and we have a fixed point precision of + * 16 bits. + */ + if ((y2 - y1) < ((1000 / 4) << 16)) + goto done; + y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2 - (u64)y2 * (u64)x1; y = div_u64(y, x2 - x1); |