media: uvcvideo: Refactor clock circular buffer

Isolate all the changes related to the clock circular buffer to its own
function, that way we can make changes easier to the buffer logic.

Also simplify the lock, by removing the circular buffer clock handling
from uvc_video_clock_decode().

And now that we are at it, unify the API of the clock functions.
Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20240323-resend-hwtimestamp-v10-5-b08e590d97c7@chromium.orgSigned-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/media/usb/uvc/uvc_video.c

@@ -466,19 +466,28 @@ static inline ktime_t uvc_video_get_time(void)
 		return ktime_get_real();
 }
 
+static void uvc_video_clock_add_sample(struct uvc_clock *clock,
+				       const struct uvc_clock_sample *sample)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&clock->lock, flags);
+
+	clock->samples[clock->head] = *sample;
+	clock->head = (clock->head + 1) % clock->size;
+	clock->count = min(clock->count + 1, clock->size);
+
+	spin_unlock_irqrestore(&clock->lock, flags);
+}
+
 static void
 uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 		       const u8 *data, int len)
 {
-	struct uvc_clock_sample *sample;
+	struct uvc_clock_sample sample;
 	unsigned int header_size;
 	bool has_pts = false;
 	bool has_scr = false;
-	unsigned long flags;
-	ktime_t time;
-	u16 host_sof;
-	u16 dev_sof;
-	u32 dev_stc;
 
 	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
 	case UVC_STREAM_PTS | UVC_STREAM_SCR:
@@ -523,11 +532,11 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * all the data packets of the same frame contains the same SOF. In that
 	 * case only the first one will match the host_sof.
 	 */
-	dev_sof = get_unaligned_le16(&data[header_size - 2]);
-	if (dev_sof == stream->clock.last_sof)
+	sample.dev_sof = get_unaligned_le16(&data[header_size - 2]);
+	if (sample.dev_sof == stream->clock.last_sof)
 		return;
 
-	dev_stc = get_unaligned_le32(&data[header_size - 6]);
+	sample.dev_stc = get_unaligned_le32(&data[header_size - 6]);
 
 	/*
 	 * STC (Source Time Clock) is the clock used by the camera. The UVC 1.5
@@ -552,12 +561,10 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * suffer from this condition.
 	 */
 	if (buf && buf->bytesused == 0 && len == header_size &&
-	    dev_stc == 0 && dev_sof == 0)
+	    sample.dev_stc == 0 && sample.dev_sof == 0)
 		return;
 
-	stream->clock.last_sof = dev_sof;
-
-	host_sof = usb_get_current_frame_number(stream->dev->udev);
+	sample.host_sof = usb_get_current_frame_number(stream->dev->udev);
 
 	/*
 	 * On some devices, like the Logitech C922, the device SOF does not run
@@ -567,9 +574,9 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * host, but the exact reason hasn't been fully determined.
 	 */
 	if (stream->dev->quirks & UVC_QUIRK_INVALID_DEVICE_SOF)
-		dev_sof = host_sof;
+		sample.dev_sof = sample.host_sof;
 
-	time = uvc_video_get_time();
+	sample.host_time = uvc_video_get_time();
 
 	/*
 	 * The UVC specification allows device implementations that can't obtain
@@ -592,46 +599,28 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 	 * the 8 LSBs of the delta are kept.
 	 */
 	if (stream->clock.sof_offset == (u16)-1) {
-		u16 delta_sof = (host_sof - dev_sof) & 255;
+		u16 delta_sof = (sample.host_sof - sample.dev_sof) & 255;
 		if (delta_sof >= 10)
 			stream->clock.sof_offset = delta_sof;
 		else
 			stream->clock.sof_offset = 0;
 	}
 
-	dev_sof = (dev_sof + stream->clock.sof_offset) & 2047;
-
-	spin_lock_irqsave(&stream->clock.lock, flags);
-
-	sample = &stream->clock.samples[stream->clock.head];
-	sample->dev_stc = dev_stc;
-	sample->dev_sof = dev_sof;
-	sample->host_sof = host_sof;
-	sample->host_time = time;
-
-	/* Update the sliding window head and count. */
-	stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
-
-	if (stream->clock.count < stream->clock.size)
-		stream->clock.count++;
-
-	spin_unlock_irqrestore(&stream->clock.lock, flags);
+	sample.dev_sof = (sample.dev_sof + stream->clock.sof_offset) & 2047;
+	uvc_video_clock_add_sample(&stream->clock, &sample);
+	stream->clock.last_sof = sample.dev_sof;
 }
 
-static void uvc_video_clock_reset(struct uvc_streaming *stream)
+static void uvc_video_clock_reset(struct uvc_clock *clock)
 {
-	struct uvc_clock *clock = &stream->clock;
-
 	clock->head = 0;
 	clock->count = 0;
 	clock->last_sof = -1;
 	clock->sof_offset = -1;
 }
 
-static int uvc_video_clock_init(struct uvc_streaming *stream)
+static int uvc_video_clock_init(struct uvc_clock *clock)
 {
-	struct uvc_clock *clock = &stream->clock;
-
 	spin_lock_init(&clock->lock);
 	clock->size = 32;
 
@@ -640,15 +629,15 @@ static int uvc_video_clock_init(struct uvc_streaming *stream)
 	if (clock->samples == NULL)
 		return -ENOMEM;
 
-	uvc_video_clock_reset(stream);
+	uvc_video_clock_reset(clock);
 
 	return 0;
 }
 
-static void uvc_video_clock_cleanup(struct uvc_streaming *stream)
+static void uvc_video_clock_cleanup(struct uvc_clock *clock)
 {
-	kfree(stream->clock.samples);
-	stream->clock.samples = NULL;
+	kfree(clock->samples);
+	clock->samples = NULL;
 }
 
 /*
@@ -2123,7 +2112,7 @@ int uvc_video_resume(struct uvc_streaming *stream, int reset)
 
 	stream->frozen = 0;
 
-	uvc_video_clock_reset(stream);
+	uvc_video_clock_reset(&stream->clock);
 
 	if (!uvc_queue_streaming(&stream->queue))
 		return 0;
@@ -2272,7 +2261,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
 {
 	int ret;
 
-	ret = uvc_video_clock_init(stream);
+	ret = uvc_video_clock_init(&stream->clock);
 	if (ret < 0)
 		return ret;
 
@@ -2290,7 +2279,7 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
 error_video:
 	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
 error_commit:
-	uvc_video_clock_cleanup(stream);
+	uvc_video_clock_cleanup(&stream->clock);
 
 	return ret;
 }
@@ -2318,5 +2307,5 @@ void uvc_video_stop_streaming(struct uvc_streaming *stream)
 		usb_clear_halt(stream->dev->udev, pipe);
 	}
 
-	uvc_video_clock_cleanup(stream);
+	uvc_video_clock_cleanup(&stream->clock);
 }