compositor-drm: deliver frame seq for feedback

Add 'msc' field to weston_output to maintain the refresh counter, and
use it in presentation_feedback.presented.

Make compositor-drm update the per-output refresh counter with the
values reported by DRM. If the DRM reported value jumps backwards,
assume it wrapped around once.

Other backends do not update weston_output::msc, and there
presentation_feedback will always deliver refresh counter as zero.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
v3 Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>

src/compositor-drm.c

@@ -725,6 +725,17 @@ finish_frame:
 	weston_output_finish_frame(output_base, &ts);
 }
 
+static void
+drm_output_update_msc(struct drm_output *output, unsigned int seq)
+{
+	uint64_t msc_hi = output->base.msc >> 32;
+
+	if (seq < (output->base.msc & 0xffffffff))
+		msc_hi++;
+
+	output->base.msc = (msc_hi << 32) + seq;
+}
+
 static void
 vblank_handler(int fd, unsigned int frame, unsigned int sec, unsigned int usec,
 	       void *data)
@@ -733,6 +744,7 @@ vblank_handler(int fd, unsigned int frame, unsigned int sec, unsigned int usec,
 	struct drm_output *output = s->output;
 	struct timespec ts;
 
+	drm_output_update_msc(output, frame);
 	output->vblank_pending = 0;
 
 	drm_output_release_fb(output, s->current);
@@ -756,6 +768,8 @@ page_flip_handler(int fd, unsigned int frame,
 	struct drm_output *output = (struct drm_output *) data;
 	struct timespec ts;
 
+	drm_output_update_msc(output, frame);
+
 	/* We don't set page_flip_pending on start_repaint_loop, in that case
 	 * we just want to page flip to the current buffer to get an accurate
 	 * timestamp */

src/compositor.c

@@ -2065,7 +2065,7 @@ weston_output_finish_frame(struct weston_output *output,
 	refresh_nsec = 1000000000000UL / output->current_mode->refresh;
 	weston_presentation_feedback_present_list(&output->feedback_list,
 						  output, refresh_nsec, stamp,
-						  0);
+						  output->msc);
 
 	output->frame_time = stamp->tv_sec * 1000 + stamp->tv_nsec / 1000000;
 

src/compositor.h

@@ -203,6 +203,7 @@ struct weston_output {
 	struct wl_signal destroy_signal;
 	int move_x, move_y;
 	uint32_t frame_time; /* presentation timestamp in milliseconds */
+	uint64_t msc;        /* media stream counter */
 	int disable_planes;
 	int destroying;
 	struct wl_list feedback_list;