[PATCH 5/7] compositor-drm: Gracefully handle vblank and flip invalid timestamps

[Miguel A. Vico]

Instant query for vblank timestamp may always fail, resulting in
never scheduling a full repaint in drm_output_start_repaint_loop().

Additionally, timestamp provided in page_flip_handler() may also be
invalid.

This change makes both drm_output_start_repaint_loop() and
page_flip_handler() to schedule a full repaint in any of the
situations above.

Signed-off-by: Miguel A Vico Moya <mvicomoya at nvidia.com>
Reviewed-by: Andy Ritger <aritger at nvidia.com>
---
 src/compositor-drm.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/compositor-drm.c b/src/compositor-drm.c
index b87acd5..b3eca88 100644
--- a/src/compositor-drm.c
+++ b/src/compositor-drm.c
@@ -1,6 +1,7 @@
 /*
  * Copyright © 2008-2011 Kristian Høgsberg
  * Copyright © 2011 Intel Corporation
+ * Copyright © 2016 NVIDIA Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -761,8 +762,16 @@ drm_output_start_repaint_loop(struct weston_output *output_base)
 	vbl.request.type |= drm_waitvblank_pipe(output);
 	ret = drmWaitVBlank(backend->drm.fd, &vbl);
 
-	/* Error ret or zero timestamp means failure to get valid timestamp */
-	if ((ret == 0) && (vbl.reply.tval_sec > 0 || vbl.reply.tval_usec > 0)) {
+	if (ret) {
+		/* Immediate query failed. It may always fail so we'll never get a valid
+		 * timestamp to update msc and call into finish frame. Hence, jump to
+		 * finish frame here.
+		 */
+		goto finish_frame;
+	}
+
+	/* Zero timestamp means failure to get valid timestamp */
+	if (vbl.reply.tval_sec > 0 || vbl.reply.tval_usec > 0) {
 		ts.tv_sec = vbl.reply.tval_sec;
 		ts.tv_nsec = vbl.reply.tval_usec * 1000;
 
@@ -783,7 +792,7 @@ drm_output_start_repaint_loop(struct weston_output *output_base)
 		}
 	}
 
-	/* Immediate query didn't provide valid timestamp.
+	/* Immediate query succeeded, but didn't provide valid timestamp.
 	 * Use pageflip fallback.
 	 */
 	fb_id = output->current->fb_id;
@@ -869,6 +878,15 @@ page_flip_handler(int fd, unsigned int frame,
 	else if (!output->vblank_pending) {
 		ts.tv_sec = sec;
 		ts.tv_nsec = usec * 1000;
+
+		/* Zero timestamp means failure to get valid timestamp, so immediately
+		 * finish frame */
+		if (ts.tv_sec == 0 && ts.tv_nsec == 0) {
+			weston_compositor_read_presentation_clock(output->base.compositor,
+			                                          &ts);
+			flags = WP_PRESENTATION_FEEDBACK_INVALID;
+		}
+
 		weston_output_finish_frame(&output->base, &ts, flags);
 
 		/* We can't call this from frame_notify, because the output's
-- 
2.7.1