[PATCH v2 3/3] present: sync flips unless requested not to

[Frank Binns]

When the display driver supports async flipping this mode of operation is
always used. This means that, when the swap interval is none 0, the present
extension relies on vblank events to get synchronised flips. However, by the
time present gets the event, requests a flip and the GPU has finished we might
have missed the vblank period. This results in tearing.

Fix this by always doing synced flips unless the client uses the
PresentOptionAsync flag when presenting a pixmap.

Signed-off-by: Frank Binns <frank.binns at imgtec.com>
---
 present/present.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/present/present.c b/present/present.c
index a717d0d..6d3cffa 100644
--- a/present/present.c
+++ b/present/present.c
@@ -706,7 +706,7 @@ present_pixmap(WindowPtr window,
             }
         } else {
             target_msc = crtc_msc;
-            if (!(options & PresentOptionAsync))
+            if (!(options & PresentOptionAsync) || !screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
                 target_msc++;
         }
     }
@@ -781,7 +781,7 @@ present_pixmap(WindowPtr window,
     vblank->notifies = notifies;
     vblank->num_notifies = num_notifies;
 
-    if (!screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
+    if (!(options & PresentOptionAsync) || !screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
         vblank->sync_flip = TRUE;
 
     if (pixmap && present_check_flip (target_crtc, window, pixmap, vblank->sync_flip, valid, x_off, y_off)) {
@@ -810,7 +810,7 @@ present_pixmap(WindowPtr window,
 
     xorg_list_add(&vblank->event_queue, &present_exec_queue);
     vblank->queued = TRUE;
-    if (target_msc >= crtc_msc) {
+    if (target_msc > crtc_msc) {
         ret = present_queue_vblank(screen, target_crtc, vblank->event_id, target_msc);
         if (ret != Success) {
             xorg_list_del(&vblank->event_queue);
-- 
1.8.5.4.gfdaaaa2