[PATCH v2] present: Fix Async swap logic

[Axel Davy]

According to the spec, PresentOptionAsync should only
trigger a different behaviour when the target msc has been reached.

In this case if the driver is able to do async swaps, we use
them to avoid a screen copy.

When the target msc hasn't been reached yet, we want to use sync swaps.

v2: Fix indentation and simplify checks for Async flips

Signed-off-by: Axel Davy <axel.davy at ens.fr>
---
 present/present.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/present/present.c b/present/present.c
index beb4ff0..6d45581 100644
--- a/present/present.c
+++ b/present/present.c
@@ -836,19 +836,20 @@ present_pixmap(WindowPtr window,
     vblank->notifies = notifies;
     vblank->num_notifies = num_notifies;
 
-    if (!(options & PresentOptionAsync))
-        vblank->sync_flip = TRUE;
-
-    if (!(options & PresentOptionCopy) &&
-        !((options & PresentOptionAsync) &&
-          (!screen_priv->info ||
-           !(screen_priv->info->capabilities & PresentCapabilityAsync))) &&
-        pixmap != NULL &&
-        present_check_flip (target_crtc, window, pixmap, vblank->sync_flip, valid, x_off, y_off))
-    {
-        vblank->flip = TRUE;
-        if (vblank->sync_flip)
+    if (pixmap != NULL &&
+        !(options & PresentOptionCopy) &&
+        screen_priv->info) {
+        if (target_msc > crtc_msc &&
+            present_check_flip (target_crtc, window, pixmap, TRUE, valid, x_off, y_off))
+        {
+            vblank->flip = TRUE;
+            vblank->sync_flip = TRUE;
             target_msc--;
+        } else if ((screen_priv->info->capabilities & PresentCapabilityAsync) &&
+            present_check_flip (target_crtc, window, pixmap, FALSE, valid, x_off, y_off))
+        {
+            vblank->flip = TRUE;
+        }
     }
 
     if (wait_fence) {
-- 
2.6.2