[PATCH 2/3] present: When cancelling a pending synchronous flip, requeue it

[Chris Wilson]

The vblank event request for a synchronous flip is scheduled for the
vblank before the target flip msc (so that the flip itself appears at
the right frame). If we cancel that flip and so wish to schedule a
copy instead, that copy needs to be postponed by a frame in order for it
be performed at the requested time.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 present/present.c      | 16 +++++++++++++++-
 present/present_priv.h |  1 +
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/present/present.c b/present/present.c
index ce978f4..a53dc11 100644
--- a/present/present.c
+++ b/present/present.c
@@ -549,8 +549,13 @@ present_check_flip_window (WindowPtr window)
 
     /* Now check any queued vblanks */
     xorg_list_for_each_entry(vblank, &window_priv->vblank, window_list) {
-        if (vblank->queued && vblank->flip && !present_check_flip(vblank->crtc, window, vblank->pixmap, vblank->sync_flip, NULL, 0, 0))
+        if (vblank->queued && vblank->flip && !present_check_flip(vblank->crtc, window, vblank->pixmap, vblank->sync_flip, NULL, 0, 0)) {
             vblank->flip = FALSE;
+            if (vblank->sync_flip) {
+                vblank->requeue = TRUE;
+                vblank->target_msc++;
+            }
+        }
     }
 }
 
@@ -585,6 +590,15 @@ present_execute(present_vblank_ptr vblank, uint64_t ust, uint64_t crtc_msc)
     present_screen_priv_ptr     screen_priv = present_screen_priv(screen);
     uint8_t                     mode;
 
+    if (vblank->requeue) {
+        vblank->requeue = FALSE;
+        if (Success == present_queue_vblank(screen,
+                                            vblank->crtc,
+                                            vblank->event_id,
+                                            vblank->target_msc))
+            return;
+    }
+
     if (vblank->wait_fence) {
         if (!present_fence_check_triggered(vblank->wait_fence)) {
             present_fence_set_callback(vblank->wait_fence, present_wait_fence_triggered, vblank);
diff --git a/present/present_priv.h b/present/present_priv.h
index 110c925..7db4321 100644
--- a/present/present_priv.h
+++ b/present/present_priv.h
@@ -70,6 +70,7 @@ struct present_vblank {
     present_notify_ptr  notifies;
     int                 num_notifies;
     Bool                queued;         /* on present_exec_queue */
+    Bool                requeue;        /* on queue, but target_msc has changed */
     Bool                flip;           /* planning on using flip */
     Bool                flip_ready;     /* wants to flip, but waiting for previous flip or unflip */
     Bool                sync_flip;      /* do flip synchronous to vblank */
-- 
2.1.4