[PATCH] present: Fix Async swap logic

[Chris Wilson]

On Tue, Nov 03, 2015 at 09:14:51AM +0100, Axel Davy wrote:
> 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.
> 
> Signed-off-by: Axel Davy <axel.davy at ens.fr>
> ---
> I'm not sure for indentation, I tried to do the same than previous check
>  present/present.c | 29 ++++++++++++++++-------------
>  1 file changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/present/present.c b/present/present.c
> index beb4ff0..3b8679c 100644
> --- a/present/present.c
> +++ b/present/present.c
> @@ -836,19 +836,22 @@ 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)
> -            target_msc--;
> +    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 (target_msc == crtc_msc &&
> +            (options & PresentOptionAsync) &&
> +            (screen_priv->info->capabilities & PresentCapabilityAsync) &&
> +            present_check_flip (target_crtc, window, pixmap, FALSE, valid, x_off, y_off))
> +        {
> +          vblank->flip = TRUE;
> +        }
>      }

For reference, this is how I fixed the async flip + swap elision:

t a/present/present.c b/present/present.c
index e9ccfb8..32522af 100644
--- a/present/present.c
+++ b/present/present.c
@@ -861,19 +861,19 @@ 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 (!(options & PresentOptionCopy) && pixmap != NULL) {
+        if (options & PresentOptionAsync &&
+            (screen_priv->info &&
+             screen_priv->info->capabilities & PresentCapabilityAsync) &&
+            present_check_flip (target_crtc, window, pixmap, FALSE, valid, x_off, y_off)) {
+            vblank->flip = TRUE;
+        }
+        else if (present_check_flip (target_crtc, window, pixmap, TRUE, valid, x_off, y_off)) {
+            vblank->flip = TRUE;
+            vblank->sync_flip = TRUE;
             target_msc--;
+        } else if (options & PresentOptionAsync)
+            target_msc++;
     }
 
     if (wait_fence) {


-- 
Chris Wilson, Intel Open Source Technology Centre