drm/vc4: Return -EBUSY if there's already a pending flip event.

As per the documentation in drm_crtc.h, atomic_commit should return
-EBUSY if an asynchronous update is requested and there is an earlier
update pending.

v2: Rebase on the s/async/nonblock/ change.

Signed-off-by: Robert Foss <robert.foss@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index cb37751bc99fcfe8976ced75f16ce4bd332c2406..861a623bc18536def731d407826cd6061df0643f 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -117,10 +117,18 @@ static int vc4_atomic_commit(struct drm_device *dev,
                return -ENOMEM;
 
        /* Make sure that any outstanding modesets have finished. */
-       ret = down_interruptible(&vc4->async_modeset);
-       if (ret) {
-               kfree(c);
-               return ret;
+       if (nonblock) {
+               ret = down_trylock(&vc4->async_modeset);
+               if (ret) {
+                       kfree(c);
+                       return -EBUSY;
+               }
+       } else {
+               ret = down_interruptible(&vc4->async_modeset);
+               if (ret) {
+                       kfree(c);
+                       return ret;
+               }
        }
 
        ret = drm_atomic_helper_prepare_planes(dev, state);