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>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index cb37751bc99f..861a623bc185 100644
--- 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);