[PATCH v4] drm: re-allow no-op changes on non-primary planes in async flips

[Xaver Hugl]

Commit fd40a63c63a1 unintentionally disallowed no-op changes on non-primary
planes that the driver doesn't allow async flips on. This broke async flips
for compositors that disable the cursor plane in every async atomic commit.
This changes drm_atomic_set_property to again only run atomic_async_check
if the plane would actually be changed by the atomic commit.

Fixes: fd40a63c63a1 ("drm/atomic: Let drivers decide which planes to async flip")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4263

Signed-off-by: Xaver Hugl <xaver.hugl at kde.org>
---
 drivers/gpu/drm/drm_atomic_uapi.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index c2726af6698e..317303cf5b8c 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1077,19 +1077,20 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 		}
 
 		if (async_flip) {
-			/* check if the prop does a nop change */
-			if ((prop != config->prop_fb_id &&
-			     prop != config->prop_in_fence_fd &&
-			     prop != config->prop_fb_damage_clips)) {
-				ret = drm_atomic_plane_get_property(plane, plane_state,
-								    prop, &old_val);
-				ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
-			}
+			/* no-op changes are always allowed */
+			ret = drm_atomic_plane_get_property(plane, plane_state,
+							    prop, &old_val);
+			ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
 
-			/* ask the driver if this non-primary plane is supported */
-			if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
-				ret = -EINVAL;
+			/* fail everything that isn't no-op or a pure flip */
+			if (ret && prop != config->prop_fb_id &&
+			    prop != config->prop_in_fence_fd &&
+			    prop != config->prop_fb_damage_clips) {
+				break;
+			}
 
+			if (ret && plane->type != DRM_PLANE_TYPE_PRIMARY) {
+				/* ask the driver if this non-primary plane is supported */
 				if (plane_funcs && plane_funcs->atomic_async_check)
 					ret = plane_funcs->atomic_async_check(plane, state, true);
 
-- 
2.50.1