drm: reset empty state in transitional helpers

Transitional drivers might not have all the state frobbing lined up
yet. But since the initial code has been merged a lot more state was
added, so we really need this.

Cc: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reported-and-tested-by: John Hunter <zhaojunwang@pku.edu.cn>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc_helper.c

@@ -927,10 +927,12 @@ int drm_helper_crtc_mode_set(struct drm_crtc *crtc, struct drm_display_mode *mod
 
 	if (crtc->funcs->atomic_duplicate_state)
 		crtc_state = crtc->funcs->atomic_duplicate_state(crtc);
-	else if (crtc->state)
+	else {
+		if (!crtc->state)
+			drm_atomic_helper_crtc_reset(crtc);
+
 		crtc_state = drm_atomic_helper_crtc_duplicate_state(crtc);
-	else
-		crtc_state = kzalloc(sizeof(*crtc_state), GFP_KERNEL);
+	}
 
 	if (!crtc_state)
 		return -ENOMEM;

drivers/gpu/drm/drm_plane_helper.c

@@ -525,10 +525,12 @@ int drm_plane_helper_update(struct drm_plane *plane, struct drm_crtc *crtc,
 
 	if (plane->funcs->atomic_duplicate_state)
 		plane_state = plane->funcs->atomic_duplicate_state(plane);
-	else if (plane->state)
+	else {
+		if (!plane->state)
+			drm_atomic_helper_plane_reset(plane);
+
 		plane_state = drm_atomic_helper_plane_duplicate_state(plane);
-	else
-		plane_state = kzalloc(sizeof(*plane_state), GFP_KERNEL);
+	}
 	if (!plane_state)
 		return -ENOMEM;
 	plane_state->plane = plane;
@@ -572,10 +574,12 @@ int drm_plane_helper_disable(struct drm_plane *plane)
 
 	if (plane->funcs->atomic_duplicate_state)
 		plane_state = plane->funcs->atomic_duplicate_state(plane);
-	else if (plane->state)
+	else {
+		if (!plane->state)
+			drm_atomic_helper_plane_reset(plane);
+
 		plane_state = drm_atomic_helper_plane_duplicate_state(plane);
-	else
-		plane_state = kzalloc(sizeof(*plane_state), GFP_KERNEL);
+	}
 	if (!plane_state)
 		return -ENOMEM;
 	plane_state->plane = plane;