drm/plane: Pass old state to ->atomic_update()

In most situations it will be useful to have the old state passed to the
->atomic_update() callback. For example if a plane is being disabled the
new state's .crtc field will be NULL, but some drivers may rely on this
field to program the CRTCs registers.

v2: rename variable to old_plane_state and remove redundant comment as
suggested by Daniel Vetter, remove an Exynos hunk that doesn't apply to
drm-next and add a hunk for pending MSM mdp5 changes

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index d981d07..2fa0840 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1046,6 +1046,7 @@
 	for (i = 0; i < nplanes; i++) {
 		struct drm_plane_helper_funcs *funcs;
 		struct drm_plane *plane = old_state->planes[i];
+		struct drm_plane_state *old_plane_state;
 
 		if (!plane)
 			continue;
@@ -1055,7 +1056,9 @@
 		if (!funcs || !funcs->atomic_update)
 			continue;
 
-		funcs->atomic_update(plane);
+		old_plane_state = old_state->plane_states[i];
+
+		funcs->atomic_update(plane, old_plane_state);
 	}
 
 	for (i = 0; i < ncrtcs; i++) {