[PATCH 3/5] drm/damage-helper: Do partial updates on legacy cursor changes

[Thomas Zimmermann]

In the case of a legacy cursor update, only update the cursor plane. Keep
other planes clear from changes. Setting the 'partial_update' flag when
these planes don't have damage-clipping areas acts as if no update will
be performed.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 drivers/gpu/drm/drm_damage_helper.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
index 16f0d5a97ee3..a603a3563c03 100644
--- a/drivers/gpu/drm/drm_damage_helper.c
+++ b/drivers/gpu/drm/drm_damage_helper.c
@@ -69,6 +69,7 @@ void drm_atomic_helper_check_plane_damage(struct drm_atomic_state *state,
 					  struct drm_plane_state *new_plane_state)
 {
 	struct drm_crtc_state *new_crtc_state;
+	struct drm_plane *plane = new_plane_state->plane;
 	struct drm_crtc *new_crtc = new_plane_state->crtc;
 	bool partial_update = false;
 
@@ -83,6 +84,17 @@ void drm_atomic_helper_check_plane_damage(struct drm_atomic_state *state,
 		 */
 		if (drm_atomic_crtc_needs_modeset(new_crtc_state))
 			goto out;
+
+		/*
+		 * On a legacy cursor update, only update the affected cursor
+		 * plane, but ignore all other planes. The non-cursor planes
+		 * won't have damage-clipping areas, so setting the flag for
+		 * a partial update acts like not doing any update.
+		 */
+		if (state->legacy_cursor_update) {
+			if (plane != new_crtc->cursor)
+				partial_update = true;
+		}
 	}
 
 	/*
-- 
2.37.3