[PATCH] drm/gud: Merge damage clips in full update mode

[Sophie D <patches@scd31.com>]

When running in full update mode, previously small updates (such as
moving the mouse across the screen) would cause many full frames to be
generated. This would bog down the bus and lower the effective framerate
significantly - I was seeing a drop from 60 FPS to 2 FPS.

This patch fixes the bug by merging damage clips together.

Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: Sophie D <patches@scd31.com>
---
 drivers/gpu/drm/gud/gud_pipe.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index 5ef887d84..20418bf81 100644
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -647,9 +647,14 @@ void gud_plane_atomic_update(struct drm_plane *plane,
 	if (ret)
 		goto out;
 
-	drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
-	drm_atomic_for_each_plane_damage(&iter, &damage)
-		gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE) {
+		if (drm_atomic_helper_damage_merged(old_state, new_state, &damage))
+			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	} else {
+		drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
+		drm_atomic_for_each_plane_damage(&iter, &damage)
+			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	}
 
 	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 
-- 
2.55.0