drm/mgag200: Optimize damage clips

When there are multiple damage clips, previous code merged them into one
big rectangle. As the Matrox memory is very slow, it's faster to copy each
damage clip.
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220504134026.283417-2-jfalempe@redhat.com

drivers/gpu/drm/mgag200/mgag200_mode.c

@@ -855,10 +855,6 @@ mgag200_handle_damage(struct mga_device *mdev, struct drm_framebuffer *fb,
 
 	dst += drm_fb_clip_offset(fb->pitches[0], fb->format, clip);
 	drm_fb_memcpy_toio(dst, fb->pitches[0], vmap, fb, clip);
-
-	/* Always scanout image at VRAM offset 0 */
-	mgag200_set_startadd(mdev, (u32)0);
-	mgag200_set_offset(mdev, fb);
 }
 
 static void
@@ -913,6 +909,10 @@ mgag200_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 
 	mgag200_handle_damage(mdev, fb, &fullscreen, &shadow_plane_state->data[0]);
 
+	/* Always scanout image at VRAM offset 0 */
+	mgag200_set_startadd(mdev, (u32)0);
+	mgag200_set_offset(mdev, fb);
+
 	mutex_unlock(&mdev->rmmio_lock);
 }
 
@@ -969,14 +969,20 @@ mgag200_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
 	struct drm_framebuffer *fb = state->fb;
 	struct drm_rect damage;
+	struct drm_atomic_helper_damage_iter iter;
 
 	if (!fb)
 		return;
 
 	mutex_lock(&mdev->rmmio_lock);
 
-	if (drm_atomic_helper_damage_merged(old_state, state, &damage))
+	drm_atomic_helper_damage_iter_init(&iter, old_state, state);
+	drm_atomic_for_each_plane_damage(&iter, &damage) {
 		mgag200_handle_damage(mdev, fb, &damage, &shadow_plane_state->data[0]);
+	}
+	/* Always scanout image at VRAM offset 0 */
+	mgag200_set_startadd(mdev, (u32)0);
+	mgag200_set_offset(mdev, fb);
 
 	mutex_unlock(&mdev->rmmio_lock);
 }