[PATCH v2] drm/atomic-helper: Don't allocated plane state in CRTC check

[Thomas Zimmermann]

In drm_atomic_helper_check_crtc_state(), do not add a new plane state
to the global state if it does not exist already. Adding a new plane
state will result in overhead for the plane during the atomic-commit
step.

For the test in drm_atomic_helper_check_crtc_state() to succeed, it is
important that the CRTC has an enabled primary plane after the commit.
This can be a newly enabled plane or an already enabled plane. So if a
plane is not part of the commit, use the plane's existing state.

v2:
	* remove unnecessary test for plane->crtc (Ville)
	* inline drm_atomic_get_next_plane_state() (Ville)
	* acquire plane lock before accessing plane->state (Ville)

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Fixes: d6b9af1097fe ("drm/atomic-helper: Add helper drm_atomic_helper_check_crtc_state()")
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Jocelyn Falempe <jfalempe at redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: dri-devel at lists.freedesktop.org
---
 drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 98cc3137c062..b7774a39712b 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -960,10 +960,18 @@ int drm_atomic_helper_check_crtc_state(struct drm_crtc_state *crtc_state,
 
 			if (plane->type != DRM_PLANE_TYPE_PRIMARY)
 				continue;
-			plane_state = drm_atomic_get_plane_state(state, plane);
-			if (IS_ERR(plane_state))
-				return PTR_ERR(plane_state);
-			if (plane_state->fb && plane_state->crtc) {
+
+			plane_state = drm_atomic_get_new_plane_state(state, plane);
+			if (!plane_state) {
+				/* plane isn't part of the update; look at existing state */
+				int ret = drm_modeset_lock(&plane->mutex, state->acquire_ctx);
+
+				if (ret)
+					return ret;
+				plane_state = plane->state;
+			}
+
+			if (plane_state->fb) {
 				has_primary_plane = true;
 				break;
 			}
-- 
2.37.3