[PATCH] drm/amd/display: Disallow enabling CRTC without primary plane with FB

[Harry Wentland]

The below commit

    "drm/atomic: Try to preserve the crtc enabled state in drm_atomic_remove_fb, v2"

introduces a slight behavioral change to rmfb. Instead of disabling a crtc
when the primary plane is disabled, it now preserves it.

Since DC is currently not equipped to handle this we need to fail such
a commit, otherwise we might see a corrupted screen.

This is based on Shirish's previous approach but avoids adding all
planes to the new atomic state which leads to a full update in DC for
any commit, and is not what we intend.

Theoretically DM should be able to deal with states with fully populated planes,
even for simple updates, such as cursor updates. This should still be
addressed in the future.

Signed-off-by: Harry Wentland <harry.wentland at amd.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 6f92a19bebd6..0bdc6b484bad 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4683,6 +4683,7 @@ static int dm_update_crtcs_state(struct amdgpu_display_manager *dm,
 		struct amdgpu_dm_connector *aconnector = NULL;
 		struct drm_connector_state *new_con_state = NULL;
 		struct dm_connector_state *dm_conn_state = NULL;
+		struct drm_plane_state *new_plane_state = NULL;
 
 		new_stream = NULL;
 
@@ -4690,6 +4691,13 @@ static int dm_update_crtcs_state(struct amdgpu_display_manager *dm,
 		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
 		acrtc = to_amdgpu_crtc(crtc);
 
+		new_plane_state = drm_atomic_get_new_plane_state(state, new_crtc_state->crtc->primary);
+
+		if (new_crtc_state->enable && new_plane_state && !new_plane_state->fb) {
+			ret = -EINVAL;
+			goto fail;
+		}
+
 		aconnector = amdgpu_dm_find_first_crtc_matching_connector(state, crtc);
 
 		/* TODO This hack should go away */
@@ -4894,7 +4902,7 @@ static int dm_update_planes_state(struct dc *dc,
 			if (!dm_old_crtc_state->stream)
 				continue;
 
-			DRM_DEBUG_DRIVER("Disabling DRM plane: %d on DRM crtc %d\n",
+			DRM_DEBUG_ATOMIC("Disabling DRM plane: %d on DRM crtc %d\n",
 					plane->base.id, old_plane_crtc->base.id);
 
 			if (!dc_remove_plane_from_context(
-- 
2.17.0