drm/amd/display: Fix hang when skipping modeset

commit da5e149 upstream.

[Why&How]

When skipping full modeset since the only state change was a front porch
change, the DC commit sequence requires extra checks to handle non
existant plane states being asked to be removed from context.

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -7673,6 +7673,8 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 			continue;
 
 		dc_plane = dm_new_plane_state->dc_state;
+		if (!dc_plane)
+			continue;
 
 		bundle->surface_updates[planes_count].surface = dc_plane;
 		if (new_pcrtc_state->color_mgmt_changed) {
@@ -9217,8 +9219,9 @@ static int dm_update_plane_state(struct dc *dc,
 			return -EINVAL;
 		}
 
+		if (dm_old_plane_state->dc_state)
+			dc_plane_state_release(dm_old_plane_state->dc_state);
 
-		dc_plane_state_release(dm_old_plane_state->dc_state);
 		dm_new_plane_state->dc_state = NULL;
 
 		*lock_and_validation_needed = true;

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -1707,6 +1707,9 @@ bool dc_remove_plane_from_context(
 	struct dc_stream_status *stream_status = NULL;
 	struct resource_pool *pool = dc->res_pool;
 
+	if (!plane_state)
+		return true;
+
 	for (i = 0; i < context->stream_count; i++)
 		if (context->streams[i] == stream) {
 			stream_status = &context->stream_status[i];