drm/amd/display: Maintain z-ordering when creating planes

[Why]
The overlay will be incorrectly placed *below* the primary plane for
commits with state->allow_modeset = true because the primary plane
won't be removed and recreated in the same commit.

[How]
Add the should_reset_plane helper to determine if the plane should be
reset or not. If we need to add or force reset any plane in the context
then we'll need to do the same for every plane on the stream.

Unfortunately we need to do the remove / recreate routine for removing
planes as well since DC currently isn't well equipped to handle the
plane with the top pipe being removed with other planes still active.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -6064,6 +6064,69 @@ fail:
 	return ret;
 }
 
+static bool should_reset_plane(struct drm_atomic_state *state,
+			       struct drm_plane *plane,
+			       struct drm_plane_state *old_plane_state,
+			       struct drm_plane_state *new_plane_state)
+{
+	struct drm_plane *other;
+	struct drm_plane_state *old_other_state, *new_other_state;
+	struct drm_crtc_state *new_crtc_state;
+	int i;
+
+	/*
+	 * TODO: Remove this hack once the checks below are sufficient
+	 * enough to determine when we need to reset all the planes on
+	 * the stream.
+	 */
+	if (state->allow_modeset)
+		return true;
+
+	/* Exit early if we know that we're adding or removing the plane. */
+	if (old_plane_state->crtc != new_plane_state->crtc)
+		return true;
+
+	/* old crtc == new_crtc == NULL, plane not in context. */
+	if (!new_plane_state->crtc)
+		return false;
+
+	new_crtc_state =
+		drm_atomic_get_new_crtc_state(state, new_plane_state->crtc);
+
+	if (!new_crtc_state)
+		return true;
+
+	if (drm_atomic_crtc_needs_modeset(new_crtc_state))
+		return true;
+
+	/*
+	 * If there are any new primary or overlay planes being added or
+	 * removed then the z-order can potentially change. To ensure
+	 * correct z-order and pipe acquisition the current DC architecture
+	 * requires us to remove and recreate all existing planes.
+	 *
+	 * TODO: Come up with a more elegant solution for this.
+	 */
+	for_each_oldnew_plane_in_state(state, other, old_other_state, new_other_state, i) {
+		if (other->type == DRM_PLANE_TYPE_CURSOR)
+			continue;
+
+		if (old_other_state->crtc != new_plane_state->crtc &&
+		    new_other_state->crtc != new_plane_state->crtc)
+			continue;
+
+		if (old_other_state->crtc != new_other_state->crtc)
+			return true;
+
+		/* TODO: Remove this once we can handle fast format changes. */
+		if (old_other_state->fb && new_other_state->fb &&
+		    old_other_state->fb->format != new_other_state->fb->format)
+			return true;
+	}
+
+	return false;
+}
+
 static int dm_update_plane_state(struct dc *dc,
 				 struct drm_atomic_state *state,
 				 struct drm_plane *plane,
@@ -6078,8 +6141,7 @@ static int dm_update_plane_state(struct dc *dc,
 	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
 	struct dm_crtc_state *dm_new_crtc_state, *dm_old_crtc_state;
 	struct dm_plane_state *dm_new_plane_state, *dm_old_plane_state;
-	/* TODO return page_flip_needed() function */
-	bool pflip_needed  = !state->allow_modeset;
+	bool needs_reset;
 	int ret = 0;
 
 
@@ -6092,10 +6154,12 @@ static int dm_update_plane_state(struct dc *dc,
 	if (plane->type == DRM_PLANE_TYPE_CURSOR)
 		return 0;
 
+	needs_reset = should_reset_plane(state, plane, old_plane_state,
+					 new_plane_state);
+
 	/* Remove any changed/removed planes */
 	if (!enable) {
-		if (pflip_needed &&
-		    plane->type != DRM_PLANE_TYPE_OVERLAY)
+		if (!needs_reset)
 			return 0;
 
 		if (!old_plane_crtc)
@@ -6146,7 +6210,7 @@ static int dm_update_plane_state(struct dc *dc,
 		if (!dm_new_crtc_state->stream)
 			return 0;
 
-		if (pflip_needed && plane->type != DRM_PLANE_TYPE_OVERLAY)
+		if (!needs_reset)
 			return 0;
 
 		WARN_ON(dm_new_plane_state->dc_state);