drm/tegra: Let core take care of normalizing the zpos

Set the drm_mode_config->normalize_zpos and call the generic
drm_atomic_helper_check() instead of duplicating it within
tegra_atomic_check().

Call tegra_display_hub_atomic_check() after the drm_atomic_helpre_check()
returned without error.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
CC: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180321102029.15248-4-peter.ujfalusi@ti.com

drivers/gpu/drm/tegra/drm.c

@@ -38,26 +38,11 @@ static int tegra_atomic_check(struct drm_device *drm,
 {
 	int err;
 
-	err = drm_atomic_helper_check_modeset(drm, state);
+	err = drm_atomic_helper_check(drm, state);
 	if (err < 0)
 		return err;
 
-	err = tegra_display_hub_atomic_check(drm, state);
-	if (err < 0)
-		return err;
-
-	err = drm_atomic_normalize_zpos(drm, state);
-	if (err < 0)
-		return err;
-
-	err = drm_atomic_helper_check_planes(drm, state);
-	if (err < 0)
-		return err;
-
-	if (state->legacy_cursor_update)
-		state->async_update = !drm_atomic_helper_async_check(drm, state);
-
-	return 0;
+	return tegra_display_hub_atomic_check(drm, state);
 }
 
 static const struct drm_mode_config_funcs tegra_drm_mode_config_funcs = {
@@ -151,6 +136,8 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 
 	drm->mode_config.allow_fb_modifiers = true;
 
+	drm->mode_config.normalize_zpos = true;
+
 	drm->mode_config.funcs = &tegra_drm_mode_config_funcs;
 	drm->mode_config.helper_private = &tegra_drm_mode_config_helpers;