drm/rcar-du: Introduce CRTCs groups

The R8A7779 DU is split in per-CRTC resources (scan-out engine, blending
unit, timings generator, ...) and device-global resources (start/stop
control, planes, ...) shared between the two CRTCs.

The R8A7790 introduced a third CRTC with its own set of global resources
This would be modeled as two separate DU device instances if it wasn't
for a handful or resources that are shared between the three CRTCs
(mostly related to input and output routing). For this reason the
R8A7790 DU must be modeled as a single device with three CRTCs, two sets
of "semi-global" resources, and a few device-global resources.

Introduce a new rcar_du_group driver-specific object, without any real
counterpart in the DU documentation, that models those semi-global
resources.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
index 5b69e98..542a7fe 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
@@ -19,7 +19,7 @@
 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
 
-struct rcar_du_device;
+struct rcar_du_group;
 struct rcar_du_plane;
 
 struct rcar_du_crtc {
@@ -34,10 +34,11 @@
 	unsigned int outputs;
 	int dpms;
 
+	struct rcar_du_group *group;
 	struct rcar_du_plane *plane;
 };
 
-int rcar_du_crtc_create(struct rcar_du_device *rcdu, unsigned int index);
+int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int index);
 void rcar_du_crtc_enable_vblank(struct rcar_du_crtc *rcrtc, bool enable);
 void rcar_du_crtc_cancel_page_flip(struct rcar_du_crtc *rcrtc,
 				   struct drm_file *file);