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_group.h b/drivers/gpu/drm/rcar-du/rcar_du_group.h
new file mode 100644
index 0000000..748331b
--- /dev/null
+++ b/drivers/gpu/drm/rcar-du/rcar_du_group.h
@@ -0,0 +1,47 @@
+/*
+ * rcar_du_group.c  --  R-Car Display Unit Planes and CRTCs Group
+ *
+ * Copyright (C) 2013 Renesas Corporation
+ *
+ * Contact: Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef __RCAR_DU_GROUP_H__
+#define __RCAR_DU_GROUP_H__
+
+#include "rcar_du_plane.h"
+
+struct rcar_du_device;
+
+/*
+ * struct rcar_du_group - CRTCs and planes group
+ * @dev: the DU device
+ * @mmio_offset: registers offset in the device memory map
+ * @index: group index
+ * @use_count: number of users of the group (rcar_du_group_(get|put))
+ * @used_crtcs: number of CRTCs currently in use
+ * @planes: planes handled by the group
+ */
+struct rcar_du_group {
+	struct rcar_du_device *dev;
+	unsigned int mmio_offset;
+	unsigned int index;
+
+	unsigned int use_count;
+	unsigned int used_crtcs;
+
+	struct rcar_du_planes planes;
+};
+
+int rcar_du_group_get(struct rcar_du_group *rgrp);
+void rcar_du_group_put(struct rcar_du_group *rgrp);
+void rcar_du_group_start_stop(struct rcar_du_group *rgrp, bool start);
+void rcar_du_group_restart(struct rcar_du_group *rgrp);
+
+
+#endif /* __RCAR_DU_GROUP_H__ */