drm: rcar-du: Stop accessing non-existent registers on gen4

The following registers do not exist on gen4, so we should not write
them: DEF6Rm, DEF7Rm, DEF8Rm, ESCRn, OTARn.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_crtc.c

@@ -298,10 +298,12 @@ static void rcar_du_crtc_set_display_timing(struct rcar_du_crtc *rcrtc)
 		escr = params.escr;
 	}
 
+	if (rcdu->info->gen < 4) {
 		dev_dbg(rcrtc->dev->dev, "%s: ESCR 0x%08x\n", __func__, escr);
 
 		rcar_du_crtc_write(rcrtc, rcrtc->index % 2 ? ESCR13 : ESCR02, escr);
 		rcar_du_crtc_write(rcrtc, rcrtc->index % 2 ? OTAR13 : OTAR02, 0);
+	}
 
 	/* Signal polarities */
 	dsmr = ((mode->flags & DRM_MODE_FLAG_PVSYNC) ? DSMR_VSL : 0)

drivers/gpu/drm/rcar-du/rcar_du_group.c

@@ -148,18 +148,22 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp)
 	}
 	rcar_du_group_write(rgrp, DEFR5, DEFR5_CODE | DEFR5_DEFE5);
 
+	if (rcdu->info->gen < 4)
 		rcar_du_group_setup_pins(rgrp);
 
+	if (rcdu->info->gen < 4) {
 		/*
-	 * TODO: Handle routing of the DU output to CMM dynamically, as we
-	 * should bypass CMM completely when no color management feature is
-	 * used.
+		 * TODO: Handle routing of the DU output to CMM dynamically, as
+		 * we should bypass CMM completely when no color management
+		 * feature is used.
 		 */
 		defr7 |= (rgrp->cmms_mask & BIT(1) ? DEFR7_CMME1 : 0) |
 			 (rgrp->cmms_mask & BIT(0) ? DEFR7_CMME0 : 0);
 		rcar_du_group_write(rgrp, DEFR7, defr7);
+	}
 
 	if (rcdu->info->gen >= 2) {
+		if (rcdu->info->gen < 4)
 			rcar_du_group_setup_defr8(rgrp);
 		rcar_du_group_setup_didsr(rgrp);
 	}