drm: rcar-du: Clamp DPMS states to on and off

The intermediate DPMS standby and suspend states are a thing from the
past. They only matter in practice for VGA CRT monitors, and are just a
power saving vs. resume time optimization. Given that they have never
been implemented properly in the rcar-du driver and that the Intel
driver has dropped them on the vga port years ago, it's safe to only
care about the on and off states.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

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

@@ -347,6 +347,9 @@ static void rcar_du_crtc_dpms(struct drm_crtc *crtc, int mode)
 {
 	struct rcar_du_crtc *rcrtc = to_rcar_crtc(crtc);
 
+	if (mode != DRM_MODE_DPMS_ON)
+		mode = DRM_MODE_DPMS_OFF;
+
 	if (rcrtc->dpms == mode)
 		return;
 

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

@@ -46,6 +46,9 @@ static void rcar_du_encoder_dpms(struct drm_encoder *encoder, int mode)
 {
 	struct rcar_du_encoder *renc = to_rcar_encoder(encoder);
 
+	if (mode != DRM_MODE_DPMS_ON)
+		mode = DRM_MODE_DPMS_OFF;
+
 	if (renc->lvds)
 		rcar_du_lvdsenc_dpms(renc->lvds, encoder->crtc, mode);
 }

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

@@ -37,6 +37,9 @@ static void rcar_du_hdmienc_dpms(struct drm_encoder *encoder, int mode)
 	struct rcar_du_hdmienc *hdmienc = to_rcar_hdmienc(encoder);
 	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
+	if (mode != DRM_MODE_DPMS_ON)
+		mode = DRM_MODE_DPMS_OFF;
+
 	if (hdmienc->dpms == mode)
 		return;