drm/vc4: crtc: Only access the PixelValve registers if we have to

The CRTC hooks are called both for the TXP and the pixelvalve, yet some
will read / write the registers as if the device was a pixelvalve, which
won't really work.

Let's make sure we only access those registers if we are running on a
PixelValve.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/b55e31869304c748920c261eba87b3275dbeb297.1591882579.git-series.maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -357,6 +357,7 @@ static void require_hvs_enabled(struct drm_device *dev)
 static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
 				    struct drm_crtc_state *old_state)
 {
+	struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
 	struct drm_device *dev = crtc->dev;
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
 	int ret;
@@ -366,10 +367,12 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
 	/* Disable vblank irq handling before crtc is disabled. */
 	drm_crtc_vblank_off(crtc);
 
+	if (!vc4_state->feed_txp) {
 		CRTC_WRITE(PV_V_CONTROL,
 			   CRTC_READ(PV_V_CONTROL) & ~PV_VCONTROL_VIDEN);
 		ret = wait_for(!(CRTC_READ(PV_V_CONTROL) & PV_VCONTROL_VIDEN), 1);
 		WARN_ONCE(ret, "Timeout waiting for !PV_VCONTROL_VIDEN\n");
+	}
 
 	vc4_hvs_atomic_disable(crtc, old_state);
 
@@ -502,6 +505,10 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
 static int vc4_enable_vblank(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
+
+	if (vc4_state->feed_txp)
+		return 0;
 
 	CRTC_WRITE(PV_INTEN, PV_INT_VFP_START);
 
@@ -511,6 +518,10 @@ static int vc4_enable_vblank(struct drm_crtc *crtc)
 static void vc4_disable_vblank(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
+
+	if (vc4_state->feed_txp)
+		return;
 
 	CRTC_WRITE(PV_INTEN, 0);
 }