drm/vc4: hdmi: Always recenter the HDMI FIFO

In order to avoid a pixel getting stuck in an unflushable FIFO, we need to
recenter the FIFO every time we're doing a modeset and not only if we're
connected to an HDMI monitor.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b3faaf05ac6c4d3c364d28fa441571eb85903269.1599120059.git-series.maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -425,6 +425,30 @@ static void vc4_hdmi_set_timings(struct vc4_hdmi *vc4_hdmi,
 		   (hsync_pos ? 0 : VC4_HD_VID_CTL_HSYNC_LOW));
 }
 
+static void vc4_hdmi_recenter_fifo(struct vc4_hdmi *vc4_hdmi)
+{
+	u32 drift;
+	int ret;
+
+	drift = HDMI_READ(HDMI_FIFO_CTL);
+	drift &= VC4_HDMI_FIFO_VALID_WRITE_MASK;
+
+	HDMI_WRITE(HDMI_FIFO_CTL,
+		   drift & ~VC4_HDMI_FIFO_CTL_RECENTER);
+	HDMI_WRITE(HDMI_FIFO_CTL,
+		   drift | VC4_HDMI_FIFO_CTL_RECENTER);
+	usleep_range(1000, 1100);
+	HDMI_WRITE(HDMI_FIFO_CTL,
+		   drift & ~VC4_HDMI_FIFO_CTL_RECENTER);
+	HDMI_WRITE(HDMI_FIFO_CTL,
+		   drift | VC4_HDMI_FIFO_CTL_RECENTER);
+
+	ret = wait_for(HDMI_READ(HDMI_FIFO_CTL) &
+		       VC4_HDMI_FIFO_CTL_RECENTER_DONE, 1);
+	WARN_ONCE(ret, "Timeout waiting for "
+		  "VC4_HDMI_FIFO_CTL_RECENTER_DONE");
+}
+
 static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
 {
 	struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;
@@ -543,8 +567,6 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
 	}
 
 	if (vc4_encoder->hdmi_monitor) {
-		u32 drift;
-
 		WARN_ON(!(HDMI_READ(HDMI_SCHEDULER_CONTROL) &
 			  VC4_HDMI_SCHEDULER_CONTROL_HDMI_ACTIVE));
 		HDMI_WRITE(HDMI_SCHEDULER_CONTROL,
@@ -555,25 +577,9 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
 			   VC4_HDMI_RAM_PACKET_ENABLE);
 
 		vc4_hdmi_set_infoframes(encoder);
-
-		drift = HDMI_READ(HDMI_FIFO_CTL);
-		drift &= VC4_HDMI_FIFO_VALID_WRITE_MASK;
-
-		HDMI_WRITE(HDMI_FIFO_CTL,
-			   drift & ~VC4_HDMI_FIFO_CTL_RECENTER);
-		HDMI_WRITE(HDMI_FIFO_CTL,
-			   drift | VC4_HDMI_FIFO_CTL_RECENTER);
-		usleep_range(1000, 1100);
-		HDMI_WRITE(HDMI_FIFO_CTL,
-			   drift & ~VC4_HDMI_FIFO_CTL_RECENTER);
-		HDMI_WRITE(HDMI_FIFO_CTL,
-			   drift | VC4_HDMI_FIFO_CTL_RECENTER);
-
-		ret = wait_for(HDMI_READ(HDMI_FIFO_CTL) &
-			       VC4_HDMI_FIFO_CTL_RECENTER_DONE, 1);
-		WARN_ONCE(ret, "Timeout waiting for "
-			  "VC4_HDMI_FIFO_CTL_RECENTER_DONE");
 	}
+
+	vc4_hdmi_recenter_fifo(vc4_hdmi);
 }
 
 static enum drm_mode_status