[PATCH v5 74/80] drm/vc4: hdmi: Switch to blank pixels when disabled

[Maxime Ripard]

In order to avoid pixels getting stuck in an unflushable FIFO, we need when
we disable the HDMI controller to switch away from getting our pixels from
the pixelvalve and instead use blank pixels, and switch back to the
pixelvalve when we enable the HDMI controller.

Reviewed-by: Dave Stevenson <dave.stevenson at raspberrypi.com>
Tested-by: Chanwoo Choi <cw00.choi at samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon at samsung.com>
Tested-by: Stefan Wahren <stefan.wahren at i2se.com>
Signed-off-by: Maxime Ripard <maxime at cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c |  9 +++++++++
 drivers/gpu/drm/vc4/vc4_regs.h |  3 +++
 2 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 8bf69cafdd7e..ab7abb409de2 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -325,6 +325,12 @@ static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder)
 	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
 
 	HDMI_WRITE(HDMI_RAM_PACKET_CONFIG, 0);
+
+	HDMI_WRITE(HDMI_VID_CTL, HDMI_READ(HDMI_VID_CTL) |
+		   VC4_HD_VID_CTL_CLRRGB | VC4_HD_VID_CTL_CLRSYNC);
+
+	HDMI_WRITE(HDMI_VID_CTL,
+		   HDMI_READ(HDMI_VID_CTL) | VC4_HD_VID_CTL_BLANKPIX);
 }
 
 static void vc4_hdmi_encoder_post_crtc_powerdown(struct drm_encoder *encoder)
@@ -563,6 +569,9 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder)
 		   (vsync_pos ? 0 : VC4_HD_VID_CTL_VSYNC_LOW) |
 		   (hsync_pos ? 0 : VC4_HD_VID_CTL_HSYNC_LOW));
 
+	HDMI_WRITE(HDMI_VID_CTL,
+		   HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_BLANKPIX);
+
 	if (vc4_encoder->hdmi_monitor) {
 		HDMI_WRITE(HDMI_SCHEDULER_CONTROL,
 			   HDMI_READ(HDMI_SCHEDULER_CONTROL) |
diff --git a/drivers/gpu/drm/vc4/vc4_regs.h b/drivers/gpu/drm/vc4/vc4_regs.h
index d1e8961edaa0..30af52b406f1 100644
--- a/drivers/gpu/drm/vc4/vc4_regs.h
+++ b/drivers/gpu/drm/vc4/vc4_regs.h
@@ -723,6 +723,9 @@
 # define VC4_HD_VID_CTL_FRAME_COUNTER_RESET	BIT(29)
 # define VC4_HD_VID_CTL_VSYNC_LOW		BIT(28)
 # define VC4_HD_VID_CTL_HSYNC_LOW		BIT(27)
+# define VC4_HD_VID_CTL_CLRSYNC			BIT(24)
+# define VC4_HD_VID_CTL_CLRRGB			BIT(23)
+# define VC4_HD_VID_CTL_BLANKPIX		BIT(18)
 
 # define VC4_HD_CSC_CTL_ORDER_MASK		VC4_MASK(7, 5)
 # define VC4_HD_CSC_CTL_ORDER_SHIFT		5
-- 
git-series 0.9.1