[PATCH v4 73/78] 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.

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 f56a718a3643..37463b016b47 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
-- 
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