linux-kernel - [PATCH] drm: vc4: Fix pixel-wrap issue with DVP teardown

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Message-Id: <20210628130533.144617-1-maxime@cerno.tech>
Date:   Mon, 28 Jun 2021 15:05:33 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Emma Anholt <emma@...olt.net>, Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <mripard@...nel.org>,
        linux-kernel@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>
Subject: [PATCH] drm: vc4: Fix pixel-wrap issue with DVP teardown

From: Tim Gover <tim.gover@...pberrypi.com>

Adjust the DVP enable/disable sequence to avoid a pixel getting stuck
in an internal, non resettable FIFO within PixelValve when changing
HDMI resolution.

The blank pixels features of the DVP can prevent signals back to
pixelvalve causing it to not clear the FIFO. Adjust the ordering
and timing of operations to ensure the clear signal makes it through to
pixelvalve.

Signed-off-by: Tim Gover <tim.gover@...pberrypi.com>
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 4ebe216b10a9..472a9d6b5866 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -605,12 +605,12 @@ static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *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_CLRRGB);
+
+	mdelay(1);
 
 	HDMI_WRITE(HDMI_VID_CTL,
-		   HDMI_READ(HDMI_VID_CTL) | VC4_HD_VID_CTL_BLANKPIX);
-
+		   HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
 	vc4_hdmi_disable_scrambling(encoder);
 }
 
@@ -620,12 +620,12 @@ static void vc4_hdmi_encoder_post_crtc_powerdown(struct drm_encoder *encoder,
 	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
 	int ret;
 
+	HDMI_WRITE(HDMI_VID_CTL,
+		   HDMI_READ(HDMI_VID_CTL) | VC4_HD_VID_CTL_BLANKPIX);
+
 	if (vc4_hdmi->variant->phy_disable)
 		vc4_hdmi->variant->phy_disable(vc4_hdmi);
 
-	HDMI_WRITE(HDMI_VID_CTL,
-		   HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
-
 	clk_disable_unprepare(vc4_hdmi->pixel_bvb_clock);
 	clk_disable_unprepare(vc4_hdmi->hsm_clock);
 	clk_disable_unprepare(vc4_hdmi->pixel_clock);
@@ -1017,6 +1017,7 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 
 	HDMI_WRITE(HDMI_VID_CTL,
 		   VC4_HD_VID_CTL_ENABLE |
+		   VC4_HD_VID_CTL_CLRRGB |
 		   VC4_HD_VID_CTL_UNDERFLOW_ENABLE |
 		   VC4_HD_VID_CTL_FRAME_COUNTER_RESET |
 		   (vsync_pos ? 0 : VC4_HD_VID_CTL_VSYNC_LOW) |
-- 
2.31.1