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From: Maxime Ripard <>
	Daniel Vetter <>,
	David Airlie <>,
	Maarten Lankhorst <>,
	Thomas Zimmermann <>,
	Maxime Ripard <>
Cc: Maxime Ripard <>, Emma Anholt <>,,
	Nicolas Saenz Julienne <>,
	Dave Stevenson <>,
	Phil Elwell <>,
	Tim Gover <>,
	Dom Cobley <>,,
Subject: [PATCH v7 01/10] drm/vc4: hdmi: Remove the DDC probing for status detection
Date: Thu, 19 Aug 2021 11:51:10 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Commit 9d44abbbb8d5 ("drm/vc4: Fall back to using an EDID probe in the
absence of a GPIO.") added some code to read the EDID through DDC in the
HDMI driver detect hook since the Pi3 had no HPD GPIO back then.
However, commit b1b8f45b3130 ("ARM: dts: bcm2837: Add missing GPIOs of
Expander") changed that a couple of years later.

This causes an issue though since some TV (like the LG 55C8) when it
comes out of standy will deassert the HPD line, but the EDID will
remain readable.

It causes an issues nn platforms without an HPD GPIO, like the Pi4,
where the DDC probing will be our primary mean to detect a display, and
thus we will never detect the HPD pulse. This was fine before since the
pulse was small enough that we would never detect it, and we also didn't
have anything (like the scrambler) that needed to be set up in the

However, now that we have both, the display during the HPD pulse will
clear its scrambler status, and since we won't detect the
disconnect/reconnect cycle we will never enable the scrambler back.

As our main reason for that DDC probing is gone, let's just remove it.

Signed-off-by: Maxime Ripard <>
 drivers/gpu/drm/vc4/vc4_hdmi.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index b7dc32a0c9bb..f9a672a641ab 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -172,8 +172,6 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
 	if (vc4_hdmi->hpd_gpio &&
 	    gpiod_get_value_cansleep(vc4_hdmi->hpd_gpio)) {
 		connected = true;
-	} else if (drm_probe_ddc(vc4_hdmi->ddc)) {
-		connected = true;
 		connected = true;

  reply	other threads:[~2021-08-19  9:51 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19  9:51 [PATCH v7 00/10] drm/vc4: hdmi: Support the 4k @ 60Hz modes Maxime Ripard
2021-08-19  9:51 ` Maxime Ripard [this message]
2021-08-19  9:51 ` [PATCH v7 02/10] drm/vc4: hdmi: Fix HPD GPIO detection Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 03/10] drm/vc4: Make vc4_crtc_get_encoder public Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 04/10] drm/vc4: crtc: Add encoder to vc4_crtc_config_pv prototype Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 05/10] drm/vc4: crtc: Rework the encoder retrieval code (again) Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 06/10] drm/vc4: crtc: Add some logging Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 07/10] drm/vc4: Leverage the load tracker on the BCM2711 Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 08/10] drm/vc4: hdmi: Raise the maximum clock rate Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 09/10] drm/vc4: hdmi: Enable the scrambler on reconnection Maxime Ripard
2021-08-19  9:51 ` [PATCH v7 10/10] drm/vc4: Increase the core clock based on HVS load Maxime Ripard

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