linux-kernel - [PATCH 5.18 0307/1095] drm/bridge: lt9611: Use both bits for HDMI sensing

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Date:   Mon, 15 Aug 2022 19:55:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yongqin Liu <yongqin.liu@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Vinod Koul <vkoul@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Robert Foss <robert.foss@...aro.org>, kernel-team@...roid.com,
        John Stultz <jstultz@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 0307/1095] drm/bridge: lt9611: Use both bits for HDMI sensing

From: John Stultz <jstultz@...gle.com>

[ Upstream commit 649eb3828fb22e829e222ebd83f4e11dc503a565 ]

In commit 19cf41b64e3b ("lontium-lt9611: check a different
register bit for HDMI sensing"), the bit flag used to detect
HDMI cable connect was switched from BIT(2) to BIT(0) to improve
compatibility with some monitors that didn't seem to set BIT(2).

However, with that change, I've seen occasional issues where the
detection failed, because BIT(2) was set, but not BIT(0).

Unfortunately, as I understand it, the bits and their function
was never clearly documented. So lets instead check both
(BIT(2) | BIT(0)) when checking the register.

Cc: Yongqin Liu <yongqin.liu@...aro.org>
Cc: Amit Pundir <amit.pundir@...aro.org>
Cc: Peter Collingbourne <pcc@...gle.com>
Cc: Vinod Koul <vkoul@...nel.org>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Robert Foss <robert.foss@...aro.org>
Cc: kernel-team@...roid.com
Fixes: 19cf41b64e3b ("lontium-lt9611: check a different register bit for HDMI sensing")
Signed-off-by: John Stultz <jstultz@...gle.com>
Reviewed-by: Robert Foss <robert.foss@...aro.org>
Signed-off-by: Robert Foss <robert.foss@...aro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220511012612.3297577-2-jstultz@google.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/lontium-lt9611.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index 63df2e8a8abc..21d1e1465981 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -586,7 +586,7 @@ lt9611_connector_detect(struct drm_connector *connector, bool force)
 	int connected = 0;
 
 	regmap_read(lt9611->regmap, 0x825e, &reg_val);
-	connected  = (reg_val & BIT(0));
+	connected  = (reg_val & (BIT(2) | BIT(0)));
 
 	lt9611->status = connected ?  connector_status_connected :
 				connector_status_disconnected;
-- 
2.35.1