linux-kernel - [PATCH 1/3] arm64: dts: qcom: msm8916: Add missing MDSS reset

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Message-Id: <20250915-msm8916-resets-v1-1-a5c705df0c45@linaro.org>
Date: Mon, 15 Sep 2025 15:28:30 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>
Cc: Vincent Knecht <vincent.knecht@...loo.org>, 
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] arm64: dts: qcom: msm8916: Add missing MDSS reset

On most MSM8916 devices (aside from the DragonBoard 410c), the bootloader
already initializes the display to show the boot splash screen. In this
situation, MDSS is already configured and left running when starting Linux.
To avoid side effects from the bootloader configuration, the MDSS reset can
be specified in the device tree to start again with a clean hardware state.

The reset for MDSS is currently missing in msm8916.dtsi, which causes
errors when the MDSS driver tries to re-initialize the registers:

 dsi_err_worker: status=6
 dsi_err_worker: status=6
 dsi_err_worker: status=6
 ...

It turns out that we have always indirectly worked around this by building
the MDSS driver as a module. Before v6.17, the power domain was temporarily
turned off until the module was loaded, long enough to clear the register
contents. In v6.17, power domains are not turned off during boot until
sync_state() happens, so this is no longer working. Even before v6.17 this
resulted in broken behavior, but notably only when the MDSS driver was
built-in instead of a module.

Cc: stable@...r.kernel.org
Fixes: 305410ffd1b2 ("arm64: dts: msm8916: Add display support")
Signed-off-by: Stephan Gerhold <stephan.gerhold@...aro.org>
---
 arch/arm64/boot/dts/qcom/msm8916.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/msm8916.dtsi b/arch/arm64/boot/dts/qcom/msm8916.dtsi
index b50c7e6e0bfcd35ab4f8b84aeabe214fd60e8d7c..de0c10b54c86c7795b7a0d1ecd80652e60e117b6 100644
--- a/arch/arm64/boot/dts/qcom/msm8916.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8916.dtsi
@@ -1562,6 +1562,8 @@ mdss: display-subsystem@...0000 {

 			interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>;

+			resets = <&gcc GCC_MDSS_BCR>;
+
 			interrupt-controller;
 			#interrupt-cells = <1>;

-- 
2.50.1