linux-kernel - Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

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Message-ID: <b5d9d47b-7fb2-4ce4-9bc8-0d28395b78db@oss.qualcomm.com>
Date: Tue, 28 Oct 2025 10:08:19 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Yongxing Mou <yongxing.mou@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel

On 10/28/25 8:04 AM, Yongxing Mou wrote:
> Previously, the eDP panel backlight was enabled via UEFI. Added backlight
> control node in kernel DTS due to some meta may not enable the backlight.
> 
> Aligned with other x1e80100-based platforms: the PWM signal is controlled
> by PMK8550, and the backlight enable signal is handled by PMC8380.
> 
> Signed-off-by: Yongxing Mou <yongxing.mou@....qualcomm.com>
> ---

The subject must say "hamoa-iot-evk:"
>  arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644
> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts
> @@ -17,6 +17,16 @@ aliases {
>  		serial1 = &uart14;
>  	};
>  
> +	backlight: backlight {
> +		compatible = "pwm-backlight";
> +		pwms = <&pmk8550_pwm 0 5000000>;

Try adjusting the backlight value.. you'll find some funny behavior
near the max level.. which reminds me I should send some fixes for
some laptop DTs

[...]

> +	vreg_edp_bl: regulator-edp-bl {
> +		compatible = "regulator-fixed";
> +
> +		regulator-name = "VBL9";
> +		regulator-min-microvolt = <3600000>;
> +		regulator-max-microvolt = <3600000>;
> +
> +		gpio = <&pmc8380_3_gpios 10 GPIO_ACTIVE_HIGH>;
> +		enable-active-high;
> +
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&edp_bl_reg_en>;

property-n
property-names

in this order, please

Konrad