linux-kernel - Re: [PATCH v3 10/11] arm64: dts: qcom: sdm845-lg-judyln: Add lab/ibb

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Message-ID: <38c70e06-f7bf-4ca6-8fe9-2a4012017cff@oss.qualcomm.com>
Date: Wed, 1 Oct 2025 11:09:37 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Paul Sajna <sajattack@...tmarketos.org>,
        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>, David Heidelberg <david@...t.cz>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org,
        Amir Dahan <system64fumo@...tonmail.com>,
        Christopher Brown <crispybrown@...il.com>
Subject: Re: [PATCH v3 10/11] arm64: dts: qcom: sdm845-lg-judyln: Add lab/ibb

On 9/29/25 7:05 AM, Paul Sajna wrote:
> These regulators seemingly help the lcd to work better

Electronics generally work better when the required power supplies
are enabled..

> 
> Signed-off-by: Paul Sajna <sajattack@...tmarketos.org>
> ---
>  arch/arm64/boot/dts/qcom/sdm845-lg-judyln.dts | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845-lg-judyln.dts b/arch/arm64/boot/dts/qcom/sdm845-lg-judyln.dts
> index 3106fdc9b679bc6a43a1a490c61b73a63003f7e1..9c3662a3d93e124667474753e0f11d0e98698aa0 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845-lg-judyln.dts
> +++ b/arch/arm64/boot/dts/qcom/sdm845-lg-judyln.dts
> @@ -48,10 +48,27 @@ zap-shader {
>  	};
>  };
>  
> +&ibb {
> +	regulator-min-microvolt = <4600000>;
> +	regulator-max-microvolt = <6000000>;
> +	regulator-over-current-protection;
> +	regulator-pull-down;
> +	regulator-soft-start;
> +	qcom,discharge-resistor-kohms = <300>;
> +};
> +
>  &ipa {
>  	firmware-name = "qcom/sdm845/lg/judyln/ipa_fws.mbn";
>  };
>  
> +&lab {
> +	regulator-min-microvolt = <4600000>;
> +	regulator-max-microvolt = <6000000>;
> +	regulator-over-current-protection;
> +	regulator-pull-down;
> +	regulator-soft-start;
> +};

This patch will allow any values between 4.6 V and 6.0 V to
be set on your phone, with the kernel defaulting to 4.6 V at
boot and staying there until (if?) any driver requests that to
change.

Your panel probably expects a *very* specific pair of voltages
and any deviation may cause unpredictable consequences, including
magic smoke if you happen to go over a certain limit.

You should most likely hardcode that specific expected voltage here

Konrad