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

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Message-ID: <64a732cdc3fe9381e2f716be9e965fbc905c1416@postmarketos.org>
Date: Thu, 02 Oct 2025 04:55:44 +0000
From: "Paul Sajna" <sajattack@...tmarketos.org>
To: "Konrad Dybcio" <konrad.dybcio@....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>, "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

October 1, 2025 at 9:09 AM, "Konrad Dybcio" <konrad.dybcio@....qualcomm.com mailto:konrad.dybcio@....qualcomm.com?to=%22Konrad%20Dybcio%22%20%3Ckonrad.dybcio%40oss.qualcomm.com%3E > wrote:


> 
> 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
>

These are the values used in downstream android dts 
https://github.com/LineageOS/android_kernel_lge_sdm845/blob/efa8458f79dffeb380d43b38b9403407f87d9f05/arch/arm64/boot/dts/qcom/pmi8998.dtsi#L484-L485