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

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Message-ID: <c7639504-e605-4dcc-90c6-4993ada0e271@oss.qualcomm.com>
Date: Mon, 6 Oct 2025 10:36:43 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Paul Sajna <sajattack@...tmarketos.org>
Cc: 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>,
        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 10/3/25 11:55 PM, Dmitry Baryshkov wrote:
> On Thu, Oct 02, 2025 at 04:55:44AM +0000, Paul Sajna wrote:
>> 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:
>>>
>>>>
>>> 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
>>
>> 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
> 
> Downstream frequently further constraints the regulators. Could you
> please check the boards's dts file and the drivers (SDE)?

Or you can read back the values at runtime.. presumably even
/sys/kernel/debug/regulator/foo should have the up-to-date info

Konrad