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Message-ID: <73651055-2a1b-75b9-3483-b180afa6f7bd@linaro.org>
Date:   Mon, 17 Oct 2022 13:22:27 -0400
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Subject: Re: [PATCH 1/5] arm64: dts: qcom: pmi8998: add rradc node
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To:     Caleb Connolly <caleb.connolly@linaro.org>
Cc:     Luca Weiss <luca@z3ntu.xyz>, Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        devicetree@vger.kernel.org,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Rob Herring <robh+dt@kernel.org>
References: <20221016180330.1912214-1-caleb.connolly@linaro.org>
 <20221016180330.1912214-2-caleb.connolly@linaro.org>
 <5929051d-d2be-5b51-0cf9-294affa51df2@linaro.org>
 <1f6d8eb9-8e6e-a201-50c6-a9fa6f25b3d6@linaro.org>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <1f6d8eb9-8e6e-a201-50c6-a9fa6f25b3d6@linaro.org>
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On 17/10/2022 11:29, Caleb Connolly wrote:

>>> +		pmi8998_rradc: adc@4500 {
>>> +			compatible = "qcom,pmi8998-rradc";
>>> +			reg = <0x4500>;
>>> +			#io-channel-cells = <1>;
>>> +
>>> +			status = "disabled";
>>
>> Why disabling it? It does not need any external/board resources, so
>> maybe it should be just like other adcs - enabled by default? What does
>> it measure? What is its input?
> 
> The RRADC mostly reports values which only make sense on mobile devices, battery 
> ID and temperature, USB and DC input voltage/current as well as a (duplicate?) 
> die temperature of the PMIC - I guess closer to the SMB/FG block.
> 
> When I last tested the DC input readings didn't work on db845c, as it just 
> produces the 4.2v you'd get from a battery.

If it is connected to some line - e.g. to the battery - then it is
operational and there is no reason to disable it.


Best regards,
Krzysztof