linux-kernel - Re: [PATCH V6 4/5] iio: adc: Add support for QCOM PMIC5 Gen3 ADC

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Message-ID: <0d0d42fd-06e1-4584-b82c-965f4fb5fa74@oss.qualcomm.com>
Date: Thu, 10 Jul 2025 14:49:26 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Jishnu Prakash <jishnu.prakash@....qualcomm.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc: robh@...nel.org, krzysztof.kozlowski@...aro.org, krzk+dt@...nel.org,
        conor+dt@...nel.org, agross@...nel.org, andersson@...nel.org,
        lumag@...nel.org, dmitry.baryshkov@....qualcomm.com,
        konradybcio@...nel.org, daniel.lezcano@...aro.org, sboyd@...nel.org,
        amitk@...nel.org, thara.gopinath@...il.com, lee@...nel.org,
        rafael@...nel.org, subbaraman.narayanamurthy@....qualcomm.com,
        david.collins@....qualcomm.com, anjelique.melendez@....qualcomm.com,
        quic_kamalw@...cinc.com, rui.zhang@...el.com, lukasz.luba@....com,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, cros-qcom-dts-watchers@...omium.org,
        quic_skakitap@...cinc.com, neil.armstrong@...aro.org,
        stephan.gerhold@...aro.org
Subject: Re: [PATCH V6 4/5] iio: adc: Add support for QCOM PMIC5 Gen3 ADC

On 7/10/25 8:44 AM, Jishnu Prakash wrote:
> Hi Jonathan,
> 
> On 6/28/2025 10:01 PM, Jonathan Cameron wrote:
>>
>>
>>>>> +	.hw_settle_1 = (unsigned int [VADC_HW_SETTLE_SAMPLES_MAX])
>>>>> +				{ 15, 100, 200, 300, 400, 500, 600, 700,
>>>>> +				  1000, 2000, 4000, 8000, 16000, 32000,
>>>>> +				  64000, 128000 },  
>>>> Andy often points this out, but I'll do it this time. Fixed numbers (typically power of 2)
>>>> elements per line make it much easier to see which element is which in these arrays.
>>>> Reduce the indent a little to allow that here.  
> 
> ...
> 
>>>>
>>>> It was never worth bothering with release until we had devm managed form but
>>>> now we do the code complexity cost is low enough to make it reasonable.
>>>>   
>>>>> +	indio_dev->name = pdev->name;  
>>>>
>>>> Just to check.  Does that end up as a part number or similar?  
>>>
>>> I printed this name and it appeared like this:
>>>
>>> indio_dev->name: c426000.spmi:pmic@0:adc@...0
>>>
>>> It only gets the DT node names, which are generic, there are 
>>> no part numbers in this name.
>> I thought it might be something along those lines.
>>
>> indio_dev->name should be the part number so hard code it rather than
>> getting it from the pdev->name
>>
> 
> Actually there would be more than one PMIC which can function as the master PMIC
> for Gen3 ADC functionality, so I don't think I can simply hard code a name here
> based on PMK8550, if we want to keep the part number correct.
> 
> Since we can't get the part number directly from the DT node names, we
> could try one of the following ways to add it:
> 
> 1. Add a devicetree property for the part number
>    This would be simple, but I'm not sure if this is the best way, 
>    if the below method looks good.
> 
> 2. Add a string in the compatible property for the part number.
>    This means updating the compatible from "qcom,spmi-adc5-gen3"
>    to something like this for PMK8550:
> 
>    compatible = "qcom,pmk8550-adc5-gen3", "qcom,spmi-adc5-gen3";
> 
>    and then extracting the part number from the first string.
> 
> Please let me know which method you would prefer.
> 
> In addition, does the below string look fine, to assign to
> indio_dev->name for PMK8550?
> 
> pmk8550_adc

I don't know if it's a good idea to intertwine the two, but we
happen to already have a mechanism to retrieve the name of the
part at runtime in drivers/soc/qcom/socinfo.c, namely
qcom_show_pmic_model()

Konrad