Message-ID: <08eb477f-ea34-4a31-b181-bfc629aef4c8@kernel.org>
Date: Thu, 9 Oct 2025 08:52:25 +0900
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jishnu Prakash <jishnu.prakash@....qualcomm.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Jonathan Cameron <jic23@...nel.org>, robh@...nel.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, kamal.wadhwa@....qualcomm.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_kotarake@...cinc.com,
 neil.armstrong@...aro.org, stephan.gerhold@...aro.org,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH V7 3/5] dt-bindings: iio: adc: Add support for QCOM PMIC5
 Gen3 ADC

On 08/10/2025 23:20, Jishnu Prakash wrote:
> Hi Krzysztof,
> 
> On 10/4/2025 12:22 PM, Krzysztof Kozlowski wrote:
>> On Sat, 4 Oct 2025 at 11:42, Jishnu Prakash
>> <jishnu.prakash@....qualcomm.com> wrote:
>>>
>>> Hi Jonathan,
>>>
>>> On 9/27/2025 7:17 PM, Jonathan Cameron wrote:
>>>> On Fri, 19 Sep 2025 20:17:43 +0530
>>>> Jishnu Prakash <jishnu.prakash@....qualcomm.com> wrote:
>>>>
>>>>> Hi Krzysztof,
>>>>>
>>>>> On 9/18/2025 5:45 AM, Krzysztof Kozlowski wrote:
>>>>>> On 18/09/2025 04:47, Jishnu Prakash wrote:
>>>>>>> Hi Krzysztof,
>>>>>>>
>>>>>>> On 9/17/2025 5:59 AM, Krzysztof Kozlowski wrote:
>>>>>>>> On 16/09/2025 16:28, Jishnu Prakash wrote:
>>>>>>>>>> You cannot have empty spaces in ID constants. These are abstract
>>>>>>>>>> numbers.
>>>>>>>>>>
>>>>>>>>>> Otherwise please point me to driver using this constant.
>>>>>>>>>
>>>>>>>>> These constants are for ADC channel numbers, which are fixed in HW.
>>>>>>>>>
>>>>>>>>> They are used in this driver: drivers/iio/adc/qcom-spmi-adc5-gen3.c,
>>>>>>>>> which is added in patch 4 of this series.
>>>>>>>>>
>>>>>>>>> They can be found in the array named adc5_gen3_chans_pmic[].
>>>>>>>>
>>>>>>>> Really? So point me to the line there using ADC5_GEN3_VREF_BAT_THERM.
>>>>>>>>
>>>>>>>
>>>>>>> We may not be using all of these channels right now - we can add them
>>>>>>> later based on requirements coming up. For now, I'll remove the channels
>>>>>>> not used in adc5_gen3_chans_pmic[].
>>>>>>
>>>>>> You are not implementing the feedback then. Please read it carefully.
>>>>>>
>>>>>
>>>>> Sorry, I misunderstood - so you actually meant I should remove the
>>>>> empty spaces in the definitions, like this?
>>>>>
>>>>> -#define ADC5_GEN3_VREF_BAT_THERM               0x15
>>>>> +#define ADC5_GEN3_VREF_BAT_THERM 0x15
>>>>>
>>>>> I thought this at first, but I somehow doubted this later, as I saw some
>>>>> other recently added files with empty spaces in #define lines, like:
>>>>>
>>>>> include/dt-bindings/iio/adc/mediatek,mt6373-auxadc.h
>>>>> include/dt-bindings/regulator/st,stm32mp15-regulator.h
>>>>>
>>>>> I can make this change, if you prefer this. Please let me know
>>>>> if I'm still missing something.
>>>>>
>>>>> Also please let me know if you want me to remove the unused
>>>>> channels - I would prefer to keep them if there's no issue,
>>>>> as we might need them later.
>>>>>
>>>> He is referring to 0x14 and below not being defined values.  So what
>>>> do they mean if they turn up in the DT?
>>>>
>>>
>>> Thanks for your clarification. To address your first point above, the macros
>>> added here only represent the ADC channel numbers which are supported for
>>> ADC5 Gen3 devices. If there are numbers missing in between (like 0x14),
>>> that is because there exist no valid ADC channels in HW matching those
>>> channel numbers.
>>>
>>> For your question above, if any of the undefined channels are used in the DT,
>>> they should ideally be treated as invalid when parsed in the driver probe and
>>> lead to an error. When I checked the code again, I saw we do not have such an
>>> explicit check right now, so I will add that in the next patch series.
>>>
>>> And to be clear on which channel numbers are supported, I think it may be
>>> best if, for now, we only add support for the channel numbers referenced in
>>> the array adc5_gen3_chans_pmic[] in drivers/iio/adc/qcom-spmi-adc5-gen3.c.
>>>
>>> There are only 18 channel numbers used in this array and I would remove
>>> all channels except for these from the binding files. During parsing, we
>>> would use this array to confirm if an ADC channel added in DT is supported.
>>>
>>> In case we need to add support for any more channels later, we could add
>>> their macros in the binding file and update the array correspondingly at
>>> that time.
>>>
>>> Does all this sound fine? Please let me know if you have any more concerns
>>> or queries.
>>
>> No, it doesn't.  You keep ignoring my arguments and responding to
>> something else. I prefer not to store hardware values as bindings,
>> because these are not bindings (and you failed to prove which SW
>> interface they bind) and it's really not necessary.
> 
> In my previous replies in this thread, I missed mentioning that the macros
> defined in include/dt-bindings/iio/adc/qcom,spmi-vadc.h are also used in
> other places than the driver file - they are also used in the PMIC-specific
> binding files added in this patch, for channel definitions. Considering
> one channel for example:
>  
> We have this in include/dt-bindings/iio/adc/qcom,spmi-vadc.h:
> +#define ADC5_GEN3_DIE_TEMP			0x03
>  
> The above is used in include/dt-bindings/iio/adc/qcom,pm8550vx-adc5-gen3.h:
> +#define PM8550VS_ADC5_GEN3_DIE_TEMP(sid)			((sid) << 8 | ADC5_GEN3_DIE_TEMP)
>  
> And the above definition may be used in device tree, like in the example added
> in Documentation/devicetree/bindings/iio/adc/qcom,spmi-adc5-gen3.yaml:
>  
> +        channel@203 {
> +          reg = <PM8550VS_ADC5_GEN3_DIE_TEMP(2)>;
> +          label = "pm8550vs_c_die_temp";
> +          qcom,pre-scaling = <1 1>;
> +        };

This is not a driver. I do not understand your argumentation at all.

Best regards,
Krzysztof

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