Re: [PATCH V7 3/5] dt-bindings: iio: adc: Add support for QCOM PMIC5 Gen3 ADC

[Krzysztof Kozlowski <krzk@kernel.org>]

On 17/10/2025 13:18, Jishnu Prakash wrote:
> Hi Krzysztof,
> 
> On 10/9/2025 5:22 AM, Krzysztof Kozlowski wrote:
>> 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@oss.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@oss.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.
> 
> Sorry about the delay in replying. Let me go step by step
> over the use of the macros and how they are used by clients
> SW.
> 
> 1. In ADC Gen3, this is the superset of channels supported on all
> PMICs (with ADC):
> 
> Ref: include/dt-bindings/iio/adc/qcom,spmi-vadc.h

That's not a driver. Not SW.

> 
> /* ADC channels for PMIC5 Gen3 */
> 
> #define ADC5_GEN3_REF_GND		0x00
> #define ADC5_GEN3_1P25VREF		0x01
> #define ADC5_GEN3_VREF_VADC		0x02
> #define ADC5_GEN3_DIE_TEMP		0x03
> ....
> 
> 
> 2. Since some PMICs may not have all of these channels supported in
> HW, we have the PMIC-specific channel definitions (starting with PMIC
> name like PM8550_..) made referencing the above definitions.
> 
> Ref: include/dt-bindings/iio/adc/qcom,pm8550-adc5-gen3.h:

That's not a driver. Not SW.


> ...
>     #define PM8550_ADC5_GEN3_DIE_TEMP(sid)	((sid) << 8 | ADC5_GEN3_DIE_TEMP)
> ...
> 
> side note: This is also used for the "reg" property in the ADC channel
> definition DT nodes.
> 
> Here `sid` is needed as there can be different instances of same PMIC
> using different `sid`s on a single SoC, and also on different SoCs, the
> same PMIC may have different `sid`s.
> 
> 
> 3. This PMIC-specific definition will be used by clients like below
> (in io-channels) to get the ADC channel they need to read.
> 
>     pmic@1 {
>         temp-alarm@a00 {
>             compatible = "qcom,spmi-temp-alarm";
> 	    ...
>             io-channels = <&pmk8550_adc PM8550_ADC5_GEN3_DIE_TEMP(1)>;
>             io-channel-names = "thermal";
>         };
>     };

That's not a driver. Not SW.

> 
> 
> Can you please provide your suggestions on changes we can make
> in the above points ?

You just pasted DT. I asked about SW, software. Please read carefully
previous comments.


Best regards,
Krzysztof