linux-kernel - Re: [PATCH v2 2/2] dt-bindings: hwmon: Add sample averaging property for ADM1275

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Date:   Fri, 25 Feb 2022 08:31:18 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Potin Lai <potin.lai@...ntatw.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Patrick Williams <patrick@...cx.xyz>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/2] dt-bindings: hwmon: Add sample averaging property
 for ADM1275

On 25/02/2022 08:06, Krzysztof Kozlowski wrote:
> On 24/02/2022 16:43, Potin Lai wrote:
>> Add new properties for binding sample averaging in PMON_CONFIG register
>>
>> - adi,volt-curr-sample-average
>> - adi,power-sample-average
>>
>> Signed-off-by: Potin Lai <potin.lai@...ntatw.com>
>> ---
>>  .../bindings/hwmon/adi,adm1275.yaml           | 44 +++++++++++++++++++
>>  1 file changed, 44 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/hwmon/adi,adm1275.yaml b/Documentation/devicetree/bindings/hwmon/adi,adm1275.yaml
>> index 223393d7cafd..325f6827648f 100644
>> --- a/Documentation/devicetree/bindings/hwmon/adi,adm1275.yaml
>> +++ b/Documentation/devicetree/bindings/hwmon/adi,adm1275.yaml
>> @@ -37,6 +37,48 @@ properties:
>>      description:
>>        Shunt resistor value in micro-Ohm.
>>  
>> +  adi,volt-curr-sample-average:
>> +    description: |
>> +      A value to configure VI_AVG in PMON_CONFIG register to indicate a
>> +      number of samples to be used to report voltage and currentvalues.
> 
> missing space after current.
> 
>> +      If set to 7, the 128 samples averaging would be used.
>> +
>> +    $ref: /schemas/types.yaml#/definitions/uint8
> 
> Make it a uint32.
> 
> The previous usage of this field was more appropriate. Instead of
> keeping register values in DT, it's better to keep logical value. What
> if in next cheap the register values have calculation method?
> 
> This should be like in v1 - enum for number of samples to take in averaging.
> 

One more thought: this field could also stay in current approach if you
change the meaning from "value to configure VI_AVG" to something like
"the exponent used to determine the number of samples, where the base is 2".

This approach would allow you to skip the "ilog" in the code. It sill
won't be that easily scalable if another chip comes with different
formula, but I think that's unlikely.

Best regards,
Krzysztof