Re: [PATCH 1/6] dt-bindings: iio: adc: Add AD7768

[Janani Sunil <jananisunil.dev@gmail.com>]

On 7/9/26 17:43, David Lechner wrote:
> On 7/9/26 3:50 AM, Janani Sunil wrote:
>> Devicetree Bindings for AD7768-4 (4 channel) and AD7768 (8 channel)
>> simultaneous sampling ADC
>>
>> Signed-off-by: Janani Sunil <janani.sunil@analog.com>
>> ---
>>   
>>
>> +
>> +  adi,power-mode:
>> +    $ref: /schemas/types.yaml#/definitions/string
>> +    enum:
>> +      - low
>> +      - median
>> +      - fast
>> +    description:
>> +      Power mode selection.
> Unless there are pins that control this, it seems like it should be
> left up to the driver to decide how to set this.
>
> In this case, it looks like the power mode also influences sample rate
> which is normally something controlled at runtime.

Hi David,

The reason we'd like to retain power mode control is that certain ODRs 
are supported across all three power modes (low/median/fast), and the 
RMS noise and power consumption differ significantly between them at the 
same ODR.

The higher the power mode, the better the noise performance, but power 
consumption nearly doubles for every ~3 dB improvement in dynamic range. 
Silently selecting one power mode in the driver would remove a 
meaningful hardware tradeoff from the user.

We'd like to propose the following instead:
- Remove adi,power-mode from the DT as suggested.
- Expose power mode as a per-device sysfs attribute.
- in_voltage<N>_sampling_frequency_available dynamically reflects only 
the ODRs valid for the currently selected power mode.

This keeps the DT clean while still giving the user explicit control 
over the noise versus power trade off. Would this approach be acceptable?

Thanks,
Jan