Re: [PATCH 2/4] dt-bindings: pinctrl: Document nuvoton ma35d1 pin control

[Krzysztof Kozlowski]

On 18/10/2023 10:18, Linus Walleij wrote:
> On Mon, Oct 16, 2023 at 9:52 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@xxxxxxxxxx> wrote:
> 
>>> I noticed that 'xlnx,zynq-pinctrl.yaml' and 'xlnx,zynq-pinctrl.yaml' use
>>> 'power source' to specify the output voltage.  Should I follow their
>>> approach or define a vendor-specific one?
>>
>> Maybe Rob or Linus have here some recommendation, but I would suggest to
>> go either with rtd1319d-pinctrl.yaml approach or add a generic property
>> to pincfg-node expressed in real units like "io-microvolt".
>>
>> Rob, Linus, any ideas for generic property replacing register-specific
>> power-source?
> 
> The existing power-source is generally used to select between (usually
> two) different chip-internal power rails, such as 1.8V and 3.3V.
> The format is a driver-specific enumerator.
> 
> We *could* just patch the documentation for power-source to
> say that microvolts is the preferred format but legacy users may
> be using a custom enumerator.
> 
> io-microvolt seems like a more long-term viable option if a wider
> range of voltages are to be supported so I'm happy with that if the
> DT folks think it's nicer. However notice that the power-source
> property is already being hard-coded into things such as SCMI
> and ACPI so it's not like it will ever be replaced by io-microvolt
> and phased out as far as Linux is concerned. Not the next 50
> years at least.

This I understand.

I think It is better in general if generic properties use units (e.g.
drive-strength-microamp, output-impedance-ohms), so it could be here
"io-microvolt". At least for the new bindings.

Best regards,
Krzysztof