linux-kernel - Re: [RFC v1 2/4] pinctrl: add polarfire soc mssio pinctrl driver

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Message-ID: <CACRpkdaM3Hkbxx99uXx6OVdSbdhNNc3voS1FoUsz2oAUEc1-qA@mail.gmail.com>
Date: Fri, 21 Nov 2025 00:13:21 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Conor Dooley <conor@...nel.org>
Cc: Conor Dooley <conor.dooley@...rochip.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
	Valentina.FernandezAlanis@...rochip.com, Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [RFC v1 2/4] pinctrl: add polarfire soc mssio pinctrl driver

On Thu, Nov 20, 2025 at 1:26 AM Conor Dooley <conor@...nel.org> wrote:
> On Wed, Nov 19, 2025 at 10:48:07PM +0100, Linus Walleij wrote:
> > On Wed, Nov 19, 2025 at 7:23 PM Conor Dooley <conor@...nel.org> wrote:

> > I looked at the bindings that look like this and are not 1:1 to the
> > in-kernel configs:
> >
> >   input-schmitt-enable:
> >     type: boolean
> >     description: enable schmitt-trigger mode
> >
> >   input-schmitt-disable:
> >     type: boolean
> >     description: disable schmitt-trigger mode
> >
> >   input-schmitt-microvolt:
> >     description: threshold strength for schmitt-trigger
> >
> > 1. input-schmitt is missing! But it is right there in
> > drivers/pinctrl/pinconf-generic.c ... All DTS files appear to be
> > using input-schmitt-enable/disable and -microvolt.
> >
> > 2. input-schmitt-microvolt should probably be used separately
> > to set the voltage threshold and can be used in conjunction
> > with input-schmitt-enable in the same node. In your case
> > you probably don't want to use it at all and disallow it.
> >
> > They are all treated individually in the parser.
> >
> > Maybe we could patch the docs in pinconf-generic.h to make it clear that
> > they are all mutually exclusive.
> >
> > The DT parser is a bit primitive for these.
> > For example right now it is fine with the schema
> > to set input-schmitt-enable and input-schmitt-disable at the same time, and
> > the result will be enabled because of parse order :/
>
> > The real trick would be to also make the
> > schema in Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
> > make them at least mutually exclusive and deprecate the
> > input-schmitt that noone is using, maybe that is simpler than I think?
>
> I think that this is probably what to do. Mutual exclusion isn't
> difficult to set up there and if there's no property for "input-schmitt"
> then deprecating it sounds pretty reasonable?

Yeah I agree.

Do you want to look into it?

Otherwise it becomes my problem now that I've noticed it :D

Yours,
Linus Walleij