linux-kernel - Re: [RFC v1 0/4] Microchip mpfs/pic64gx pinctrl part 2

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Message-ID: <CACRpkdZOak-+Aahj7fte9gk9m+76LOguEsO7bBbHTMTfLExWcA@mail.gmail.com>
Date: Wed, 19 Nov 2025 22:31:47 +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
Subject: Re: [RFC v1 0/4] Microchip mpfs/pic64gx pinctrl part 2

On Wed, Nov 19, 2025 at 7:06 PM Conor Dooley <conor@...nel.org> wrote:
> On Wed, Nov 19, 2025 at 01:16:16PM +0100, Linus Walleij wrote:
> > On Wed, Nov 12, 2025 at 3:33 PM Conor Dooley <conor@...nel.org> wrote:

> > > and b) how the bank voltage
> > > interacts with the schmitt trigger setting.
> >
> > Please check if "bank voltage" is somewhat analogous to
> > this generic config:
> >
> > * @PIN_CONFIG_POWER_SOURCE: if the pin can select between different power
> >  *      supplies, the argument to this parameter (on a custom format) tells
> >  *      the driver which alternative power source to use.
>
> It's not pin based, the whole bank it is connected to has to be changed.

So there *is* such a thing as a group pin config setting for a
whole group of pins. Groups are not just for functions...

And I don't know what is meant by a bank here, but it seems
to be exactly a group of pins.

>From arch/arm/boot/dts/gemini/gemini-sq201.dts:

 /* Set up drive strength on GMAC0 and GMAC1 to 16 mA */
conf9 {
    groups = "gmii_gmac0_grp", "gmii_gmac1_grp";
    drive-strength = <16>;
};

If you look in driver/pinctrl/pinctrl-gemini.c you find:
gemini_pinconf_group_set()

static const struct pinconf_ops gemini_pinconf_ops = {
        .pin_config_get = gemini_pinconf_get,
        .pin_config_set = gemini_pinconf_set,
        .pin_config_group_set = gemini_pinconf_group_set,
        .is_generic = true,
};

OTOMH it's actually *fine* to *just* use groups for pin config like this
and *not* use it for muxing, i.e. have this group correspond to
a bank and not use that group for anything else than to set this
or any other per-bank property. But have a look!

Yours,
Linus Walleij