linux-kernel - Re: [PATCH v3 12/12] ARM: dtsi: axp81x: set pinmux for GPIO0/1 when used as LDOs

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Date:   Tue, 3 Oct 2017 11:27:17 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Quentin Schulz <quentin.schulz@...e-electrons.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        Russell King <linux@...linux.org.uk>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Lee Jones <lee.jones@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v3 12/12] ARM: dtsi: axp81x: set pinmux for GPIO0/1 when
 used as LDOs

On Mon, Oct 2, 2017 at 2:08 PM, Quentin Schulz
<quentin.schulz@...e-electrons.com> wrote:

> On AXP813/818, GPIO0 and GPIO1 can be used as LDO as (respectively)
> ldo_io0 and ldo_io1.
(...)
> +               gpio0_ldo: gpio0_ldo {
> +                       pins = "GPIO0";
> +                       function = "ldo";
> +               };
(...)
> +                       pinctrl-names = "default";
> +                       pinctrl-0 = <&gpio0_ldo>;
>                         /* Disable by default to avoid conflicts with GPIO */
>                         status = "disabled";

So this is still by default disabled, but you make the default
mode something called "ldo".

And I think that is to be understood as a low-dropout regulator?

So is the idea that this should be represented as a regulator
in the end?

Then I think the state name should not be "default" rather
something like "regulator" and "default" should be the GPIO
mode, as I guess something like that exists.

Activating a regulator using pin control "default" mode is
not very pretty. It would probably be unintuitive and end
up wasting power because people will get confused about
what is going on.

Instead, call this state "regulator" and when using, in Linux
create a regulator device that set the pin into "regulator" state to
start using it as a LDO, and "default" to deactivate it as
LDO, if that is how the usage is intended.

Yours,
Linus Walleij