linux-kernel - Re: [PATCH v2] regulator: gpio: Correct default GPIO state to LOW

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Date: Wed, 29 May 2024 15:19:04 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Mark Brown <broonie@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>, Linus Walleij <linus.walleij@...aro.org>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, devicetree@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] regulator: gpio: Correct default GPIO state to LOW

Hi Mark,

On Wed, May 29, 2024 at 3:15 PM Mark Brown <broonie@...nel.org> wrote:
> On Wed, May 29, 2024 at 11:49:51AM +0200, Geert Uytterhoeven wrote:
> > According to the GPIO regulator DT bindings[1], the default GPIO state
> > is LOW.  However, the driver defaults to HIGH.
>
> > Before the conversion to descriptors in commit d6cd33ad71029a3f
> > ("regulator: gpio: Convert to use descriptors"), the default state used
> > by the driver was rather ill-defined, too:
>
> That was 4 years ago...
>
> > I have no idea if this has any impact.
> > I guess most/all DTS files have proper gpios-states properties?
>
> That seems optimistic, and a grep in mainline shows some users but not
> really as many as I'd intuitively expect.
>
> > -                     /* Default to high per specification */
> > +                     /* Default to low per specification */
> >                       if (ret)
> > -                             config->gflags[i] = GPIOD_OUT_HIGH;
> > +                             config->gflags[i] = GPIOD_OUT_LOW;
> >                       else
>
> The risk here is that we start glitching the power where previously we
> didn't.  This does make me nervous.

/me too

The alternative is to change the GPIO regulator DT bindings document
to match the code...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds