linux-kernel - Re: [PATCH v3 3/6] dt-bindings: mfd: da9062: add regulator voltage selection documentation

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Message-ID: <20191217123116.GB29666@pengutronix.de>
Date:   Tue, 17 Dec 2019 13:31:16 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Mark Brown <broonie@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "andrew@...id.au" <andrew@...id.au>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "joel@....id.au" <joel@....id.au>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 3/6] dt-bindings: mfd: da9062: add regulator voltage
 selection documentation

On 19-12-17 09:53, Adam Thomson wrote:
> On 17 December 2019 09:01, Marco Felsch wrote:
> 
> > > > The enabel control signal is always available, please check [1] table
> > > > 63. There is a mux in front of the enable pin so:
> > > >
> > > >              +-------------
> > > >  Seq. |\     |   Regulator
> > > >  GPI1 | \    |
> > > >  GPI2 | | -- > Enable
> > > >  GPI3 | /    |
> > > >       |/     .
> > > >              .
> > > >              .
> > > >
> > > > Adam please correct me if this is wrong.
> > >
> > > Yes the register can always be configured regardless of the associated pin
> > > configuration, but if say GPIO1 was configured as a GPO but a regulator was
> > > configured to use GPIO1 as its GPI control mechanism, the output signal from
> > > GPIO1 would be ignored, the sequencer control would not have any effect and
> > > you're simply left with manual I2C control. Really we shouldn't be getting into
> > > that situation though. If a GPIO is to be used as a regulator control signal
> > > then it should be marked as such and I don't think we should be able to use that
> > > pin for anything other than regulator control.
> > 
> > I see, so we have to guarantee that the requested gpio is configured as
> > input. This can be done by:
> 
> This is one of the reasons I thought this was better suited to being done in the
> pinctrl/pinmux side. If you configure the GPIO as for regulator control then
> the code can automatically configure the GPIO for input. That doesn't then need
> to be in the regulator driver.

I still don't prefer that way.. pls check my arguments I already made
and I don't wanna repeat it again.

> But yes we wouldn't really want to configure a regulator to be controlled via a
> GPI when it's configured as a GPO as it makes no sense.

Okay, so the check is all we need to hardening the driver against wrong
usage :)

Regards,
  Marco

> 
> > 
> >   if (gpi->flags & FLAG_IS_OUT)
> >   	return -EINVAL;
> > 
> > Regards,
> >   Marco
> 

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