Message-ID: <20191217090034.GD31182@pengutronix.de>
Date:   Tue, 17 Dec 2019 10:00:34 +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 19-12-16 16:32, Adam Thomson wrote:
> On 16 December 2019 08:55, Marco Felsch wrote:
> 
> > On 19-12-12 16:51, Mark Brown wrote:
> > > On Thu, Dec 12, 2019 at 05:21:53PM +0100, Marco Felsch wrote:
> > >
> > > > "... what's driving the input ..":
> > > > Sorry I didn't get you here. What did you mean? The input is driven by
> > > > the host. This can be any gpio line and in my case it is a gpio line
> > > > driven by the soc-hw during a suspend operation.
> > >
> > > Something needs to say what that thing is, especially if it's runtime
> > > controllable.  In your case from the point of view of software there is
> > > actually no enable control so we shouldn't be providing an enable
> > > operation to the framework.
> > 
> > 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:

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

Regards,
  Marco

> > 
> > [1] https://www.dialog-
> > semiconductor.com/sites/default/files/da9062_datasheet_3v6.pdf
> > 
> > Regards,
> >   Marco
> > 
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
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