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

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Message-ID: <20191217091236.GA15806@pengutronix.de>
Date:   Tue, 17 Dec 2019 10:12:36 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "andrew@...id.au" <andrew@...id.au>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        Mark Brown <broonie@...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 10:00, Marco Felsch wrote:
> 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;

Sorry didn't noticed that the flags are only used internally. The
correct check must be:

	/* GPIO must be configured as input */
	if (!gpiod_get_direction(gpi)) {
		ret = -EINVAL;
		goto free;
	}

> 
> 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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> > 
> 
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