linux-kernel - Re: [PATCH v2] pinctrl: Enable "power-source" to be extracted from DT files

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Date:	Wed, 28 May 2014 10:36:17 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	James Hogan <james.hogan@...tec.com>,
	Stephen Warren <swarren@...dia.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] pinctrl: Enable "power-source" to be extracted from DT files

Am Mittwoch, 28. Mai 2014, 10:15:43 schrieb Linus Walleij:
> On Tue, May 27, 2014 at 3:09 PM, Heiko Stübner <heiko@...ech.de> wrote:
> > Am Dienstag, 27. Mai 2014, 09:27:36 schrieb Ivan T. Ivanov:
> >> From: "Ivan T. Ivanov" <iivanov@...sol.com>
> >> 
> >> Add "power-source" property to generic options used for DT parsing files.
> >> This  enables drivers, which use generic pin configurations, to get the
> >> value passed to this property.
> > 
> > I think the main problem here is, that pinconf-generic.h defines the
> > power-
> > source as having a "custom format". With DT as a hardware description,
> > implementaton specific values do not work well - instead it should have a
> > regular unit-value.
> > 
> > For the power-source I think volts could work well - as this is the main
> > use- case for pinctrl I know. The regulator-binding uses microvolts,
> > maybe it would be good use a similar unit.
> 
> (...)
> 
> >         pcfg_1v8 {
> >         
> >                 power-source = <1800000>;
> >         
> >         };
> 
> I don't think this is what it's meant for actually. In this case the thing
> would be modeled as a regulator rather than some pin control option I
> guess?
> 
> I think it's more like a selector, such as found on old amplifiers,
> input source A, B or C? So it's just some discrete number.

as I said, you know this better than me ;-)

I was thinking more of these io-voltages, where one can select between say 1.8 
and 3.3V for the pins.

I have this somewhere on my todo list for the rockchips too.

So essentially the pinctrl driver [as it is a pin-group specific setting] 
should just export regulators for these voltage settings, without touching the 
pinconfig itself, right?


Thanks
Heiko

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