linux-kernel - Re: [PATCH 2/3] pinctrl: meson: add device tree bindings documentation

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Message-ID: <20141026182541.GA23020@gmail.com>
Date:	Sun, 26 Oct 2014 19:25:41 +0100
From:	Beniamino Galvani <b.galvani@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Russell King <linux@....linux.org.uk>,
	Carlo Caione <carlo@...one.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	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>,
	Jerry Cao <jerry.cao@...ogic.com>,
	Victor Wan <victor.wan@...ogic.com>
Subject: Re: [PATCH 2/3] pinctrl: meson: add device tree bindings
 documentation

On Fri, Oct 24, 2014 at 01:53:28PM +0200, Linus Walleij wrote:
> On Tue, Oct 7, 2014 at 11:32 PM, Beniamino Galvani <b.galvani@...il.com> wrote:
> 
> > Add device tree bindings documentation for Amlogic Meson pinmux and
> > GPIO controller.
> >
> > Signed-off-by: Beniamino Galvani <b.galvani@...il.com>
> (...)
> > +Required properties for gpio sub-nodes:
> > + - reg: should contain address and size for mux, pull-enable, pull and
> > +   gpio register sets
> > + - reg-names: an array of strings describing the "reg" entries. Must
> > +   contain "mux", "pull" and "gpio". "pull-enable" is optional and
> > +   when it is missing the "pull" registers are used instead
> 
> So it seems segmenting the registers is done to sort of control the
> hardware versioning.
> 
> I think it's better to use the compatible string to indicate different
> versions of the hardware and then have just have one big
> regs to cover all registers.

The problem here is that the register ranges are not contiguous and
the holes in between are used by other devices, so I can't use a
single range.

> 
> > +Valid gpio sub-nodes name are:
> > + - "banks" for the standard banks
> > + - "ao-bank" for the AO bank which belong to the special always-on
> > +   power domain
> 
> I think it's unnecessary to split up banks, the compatible property
> should be enough to know how many banks this controller has
> and where they are located in relation to the base offset.

I wanted to avoid a reg property with a list of 7 ranges. Anyway, I
agree that the split seems a bit arbitrary; I'll remove it.

> > +Required properties for configuration nodes:
> > + - pins: the name of a pin group. The list of all available groups can
> > +   be found in driver sources.
> > + - function: the name of a function to activate for the specified set
> > +   of groups. The list of all available functions can be found in
> > +   driver sources.
> 
> This is interesting. I have established that for controllers mapping
> functions to groups we use
> "function" and "groups".
> 
> So for per-pin configuration, "function" and "pins" would be
> apropriate.

I will use "groups" instead of "pins" for the pinmux configuration.

Thanks!
Beniamino
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