linux-kernel - Re: [RFC PATCH v2 00/13] arm/tegra: Initialize GPIO & pinmux from DT

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Date:	Tue, 16 Aug 2011 16:45:42 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Stephen Warren <swarren@...dia.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Colin Cross <ccross@...roid.com>,
	Erik Gilling <konkers@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Russell King <linux@....linux.org.uk>,
	devicetree-discuss@...ts.ozlabs.org, linux-tegra@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Belisko Marek <marek.belisko@...il.com>,
	Jamie Iles <jamie@...ieiles.com>,
	Shawn Guo <shawn.guo@...escale.com>,
	Sergei Shtylyov <sshtylyov@...sta.com>
Subject: Re: [RFC PATCH v2 00/13] arm/tegra: Initialize GPIO & pinmux from DT

On Tue, Aug 16, 2011 at 4:37 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 16 August 2011, Linus Walleij wrote:
>> Say mmc instance 0 need pingroup foo on pincontroller bar
>> means that there must be a specific reference from mmc.0:s
>> struct device * to pinctrl bar:s struct device *. Maybe this is
>> peanuts in DT, sorry not enough insight.
>
> I think what you are looking for is the equivalent of the
> interrupt-parent property for pinmux. The idea is that each
> node in the device tree can point to a device managing the
> pinmux, so reference would point to a local number in that
> space. We have discussed this for the GPIO case already, and
> I suspect that the two should be identical (gpio-controller
> and pinmux-controller using the same device node and same
> property to refer to them).

Yes. I discussed with Grant and his idea is for e.g.
advanced combined pincontrol + GPIO blocks that handle
a lot of stuff like muxing, biasing and GPIO, to expose
a single pinctrl device that in turn provide also a gpio_chip
in addition to the pinctrl interfaces so tehy should be
all on the same struct device *

> Since the pinmux-parent
> (gpio-parent, ...) property gets inherited by all child
> devices, you only need to set it once at the root of the
> device tree for the simple case where there is only one
> controller.

This will likely be the case for most of the advanced muxes
I know of, OMAP, Tegra and Nomadik.

Thanks,
Linus Walleij
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