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

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Message-ID: <74CDBE0F657A3D45AFBB94109FB122FF04B24A3687@HQMAIL01.nvidia.com>
Date:	Mon, 22 Aug 2011 12:56:28 -0700
From:	Stephen Warren <swarren@...dia.com>
To:	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>
CC:	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.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

Stephen Warren wrote at Monday, August 15, 2011 2:28 PM:
> ...
> This patch modifies Tegra's device tree support to remove the dependency
> on harmony_pinmux_init(), thus making it completely board-independent.

I had the good fortune of meeting Grant at LinuxCon last week and talked
through this patchset a little (thanks!)

The message I got from Grant was that the patches are basically OK. He
did have a couple of concerns:

* Does this cause the compiled DTB to blow up in size.

The DTB goes from ~3-4K to ~8-9K with these patches added. While that
is a large % increase, Grant said that as an absolute value, that size
shouldn't be an issue.

* There's lots of repetition in the .dts representation; can this be improved?

We discussed enhancing the syntax a little, so that you can configure
multiple pins/pingroups from a single node. In particular, the syntax
in my patches was:

ld0 {
    nvidia,function = "displaya";
    nvidia,pull-down;
};
ld1 {
    nvidia,function = "displaya";
    nvidia,pull-down;
};

Which we discussed enhancing to something like:

ld0 {
    additional-pins = "ld1", "ld2", ...;
    nvidia,function = "displaya";
    nvidia,pull-down;
};

or:

meaningless-name { // typically would just use the pin name
    pins = "ld0", "ld1", "ld2", ...;
    nvidia,function = "displaya";
    nvidia,pull-down;
};

* We also briefly discussed that dtc could be modified to support symbolic
constants, so we could use named integers for the function names (perhaps
pin names too). I'll look into how easy it is to modify dtc for this.

I'll look into implementing these enhancements, and others discussed in
this email thread, and repost.

> ...
> Stephen Warren (13):
>   arm/tegra: Prep boards for gpio/pinmux conversion to pdevs
>   arm/tegra: Avoid duplicate gpio/pinmux devices with dt
>   arm/tegra: board-dt: Add AUXDATA for tegra-gpio and tegra-pinmux
>   docs/dt: Document nvidia,tegra20-gpio's nvidia,enabled-gpios property
>   arm/dt: Tegra: Add nvidia,gpios property to GPIO controller
>   docs/dt: Document nvidia,tegra20-pinmux binding
>   arm/dt: Tegra: Add pinmux node
>   gpio/tegra: Convert to a platform device
>   gpio/tegra: Add device tree support
>   arm/tegra: Convert pinmux driver to a platform device
>   arm/tegra: Add device tree support to pinmux driver
>   arm/tegra: board-dt: Remove dependency on non-dt pinmux functions
>   arm/tegra: Remove temporary gpio/pinmux registration workaround
> 
>  .../devicetree/bindings/gpio/gpio_nvidia.txt       |   20 +
>  .../devicetree/bindings/pinmux/pinmux_nvidia.txt   |  294 ++++++++++++
>  arch/arm/boot/dts/tegra-harmony.dts                |  483 ++++++++++++++++++++
>  arch/arm/boot/dts/tegra-seaboard.dts               |  421 +++++++++++++++++
>  arch/arm/boot/dts/tegra20.dtsi                     |    5 +
>  arch/arm/mach-tegra/Makefile                       |    1 -
>  arch/arm/mach-tegra/board-dt.c                     |   12 +-
>  arch/arm/mach-tegra/board-harmony-pinmux.c         |    8 +
>  arch/arm/mach-tegra/board-paz00-pinmux.c           |    8 +
>  arch/arm/mach-tegra/board-seaboard-pinmux.c        |    9 +-
>  arch/arm/mach-tegra/board-trimslice-pinmux.c       |    7 +
>  arch/arm/mach-tegra/devices.c                      |   10 +
>  arch/arm/mach-tegra/devices.h                      |    2 +
>  arch/arm/mach-tegra/pinmux.c                       |  269 +++++++++++
>  drivers/gpio/gpio-tegra.c                          |   57 ++-
>  15 files changed, 1582 insertions(+), 24 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/pinmux/pinmux_nvidia.txt

-- 
nvpublic

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