Tegra pinmux Device Tree support

[Stephen Warren]

Grant, Linus, & all,

I was thinking of adding some Device Tree support to Tegra's existing
pinmux driver. This would remove the dependence of mach-tegra/board-dt.c
on board-{harmony,seaboard}-pinmux.c, and make the DT board stand on its
own.

My thoughts were:

a) Every Tegra board currently has a board-$name-pinmux.c which contains
a table like:

static struct tegra_pingroup_config harmony_pinmux[] = {
	{TEGRA_PINGROUP_ATA,   TEGRA_MUX_IDE,           TEGRA_PUPD_NORMAL,    TEGRA_TRI_NORMAL},

I'd just move that table into the Device Tree, keeping logically the same
structure, but just changing the syntax as appropriate for DT.

(I'm slightly worried that DT wants me to encode all that using an
unformatted table consistent of integers without any pre-processor macros
or named constants though...)

b) I'd probably need to modify the pinmux driver to be a platform device
in order to simplify integration with DT parsing etc.

c) I think the DT binding would not be affected by Linus W's work on a
pinctrl API; I see this table as platform data that sets up the initial
state of the SoC at boot-time, whereas the pinmux driver is more about
drivers dynamically altering the pinmux at run-time. Is this a reasonable
assertion? The alternative would be that once the new pinctrl API is
available, it would have an associated DT binding that represented this
data in a completely cross-SoC manner. Hence, any work on Tegra's pinmux
right now would be throwaway. I'm interested in people's thoughts here.

Finally, I was thinking that a similar thing could be done for the Tegra
GPIO driver, to replace gpio_table[] also in board-*-pinmux.c.

If this isn't useful right now, is there anything else that would help
out on Tegra?

Thanks.

-- 
nvpublic