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

[Linus Walleij <linus.ml.walleij-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

2011/8/23 Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>:
> Linus Walleij wrote at Tuesday, August 23, 2011 6:51 AM:
>> Each GPIO chip may have it's respective pin controller as parent
                               ^^^^^
>> I guess, or they may simply be the same struct device * whatdoIknow.
>
> I'm not clear on why the GPIO and pinmux would have any kind of parent
> relationship. Perhaps that's how your HW is designed. In Tegra, GPIO
> and pinmux are completely separate HW blocks without much of a defined
> relationship.
>
> I can certainly see both being implemented by the same code if it makes
> sense to do so. On Tegra, I think I'd still lean towards keeping them
> as separate devices, since they have separate register spaces and are
> documented separately etc. However, I can certainly see that other HW
> might have both sets of functionality in one HW block.

Makes sense, for U300 I will probably also keep them separate
like this:

pinctrl.0 - deal with muxing
pinctrl.1 - deal with biasing, driving etc
gpio.0 - the GPIO driver using both of the above, no relationship

The only thing they have in common is some relation to the
global GPIO pin space. (When/if we get rid of that - something
better.)

Yours,
Linus Walleij