Tegra pinmux Device Tree support

[Olof Johansson]

On Tue, Aug 9, 2011 at 10:34 AM, Grant Likely <grant.likely at secretlab.ca> wrote:

> We talked about this a bit at Linaro connect.  Outside of the more
> complex runtime-reconfiguration of pin mux, there is a general need
> for arbitrary initialization sequences to registers.  Also, pretty
> much exactly what you need for tegra is needed for imx, omap and many
> others.  The though was, rather than trying to come up with some kind
> of pinmux-specific binding for pin states, which could end up being
> very verbose if everything was split out into properties, we could
> instead have a binding for register initialization sequences.
> Something like this:
>
>        pinmux-initseq = <reg1 value1> <reg1 value2> ...;
>
> And then add some macros for DTC to make it easier to define things
> like pinmux setup tables.  Although the binding above is probably too
> simple and naive.

This seems to break the philosophy of what the device tree should do
-- it should describe the hardware so that the driver will know how to
program it, not include the code itself?

I know it's a hairy problem to deal with one compact pinmux
representation that fits all needs. Maybe making it overly generic is
the wrong way to go about it, and let each implementation define what
it needs? That way the simpler implementations can do something
reasonably simple without having to deal with the overly complex
options of the (over?) generalized platforms out there.


-Olof