Pinmux bindings proposal V2

[Tony Lindgren]

* Simon Glass <sjg at chromium.org> [120127 07:12]:
> 
> On Thu, Jan 26, 2012 at 6:21 PM, Tony Lindgren <tony at atomide.com> wrote:
> >
> > Maybe we need two bindings: A minimal subset of what Stephen is suggesting
> > that can handle 95% of the muxes with minimal overhead, then what you're
> > suggesting for the few muxes that need multiple states?
> 
> Perhaps that would work, it certainly deals nicely with making the
> rare cases less ugly if indeed they are rare. Of course a single
> binding that is not too ugly and still reasonably efficient would be
> best.
> 
> I will have a think about this a bit more and see if anything leaps
> out. It's quite an interesting problem...

Just to try to recap what has come up so far:

1. We need to avoid bloating things for basic cases to initialize
   several hundred pins.

2. Some muxes need to define multiple states.

3. We need to pass a flag for each mux to know whether or
   not it can be freed after init.

So how about let's do separate static and dynamic bindings,
something like this:

	/*
	 * Static init time only mux where
	 * we only specify phandle to driver
	 * and, offset of the mux, and the value.
	 * These pins are discarded after init.
	 *
	 * Format:	  mux_ctrl      offset value
	 */
	pinctrl-static = <&pmx_driver1  0x0020 0x1245
			   &pmx_driver2 0x0022 0x6578>;

	/*
	 * Dynamic mux where the mux is kept around after
	 * init and multiple states can be defined for
	 * a mux as a subnode of the pinmux controller.
	 *
	 * Format:	   mux_phandle   initial state
	 */ 
	pinctrl-dynamic = <&pmx_sdhci    PMX_STATE_ENABLED
			   &pmx_ehci_xcv PMX_STATE_ENABLED>;

This would make pinctrl-static binding follow the same
standard as GPIO binding and can be parsed easily with
of_parse_phandle_with_args.

Then for pinctrl-dynamic we can make a custom parser,
and the binding can follow the more readable format as
Simon posted.

Regards,

Tony