Re: pinctrl-single: num_maps in generic pinconf support?

[Drew Fustini <drew@beagleboard.org>]

On Wed, May 27, 2020 at 09:51:22AM -0700, Tony Lindgren wrote:
> * Drew Fustini <drew@beagleboard.org> [200526 12:22]:
> > Hello Haojian and Linus,
> > 
> > For pcs_parse_one_pinctrl_entry() in drivers/pinctrl/pinctrl-single.c,
> > I see that num_maps is set to 2 if PCS_HAS_PINCONF is enabled:
> > 
> > 1057         if (PCS_HAS_PINCONF && function) {
> > 1058                 res = pcs_parse_pinconf(pcs, np, function, map);
> > 1059                 if (res)
> > 1060                         goto free_pingroups;
> > 1061                 *num_maps = 2;
> > 1062         } else {
> > 1063                 *num_maps = 1;
> > 1064         }
> > 1065         mutex_unlock(&pcs->mutex);
> > 
> > git blame shows me that came from 9dddb4df90d13:
> > "pinctrl: single: support generic pinconf"
> > 
> > Would you be able to provide any insight as to num_maps needs to be 2
> > when pinconf is enabled?
> 
> Only slightly related, but we should really eventually move omaps to use
> #pinctrl-cells = <2> (or 3) instead of 1, and pass the pinconf seprately
> from the mux mode. 

Thanks for the insight, Tony.

I was not considering the situation where pinctrl-cells would be more
than 1.

I see now from pinctrl-single.txt bindings doc that:

- #pinctrl-cells : number of cells in addition to the index, set to 1
  for pinctrl-single,pins and 2 for pinctrl-single,bits

I am now wondering if it wrong for me to expect compatible string of 
"pinconf-single" to work with pinctrl-cells of 1.

I see that arch/arm/boot/dts/da850.dtsi has:

154                 pmx_core: pinmux@14120 {
155                         compatible = "pinctrl-single";
156                         reg = <0x14120 0x50>;
157                         #pinctrl-cells = <2>;
158                         pinctrl-single,bit-per-mux;

and arch/arm/boot/dts/keystone-k2l.dtsi has:

108                 k2l_pmx: pinmux@2620690 {
109                         compatible = "pinctrl-single";
110                         reg = <0x02620690 0xc>;
111                         #address-cells = <1>;
112                         #size-cells = <0>;
113                         #pinctrl-cells = <2>;
114                         pinctrl-single,bit-per-mux;

> We already treat them separately with the new
> AM33XX_PADCONF macro, so we'd only have to change one SoC at a time to
> use updated #pinctrl-cells. But I think pinctrl-single might need some
> changes before we can do that.

Do you mean that it would be possible to make the change just for AM335x
to start with?

Do you think the changes would be limited to pinctrl-single.c and the
associated device tree files like am33xx-l4.dtsi ?


thanks,
drew