Re: [PATCH 3/6] dt-bindings: pinctrl: Add fsl,ls1012a-pinctrl yaml file

[David Leonard <David.Leonard@digi.com>]

On Wed, 28 Aug 2024, David Leonard wrote:

>> OK, but I still wonder why is it here. Without it the hardware will work
>> in little-endian?
>
> Well, it's here firstly because I was trying to follow a perceived convention 
> in
> dts/freescale/fsl,ls1012a.dtsi. That DT uses big-endian in child
> nodes of /soc that match up with memory map tables from the datasheet.
> (Not only do different and adjacent parts of the register map have
> opposing endianess, some register layouts also seem to be reversed
> bitwise, others bytewise.)
>
> The second reason is practical/dodgy. The pinctrl driver should logically
> be a child of the scfg node, but the syscon driver doesn't populate its
> child nodes. To get the pinctrl driver to work meant making it a sibling
> node with an unsatisfactory overlap with the scfg's address region
> 0x1570000+0x10000. (No driver binds to "fsl,ls1012a-scfg".)

Sorry, my examples had mixed up some ls1046a with ls1012a, which
must be confusing. Corrections follow, should the meaning have been lost:

         soc {
                 compatible = "simple-bus";
                 #address-cells = <2>;
                 #size-cells = <2>;
                 ...

                 scfg: scfg@1570000 {
                         compatible = "fsl,ls1012a-scfg", "syscon";
                         reg = <0x0 0x1570000 0x0 0x10000>;
                         big-endian;
                 };

                 pinctrl: pinctrl@1570430 {
                         compatible = "fsl,ls1012a-pinctrl";
                         reg = <0x0 0x1570430 0x0 0x4>; /* SCFG PMUXCR0 */
                         big-endian;
                         fsl,dcfg-regmap = <&dcfg>;
                         ...
                 };
         };

> The better device tree would be:

         soc {
                 compatible = "simple-bus";
                 #address-cells = <2>;
                 #size-cells = <2>;
                 ...

                 scfg: scfg@1570000 {
                         compatible = "fsl,ls1012a-scfg", "syscon";
                         reg = <0x0 0x1570000 0x0 0x10000>;
                         big-endian;
                         #address-cells = <1>;
                         #size-cells = <1>;
                         ...

                         pinctrl: pinctrl@430 {
                                 compatible = "fsl,ls1012a-pinctrl";
                                 reg = <0x430 0x4>; /* SCFG PMUXCR0 */
                                 fsl,dcfg-regmap = <&dcfg (416/8)>;
                                 ...
                         };
                 };
         };

> And this would resolve the big-endian property issue.
>
> There was a discussion of syscon populating its child nodes at
> https://lore.kernel.org/lkml/1403513950.4136.34.camel@paszta.hi.pengutronix.de/T/