On Tue, Jun 09, 2020 at 04:38:31PM +0200, Michael Walle wrote:
> mfd-device@10 {
> compatible = "simple-regmap", "simple-mfd";
> reg = <10>;
> regmap,reg-bits = <8>;
> regmap,val-bits = <8>;
> sub-device@0 {
> compatible = "vendor,sub-device0";
> reg = <0>;
> };
A DT binding like this is not a good idea, encoding the details of the
register map into the DT binding makes it an ABI which is begging for
trouble. I'd also suggest that any device using a generic driver like
this should have a specific compatible string for the device so we can
go back and add quirks later if we need them.
> ...
> };
>
> Or if you just want the regmap:
>
> &soc {
> regmap: regmap@fff0000 {
> compatible = "simple-regmap";
> reg = <0xfff0000>;
> regmap,reg-bits = <16>;
> regmap,val-bits = <32>;
> };
>
> enet-which-needs-syscon-too@1000000 {
> vendor,ctrl-regmap = <®map>;
> };
> };
>
> Similar to the current syscon (which is MMIO only..).
>
> -michael
>
> >
> > I can't think of any reasons why not, off the top of my head.
> >
> > Does Regmap only deal with shared accesses from multiple devices
> > accessing a single register map, or can it also handle multiple
> > devices communicating over a single I2C channel?
> >
> > One for Mark perhaps.
> >
> > > > The issues I wish to resolve using 'simple-mfd' are when sub-devices
> > > > register maps overlap and intertwine.
> >
> > [...]
> >
> > > > > > > What do these bits configure?
> > > > >
> > > > > - hardware strappings which have to be there before the board powers
> > > > > up,
> > > > > like clocking mode for different SerDes settings
> > > > > - "keep-in-reset" bits for onboard peripherals if you want to save
> > > > > power
> > > > > - disable watchdog bits (there is a watchdog which is active right
> > > > > from
> > > > > the start and supervises the bootloader start and switches to
> > > > > failsafe
> > > > > mode if it wasn't successfully started)
> > > > > - special boot modes, like eMMC, etc.
> > > > >
> > > > > Think of it as a 16bit configuration word.
> > > >
> > > > And you wish for users to be able to view these at run-time?
> > >
> > > And esp. change them.
> > >
> > > > Can they adapt any of them on-the-fly or will the be RO?
> > >
> > > They are R/W but only will only affect the board behavior after a
> > > reset.
> >
> > I see. Makes sense. This is board controller territory. Perhaps
> > suitable for inclusion into drivers/soc or drivers/platform.
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