Re: [PATCH 2/2] ARM: dts: meson: Adding hwrev syscon node

Arnd Bergmann
2016-02-19T11:53:52Z

On Thursday 18 February 2016 15:27:06 Daniel Drake wrote:
> On Thu, Feb 18, 2016 at 3:04 PM, Carlo Caione <carlo@caione.org> wrote:
> >> However, if some or all of the other devices actually are entirely
> >> made up of register ranges within cbus, that would indicate that
> >> cbus itself is not just a collection of random registers but something
> >> that could be considered a bus of itself in hardware, and then
> >> we could represent the other devices as children of this bus.
> >
> > I think that this is exactly the case. We are missing this cbus in the
> > DTS because (for lacking of proper documentation) we are not sure
> > about start / end / size.
>
> Here's a hint from the vendor kernel
> https://github.com/endlessm/linux-meson/blob/master/arch/arm/mach-meson8b/iomapping.c#L87
>
> Having a cbus bus node with child devices does sound like it would
> reflect this particular view of the hardware design. How would we then
> represent the hwrev registers under that?
>
> I am also curious if this is the common practice. We were working with
> Exynos devices before, and even though many of the components are on
> the AXI bus there, there is no AXI bus representation in the DT. But
> now that I go digging, I see other SoCs that do have a DT bus
> representation very similar to what's being described, such as the apb
> and axi busses in mmp2.dtsi. Is one approach preferred over the other
> for new SoC support?

I would always prefer having the dts files describe the hardware as best
as they can.

Arnd