[RFC PATCH 2/2] lib: reset: thead: Correct the naming convention of dts

[Conor Dooley]

On Wed, May 24, 2023 at 04:55:04PM +0100, Jessica Clarke wrote:
> On 24 May 2023, at 15:46, Conor Dooley <conor at kernel.org> wrote:
> > 
> > On Wed, May 24, 2023 at 06:39:47PM +0800, Guo Ren wrote:
> > 
> >> We remove reset-ctrl-val, but still keep csr-copy. Because it contains
> >> the index, not value. It didn't viloate anything. okay?
> > 
> > If it is set per-soc, which apparently it is, then you don't need to
> > fill the values into a property to communicate it to software because
> > you already have a compatible that tells you exactly what implementation
> > you have. Just like it is normal for a driver to use #defines etc for
> > register access, since it knows those registers exist on a particular
> > implementation. I don't know what OpenSBI calls this, but in Linux it
> > is called match_data.
> > Either way - we are just going around in circles here :)

> The SoC-specific compatible does have value in case the specific IP
> needs identifying to work around quirks, but IMO using that to derive
> all the parameters rather than having them in the FDT makes drivers
> worse.

The other thing to consider is whether the csr copy property is actually
SoC specific, or varies more/less frequently than that. For example, is
it actually set by the cpu core, rather than the SoC, and a number of SoCs
would use the same values? Or would it vary depending on use-case (AMP
etc).
I tried to do some reading up on the documentation, although I struggled
to find detail in a language that I understand. The documentation that I
did find though, looked like you might want to use the same ones for all
c910s.
I'm certainly not diametrically opposed to this property & adding to a
fallback compatible (something like "thead,c910-cpu-reset"?).
If it actually is the case that the CSRs you want to copy is a property
of the cpu core, you wouldn't even need match data & could copy the
default set of CSRs always*.
And when a real use case comes along that needs a property to set
arbitrary values a specific property can always be added with a fallback
to the base cpu values?
It would desperately need an explanation that is better than "copy these
csrs" though, explaining the which & why, and the binding should enforce
that only valid CSRs for an SoC pass validation.

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