Re: [PATCH 7/8] riscv: dts: spacemit: add initial device tree of SpacemiT K3 SoC

[Conor Dooley <conor@kernel.org>]

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On Fri, Dec 19, 2025 at 10:03:24AM +0800, Guodong Xu wrote:
> Hi, Conor and Heinrich
> 
> On Thu, Dec 18, 2025 at 8:56 AM Conor Dooley <conor@kernel.org> wrote:
> >
> > On Wed, Dec 17, 2025 at 09:07:14AM +0100, Heinrich Schuchardt wrote:
> > > On 12/17/25 08:11, Guodong Xu wrote:
> >
> > > > Specifically, I must adhere to
> > > > Documentation/devicetree/bindings/riscv/extensions.yaml (and cpus.yaml for
> > > > properties like 'riscv,sv39' which stands for the extension Sv39). If I
> > > > add extension strings that are not yet defined in these schemas, such as
> > > > supm, running 'make dtbs_check W=3' fails with: 'supm' is not one of
> > > > ['i', 'm', 'a', ...], followed by "Unevaluated properties are not allowed."
> > >
> > > If Documentation/devicetree/bindings/riscv/extensions.yaml is incomplete
> > > with respect to ratified extensions, I guess the right approach is to amend
> > > it and not to curtail the CPU description.
> >
> > Absolutely. If the cpu supports something that is not documented, then
> > please document it rather than omit from the devicetree.
> 
> Thanks for the review. May I clarify one thing? Both of you mentioned
> document them, given the amount of missing extensions, is it acceptable if
> I submit a prerequisite patch that only documents these strings in
> riscv/extensions.yaml plus the necessary hwprobe export? Leaving the actual
> usage of these extensions (named features) to the future patches.
> 
> To provide some context on why I ask: I've investigated the commits & lkml
> history of RISC-V extensions since v6.5, and I summarized the current status
> regarding the RVA23 profile here:
> [1] status in v6.18 (inc. v6.19-rc1):
> https://docularxu.github.io/rva23/linux-kernel-coverage.html
> [2] support evolution since v6.5:
> https://docularxu.github.io/rva23/rva23-kernel-support-evolution.html
> 
> Strictly describing the SpacemiT X100/K3 (or any core) as RVA23-compliant
> requires adding these extensions that are currently missing from
> the kernel bindings:
> RVA23U64: Ziccif, Ziccamoa, Zicclsm, Za64rs
> RVA23S64: Ss1p13, Ssccptr, Sstvecd, Sstvala, Sscounterenw, Ssu64xl,
>           Sha, Shcounterenw, Shvstvala, Shtvala, Shvstvecd, Shvsatpa, Shgatpa


> Plus 'Supm', 'Zic64b', 'Ssstateen', 'B' where the kernel supports them but
> they are not literally documented in yaml.

I don't think Supm is suitable for devicetree, doesn't it describe
what the kernel/userspace are capable of rather than hardware?
Zic64b doesn't sound like hardware description (so not really suitable
for devicetree either) but block size information is already represented
by some existing properties (see riscv,cbo*-block-size in riscv/cpus.yaml)
and duplicating that information is not really a great idea.

I'll admit that I do not really understand Sxstateen and how they work,
but my understanding was that knowing about Smstateen is sufficient and
implied Sstateen, but having Ssstateen defined seems harmless and
possible. I think kvm is the only user of this at the moment, so
probably worth CCing Anup and maybe Drew Jones on the patch adding
Ssstateen to make sure it makes sense.

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