Re: [PATCH V4 1/2] dt-bindings: riscv: add MMU Standard Extensions support for Svpbmt

[Heiko Stübner]

Am Montag, 29. November 2021, 13:06:23 CET schrieb Heiko Stübner:
> Am Montag, 29. November 2021, 09:54:39 CET schrieb Heinrich Schuchardt:
> > On 11/29/21 02:40, wefu@xxxxxxxxxx wrote:
> > > From: Wei Fu <wefu@xxxxxxxxxx>
> > > 
> > > Previous patch has added svpbmt in arch/riscv and add "riscv,svpmbt"
> > > in the DT mmu node. Update dt-bindings related property here.
> > > 
> > > Signed-off-by: Wei Fu <wefu@xxxxxxxxxx>
> > > Co-developed-by: Guo Ren <guoren@xxxxxxxxxx>
> > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > > Cc: Anup Patel <anup@xxxxxxxxxxxxxx>
> > > Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> > > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > > ---
> > >   Documentation/devicetree/bindings/riscv/cpus.yaml | 10 ++++++++++
> > >   1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > index aa5fb64d57eb..9ff9cbdd8a85 100644
> > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > @@ -63,6 +63,16 @@ properties:
> > >         - riscv,sv48
> > >         - riscv,none
> > >   
> > > +  mmu:
> > 
> > Shouldn't we keep the items be in alphabetic order, i.e. mmu before 
> > mmu-type?
> > 
> > > +    description:
> > > +      Describes the CPU's MMU Standard Extensions support.
> > > +      These values originate from the RISC-V Privileged
> > > +      Specification document, available from
> > > +      https://riscv.org/specifications/
> > > +    $ref: '/schemas/types.yaml#/definitions/string'
> > > +    enum:
> > > +      - riscv,svpmbt
> > 
> > The privileged specification has multiple MMU related extensions: 
> > Svnapot, Svpbmt, Svinval. Shall they all be modeled in this enum?
> 
> I remember in some earlier version some way back there was the
> suggestion of using a sub-node instead and then adding boolean
> properties for the supported extensions.
> 
> Aka something like
> 	mmu {
> 		riscv,svpbmt;	
> 	};

For the record, I'm talking about the mail from september
https://lore.kernel.org/linux-riscv/CAAeLtUChjjzG+P8yg45GLZMJy5UR2K5RRBoLFVZhtOaZ5pPtEA@xxxxxxxxxxxxxx/

So having a sub-node would make adding future extensions
way nicer.

> 
> Which I guess would be a lot nicer. Also right now there is string-
> comparison done on the code side, which would look way easier
> when just looking for booleans in the dt instead.
> 
> Also isn't an enum a "one-of" selection, so wouldn't work directly
> for multiple extensions?
> 
> 
> Heiko
> 
> 
> > 
> > Best regards
> > 
> > Heinrich
> > 
> > > +
> > >     riscv,isa:
> > >       description:
> > >         Identifies the specific RISC-V instruction set architecture
> > > 
> > 
> > 
> > _______________________________________________
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> > 
> 
> 
> 
> 
> 
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