Re: [PATCH v2 1/3] dt-bindings: riscv: document cbom-block-size

Christoph Müllner
2022-05-13T10:29:11Z

Hi Anup and Heiko,

The CBO specification says:
"""
2.7. Software Discovery
The initial set of CMO extensions requires the following information
to be discovered by software:
• The size of the cache block for management and prefetch instructions
• The size of the cache block for zero instructions
"""

Therefore we should add riscv,cboz-block-size as well, or?
Additionally, should we add riscv,cbop-block-size as well or rename
riscv,cbom-block-size into
riscv,cbom-cbop-block-size to reflect that this size is also used for
prefetch instructions?

BR
Christoph

On Thu, May 12, 2022 at 6:18 AM Anup Patel <anup@brainfault.org> wrote:
>
> On Thu, May 12, 2022 at 3:11 AM Heiko Stuebner <heiko@sntech.de> wrote:
> >
> > The Zicbom operates on a block-size defined for the cpu-core,
> > which does not necessarily match other cache-sizes used.
> >
> > So add the necessary property for the system to know the core's
> > block-size.
> >
> > Signed-off-by: Heiko Stuebner <heiko@sntech.de>
>
> Looks good to me.
>
> Reviewed-by: Anup Patel <anup@brainfault.org>
>
> Regards,
> Anup
>
> > ---
> > Documentation/devicetree/bindings/riscv/cpus.yaml | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > index d632ac76532e..b179bfd155a3 100644
> > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > @@ -63,6 +63,13 @@ properties:
> > - riscv,sv48
> > - riscv,none
> >
> > + riscv,cbom-block-size:
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + description:
> > + Blocksize in bytes for the Zicbom cache operations. The block
> > + size is a property of the core itself and does not necessarily
> > + match other software defined cache sizes.
> > +
> > riscv,isa:
> > description:
> > Identifies the specific RISC-V instruction set architecture
> > --
> > 2.35.1
> >