Re: [PATCH 01/12] dt-bindings: riscv: sifive-ccache: Add compatible for StarFive JH7100 SoC

[Emil Renner Berthing <emil.renner.berthing@canonical.com>]

On Tue, 14 Feb 2023 at 21:42, Conor Dooley <conor@kernel.org> wrote:
>
> Hey all,
>
> On Sat, Feb 11, 2023 at 05:18:10AM +0200, Cristian Ciocaltea wrote:
> > Document the compatible for the SiFive Composable Cache Controller found
> > on the StarFive JH7100 SoC.
> >
> > This also requires extending the 'reg' property to handle distinct
> > ranges, as specified via 'reg-names'.
> >
> > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
> > ---
> >  .../bindings/riscv/sifive,ccache0.yaml        | 28 ++++++++++++++++++-
> >  1 file changed, 27 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/riscv/sifive,ccache0.yaml b/Documentation/devicetree/bindings/riscv/sifive,ccache0.yaml
> > index 31d20efaa6d3..2b864b2f12c9 100644
> > --- a/Documentation/devicetree/bindings/riscv/sifive,ccache0.yaml
> > +++ b/Documentation/devicetree/bindings/riscv/sifive,ccache0.yaml
> > @@ -25,6 +25,7 @@ select:
> >            - sifive,ccache0
> >            - sifive,fu540-c000-ccache
> >            - sifive,fu740-c000-ccache
> > +          - starfive,jh7100-ccache
> >
> >    required:
> >      - compatible
> > @@ -37,6 +38,7 @@ properties:
> >                - sifive,ccache0
> >                - sifive,fu540-c000-ccache
> >                - sifive,fu740-c000-ccache
> > +              - starfive,jh7100-ccache
> >            - const: cache
> >        - items:
> >            - const: starfive,jh7110-ccache
> > @@ -70,7 +72,13 @@ properties:
> >        - description: DirFail interrupt
> >
> >    reg:
> > -    maxItems: 1
> > +    minItems: 1
> > +    maxItems: 2
> > +
> > +  reg-names:
> > +    items:
> > +      - const: control
> > +      - const: sideband
>
> So why is this called "sideband"?
> In the docs for the JH7100 it is called LIM & it's called LIM in our
> docs for the PolarFire SoC (at the same address btw) and we run the HSS
> out of it! LIM being "loosely integrated memory", which by the limit
> hits on Google may be a SiFive-ism?
>
> I'm not really sure if adding it as a "reg" section is the right thing
> to do as it's not "just" a register bank.
> Perhaps Rob/Krzysztof have a take on that one?

Yes, this seems to be a leftover I didn't manage to clean up yet. The
"sideband" range is called L2 LIM in the datasheet and seems to be a
way to use the cache directly. The Sifive docs read "When cache ways
are disabled, they are addressable in the L2 Loosely-Integrated Memory
(L2 LIM) address space [..]". This feature is not used by Linux on the
JH7100, so can just be removed here.

/Emil

> >
> >    next-level-cache: true
> >
> > @@ -89,6 +97,7 @@ allOf:
> >            contains:
> >              enum:
> >                - sifive,fu740-c000-ccache
> > +              - starfive,jh7100-ccache
> >                - starfive,jh7110-ccache
> >                - microchip,mpfs-ccache
> >
> > @@ -106,12 +115,29 @@ allOf:
> >              Must contain entries for DirError, DataError and DataFail signals.
> >            maxItems: 3
> >
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: starfive,jh7100-ccache
> > +
> > +    then:
> > +      properties:
> > +        reg:
> > +          maxItems: 2
> > +
> > +    else:
> > +      properties:
> > +        reg:
> > +          maxItems: 1
> > +
> >    - if:
> >        properties:
> >          compatible:
> >            contains:
> >              enum:
> >                - sifive,fu740-c000-ccache
> > +              - starfive,jh7100-ccache
> >                - starfive,jh7110-ccache
> >
> >      then:
> > --
> > 2.39.1
> >
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