linux-kernel - Re: [PATCH v2 1/2] dt-bindings: sifive: add cache-set value of 2048

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Date:   Thu, 9 Jun 2022 09:08:25 -0600
From:   Rob Herring <robh@...nel.org>
To:     Atul Khare <atulkhare@...osinc.com>
Cc:     Palmer Dabbelt <palmer@...osinc.com>,
        Conor Dooley <Conor.Dooley@...rochip.com>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: sifive: add cache-set value of 2048

On Wed, Jun 08, 2022 at 04:39:31PM -0700, Atul Khare wrote:
> Fixes Running device tree schema validation error messages like
> '... cache-sets:0:0: 1024 was expected'.
> 
> The existing bindings had a single enumerated value of 1024, which
> trips up the dt-schema checks. The ISA permits any arbitrary power
> of two for the cache-sets value, but we decided to add the single
> additional value of 2048 because we couldn't spot an obvious way
> to express the constraint in the schema.

There is not any way to express power of 2, so you have to list values. 
Rather than just adding 1 more value, I would add at least a few more so 
we're not adding these one by one. This is for a specific cache 
implementation, so it can't really be *any* power of 2. Designs have 
some limits or physics does.

> 
> Signed-off-by: Atul Khare <atulkhare@...osinc.com>
> ---
> Changes since v1 [1]: Rebased on latest version

What version is that because this did not apply to v5.19-rc1 for some 
reason.

> [1]: https://tinyurl.com/yvdvmsjd
> ---
> ---
>  Documentation/devicetree/bindings/riscv/sifive-l2-cache.yaml | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/sifive-l2-cache.yaml
> b/Documentation/devicetree/bindings/riscv/sifive-l2-cache.yaml
> index e2d330bd4608..309517b78e84 100644
> --- a/Documentation/devicetree/bindings/riscv/sifive-l2-cache.yaml
> +++ b/Documentation/devicetree/bindings/riscv/sifive-l2-cache.yaml
> @@ -46,7 +46,9 @@ properties:
>      const: 2
> 
>    cache-sets:
> -    const: 1024
> +    # Note: Technically this can be any power of 2, but we didn't see
> an obvious way
> +    # to express the constraint in Yaml
> +    enum: [1024, 2048]
> 
>    cache-size:
>      const: 2097152

Surely this is not fixed either?

> --
> 2.34.1
>