Re: [PATCH v4 08/16] dt-bindings: riscv: Add Zic64b extension description

[Conor Dooley <conor.dooley@microchip.com>]

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On Thu, Jun 11, 2026 at 04:12:45PM -0400, Guodong Xu wrote:
> Zic64b mandates that cache blocks are 64 bytes in size and naturally
> aligned in the address space.  It is a mandatory extension of both the
> RVA22 (U64/S64) and RVA23 (U64/S64) profiles, ratified with RISC-V
> Profiles Version 1.0.
> 
> Document it so it can be described in the riscv,isa-extensions property,
> alongside the related Zicbom/Zicbop/Zicboz cache-block extensions. Since
> Zic64b fixes the cache block size at 64 bytes, also add a  schema check
                                                           ^^
Not that it matters, but there's an extra space here.

> requiring any present cbom/cbop/cboz block size to be 64.
> 
> Signed-off-by: Guodong Xu <docular.xu@gmail.com>
> ---
> v4: Insert zic64b at its sorted position (before zicbom).
>     Update the commit message.
> v3: New patch.
> ---
>  .../devicetree/bindings/riscv/extensions.yaml        | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
> index 5ffc40d599c02..1c24999beb59e 100644
> --- a/Documentation/devicetree/bindings/riscv/extensions.yaml
> +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
> @@ -494,6 +494,12 @@ properties:
>              in commit 64074bc ("Update version numbers for Zfh/Zfinx") of
>              riscv-isa-manual.
>  
> +        - const: zic64b
> +          description:
> +            The standard Zic64b extension for 64-byte naturally aligned cache
> +            blocks, as ratified in RISC-V Profiles Version 1.0, with commit
> +            b1d806605f87 ("Updated to ratified state.")
> +
>          - const: zicbom
>            description:
>              The standard Zicbom extension for base cache management operations as
> @@ -1142,6 +1148,20 @@ allOf:
>            not:
>              contains:
>                const: zilsd
> +  # Zic64b mandates 64-byte naturally aligned cache blocks
> +  - if:
> +      properties:
> +        riscv,isa-extensions:
> +          contains:
> +            const: zic64b
> +    then:
> +      properties:
> +        riscv,cbom-block-size:
> +          const: 64
> +        riscv,cbop-block-size:
> +          const: 64
> +        riscv,cboz-block-size:
> +          const: 64

I think we also need to have
diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
index 1c24999beb59e..bbd442cfbd904 100644
--- a/Documentation/devicetree/bindings/riscv/extensions.yaml
+++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
@@ -1162,6 +1162,32 @@ allOf:
           const: 64
         riscv,cboz-block-size:
           const: 64
+  # All three Zicbo* extensions require their block size property as there's no
+  # default.
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicbom
+    then:
+      required:
+        - riscv,cbom-block-size
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicbop
+    then:
+      required:
+        - riscv,cbop-block-size
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicboz
+    then:
+      required:
+        - riscv,cboz-block-size
 
 additionalProperties: true
 ...

because I don't think there's a warning generated at present* if someone
does "zicbom" + "zic64b" and doesn't have a riscv,cbom-block-size property,
only if they have one and it isn't 64. I think the former is a bigger
problem than the latter.

Probably needs to be an additional patch, because it has value whether
or not we permit zic64b.

pwbot: cr

Cheers,
Conor.

*: the kernel will warn at runtime, but nothing in dtbs_check etc.

>  
>  additionalProperties: true
>  ...
> 
> -- 
> 2.43.0
> 

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