Re: [PATCH v3] dt-bindings: timer: Add SiFive CLINT2

[Charles Perry <charles.perry@microchip.com>]

On Fri, Mar 21, 2025 at 04:35:06PM +0800, Nick Hu wrote:
> Add compatible string and property for the SiFive CLINT v2. The SiFive
> CLINT v2 is incompatible with the SiFive CLINT v0 due to differences
> in their control methods.

Hello Nick,

Can you help me understand what is this different control method? I've
found that both OpenSBI [1] and U-Boot [2] use the same match data in their
clint driver which would indicate that they are compatible.

Also, do you know if there's an easy way to tell if a sifive clint is a v0
or v2?

Thanks,
Charles

[1]: https://elixir.bootlin.com/opensbi/v1.8.1/source/lib/utils/timer/fdt_timer_mtimer.c#L163
[2]: https://elixir.bootlin.com/u-boot/v2026.01/source/drivers/timer/riscv_aclint_timer.c#L86

> 
> Signed-off-by: Nick Hu <nick.hu@sifive.com>
> Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
> ---
> - v3 changes:
>   - Add the reason for the incompatibility between sifive,clint2 and
>     sifive,clint0.
> - v2 changes:
>   - Don't allow sifive,clint2 by itself. Add '-{}' to the first entry
>   - Mark the sifive,fine-ctr-bits as the required property when
>     the compatible includes the sifive,clint2
> 
>  .../bindings/timer/sifive,clint.yaml          | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> index 76d83aea4e2b..34684cda8b15 100644
> --- a/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> +++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> @@ -36,6 +36,12 @@ properties:
>                - starfive,jh7110-clint   # StarFive JH7110
>                - starfive,jh8100-clint   # StarFive JH8100
>            - const: sifive,clint0        # SiFive CLINT v0 IP block
> +      - items:
> +          - {}
> +          - const: sifive,clint2        # SiFive CLINT v2 IP block
> +        description:
> +          SiFive CLINT v2 is the HRT that supports the Zicntr. The control of sifive,clint2
> +          differs from that of sifive,clint0, making them incompatible.
>        - items:
>            - enum:
>                - allwinner,sun20i-d1-clint
> @@ -62,6 +68,22 @@ properties:
>      minItems: 1
>      maxItems: 4095
>  
> +  sifive,fine-ctr-bits:
> +    maximum: 15
> +    description: The width in bits of the fine counter.
> +
> +if:
> +  properties:
> +    compatible:
> +      contains:
> +        const: sifive,clint2
> +then:
> +  required:
> +    - sifive,fine-ctr-bits
> +else:
> +  properties:
> +    sifive,fine-ctr-bits: false
> +
>  additionalProperties: false
>  
>  required:
> -- 
> 2.17.1
> 
>