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

[Conor Dooley <conor@kernel.org>]

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On Thu, Mar 26, 2026 at 01:55:38PM -0700, Charles Perry wrote:
> 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.

Hmm, good point. I didn't see that the drivers were not doing anything
different. I guess really the clintv2 should fall back to the clintv0,
and the difference in hardware should be elaborated on.

I think I also dropped the ball on sifive,fine-ctr-bits, and that should
be removed and the counter width determined from the compatible.
There's no users for that yet I think, and there's no valid users of the
clintv2 compatible /at all/ so maybe it can just get culled.

> 
> 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
> > 
> > 

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