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

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Message-ID: <20250313-kimono-passport-496a312a849c@spud>
Date: Thu, 13 Mar 2025 22:34:04 +0000
From: Conor Dooley <conor@...nel.org>
To: Nick Hu <nick.hu@...ive.com>
Cc: Rob Herring <robh@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Anup Patel <anup@...infault.org>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] dt-bindings: timer: Add SiFive CLINT2

On Thu, Mar 13, 2025 at 03:58:05PM +0800, Nick Hu wrote:
> Hi Rob and Conor
> 
> Thanks to all your feedback.
> 
> On Wed, Mar 12, 2025 at 4:46 AM Conor Dooley <conor@...nel.org> wrote:
> >
> > On Tue, Mar 11, 2025 at 02:59:53PM -0500, Rob Herring wrote:
> > > On Tue, Mar 11, 2025 at 01:19:03PM +0800, Nick Hu wrote:
> > > > Add compatible string and property for the SiFive CLINT v2.
> > > >
> > > > Signed-off-by: Nick Hu <nick.hu@...ive.com>
> > > > Reviewed-by: Samuel Holland <samuel.holland@...ive.com>
> > > > ---
> > > >  .../bindings/timer/sifive,clint.yaml          | 19 +++++++++++++++++++
> > > >  1 file changed, 19 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> > > > index 76d83aea4e2b..93d74c504b5f 100644
> > > > --- a/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> > > > +++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> > > > @@ -36,6 +36,9 @@ properties:
> > > >                - starfive,jh7110-clint   # StarFive JH7110
> > > >                - starfive,jh8100-clint   # StarFive JH8100
> > > >            - const: sifive,clint0        # SiFive CLINT v0 IP block
> > >
> > > Notice that we don't allow clint0 by itself. We shouldn't start now.
> > >
> > > > +      - items:
> > >
> > > If you don't have a specific one yet, then add '- {}' for the first
> > > entry.
> > >
> Do you suggest something like the following?
>      - items:
>           - {}
>           - const: sifive,clint2        # SiFive CLINT v2 IP block
>         description: SiFive CLINT v2 is the HRT that supports the Zicntr
> 
> > > > +          - const: sifive,clint2        # SiFive CLINT v2 IP block
> > > > +        description: SiFive CLINT v2 is the HRT that supports the Zicntr
> > > >        - items:
> > > >            - enum:
> > > >                - allwinner,sun20i-d1-clint
> > > > @@ -62,6 +65,22 @@ properties:
> > > >      minItems: 1
> > > >      maxItems: 4095
> > > >
> > > > +  sifive,fine-ctr-bits:
> > > > +    description: The width in bits of the fine counter.
> > >
> > > maximum: 15
> > >
> > > Unless you know of a different maximum in which case why aren't you
> > > documenting that too?
> >
> You are right. It's my bad. The maximum width should always be 15 in
> sifive,clint2.
> I should update to:
>  sifive,fine-ctr-bits:
>     maximum: 15
>     description: The width in bits of the fine counter.
> 
> if:
>   not:
>     properties:
>       compatible:
>         contains:
>           const: sifive,clint2
> then:
>   properties:
>     sifive,fine-ctr-bits: false

I think this should be inverted, to

if: properties: compatible: contains: const: sifive,clint2
then: required: - sifive,fine-counter-bits
else: sifive,fine-counter-bits: false

since the property has no default.

> 
> > I'm curious why this is not something that can be discerned from the
> > compatible. It's max 15, but are there actually versions of this with a
> > less-than-15-bit width?
> >
> The width may be various on different platforms so it is possible to
> have a less-than-15-bit width.
> 
> > >
> > > > +
> > > > +if:
> > > > +  properties:
> > > > +    compatible:
> > > > +      contains:
> > > > +        const: sifive,clint2
> > > > +then:
> > > > +  properties:
> > > > +    sifive,fine-ctr-bits:
> > > > +      maximum: 15
> > > > +else:
> > > > +  properties:
> > > > +    sifive,fine-ctr-bits: false
> > > > +
> > > >  additionalProperties: false
> > > >
> > > >  required:
> > > > --
> > > > 2.17.1
> > > >
> 
> Best Regards,
> Nick

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