linux-kernel - Re: [PATCH V3 1/2] dt-bindings: update riscv plic compatible string

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Message-ID: <4245323.jvX0RauA9x@diego>
Date:   Wed, 13 Oct 2021 11:14:43 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Anup Patel <anup@...infault.org>
Cc:     Guo Ren <guoren@...nel.org>, Atish Patra <atish.patra@....com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Rob Herring <robh@...nel.org>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH V3 1/2] dt-bindings: update riscv plic compatible string

Am Mittwoch, 13. Oktober 2021, 11:11:26 CEST schrieb Anup Patel:
> On Wed, Oct 13, 2021 at 2:27 PM Heiko Stübner <heiko@...ech.de> wrote:
> >
> > Hi Anup,
> >
> > Am Mittwoch, 13. Oktober 2021, 07:11:46 CEST schrieb Anup Patel:
> > > On Wed, Oct 13, 2021 at 6:52 AM <guoren@...nel.org> wrote:
> > > >
> > > > From: Guo Ren <guoren@...ux.alibaba.com>
> > > >
> > > > Add the compatible string "thead,c900-plic" to the riscv plic
> > > > bindings to support SOCs with thead,c9xx processor cores.
> > > >
> > > > Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> > > > Cc: Rob Herring <robh@...nel.org>
> > > > Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> > > > Cc: Anup Patel <anup@...infault.org>
> > > > Cc: Atish Patra <atish.patra@....com>
> > > >
> > > > ---
> > > >
> > > > Changes since V3:
> > > >  - Rename "c9xx" to "c900"
> > > >  - Add thead,c900-plic in the description section
> > > > ---
> > > >  .../bindings/interrupt-controller/sifive,plic-1.0.0.yaml    | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > index 08d5a57ce00f..82629832e5a5 100644
> > > > --- a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > +++ b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > @@ -35,6 +35,11 @@ description:
> > > >    contains a specific memory layout, which is documented in chapter 8 of the
> > > >    SiFive U5 Coreplex Series Manual <https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf>.
> > > >
> > > > +  While the "thead,c900-plic" would mask IRQ with readl(claim), so it needn't
> > > > +  mask/unmask which needed in RISC-V PLIC. When in IRQS_ONESHOT & IRQCHIP_EOI_THREADED
> > > > +  path, unnecessary mask operation would cause a blocking irq bug in thead,c900-plic.
> > > > +  Because when IRQ is disabled in c900, writel(hwirq, claim) would be invalid.
> > >
> > > This is a totally incorrect description of the errata required for C9xx PLIC.
> > >
> > > Please don't project non-compliance as a feature of C9xx PLIC.
> > >
> > > > +
> > > >  maintainers:
> > > >    - Sagar Kadam <sagar.kadam@...ive.com>
> > > >    - Paul Walmsley  <paul.walmsley@...ive.com>
> > > > @@ -46,6 +51,7 @@ properties:
> > > >        - enum:
> > > >            - sifive,fu540-c000-plic
> > > >            - canaan,k210-plic
> > > > +          - thead,c900-plic
> >
> > we still want specific SoC names in the compatible, the "c900"
> > is still a sort-of placeholder.
> 
> Yes, we need "c900" compatible string as well. The "c9xx"
> compatible string is for the custom PLIC spec followed by T-HEAD.

What I meant was that the soc-specific string should name the
actual SoC (c906, c910) and not some imaginary chip ;-)

See for example mali gpu bindings for a similar reference
in devicetree/bindings/gpu/arm,mali-bifrost.yaml .




> 
> >
> >
> > > >        - const: sifive,plic-1.0.0
> > >
> > > The PLIC DT node requires two compatible string:
> > > <implementation_compat>, <spec_compat>
> > >
> > > The C9xx PLIC is not RISC-V PLIC so, the DT node should
> > > be: "thead,c900-plic", "thead,c9xx-plic"
> > >
> > > You need to change "- const: sifive,plic-1.0.0" to
> > > - enum:
> > >     - sifive,plic-1.0.0
> > >     - thead,c9xx-plic
> >
> >
> 
> Regards,
> Anup
>