linux-kernel - Re: [PATCH V5 2/3] dt-bindings: update riscv plic compatible string

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Message-ID: <CAAhSdy1FfMGPWBExEVe9Vdh2s_fNP43Rp7jNdEMNmP1nmPZL_Q@mail.gmail.com>
Date:   Sun, 24 Oct 2021 14:48:38 +0530
From:   Anup Patel <anup@...infault.org>
To:     Guo Ren <guoren@...nel.org>
Cc:     Atish Patra <atish.patra@....com>, Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heiko Stübner <heiko@...ech.de>,
        Rob Herring <robh@...nel.org>,
        "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+dt@...nel.org>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH V5 2/3] dt-bindings: update riscv plic compatible string

On Sun, Oct 24, 2021 at 2:31 PM Guo Ren <guoren@...nel.org> wrote:
>
> On Sun, Oct 24, 2021 at 3:35 PM Anup Patel <anup@...infault.org> wrote:
> >
> > On Sun, Oct 24, 2021 at 7:03 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 allwinner d1 SOC which contains c906 core.
> > >
> > > Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> > > Cc: Anup Patel <anup@...infault.org>
> > > Cc: Atish Patra <atish.patra@....com>
> > > Cc: Heiko Stuebner <heiko@...ech.de>
> > > Cc: Rob Herring <robh@...nel.org>
> > > Cc: Rob Herring <robh+dt@...nel.org>
> > > Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> > >
> > > ---
> > >
> > > Changes since V5:
> > >  - Add DT list
> > >  - Fixup compatible string
> > >  - Remove allwinner-d1 compatible
> > >  - make dt_binding_check
> > >
> > > Changes since V4:
> > >  - Update description in errata style
> > >  - Update enum suggested by Anup, Heiko, Samuel
> > >
> > > Changes since V3:
> > >  - Rename "c9xx" to "c900"
> > >  - Add thead,c900-plic in the description section
> > > ---
> > >  .../interrupt-controller/sifive,plic-1.0.0.yaml   | 15 ++++++++++++---
> > >  1 file changed, 12 insertions(+), 3 deletions(-)
> > >
> > > 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..18b97bfd7954 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 +35,10 @@ 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>.
> > >
> > > +  The thead,c900-plic couldn't complete masked irq source which has been disabled in
> > > +  enable register. Add thead_plic_chip which fix up c906-plic irq source completion
> > > +  problem by unmask/mask wrapper.
> > > +
> >
> > This is an incomplete description about how T-HEAD PLIC is different from
> > RISC-V PLIC.
> >
> > I would suggest the following:
> >
> > The T-HEAD C9xx SoC implements a modified/custom T-HEAD PLIC specification
> > which will mask current IRQ upon read to CLAIM register and will unmask the IRQ
> > upon write to CLAIM register. The thead,c900-plic compatible string
> > represents the
> > custom T-HEAD PLIC specification.
> The patch fixup the problem that when "thead,c900-plic" couldn't
> complete masked irq source which has been disabled.
>
> This patch is different from the last one in that there is no
> relationship with the auto-mask feature.

This patch adds compatible string for T-HEAD PLIC so it
should describe how T-HEAD PLIC is different from RISC-V
PLIC. The DT bindings document describes HW and not
the software work-around implemented using DT bindings.

Your irqchip patch uses T-HEAD PLIC compatible string to
implement a work-around.

In other words, this patch is different from the irqchip patch.

Regards,
Anup

>
> >
> > Regards,
> > Anup
> >
> > >  maintainers:
> > >    - Sagar Kadam <sagar.kadam@...ive.com>
> > >    - Paul Walmsley  <paul.walmsley@...ive.com>
> > > @@ -42,11 +46,16 @@ maintainers:
> > >
> > >  properties:
> > >    compatible:
> > > -    items:
> > > +   oneOf:
> > > +    - items:
> > >        - enum:
> > > -          - sifive,fu540-c000-plic
> > > -          - canaan,k210-plic
> > > +        - sifive,fu540-c000-plic
> > > +        - canaan,k210-plic
> > >        - const: sifive,plic-1.0.0
> > > +    - items:
> > > +      - enum:
> > > +        - allwinner,sun20i-d1-plic
> > > +      - const: thead,c900-plic
> > >
> > >    reg:
> > >      maxItems: 1
> > > --
> > > 2.25.1
> > >
>
>
>
> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/