linux-kernel - Re: [PATCH] dt-bindings: interrupt-controller: sifive, plic: Fix number of interrupts

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Date:   Fri, 26 Nov 2021 14:35:14 +0530
From:   Anup Patel <anup@...infault.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Jessica Clarke <jrtc27@...c27.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Michael Zhu <michael.zhu@...rfivetech.com>
Subject: Re: [PATCH] dt-bindings: interrupt-controller: sifive, plic: Fix
 number of interrupts

On Fri, Nov 26, 2021 at 2:28 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Jessica,
>
> On Thu, Nov 25, 2021 at 5:08 PM Jessica Clarke <jrtc27@...c27.com> wrote:
> > On 25 Nov 2021, at 15:22, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > To improve human readability and enable automatic validation, the tuples
> > > in "interrupts-extended" properties should be grouped using angle
> > > brackets.  As the DT bindings lack an upper bound on the number of
> > > interrupts, thus assuming one, proper grouping is currently flagged as
> > > an error.
>
> Rob: Is this a bug in the tooling that should be fixed?
> Regardless, specifying a real upper limit is always a good idea.
>
> > > Fix this by adding the missing "maxItems", limiting it to 9 interrupts
> > > (one interrupt for a system management core, and two interrupts per core
> > > for other cores), which should be sufficient for now.
> >
> > This is SiFive’s IP, so is this actually true? I would imagine it’s
> > just parameterised and could be generated with as many targets as fit
> > in the MMIO space, and that this is thus inaccurate. Besides, such a
>
> Yes, this is implementation-defined.  I just used the maximum value
> currently in use.
>
> drivers/irqchip/irq-sifive-plic.c has #define MAX_CONTEXTS 15872,
> which matches the value of CONTEXT_PER_HART and the available address
> space in the driver and in [1].
> Would you be more comfortable with "maxItems: 15872"?
> Or do you prefer setting the maximum based on the compatible value
> (2 for k210, 9 for fu540, 4 for jh7100[2])?

Yes, 15872 is an appropriate value for "maxItems".

Regards,
Anup

>
> > function change should be made separately from the grouping change.
>
> OK, will split in v2.
>
> > The same goes for your equivalent sifive,clint0 patch.
>
> OK.
>
> > > Group the tuples in the example.
> > >
> > > Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > ---
> > > .../interrupt-controller/sifive,plic-1.0.0.yaml      | 12 ++++++------
> > > 1 file changed, 6 insertions(+), 6 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 08d5a57ce00ff446..198b373f984f3438 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
> > > @@ -61,6 +61,7 @@ properties:
> > >
> > >   interrupts-extended:
> > >     minItems: 1
> > > +    maxItems: 9
> > >     description:
> > >       Specifies which contexts are connected to the PLIC, with "-1" specifying
> > >       that a context is not present. Each node pointed to should be a
>
> [1] https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
> [2] The PLIC memory map in
>     https://github.com/starfive-tech/JH7100_Docs/blob/main/vic_u7_manual_with_creativecommons.pdf
>     indicate other values of ENABLE_PER_HART and CONTEXT_PER_HART?
>     Is memory the map correct?
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
>
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> linux-riscv@...ts.infradead.org
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