linux-kernel - Re: [PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

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Date:   Tue, 14 Jul 2020 09:17:39 +0530
From:   Anup Patel <anup@...infault.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Anup Patel <anup.patel@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Damien Le Moal <damien.lemoal@....com>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

On Tue, Jul 14, 2020 at 8:07 AM Rob Herring <robh@...nel.org> wrote:
>
> On Sat, Jun 27, 2020 at 09:49:57PM +0530, Anup Patel wrote:
> > We add DT bindings documentation for CLINT device.
> >
> > Signed-off-by: Anup Patel <anup.patel@....com>
> > Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> > ---
> >  .../bindings/timer/sifive,clint.txt           | 34 +++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
>
> Bindings should be in DT schema format now.

Okay, will update.

>
> >
> > diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.txt b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > new file mode 100644
> > index 000000000000..45b75347a7d5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > @@ -0,0 +1,34 @@
> > +SiFive Core Local Interruptor (CLINT)
> > +-------------------------------------
> > +
> > +SiFive (and other RISC-V) SOCs include an implementation of the SiFive Core
> > +Local Interruptor (CLINT) for M-mode timer and inter-processor interrupts.
> > +
> > +It directly connects to the timer and inter-processor interrupt lines of
> > +various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local interrupt
> > +controller is the parent interrupt controller for CLINT device.
> > +
> > +The clock frequency of CLINT is specified via "timebase-frequency" DT
> > +property of "/cpus" DT node. The "timebase-frequency" DT property is
> > +described in: Documentation/devicetree/bindings/riscv/cpus.yaml
> > +
> > +Required properties:
> > +- compatible : should be "riscv,clint0" or "sifive,clint-1.0.0". A specific
>
> A new versioning scheme from SiFive? To review, we don't do version
> numbers unless there's a well defined and documented scheme. IOW, one
> that's not s/w folks just making up v1, v2, v3, etc.

The "riscv,clint0" is already used by various RISC-V systems (including QEMU).

The "sifive,clint-1.0.0" is for being consistent with the PLIC
versioning scheme.

There is no clear documentation of CLINT versioning scheme. I think it's best
to just drop "sifive,clint-1.0.0" . Agree ??

>
> > +  string identifying the actual implementation can be added if implementation
> > +  specific worked arounds are needed.
> > +- reg : Should contain 1 register range (address and length).
> > +- interrupts-extended : Specifies which HARTs (or CPUs) are connected to
> > +  the CLINT.  Each node pointed to should be a riscv,cpu-intc node, which
> > +  has a riscv node as parent.
> > +
> > +Example:
> > +
> > +     clint@...0000 {
> > +             compatible = "sifive,clint-1.0.0", "sifive,fu540-c000-clint";
>
> Doesn't match the binding.

Okay, will update.

>
> > +             interrupts-extended = <
> > +                     &cpu1-intc 3 &cpu1-intc 7
> > +                     &cpu2-intc 3 &cpu2-intc 7
> > +                     &cpu3-intc 3 &cpu3-intc 7
> > +                     &cpu4-intc 3 &cpu4-intc 7>;
> > +             reg = <0x2000000 0x4000000>;
> > +     };
> > --
> > 2.25.1
> >

Regards,
Anup