linux-kernel - Re: [PATCH v4 4/4] dt-bindings: timer: Add CLINT bindings

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Date:   Wed, 22 Jul 2020 09:25:31 +0530
From:   Anup Patel <anup@...infault.org>
To:     Sean Anderson <seanga2@...il.com>
Cc:     Atish Patra <atishp@...shpatra.org>, devicetree@...r.kernel.org,
        Damien Le Moal <damien.lemoal@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Emil Renner Berhing <kernel@...il.dk>,
        Anup Patel <anup.patel@....com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Atish Patra <atish.patra@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Alistair Francis <Alistair.Francis@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Albert Ou <aou@...s.berkeley.edu>
Subject: Re: [PATCH v4 4/4] dt-bindings: timer: Add CLINT bindings

On Tue, Jul 21, 2020 at 5:48 PM Sean Anderson <seanga2@...il.com> wrote:
>
> On 7/20/20 9:15 PM, Atish Patra wrote:
> > On Fri, Jul 17, 2020 at 12:52 AM Anup Patel <anup.patel@....com> wrote:
> >>
> >> We add DT bindings documentation for CLINT device.
> >>
> >> Signed-off-by: Anup Patel <anup.patel@....com>
> >> Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> >> Tested-by: Emil Renner Berhing <kernel@...il.dk>
> >> ---
> >>  .../bindings/timer/sifive,clint.yaml          | 58 +++++++++++++++++++
> >>  1 file changed, 58 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> >> new file mode 100644
> >> index 000000000000..8ad115611860
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> >> @@ -0,0 +1,58 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/timer/sifive,clint.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: SiFive Core Local Interruptor
> >> +
> >> +maintainers:
> >> +  - Palmer Dabbelt <palmer@...belt.com>
> >> +  - Anup Patel <anup.patel@....com>
> >> +
> >> +description:
> >> +  SiFive (and other RISC-V) SOCs include an implementation of the SiFive
> >> +  Core Local Interruptor (CLINT) for M-mode timer and M-mode 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
> >> +
> >> +properties:
> >> +  compatible:
> >> +    items:
> >> +      - const: sifive,clint0
> >> +      - const: sifive,fu540-c000-clint
> >> +
> >> +    description:
> >> +      Should be "sifive,<chip>-clint" and "sifive,clint<version>".
> >> +      Supported compatible strings are -
> >> +      "sifive,fu540-c000-clint" for the SiFive CLINT v0 as integrated
> >> +      onto the SiFive FU540 chip, and "sifive,clint0" for the SiFive
> >> +      CLINT v0 IP block with no chip integration tweaks.
> >> +      Please refer to sifive-blocks-ip-versioning.txt for details
> >> +
> >
> > As the DT binding suggests that the clint device should be named as "sifive,**",
> > I think we should change the DT property in kendryte dts as well.
>
> The kendryte device is based on Rocket Chip, not any SiFive IP/device.
> If anything, the general binding should be "chipsalliance,clint" and the
> specific bindings should be "sifive,clint" and "kendryte,clint" (or
> "canaan,clint").

AFAIK, Palmer clearly mentioned in previous discussion that CLINT
spec is still owned by SiFive. No matter who implements CLINT device
in their SOC, we will need one compatible string to represent the
spec version (i.e. "sifive,clint0") and another compatible representing
specific implementation (for kendryte this can be "kendryte,k210-clint").

Regards,
Anup