linux-kernel - Re: [RFC PATCH v4 08/10] dt-bindings: timer: Add ACLINT MTIMER bindings

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Message-ID: <YWCj6CcB29fEQkFI@robh.at.kernel.org>
Date:   Fri, 8 Oct 2021 15:02:48 -0500
From:   Rob Herring <robh@...nel.org>
To:     Anup Patel <anup.patel@....com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Bin Meng <bmeng.cn@...il.com>
Subject: Re: [RFC PATCH v4 08/10] dt-bindings: timer: Add ACLINT MTIMER
 bindings

On Thu, Oct 07, 2021 at 06:06:30PM +0530, Anup Patel wrote:
> We add DT bindings documentation for the ACLINT MTIMER device
> found on RISC-V SOCs.
> 
> Signed-off-by: Anup Patel <anup.patel@....com>
> Reviewed-by: Bin Meng <bmeng.cn@...il.com>
> ---
>  .../bindings/timer/riscv,aclint-mtimer.yaml   | 67 +++++++++++++++++++
>  1 file changed, 67 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> 
> diff --git a/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml b/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> new file mode 100644
> index 000000000000..ebb7e81a5a12
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> @@ -0,0 +1,67 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/timer/riscv,aclint-mtimer.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V ACLINT M-level Timer
> +
> +maintainers:
> +  - Anup Patel <anup.patel@....com>
> +
> +description:

You need '|' if you want to maintain the paragraphs.

> +  RISC-V SOCs include an implementation of the M-level timer (MTIMER) defined
> +  in the RISC-V Advanced Core Local Interruptor (ACLINT) specification. The
> +  ACLINT MTIMER device is documented in the RISC-V ACLINT specification found
> +  at https://github.com/riscv/riscv-aclint/blob/main/riscv-aclint.adoc.
> +
> +  The ACLINT MTIMER device directly connects to the M-level timer interrupt
> +  lines of various HARTs (or CPUs) so the RISC-V per-HART (or per-CPU) local
> +  interrupt controller is the parent interrupt controller for the ACLINT
> +  MTIMER device.
> +
> +  The clock frequency of ACLINT 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:
> +      - enum:
> +         - sifive,fu540-c000-aclint-mtimer
> +      - const: riscv,aclint-mtimer
> +
> +    description:
> +      Should be "<vendor>,<chip>-aclint-mtimer" and "riscv,aclint-mtimer".
> +
> +  reg:
> +    description: |
> +      Specifies base physical address(s) of the MTIME register and MTIMECMPx
> +      registers. The 1st region is the MTIME register base and size. The 2nd
> +      region is the MTIMECMPx registers base and size.
> +    minItems: 2
> +    maxItems: 2

All this can be expressed as:

items:
  - description: The MTIME registers
  - description: The MTIMECMPx registers

'reg' is always the physical address and size, so no need to redefine 
common properties.


> +
> +  interrupts-extended:
> +    minItems: 1
> +    maxItems: 4095
> +
> +additionalProperties: false
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts-extended
> +
> +examples:
> +  - |
> +    timer@...4000 {
> +      compatible = "sifive,fu540-c000-aclint-mtimer", "riscv,aclint-mtimer";
> +      reg = <0x200bff8 0x8>,
> +            <0x2004000 0x7ff8>;
> +      interrupts-extended = <&cpu1intc 7>,
> +                            <&cpu2intc 7>,
> +                            <&cpu3intc 7>,
> +                            <&cpu4intc 7>;
> +    };
> +...
> -- 
> 2.25.1
> 
>