linux-kernel - Re: [RFC PATCH v2 08/17] dt-bindings: clock: Add bindings for RISC-V RPMI clock service group

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Message-ID: <20250203225140.GA483650-robh@kernel.org>
Date: Mon, 3 Feb 2025 16:51:40 -0600
From: Rob Herring <robh@...nel.org>
To: Anup Patel <apatel@...tanamicro.com>
Cc: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Len Brown <lenb@...nel.org>, Sunil V L <sunilvl@...tanamicro.com>,
	Rahul Pathak <rpathak@...tanamicro.com>,
	Leyfoon Tan <leyfoon.tan@...rfivetech.com>,
	Atish Patra <atishp@...shpatra.org>,
	Andrew Jones <ajones@...tanamicro.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	Anup Patel <anup@...infault.org>, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 08/17] dt-bindings: clock: Add bindings for RISC-V
 RPMI clock service group

On Mon, Feb 03, 2025 at 02:18:57PM +0530, Anup Patel wrote:
> Add device tree bindings for the clock service group defined by the
> RISC-V platform management interface (RPMI) specification.
> 
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  .../bindings/clock/riscv,rpmi-clock.yaml      | 77 +++++++++++++++++++
>  1 file changed, 77 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/clock/riscv,rpmi-clock.yaml
> 
> diff --git a/Documentation/devicetree/bindings/clock/riscv,rpmi-clock.yaml b/Documentation/devicetree/bindings/clock/riscv,rpmi-clock.yaml
> new file mode 100644
> index 000000000000..c08491c04926
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/riscv,rpmi-clock.yaml
> @@ -0,0 +1,77 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/clock/riscv,rpmi-clock.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V RPMI clock service group based clock controller
> +
> +maintainers:
> +  - Anup Patel <anup@...infault.org>
> +
> +description: |
> +  The RISC-V Platform Management Interface (RPMI) [1] defines a
> +  messaging protocol which is modular and extensible. The supervisor
> +  software can send/receive RPMI messages via SBI MPXY extension [2]
> +  or some dedicated supervisor-mode RPMI transport.
> +
> +  The RPMI specification [1] defines clock service group for accessing
> +  system clocks managed by a platform microcontroller.
> +
> +  ===========================================
> +  References
> +  ===========================================
> +
> +  [1] RISC-V Platform Management Interface (RPMI)
> +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> +
> +  [2] RISC-V Supervisor Binary Interface (SBI)
> +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - description:
> +          Intended for use by the SBI implementation in machine mode or
> +          software in supervisor mode.
> +        const: riscv,rpmi-clock
> +
> +      - description:
> +          Intended for use by the SBI implementation in machine mode.
> +        const: riscv,rpmi-mpxy-clock
> +
> +  mboxes:
> +    maxItems: 1
> +    description:
> +      Mailbox channel of the underlying RPMI transport or SBI message proxy.
> +
> +  riscv,sbi-mpxy-channel-id:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The SBI MPXY channel id to be used for providing RPMI access to
> +      the supervisor software. This property is mandatory when using
> +      riscv,rpmi-mpxy-clock compatible string.

That constraint can be expressed as:

dependentSchemas:
  riscv,sbi-mpxy-channel-id:
    properties:
      compatible:
        const: riscv,rpmi-mpxy-clock

Please double check that works.

> +
> +  "#clock-cells":
> +    const: 1
> +    description:
> +      This property is mandatory when using riscv,rpmi-clock compatible string.

Similar constraint here.

Though the only thing the 2 compatibles have in common is 'mboxes'. I 
think it would be better to just split this into 2 docs.

> +
> +required:
> +  - compatible
> +  - mboxes
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    mpxy_mbox: sbi-mpxy-mbox {

mailbox {

> +          compatible = "riscv,sbi-mpxy-mbox";
> +          #mbox-cells = <2>;
> +    };
> +    rpmi-clk {

clock-controller {

> +        compatible = "riscv,rpmi-clock";
> +        mboxes = <&mpxy_mbox 0x1000 0x0>;
> +        #clock-cells = <1>;
> +    };
> +...
> -- 
> 2.43.0
>