Re: [PATCH v2 2/7] dt-bindings: dvfs: Add RPMI performance service bindings

[Conor Dooley <conor@kernel.org>]

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On Thu, Oct 08, 2026 at 05:10:26PM +0800, Joshua Yeong wrote:
> Add device tree bindings for the RPMI performance service group based
> controller for the supervisor software.
> 
> A CPU names its performance domain through "performance-domains". Any
> other device names it through "power-domains": the controller is also a
> power domain provider, with one power domain per performance domain and
> the levels the domain advertises as the performance states of that
> power domain.
> 
> The RPMI performance service group is defined by the RISC-V Platform
> Management Interface (RPMI) specification.
> 
> Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
> ---
>  .../bindings/dvfs/riscv,rpmi-performance.yaml | 88 +++++++++++++++++++
>  1 file changed, 88 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dvfs/riscv,rpmi-performance.yaml
> 
> diff --git a/Documentation/devicetree/bindings/dvfs/riscv,rpmi-performance.yaml b/Documentation/devicetree/bindings/dvfs/riscv,rpmi-performance.yaml
> new file mode 100644
> index 000000000000..ec7856cb7257
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dvfs/riscv,rpmi-performance.yaml
> @@ -0,0 +1,88 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dvfs/riscv,rpmi-performance.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V RPMI performance service group
> +
> +maintainers:
> +  - Joshua Yeong <joshua.yeong@starfivetech.com>
> +
> +description: |
> +  The RISC-V Platform Management Interface (RPMI) [1] defines a modular and
> +  extensible messaging protocol for platform management functions. The supervisor
> +  software can send and receive RPMI messages via SBI MPXY extension [2]
> +  or via a dedicated supervisor-mode RPMI transport.
> +
> +  The RPMI specification [1] defines performance service group (performance
> +  domain) for accessing and controlling platform-managed performance-related
> +  resources, as implemented by a platform microcontroller. Supervisor software
> +  can interact with the RPMI performance service group through an SBI MPXY
> +  channel or through a dedicated supervisor-mode RPMI transport.
> +
> +  The node is a performance domain provider. A CPU references its domain
> +  through the generic "performance-domains" property described in
> +  dvfs/performance-domain.yaml.
> +
> +  The node can also be a power domain provider, with one power domain for each
> +  performance domain. Any other device that runs in one of the domains
> +  references it through "power-domains", and each level the domain advertises
> +  is a performance state of that power domain.
> +
> +  For example, with the provider labelled "performance", a CPU that runs in
> +  domain 0 and a device that runs in domain 1 reference their domains as:
> +
> +    cpu@0 {
> +        ...
> +        performance-domains = <&performance 0>;
> +    };
> +
> +    gpu@40000000 {
> +        ...
> +        power-domains = <&performance 1>;
> +    };
> +
> +  ===========================================
> +  References
> +  ===========================================
> +
> +  [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
> +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> +
> +  [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
> +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> +
> +properties:
> +  compatible:
> +    description:
> +      Intended for use by the supervisor software.
> +    const: riscv,rpmi-performance
> +
> +  mboxes:
> +    maxItems: 1
> +    description:
> +      Mailbox channel of the underlying RPMI transport or SBI message proxy channel.
> +
> +  "#performance-domain-cells":
> +    const: 1
> +
> +  "#power-domain-cells":
> +    const: 1
> +
> +required:
> +  - compatible
> +  - mboxes
> +  - "#performance-domain-cells"

Why is performance-domain-cells mandatory? Is it not possible for a
domain to only control non-cpu devices? If that's the case, this should
be relaxed to require that either cells property is present I think.

Also, all other rpmi/mpxy series have been written such that there's
both M and S mode bindings in a single file. Why has that approach not
been taken here?

Thanks,
Conor.

      
  -
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    rpmi-performance {
> +        compatible = "riscv,rpmi-performance";
> +        mboxes = <&mpxy_mbox 0x1003 0x0>;
> +        #performance-domain-cells = <0x01>;
> +        #power-domain-cells = <0x01>;
> +    };
> +...
> -- 
> 2.43.0
> 

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