Re: [PATCH v5 2/4] dt-bindings: cpufreq: apple,soc-cpufreq: Add binding for Apple SoC cpufreq

[Ulf Hansson]

On Mon, 28 Nov 2022 at 15:29, Hector Martin <marcan@xxxxxxxxx> wrote:
>
> This binding represents the cpufreq/DVFS hardware present in Apple SoCs.
> The hardware has an independent controller per CPU cluster, and we
> represent them as unique nodes in order to accurately describe the
> hardware. The driver is responsible for binding them as a single cpufreq
> device (in the Linux cpufreq model).
>
> Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
> Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
> ---
>  .../cpufreq/apple,cluster-cpufreq.yaml        | 117 ++++++++++++++++++
>  1 file changed, 117 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml
>
> diff --git a/Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml b/Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml
> new file mode 100644
> index 000000000000..76cb9726660e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml
> @@ -0,0 +1,117 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/cpufreq/apple,cluster-cpufreq.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Apple SoC cluster cpufreq device
> +
> +maintainers:
> +  - Hector Martin <marcan@xxxxxxxxx>
> +
> +description: |
> +  Apple SoCs (e.g. M1) have a per-cpu-cluster DVFS controller that is part of
> +  the cluster management register block. This binding uses the standard
> +  operating-points-v2 table to define the CPU performance states, with the
> +  opp-level property specifying the hardware p-state index for that level.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - apple,t8103-cluster-cpufreq
> +              - apple,t8112-cluster-cpufreq
> +          - const: apple,cluster-cpufreq
> +      - items:
> +          - const: apple,t6000-cluster-cpufreq
> +          - const: apple,t8103-cluster-cpufreq
> +          - const: apple,cluster-cpufreq
> +
> +  reg:
> +    maxItems: 1
> +
> +  '#performance-domain-cells':
> +    const: 0
> +
> +required:
> +  - compatible
> +  - reg
> +  - '#performance-domain-cells'
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    // This example shows a single CPU per domain and 2 domains,
> +    // with two p-states per domain.
> +    // Shipping hardware has 2-4 CPUs per domain and 2-6 domains.
> +    cpus {
> +      #address-cells = <2>;
> +      #size-cells = <0>;
> +
> +      cpu@0 {
> +        compatible = "apple,icestorm";
> +        device_type = "cpu";
> +        reg = <0x0 0x0>;
> +        operating-points-v2 = <&ecluster_opp>;

To me, it looks like the operating-points-v2 phandle better belongs in
the performance-domains provider node. I mean, isn't the OPPs really a
description of the performance-domain provider?

That said, I suggest we try to extend the generic performance-domain
binding [1] with an "operating-points-v2". In that way, we should
instead be able to reference it from this binding.

In fact, that would be very similar to what already exists for the
generic power-domain binding [2]. I think it would be rather nice to
follow a similar pattern for the performance-domain binding.

> +        performance-domains = <&cpufreq_e>;
> +      };
> +
> +      cpu@10100 {
> +        compatible = "apple,firestorm";
> +        device_type = "cpu";
> +        reg = <0x0 0x10100>;
> +        operating-points-v2 = <&pcluster_opp>;
> +        performance-domains = <&cpufreq_p>;
> +      };
> +    };
> +
> +    ecluster_opp: opp-table-0 {
> +      compatible = "operating-points-v2";
> +      opp-shared;
> +
> +      opp01 {
> +        opp-hz = /bits/ 64 <600000000>;
> +        opp-level = <1>;
> +        clock-latency-ns = <7500>;
> +      };
> +      opp02 {
> +        opp-hz = /bits/ 64 <972000000>;
> +        opp-level = <2>;
> +        clock-latency-ns = <22000>;
> +      };
> +    };
> +
> +    pcluster_opp: opp-table-1 {
> +      compatible = "operating-points-v2";
> +      opp-shared;
> +
> +      opp01 {
> +        opp-hz = /bits/ 64 <600000000>;
> +        opp-level = <1>;
> +        clock-latency-ns = <8000>;
> +      };
> +      opp02 {
> +        opp-hz = /bits/ 64 <828000000>;
> +        opp-level = <2>;
> +        clock-latency-ns = <19000>;
> +      };
> +    };
> +
> +    soc {
> +      #address-cells = <2>;
> +      #size-cells = <2>;
> +
> +      cpufreq_e: performance-controller@210e20000 {
> +        compatible = "apple,t8103-cluster-cpufreq", "apple,cluster-cpufreq";
> +        reg = <0x2 0x10e20000 0 0x1000>;
> +        #performance-domain-cells = <0>;
> +      };
> +
> +      cpufreq_p: performance-controller@211e20000 {
> +        compatible = "apple,t8103-cluster-cpufreq", "apple,cluster-cpufreq";
> +        reg = <0x2 0x11e20000 0 0x1000>;
> +        #performance-domain-cells = <0>;
> +      };
> +    };

Kind regards
Uffe

[1]
Documentation/devicetree/bindings/dvfs/performance-domain.yaml
[2]
Documentation/devicetree/bindings/power/power-domain.yaml