linux-kernel - Re: [PATCH 1/3] dt-bindings: power: Introduce 'assigned-performance-states' property

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Date:   Tue, 04 Aug 2020 23:39:02 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>, bjorn.andersson@...aro.org,
        robh+dt@...nel.org, ulf.hansson@...aro.org
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>
Subject: Re: [PATCH 1/3] dt-bindings: power: Introduce 'assigned-performance-states' property

Quoting Rajendra Nayak (2020-08-04 04:46:54)
> While most devices within power-domains which support performance states,
> scale the performance state dynamically, some devices might want to
> set a static/default performance state while the device is active.
> These devices typically would also run of a fixed clock and not support

s/of/off/

> dyamically scaling the device's performance, also known as DVFS techniques.

s/dyamically/dynamically/

> Add a property 'assigned-performance-states' which client devices can
> use to set this default performance state on their power-domains.
> 
> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> ---
>  .../devicetree/bindings/power/power-domain.yaml    | 47 ++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/power/power-domain.yaml b/Documentation/devicetree/bindings/power/power-domain.yaml
> index ff5936e..48e9319 100644
> --- a/Documentation/devicetree/bindings/power/power-domain.yaml
> +++ b/Documentation/devicetree/bindings/power/power-domain.yaml
> @@ -66,6 +66,16 @@ properties:
>         by the given provider should be subdomains of the domain specified
>         by this binding.
>  
> +  assigned-performance-states:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description:
> +       Some devices might need to configure their power domains in a default
> +       performance state while the device is active. These devices typcially
> +       would also run of a fixed clock and not support dyamically scaling the

Same of and dynamically comment.

> +       device's performance, also known as DVFS techniques. The list of performance
> +       state values should correspond to the list of power domains specified as part
> +       of the power-domains property.

This is different than assigned-clock-rates. I guess that's OK because
we don't need to assign parents with more specifiers. Maybe it should be
worded more strongly to clearly state that each cell corresponds to one
power domain? And that it should match the opp-level inside any OPP
table for the power domain?

> +
>  required:
>    - "#power-domain-cells"
>  
> @@ -129,3 +139,40 @@ examples:
>              min-residency-us = <7000>;
>          };
>      };
> +
> +  - |
> +    parent4: power-controller@...40000 {
> +        compatible = "foo,power-controller";
> +        reg = <0x12340000 0x1000>;
> +        #power-domain-cells = <0>;
> +    };
> +
> +    parent5: power-controller@...10000 {
> +        compatible = "foo,power-controller";
> +        reg = <0x43210000 0x1000>;
> +        #power-domain-cells = <0>;
> +        operating-points-v2 = <&power_opp_table>;
> +
> +        power_opp_table: opp-table {
> +            compatible = "operating-points-v2";
> +
> +            power_opp_low: opp1 {
> +                opp-level = <16>;
> +            };
> +
> +            rpmpd_opp_ret: opp2 {
> +                opp-level = <64>;
> +            };
> +
> +            rpmpd_opp_svs: opp3 {
> +                opp-level = <256>;
> +            };
> +        };
> +    };
> +
> +    child4: consumer@...41000 {
> +        compatible = "foo,consumer";
> +        reg = <0x12341000 0x1000>;
> +        power-domains = <&parent4>, <&parent5>;
> +        assigned-performance-states = <0>, <256>;

I guess <0> means don't set anything?