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

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Date:   Mon, 18 Jan 2021 11:09:40 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Roja Rani Yarubandi <rojay@...eaurora.org>
Cc:     ulf.hansson@...aro.org, robh+dt@...nel.org, wsa@...nel.org,
        swboyd@...omium.org, dianders@...omium.org,
        saiprakash.ranjan@...eaurora.org, mka@...omium.org,
        akashast@...eaurora.org, msavaliy@....qualcomm.com,
        parashar@...eaurora.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, agross@...nel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: power: Introduce
 'assigned-performance-states' property


On 1/15/2021 9:45 PM, Bjorn Andersson wrote:
> On Thu 24 Dec 05:12 CST 2020, Roja Rani Yarubandi wrote:
> 
>> 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 off a fixed clock and not support
>> dynamically scaling the device's performance, also known as DVFS
>> techniques.
>>
>> Add a property 'assigned-performance-states' which client devices can
>> use to set this default performance state on their power-domains.
>>
>> Signed-off-by: Roja Rani Yarubandi <rojay@...eaurora.org>
>> ---
>>   .../bindings/power/power-domain.yaml          | 49 +++++++++++++++++++
>>   1 file changed, 49 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/power/power-domain.yaml b/Documentation/devicetree/bindings/power/power-domain.yaml
>> index aed51e9dcb11..a42977a82d06 100644
>> --- a/Documentation/devicetree/bindings/power/power-domain.yaml
>> +++ b/Documentation/devicetree/bindings/power/power-domain.yaml
>> @@ -66,6 +66,18 @@ 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 off a fixed clock and not support dynamically scaling
>> +       the device's performance, also known as DVFS techniques. Each cell in
>> +       performance state value corresponds to one power domain specified as
>> +       part of the power-domains property. Performance state value can be an
>> +       opp-level inside an OPP table of the power-domain and need not match
>> +       with any OPP table performance state.
>> +
>>   required:
>>     - "#power-domain-cells"
>>   
>> @@ -131,3 +143,40 @@ 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>;
> 
> May I ask how this is different from saying something like:
> 
> 	required-opps = <&??>, <&rpmpd_opp_svs>:

I think its potentially the same. We just don't have any code to handle this
binding in kernel yet (when this property is part of the device/consumer node)

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