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

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Date:   Wed, 5 Aug 2020 13:43:06 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.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
Subject: Re: [PATCH 1/3] dt-bindings: power: Introduce
 'assigned-performance-states' property


On 8/5/2020 12:09 PM, Stephen Boyd wrote:
> 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?

Sure, I'll reword it to make it clear that we need the same number of cells
as power-domains, and as you pointed out below that 0 corresponds to not setting
anything.

For the matching of opp-level inside the OPP table of the power-domain, I don't
think from the power-domain bindings we limit providers with only OPP tables to
support performance states? It could be just a range that the provider manages
internally?

And thanks for catching all my typos :), I'll have them fixed when I re-spin.

> 
>> +
>>   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?
> 

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