linux-kernel - Re: [PATCH v2 1/3] dt-bindings: power: Introduce 'assigned-performance-states' property

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Message-ID: <20210601114426.3vhh2twocqx254b6@vireshk-i7>
Date:   Tue, 1 Jun 2021 17:14:26 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     Rajendra Nayak <rnayak@...eaurora.org>, ulf.hansson@...aro.org,
        robh+dt@...nel.org, bjorn.andersson@...aro.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        swboyd@...omium.org, rojay@...eaurora.org
Subject: Re: [PATCH v2 1/3] dt-bindings: power: Introduce
 'assigned-performance-states' property

On 01-06-21, 13:12, Stephan Gerhold wrote:
> > +    child4: consumer@...41000 {
> > +        compatible = "foo,consumer";
> > +        reg = <0x12341000 0x1000>;
> > +        power-domains = <&parent4>, <&parent5>;
> > +        assigned-performance-states = <0>, <256>;
> > +    };
> 
> Bjorn already asked this in v1 [1]:
> 
> > May I ask how this is different from saying something like:
> >
> > 	required-opps = <&??>, <&rpmpd_opp_svs>;
> 
> and maybe this was already discussed further elsewhere. But I think at
> the very least we need some clarification in the commit message + the
> binding documentation how your new property relates to the existing
> "required-opps" binding.
> 
> Because even if it might not be implemented at the moment,
> Documentation/devicetree/bindings/power/power_domain.txt actually also
> specifies "required-opps" for device nodes e.g. with the following example:
> 
> 	leaky-device0@...50000 {
> 		compatible = "foo,i-leak-current";
> 		reg = <0x12350000 0x1000>;
> 		power-domains = <&power 0>;
> 		required-opps = <&domain0_opp_0>;
> 	};
> 
> It looks like Viresh added that in commit e856f078bcf1
> ("OPP: Introduce "required-opp" property").
> 
> And in general I think it's a bit inconsistent that we usually refer to
> performance states with phandles into the OPP table, but the
> assigned-performance-states suddenly use "raw numbers".

I must have missed that discussion, sorry about that.

The required-opps property, when present in device's node directly, is about the
(default) OPPs to choose for that device's normal functioning as they may not do
DVFS.

Good point Stephan.

-- 
viresh