linux-kernel - Re: [PATCH V2 1/2] PM / Domains: Introduce domain-performance-states binding

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Date:   Fri, 06 Jan 2017 16:06:26 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     Rafael Wysocki <rjw@...ysocki.net>, linaro-kernel@...ts.linaro.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephen Boyd <sboyd@...eaurora.org>,
        Nishanth Menon <nm@...com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kevin Hilman <khilman@...libre.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Lina Iyer <lina.iyer@...aro.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH V2 1/2] PM / Domains: Introduce domain-performance-states
 binding



On 01/06/2017 03:53 PM, Viresh Kumar wrote:
> On 06-01-17, 15:42, Rajendra Nayak wrote:
>> I read through that discussion, and I thought that was to do we
>> handling multiple powerdomains with performance states
>> (or in other words multiple voltage rails controlled by the M3)
> 
> I thought about it as multiple power domains available for a device,
> and the device will be in a single domain out of those at a time. So
> perhaps it is about the problem you mentioned.
> 
>> What I was pointing to, was that devices quite often (again on qcom
>> platforms) have a power-switch (gdscs as we call it) which are modeled
>> as powerdomains (which have nothing to do with taking to the M3 core),
>> and with the proposed bindings one or more voltage rails controlled by the M3
>> also as powerdomains associated with a device and the bindings have just one
>> power-domains property in the device node, which runtime PM would use
>> to power_on/off the device and OPP core would use to set the performance
>> state?
>>
>> +	leaky-device@...50000 {
>> +		compatible = "foo,i-leak-current";
>> +		reg = <0x12350000 0x1000>;
>> +		power-domains = <&power 0>;
>> +		domain-performance-state = <&domain_perf_state2>;
>> +	};
>>
>> Lets say leaky-device needs to switch on/off a gdsc and also send a
>> value to M3 to set a minimum performance state (so M3 configures the
>> voltage rails accordingly) how would it work?
> 
> So the way I proposed this earlier is that every device will have a
> single power domain for it. In your case that power domain will
> represent gdscs. Idle state and performance state request will go to
> that level and then its up to the gdscs domain specific code to choose
> the right domain and its performance state. The parent domain shall
> then pass on the performance state to the next level power domain
> controlled by the M3 core.
> 
> For example a device can have I power domain for idle state management
> and A power domain for active state management. The device will also
> have a M power domain which represents the gdscs. M can choose I or A
> as its parent. The power domain A (and similar power domains for all
> other devices) will have a parent power domain P. Now P is controlled
> or configured via the M3. Will that make sense ?

No, I am thoroughly confused :)
I was struggling with 2 powerdomains and now there are way too many of them :P

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