linux-kernel - Re: [PATCH V3 2/7] PM / OPP: Introduce "domain-performance-state" binding to OPP nodes

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Message-ID: <58B669DD.5010309@codeaurora.org>
Date:   Wed, 01 Mar 2017 11:57:41 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Rob Herring <robh@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>
CC:     Viresh Kumar <viresh.kumar@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Lina Iyer <lina.iyer@...aro.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH V3 2/7] PM / OPP: Introduce "domain-performance-state"
 binding to OPP nodes



On 02/28/2017 09:22 PM, Rob Herring wrote:
> On Tue, Feb 28, 2017 at 9:14 AM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>> [...]
>>
>>>>                                     ---> Parent domain-2 (Contains Perfomance states)
>>>>                                     |
>>>>                                     |
>>>> C.) DeviceX  --->  Parent-domain-1  |
>>>>                                     |
>>>>                                     |
>>>>                                     ---> Parent domain-3 (Contains Perfomance states)
>>>
>>> I'm a bit confused. How does a domain have 2 parent domains?
>>
>> This comes from the early design of the generic PM domain, thus I
>> assume we have some HW with such complex PM topology. However, I don't
>> know if it is actually being used.
>>
>> Moreover, the corresponding DT bindings for "power-domains" parents,
>> can easily be extended to cover more than one parent. See more in
>> Documentation/devicetree/bindings/power/power_domain.txt
> 
> I could easily see device having 2 power domains. For example a cpu
> may have separate domains for RAM/caches and logic. And nesting of

yet the bindings for power-domains (for consumer devices) only allows for
one powerdomain to be associated with a device.

> power domains is certainly common, but a power domain being contained
> in 2 different parents? I don't even see how that is possible in the
> physical design. Now if we're mixing PM and power domains again and
> the cpu device is pointing to the cpu PM domain which contains 2 power
> domains, then certainly that is possible.
> 
> Rob
> 

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