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

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Message-ID: <58B791E9.4000505@codeaurora.org>
Date:   Thu, 02 Mar 2017 09:00:49 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Rob Herring <robh@...nel.org>
CC:     Ulf Hansson <ulf.hansson@...aro.org>,
        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 03/02/2017 04:43 AM, Rob Herring wrote:
> On Wed, Mar 1, 2017 at 12:27 AM, Rajendra Nayak <rnayak@...eaurora.org> wrote:
>>
>>
>> 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.
> 
> There's nothing in the binding only allowing that. If that was true,
> then #powerdomain-cells would be pointless

Is't #powerdomain-cells a powerdomain provider property? and used to
specify if a powerdomain provider supports providing 1 or many powerdomains?
I was talking about the power domain consumer property.
Looking at Documentation/devicetree/bindings/power/power_domain.txt..

==PM domain consumers==

Required properties:
 - power-domains : A phandle and PM domain specifier as defined by bindings of
                   the power controller specified by phandle.

It clearly says 'A phandle'. If there was a way to specify multiple power-domains
for a consumer device should it not be saying a list of phandles? Like we do for
clocks and regulators?

> as the property size would
> tell you the number of cells. Now it may be that we simply don't have
> any cases with more than 1. Hopefully that's not because bindings are
> working around PM domain limitations/requirements.
> 
> Rob
> 

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