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

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Date:   Wed, 1 Mar 2017 14:24:12 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Rob Herring <robh@...nel.org>,
        Ulf Hansson <ulf.hansson@...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>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH V3 2/7] PM / OPP: Introduce "domain-performance-state"
 binding to OPP nodes

On 01-03-17, 09:45, Geert Uytterhoeven wrote:
> On Wed, Mar 1, 2017 at 7:14 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > On 28-02-17, 09:52, Rob Herring wrote:
> >> On Tue, Feb 28, 2017 at 9:14 AM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >> > 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.
> >
> > An important thing here is that PM domain doesn't support such devices. i.e. a
> > device isn't allowed to have multiple PM domains today. So a way to support such
> > devices can be to create a virtual PM domain, that has two parents and device as
> > its child.
> 
> As clock domains (and their support code) are fairly orthogonal to power
> areas, currently our power area controller driver just forwards the
> clock handling
> to the clock driver (cfr. rcar-sysc).

Perhaps Rajendra can explain better but Qcom have a case where they need to
program two power domains as well.

-- 
viresh