linux-kernel - Re: [PATCH V6 1/9] PM / OPP: Introduce "power-domain-opp" property

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Message-ID: <20170508071146.GG17010@vireshk-i7>
Date:   Mon, 8 May 2017 12:41:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     Kevin Hilman <khilman@...libre.com>, Rob Herring <robh@...nel.org>,
        Rafael Wysocki <rjw@...ysocki.net>, ulf.hansson@...aro.org,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        lina.iyer@...aro.org, sudeep.holla@....com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V6 1/9] PM / OPP: Introduce "power-domain-opp" property

I had a long chat with Rajendra offline and clarified few things..

On 08-05-17, 11:06, Rajendra Nayak wrote:
> On 05/08/2017 09:45 AM, Viresh Kumar wrote:
> > On 06-05-17, 11:58, Kevin Hilman wrote:

> >> I had the same question.  Seems the same comment about an abstract
> >> "index" is needed for voltage also.
> > 
> > Why should we do that? Here are the cases that I had in mind while writing this:
> > 
> > - DT only contains the performance-index and nothing else (i.e. voltages aren't
> >   exposed).
> > 
> >   We wouldn't be required to fill the microvolt property as it is optional.
> 
> So the performance-index is specified in opp-hz property?

Yes, but in the OPP table of the power-domain and not the device. The
device can still have its own OPP table with normal freq/voltage
values (for a separate regulator).

> What if the microcontroller firmware maps the performance-index to voltage but
> expects linux to scale the frequency?

As you clarified on the chat, you were talking about the device here.
It isn't a problem as we will have two separate tables here, one for
the device and one for the domain.

-- 
viresh