linux-kernel - Re: [PATCH V2 0/2] PM / Domains / OPP: Introduce domain-performance-state binding

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Message-ID: <20161222181422.2cpmdfzeyxdi6vpa@rob-hp-laptop>
Date:   Thu, 22 Dec 2016 12:14:22 -0600
From:   Rob Herring <robh@...nel.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>,
        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,
        Nayak Rajendra <rnayak@...eaurora.org>
Subject: Re: [PATCH V2 0/2] PM / Domains / OPP: Introduce
 domain-performance-state binding

On Mon, Dec 12, 2016 at 04:26:17PM +0530, Viresh Kumar wrote:
> Hello,
> 
> Some platforms have the capability to configure the performance state of
> their Power Domains. The performance levels are represented by positive
> integer values, a lower value represents lower performance state.
> 
> We had some discussions about it in the past on the PM list [1], which is
> followed by discussions during the LPC. The outcome of all that was that we
> should extend Power Domain framework to support active state power management
> as well.
> 
> The power-domains until now were only concentrating on the idle state
> management of the device and this needs to change in order to reuse the
> infrastructure of power domains for active state management.

>From a h/w perspective, are idle states really different from 
performance states? 

> 
> To get a complete picture of the proposed plan, following is what we
> need to do:
> - Create DT bindings to get domain performance state information for the
>   platforms.

I would do this last so you can evolve things if you're not certain 
about what the bindings should look like. You can always start with 
things in the kernel and add to DT later.

While in theory we should be able to just "describe the h/w" in DT and 
develop the Linux side independently, this feels too much like the 
bindings are just evolving with Linux needs.

Rob