linux-kernel - Re: [PATCH V3 0/7] PM / Domains: Implement domain performance states

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Date:   Wed, 15 Mar 2017 16:19:57 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Kevin Hilman <khilman@...libre.com>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Nishanth Menon <nm@...com>,
        Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Nayak, Rajendra" <rnayak@...eaurora.org>,
        Lina Iyer <lina.iyer@...aro.org>
Subject: Re: [PATCH V3 0/7] PM / Domains: Implement domain performance states

On 13 March 2017 at 16:09, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 10-03-17, 12:38, Kevin Hilman wrote:
>> Why limit it to just voltage levels.
>>
>> As I suggested earlier, I think this should use OPPs.  Remember that a
>> PM domain is not limited to a hardware power domain, but is just a
>> grouping mechanism for devices that share some PM properties.  As
>> mentioned by Geert, this can also be a clock domain, where frequencies
>> would make sense as well.  One can imagine using this type of PM domain
>> to manage an interconnect/bus which has scalable voltage/frequencies as
>> well.
>
> Okay, I tried to do that change today and am blocked a bit right now.
>
> The OPP core and all of its APIs/interfaces have dependency on the
> "struct device" for their working. It gets the of_node from it, stores
> the device pointer to manage cases where multiple devices share OPP
> table, uses it to get clk and regulators.
>
> But the "genpd" structure doesn't have a 'struct device' associated
> with it. How should I make both of them work together?
>
> I tried to create separate helpers that don't accept 'dev', but that
> is also not good.  Just too much redundant code everywhere.
>
> Would creating a 'dev' structure within 'generic_pm_domain' be
> acceptable? Or should we ask the domain-drivers to call something like
> of_genpd_parse_idle_states(), with a fake 'dev' structure which has
> its of_node initialized? Or maybe move that hack within the OPP-core
> API, which can create a dev structure at runtime for the genpd passed
> to it and get the OPP table out?

Ulf/Kevin,

I am currently blocked on this decision. Will it be possible for you guys
to suggest something, so that I can send V3 soon ?

The most ideal solution seems to be adding a device structure in genpd
structure and add a genpd bus as well probably.

--
viresh