linux-kernel - Re: [PATCH V8 1/6] PM / Domains: Add support to select performance-state of domains

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Date:   Wed, 2 Aug 2017 13:51:51 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Nishanth Menon <nm@...com>, Rob Herring <robh+dt@...nel.org>,
        Lina Iyer <lina.iyer@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>
Subject: Re: [PATCH V8 1/6] PM / Domains: Add support to select
 performance-state of domains

On 31-07-17, 09:44, Viresh Kumar wrote:
> On 29-07-17, 10:24, Ulf Hansson wrote:
> > Let's invent a new genpd flag, GENPD_FLAG_PERF_STATE!
> > 
> > The creator of the genpd then needs to set this before calling
> > pm_genpd_init(). Similar as we are dealing with GENPD_FLAG_PM_CLK.
> > 
> > The requirement for GENPD_FLAG_PERF_STATES, is to have the
> > ->get_performance_state() assigned. This shall be verified during
> > pm_genpd_init().
> > 
> > The pm_genpd_has_performance_state() then only need to return true, in
> > cases the device's genpd has GENPD_FLAG_PERF_STATE set - else false.
> > 
> > Regarding ->set_performance_state(), let's just make it optional - and
> > when trying to set a new performance state, just walk the genpd
> > hierarchy, from bottom to up, then invoke the callback when it's
> > assigned.
> 
> Sounds good.

Actually, I don't think we need this flag at all. The presence of the
get_performance_state() callback itself can be used as a flag here instead of
defining a new one.

As with both, your above solution and my solution, we pretty much don't check
presence of set_performance_state() callbacks in the master hierarchy. If its
present, we call it, else nothing happens.

-- 
viresh