linux-kernel - Re: [PATCH v1 0/3] Add required-opps support to devfreq passive gov

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Date:   Mon, 24 Jun 2019 22:29:02 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 0/3] Add required-opps support to devfreq passive gov

On Mon, Jun 24, 2019 at 10:22 PM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 24-06-19, 22:00, Saravana Kannan wrote:
> > All of the cases above are some real world scenarios I've come across.
> > CPU and L2/L3 on ARM systems are a good example of (2) but the passive
> > governor doesn't work with CPUs yet. But I plan to work on that later
> > as that's not related to this patch series.
>
> So in case of CPUs, the cache will be the parent device and CPU be the
> children ? And CPUs nodes will contain the required-opps property ?

No, the CPUs will be the "parent" and the cache will be the "child".
CPU is a special case when it comes to the actual software (not DT) as
we'll need the devfreq governor to look at all the CPUfreq policies to
decide the cache frequency (max of all their requirements).

I think "master" and "slave" would have been a better term as the
master device determines its frequency using whatever means and the
"slave" device just "follows" the master device.

-Saravana