From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: myungjoo.ham@gmail.com
Subject: Re: [PATCH v2 2/3] PM / DEVFREQ: add example governors
Date: Wed, 18 May 2011 21:46:51 +0200
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Cc: linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        "Greg Kroah-Hartman" <gregkh@suse.de>,
        Mark Brown <broonie@sirena.org.uk>, Jiejing Zhang <kzjeef@gmail.com>,
        Pavel Machek <pavel@ucw.cz>, Colin Cross <ccross@google.com>,
        Nishanth Menon <nm@ti.com>, Thomas Gleixner <tglx@linutronix.de>,
        Len Brown <len.brown@intel.com>,
        Kyungmin Park <kyungmin.park@samsung.com>
References: <1305100723-29161-1-git-send-email-myungjoo.ham@samsung.com> <201105180039.56806.rjw@sisk.pl> <BANLkTim0DkhcjWw7fM0e-UhyB3=GkQ7nKw@mail.gmail.com>
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On Wednesday, May 18, 2011, MyungJoo Ham wrote:
> 2011/5/18 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Wednesday, May 11, 2011, MyungJoo Ham wrote:
> >> Three CPUFREQ-like governors are provided as examples.
> >>
> >> powersave: use the lowest frequency possible. The user (device) should
> >> set the polling_ms as 0 because polling is useless for this governor.
> >>
> >> performance: use the highest freqeuncy possible. The user (device)
> >> should set the polling_ms as 0 because polling is useless for this
> >> governor.
> >>
> >> simple_ondemand: simplified version of CPUFREQ's ONDEMAND governor.
> >>
> >> When a user updates OPP entries (enable/disable/add), OPP framework
> >> automatically notifies DEVFREQ to update operating frequency
> >> accordingly. Thus, DEVFREQ users (device drivers) do not need to update
> >> DEVFREQ manually with OPP entry updates or set polling_ms for powersave
> >> , performance, or any other "static" governors.
> >
> > Well, do you expect anyone to actually use them?  If not, it would make
> > more sense to put them into a doc.
> 
> According to our experiences of DVFS(although this "DEVFREQ" is not
> applied to them, yet) in memory-bus and GPU,
> I expect most DEVFREQ users might use "simple_ondemand" and
> expect "powersave" and "performance" will probably mostly used while
> testing and debugging.
> ("userspace"-like governor would be also useful for that purpose, but
> I'd add it later)

It would be good to have at least one in-tree user for each of them
(not necessarily from the start, but at one point in the future at least).

So if you have any _specific_ users in mind, please let me know.

Thanks,
Rafael
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