linux-kernel - Re: [RFC v2 0/3][TESTS] LAB: Support for Legacy Application Booster governor

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Message-ID: <CAKohpo=6Tk3NmcJw_fqnePu_skHKNB0rFBOUzEsCDyeLqxg4xA@mail.gmail.com>
Date:	Tue, 28 May 2013 15:14:26 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lukasz Majewski <l.majewski@...sung.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Vicent Guittot <vincent.guittot@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>
Subject: Re: [RFC v2 0/3][TESTS] LAB: Support for Legacy Application Booster
 governor - tests results

On 28 May 2013 12:10, Lukasz Majewski <l.majewski@...sung.com> wrote:
> On 27 May 2013 17:30, Rafael J. Wysocki <rjw@...k.pl> wrote: <manually added by viresh>
>> On Monday, May 27, 2013 06:54:49 PM Viresh Kumar wrote:
>> > On 27 May 2013 17:30, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> I was talking about /sys/devices/system/cpu/cpufreq/boost that
>> appears to have been added by commit 615b730 (acpi-cpufreq: Add
>> support for disabling dynamic overclocking).
>>
>> That's in acpi-cpufreq, but since that setting seems to be generally
>> useful, it may be a good idea to move it to the core somehow.

Problem is in breaking existing cpufreq userspace for this driver.
Is this allowed?

> I think that Viresh wanted to add "boost" option to
> /sys/devices/system/cpu/cpuX/cpufreq/ to be able to control boost
> at separate cores (policies).
>
> The localization, which you have proposed:
> /sys/devices/system/cpu/cpufreq/boost
>
> implies, that boost is a global feature (enabled for all cores and for
> all available policies).
>
> Which approach shall be used then?

We can use: get_governor_parent_kobj() to get the best location
for boost. But I had some other issues in mind:
- boost is governor dependent.. i.e. It is only required for ondemand
governor (And LAB if it makes it to mainline :) ).. Other governors
doesn't need it. So, it would be better to add it in governor's directory.
- This will break existing users of acpi-cpufreq driver.

@Rafael: Please suggest what to do here.
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