linux-kernel - Re: [PATCH v3 1/3] cpufreq: Add boost frequency support in core

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Date:	Mon, 17 Jun 2013 18:40:50 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lukasz Majewski <l.majewski@...sung.com>
Cc:	"Rafael J. Wysocky" <rjw@...k.pl>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	Myungjoo Ham <myungjoo.ham@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	Andre Przywara <andre.przywara@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Amit Daniel Kachhap <amit.daniel@...sung.com>
Subject: Re: [PATCH v3 1/3] cpufreq: Add boost frequency support in core

On 17 June 2013 15:28, Lukasz Majewski <l.majewski@...sung.com> wrote:
> Yes. But I don't want to hardcode anything. Especially starting CPU
> number.

There is nothing wrong with it. for_each_online_cpu() is good enough
on these cases.

>> > How one can control the boost? I'm now (on my setup) using thermal
>> > subsystem. I set proper trip points and when one of them is met,
>> > then boost is disabled. Moreover the thermal governor (stepwise)
>> > also reduces frequency.
>> >
>> > It works stable with v3.10 (with 3.8 there were some bugs - now they
>> > are fixed).
>> >
>> >
>> > The core acpi-cpufreq.c code hadn't been changed by me, so I assume
>> > that it will work as before.
>>
>> That should adapt your patch in your patchset.

??

>> From sysfs?? I thought we are going to have some automatic control
>> of this stuff from inside kernel.
>
> From sysfs I just enable the boost. I do not order from userpace the
> cpufreq to run with a particular (boosted) frequency.
>
> When I enable boost - I ask (politely) the cpufreq core to reevaluate
> policies and when applicable increase policy->max.
>
> Then governor can use this new frequencies for normal operation.

So, with your current patchset in, ondemand or conservative governors
will start using boost frequencies. Which might burn your chip.
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