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

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Date:	Mon, 27 May 2013 11:03:38 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lukasz Majewski <l.majewski@...sung.com>
Cc:	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	"Rafael J. Wysocky" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	cpufreq@...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 24 May 2013 16:50, Lukasz Majewski <l.majewski@...sung.com> wrote:
>> On 24 May 2013 14:00, Lukasz Majewski <l.majewski@...sung.com> wrote:

> This is not safe IMHO to add permanently overclocked frequency to the
> freq table. Since, for example, thermal framework also asks for
> reference to this table.

Yes, its wrong. Even adding it permanently this way would be a problem
if governor is changed to performance. :)

> The idea beneath overclocking is to add "dangerous" frequency to the
> frequency table only when necessary (and remove it when not needed).

Hmm.. probably the idea beneath is to use dangerous frequency only
when we are assured that we will not break system.. It doesn't have
anything to do with cpufreq table entries :)

> In this way, the thermal framework (as it is done at our platform) will
> decrease the frequency (according to thermal governor :-) ) to safe
> level.
>
> Overclocking is disabled in 2 ways (at our setup):
> - thermal framework is here to help us
> - lab governor disables the overclocking when favorable conditions are
>   gone.

I don't want to discuss OR think about LAB for now.. Want to get
overclocking feature in first.

> One more remark - enabling tb_en_over_clk at sysfs (echo 1
>> /sys/devices/system/cpu/cpu0/cpufreq/tb_en_over_clk)
> adds overclock frequency to frequency table and updates policy.

What if it is enabled and governor is changed to performance
without disabling it... Who will take care of disabling dangerous
frequencies?

One thing I am certain about is to make overclocking a generic and
core feature, rather than platform specific...

What about adding overdrive frequencies in freq table permanently
but with .index field as: CPUFREQ_ENTRY_OVERDRIVE ??

This way we will use frequencies marked with
CPUFREQ_ENTRY_OVERDRIVE only when we have overclocking
enabled. And not at other times?
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