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

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Date:	Mon, 27 May 2013 14:16:35 +0200
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	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

Hi Rafael,

> On Monday, May 27, 2013 11:03:38 AM Viresh Kumar wrote:
> > 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?
> 
> Well, this really looks like software turbo modes, so let's call them
> "TURBO" instead of "OVERDRIVE" and I seem to remember having a switch
> for disabling/enabling turbo modes already.

Indeed, overclocking is a software implemented TURBO mode. I can stick
to CPUFREQ_ENTRY_TURBO name.

I will check the disable/enable flag. Thanks for pointing out.

> 
> Thanks,
> Rafael
> 
> 



-- 
Best regards,

Lukasz Majewski

Samsung R&D Poland (SRPOL) | Linux Platform Group
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