linux-kernel - Re: [RFC v3 0/5] cpufreq:LAB: Support for LAB governor.

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Date:	Mon, 17 Mar 2014 16:38:24 +0100
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Lukasz Majewski <l.majewski@...sung.com>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Myungjoo Ham <myungjoo.ham@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>,
	Thomas Abraham <ta.omasab@...il.com>, thomas.ab@...sung.com,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [RFC v3 0/5] cpufreq:LAB: Support for LAB governor.

Dear all,

> Despite this patch set is working and applicable on top of 3.14-rc5, 
> please regard it solely as a pure RFC.
> 
> This patch provides support for LAB governor build on top of ondemand.
> Previous version of LAB can be found here:
> http://thread.gmane.org/gmane.linux.kernel/1484746/match=cpufreq
> 
> LAB short reminder:
> 
> LAB uses information about how many cores are in "idle" state (the
> core idleness is represented as the value between 0 and 100) and the
> overall load of the system (from 0 to 100) to decide about frequency
> to be set. It is extremely useful with SoCs like Exynos4412, which
> can set only one frequency for all cores.
> 
> Important design decisions:
> 
> - Reuse well established ondemand governor's internal code. To do this
>   I had to expose some previously static internal ondemand code. 
>   This allowed smaller LAB code when compared to previous version.
> 	
> - LAB works on top of ondemand, which means that one via device tree
>   attributes can specify if and when e.g. BOOST shall be enabled or
> if any particular frequency shall be imposed. For situation NOT
> important from the power consumption reduction viewpoint the ondemand
> is used to set proper frequency.
> 
> - It is only possible to either compile in or not the LAB into the
> kernel. There is no "M" option for Kconfig. It is done on purpose,
> since ondemand itself can be also compiled as a module and then it
> would be possible to remove ondemand when LAB is working on top of it.
> 
> - The LAB operation is specified (and thereof extendable) via device
> tree lab-ctrl-freq attribute defined at /cpus/cpu0.
> 
> 
> Problems:
> - How the governor will work for big.LITTLE systems (especially
> Global Task Scheduling).
> - Will there be agreement to expose internal ondemand code to be
> reused for more specialized governors.
> 
> Test HW:
> 	Exynos4412 - Trats2 board.
> Above patches were posted on top of Linux 3.14-rc5
> (SHA1: 3f9590c281c66162bf8ae9b7b2d987f0a89043c6)
> 

Any comments about those patches?

> Lukasz Majewski (5):
>   cpufreq:LAB:ondemand Adjust ondemand to be able to reuse its methods
>   cpufreq:LAB:cpufreq_governor Adjust cpufreq_governor.[h|c] to
> support LAB
>   cpufreq:LAB:lab Add LAB governor code
>   cpufreq:LAB:Kconfig Add LAB definitions to Kconfig
>   cpufreq:LAB:dts:trats2: Add DTS nodes for LAB governor
> 
>  arch/arm/boot/dts/exynos4412-trats2.dts |   29 ++
>  drivers/cpufreq/Kconfig                 |   28 ++
>  drivers/cpufreq/Makefile                |    1 +
>  drivers/cpufreq/cpufreq_governor.c      |    7 +
>  drivers/cpufreq/cpufreq_governor.h      |   12 +
>  drivers/cpufreq/cpufreq_lab.c           |  457
> +++++++++++++++++++++++++++++++
> drivers/cpufreq/cpufreq_ondemand.c      |   24 +- 7 files changed,
> 550 insertions(+), 8 deletions(-) create mode 100644
> drivers/cpufreq/cpufreq_lab.c
> 



-- 
Best regards,

Lukasz Majewski

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