linux-kernel - Re: [PATCH 0/4] CPUFreq: Implement per policy instances of governors

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Message-ID: <20130204130403.GD13909@pd.tnic>
Date:	Mon, 4 Feb 2013 14:04:03 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linaro-dev@...ts.linaro.org, robin.randhawa@....com,
	Steve.Bannister@....com, Liviu.Dudau@....com
Subject: Re: [PATCH 0/4] CPUFreq: Implement per policy instances of governors

On Mon, Feb 04, 2013 at 06:24:19PM +0530, Viresh Kumar wrote:
> That's why i am highlighting it again and again. :)

Ah, see, someone caught up with it :).

> What i believe is, the place where this directory was present earlier
> (cpu/cpufreq/) wasn't the right place. Everything else was in cpu/cpu*/cpufreq,
> then why this in cpu/cpufreq/ ?

For the simple reason that the "cpu*" stuff is per-cpu - the
"cpu/cpufreq" is per system, i.e. one governor for the whole system.

> I don't know how much of a pain it would be to fix userspace for it,
> but i know it wouldn't be that small.

I wouldn't fix userspace but simply not touch it. You can add your
per-policy stuff in "cpu/cpu*" as new sysfs nodes and no need to
change anything. And, also, as I suggested earlier, you should make it
configurable since this code wouldn't make sense on x86, for example,
where one system-wide governor should suffice.

> I had another idea of doing this only for platforms where we have
> multiple struct policy alive at the same time. But didn't wanted to
> implement it before discussing this further.

Simply put it behind a config option like
CONFIG_CPU_IDLE_MULTIPLE_DRIVERS, call the whole menu
"Multi-power-domain-policy" something and that should be modulary
enough.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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