linux-kernel - Re: cpufreq terminally broken [was Re: community PM requirements/issues and PowerOP]

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Date:	Mon, 11 Sep 2006 20:37:00 -0700
From:	Greg KH <greg@...ah.com>
To:	Mark Gross <mgross@...ux.intel.com>
Cc:	Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eugeny S. Mints" <eugeny.mints@...il.com>,
	Matthew Locke <matt@...adgs.com>,
	Amit Kucheria <amit.kucheria@...ia.com>,
	pm list <linux-pm@...ts.osdl.org>,
	Preece Scott-PREECE <scott.preece@...orola.com>,
	Igor Stoppa <igor.stoppa@...ia.com>
Subject: Re: cpufreq terminally broken [was Re: community PM requirements/issues and PowerOP]

On Mon, Sep 11, 2006 at 05:17:01PM -0700, Mark Gross wrote:
> 
> cpufreq is broken at the cpufreq_driver interface for embedded
> applications needing control over more than one control variable at a
> time.
> 
> That interface only supports setting target frequencies, and expanding it
> to set target frequencies and voltages is not possible without something
> like PowerOP.  Adding the types of parameters to cpufreq would likely
> make cpufreq a mess.  I think we would be better off with something that
> coexists with cpufreq, like the powerop patch from Eugeny.
> 
> God help you if you try to use cpufreq on a complex non-PC platform with
> multiple power and clock domains that need to be tweaked to squeeze out
> competitive battery life.
> 
> Because of the existing user base of cpufreq removing cpufreq will never
> happen.  No one supporting the PowerOP patch has never recommended
> such a thing.  However; holding back innovation because of an existing
> solution that doesn't support a large class of users seems dumb.

But you can't break the existing stuff, and it seems that some of these
proposals are doing just that. :(

thanks,

greg k-h
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