linux-kernel - Re: [PATCH 2/2] CPUFREQ: Mark e_powersaver driver as EXPERIMENTAL and DANGEROUS

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Message-Id: <200906080800.10312.lkml@morethan.org>
Date:	Mon, 8 Jun 2009 08:00:07 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	Harald Welte <HaraldWelte@...tech.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Duane Griffin <duaneg@...da.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH 2/2] CPUFREQ: Mark e_powersaver driver as EXPERIMENTAL and DANGEROUS

On Mon June 8 2009, Matthew Garrett wrote:
> On Mon, Jun 08, 2009 at 06:29:36PM +0800, Harald Welte wrote:
> > The e_powersaver driver for VIA's C7 CPU's needs to be marked as
> > DANGEROUS as it configures the CPU to power states that are out
> > of specification.
> > 
> > According to Centaur, all systems with C7 and Nano CPU's support
> > the ACPI p-state method.  Thus, the acpi-cpufreq driver should
> > be used instead.
> 
> Do we know if vendors are actually shipping with the appropriate BIOS 
> tables? The number of people using e_powersaver seems to be suspiciously 
> large, though perhaps that's just because the help text implied it was 
> the right choice for C7.
> 

In part, it was because acpi_freq would not load - H.W. in another post
has proposed a fix for that.

My test machine is a "first production" of the Everex Cloudbook - -
About as early as you can get of something in the public hands -
If there is something lacking in a machine's BIOS - it should be
missing in this one - I can test for that condition.
(This one is hitting user code with the silicon still setup
in the state set by "#reset" - untouched by the BIOS.)

Of course, that says nothing about other and/or newer machines -
At the moment I am toying with the idea of a cpu-quirks routine
that could check/correct for an incompletely setup chip.
On the Model-D chips, that could also switch the processor over
to its on-silicon thermal/power/freq adaptive controller.

All of the Netbooks that I know of have shipped with the Model-D
processor (ULV) - so the above cpu-quirks routine would "fix" those.

Machines running other C7 models...
They will just have to trust the BIOS and/or a repaired e_powersaver.

Mike
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