From: "Michael S. Zick" <lkml@morethan.org>
Reply-To: lkml@morethan.org
To: Harald Welte <HaraldWelte@viatech.com>
Subject: Re: e_powersaver / underclocking (was Re: Linux 2.6.30-rc8 [also: VIA Support])
Date: Sat, 6 Jun 2009 08:56:12 -0500
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Duane Griffin <duaneg@dghda.com>,
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On Sat June 6 2009, Michael S. Zick wrote:
> On Sat June 6 2009, Harald Welte wrote:
> > On Sat, Jun 06, 2009 at 07:17:44AM -0500, Michael S. Zick wrote:
> > 
> > > I can respond to that point now; VIA Tech has answered some of my questions -
> > > 
> > > The mainstream kernel, e_powersaver, is *under-clocking* my machine -
> > > 
> > > The cpuid instruction provides the minimum and maximum GSF values 
> > > (Guaranteed Stable Frequency) for that processor mask run -
> > > Passing that on as the lower and upper limits to e_powersaver should
> > > stop that problem.  Will be testing this RSN.
> > 
> > It's really surprising to me that none of this seems to be handled correct so
> > far, I'll talk to Centaur and try to find out how we could have ended up in
> > this situation.
> >
> 
> Ah, but we are talking here of the *second* NetBook ever produced.
> If one is to believe the dmidecode output - it is using the VIA demo board
> BIOS. 
> 
> I bet the demo board BIOS is intended to demo the features of the product -
> not the correctness or completeness of the ACPI support.  ;)
> 
> If I where shipping demo boards - they would be demonstrating **my** product's
> features.  Maybe I am just projecting what I would do. 
> 
> 
> > My assumption is that e_powersavre is no longer supposd to do any of those
> > low-level bits - rather the ACPI code is expected to get it right, hiding the
> > details from the OS.  But in this case, there needs to be some run-time detection
> > whether the ACPI cpufreq should be used, or e_powersaver.  And I don't see any
> > of that right now.
> > 
> 
> I can keep my eyes open for a way to do that -
> First, I want to get the machine running **with-in** the specs it can provide.
> The one I have is running at 2/3rds of the reported *minimum* clockspeed.
> I must have gotten a high quality "mask/process run" for it to be running at all.
>

If any readers have noticed, the links I post go to what was originally named
"Cloudbookuser" - the first forum for the second machine - -

Ever since day 3 or 4 - people have been writing scripts to change the on-demand
governor's minimum from 400Mhz to 600Mhz - without knowing "why" other than
it was required to keep the machine running (even on distribution kernels).

_Now_ I know why.  Tell the VIA Tech folks "thanks" for the information.

Mike 
> > Also note that now with OLPC XO1.5 going for the C7-M (on a VX855 chipset,
> > though), many of those issues should soon receive much more attention -
> > especially on the power management front.  And as you know, they don't use any
> > legacy BIOS...
> > 
> 
> I'll keep my eyes open on that subject also when looking at the e_powersaver code -
> The OLPC project will probably be requesting chip runs that **do** run at
> the minimums the design is capable of and it will **have to** be stable for OLPC.
> 
> Mike
> > Regards,
> 
> 
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