linux-kernel - Re: ACPI regression in 2.6.29 - cpufreq

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Message-ID: <20090211064253.GC641@kamineko.org>
Date:	Wed, 11 Feb 2009 15:42:53 +0900
From:	Mattia Dongili <malattia@...ux.it>
To:	Guilherme Malschitzky Schroeder <guilherme.m.schroeder@...il.com>
Cc:	linux-kernel@...r.kernel.org, venkatesh.pallipadi@...el.com,
	CPUFreq Mailing List <cpufreq@...ts.linux.org.uk>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>
Subject: Re: ACPI regression in 2.6.29 - cpufreq_performance doesn't work

On Wed, Feb 11, 2009 at 03:58:07AM -0200, Guilherme Malschitzky Schroeder wrote:
> On Wed, Feb 11, 2009 at 3:10 AM, Mattia Dongili <malattia@...ux.it> wrote:
> > On Wed, Feb 11, 2009 at 12:15:35AM -0200, Guilherme Malschitzky Schroeder wrote:
...
> > Ha! can you check the value for
> > /sys/devices/system/cpu/cpu{0,1}/cpufreq/related_cpus
> > ?

errr... sorry, I meant to say
/sys/devices/system/cpu/cpu{0,1}/cpufreq/affected_cpus

> > or even include the full output of cpufreq-info with both kernels.

anyway from this you can see that there is actually a change
(cpufreq-info reads from affected_cpus and in 2.6.28
sys/.../cpu1/cpufreq should be a link to ../cpu0/cpufreq):

> Here it's:
> 
> 2.6.28.4
...
> # cpufreq-info
> cpufrequtils 004: cpufreq-info (C) Dominik Brodowski 2004-2006
> Report errors and bugs to cpufreq@...ts.linux.org.uk, please.
> analyzing CPU 0:
>   driver: acpi-cpufreq
>   CPUs which need to switch frequency at the same time: 0 1
...
> 2.6.29-rc4
...
> # cpufreq-info
> cpufrequtils 004: cpufreq-info (C) Dominik Brodowski 2004-2006
> Report errors and bugs to cpufreq@...ts.linux.org.uk, please.
> analyzing CPU 0:
>   driver: acpi-cpufreq
>   CPUs which need to switch frequency at the same time: 0
...
> analyzing CPU 1:
>   driver: acpi-cpufreq
>   CPUs which need to switch frequency at the same time: 1

So I guess you have one of those bioses that prefer sw coordination if
not told to use hw's as explained in the commit message.
And cpufreq-set behaves as it always did ;)

...
> >> >> >> commit d96f94c604453f87fe24154b87e1e9a3a72511f8
> >> >> >> Author: Pallipadi, Venkatesh <venkatesh.pallipadi@...el.com>
> >> >> >> Date:   Mon Feb 2 11:57:18 2009 -0800
> >> >> >>
> >> >> >>     ACPI: Enable bit 11 in _PDC to advertise hw coord
> >> >> >>
> >> >> >>     Bit 11 in intel PDC definitions is meant for OS capability to handle
> >> >> >>     hardware coordination of P-states. In Linux we have always supported
> >> >> >>     hwardware coordination of P-states. Just let the BIOSes know that we
> >> >> >>     support it, by setting this bit.
> >> >> >>
> >> >> >>     Some BIOSes use this bit to choose between hardware or software coordination
> >> >> >>     and without this change below, BIOSes switch to software coordination, which
> >> >> >>     is not very optimal in terms of power consumption and extra
> >> >> >> wakeups from idle.
> >> >> >>
> >> >> >>     Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> >> >> >>     Signed-off-by: Len Brown <len.brown@...el.com>

-- 
mattia
:wq!
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