Date: Fri, 06 Jun 2008 22:46:17 -0400 (EDT)
From: Len Brown <lenb@kernel.org>
Subject: Re: bug? acpi p-state + ondemand keeps dropping max freq
In-reply-to: <48486920.4040006@intel.com>
To: "Kok, Auke" <auke-jan.h.kok@intel.com>
Cc: linux-acpi@vger.kernel.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Dave Jones <davej@codemonkey.org.uk>,
       "Brown, Len" <len.brown@intel.com>, cpufreq@lists.linux.org.uk
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On Thu, 5 Jun 2008, Kok, Auke wrote:

> 
> I've consistently experienced the following bizarre problem since 2.6.20, all the
> way up to 2.6.25.3 (regressed yesterday and each of these kernels exposes this
> behaviour):
> 
> /sys/devices/system/cpu/cpu0/cpufreq # grep . *
> affected_cpus:0
> cpuinfo_cur_freq:800000
> cpuinfo_max_freq:1866000
> cpuinfo_min_freq:800000
> scaling_available_frequencies:1866000 1600000 1333000 1066000 800000
> scaling_available_governors:ondemand performance
> scaling_cur_freq:800000
> scaling_driver:acpi-cpufreq
> scaling_governor:ondemand
> scaling_max_freq:800000
> scaling_min_freq:800000
> 
> 
> 
> Notice that scaling_mx_freq dropped down to the lowest possible value and as such
> my CPU is only working at 800MHz. At boot time this field properly displays
> 1866MHz and everything works OK. After a certain period (?) this value drops down
> and I cannot manually elevate it back to the normal level:
> 
> # echo 1866000 > scaling_max_freq ; cat scaling_max_freq
> 800000
> # echo 1866000 > scaling_max_freq ; cat scaling_max_freq
> 800000
> 
> 
> This renders my Dothan to utterly poor speeds. (standard T43)
> 
> performance cpufreq governor makes no difference - I still can't change the
> frequency upper/lower values.

could be two causes:
1. thermal
2. user space

for #1....

watch grep . /proc/acpi/thermal_zone/THM*/*
and see if anythign is climbing
you can build w/o CONFIG_ACPI_THERMAL
and see if they symptom goes away -- for that
is the module which would force cpufreq to Pn.


for #2...

see if it happens in single user mode without
hal or distro daemons running.

cheers,
-Len

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