linux-kernel - Re: bug? acpi p-state + ondemand keeps dropping max freq

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Message-ID: <20080607232219.GA25693@atjola.homenet>
Date:	Sun, 8 Jun 2008 01:22:19 +0200
From:	Björn Steinbrink <B.Steinbrink@....de>
To:	"Kok, Auke" <auke-jan.h.kok@...el.com>
Cc:	linux-acpi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Brown, Len" <len.brown@...el.com>, cpufreq@...ts.linux.org.uk,
	Dave Jones <davej@...emonkey.org.uk>
Subject: Re: bug? acpi p-state + ondemand keeps dropping max freq

On 2008.06.05 15:30:56 -0700, 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
> 

I also saw that on my T43, didn't have time to investigate any further
and forgot about it shortly after :-(

> 
> 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

Try with "echo -n", seems that sysfs (or at least that file) doesn't
like newlines.

Björn
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