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

[Arkadiusz Miskiewicz <arekm@maven.pl>]

On Friday 13 June 2008, Thomas Renninger wrote:
> On Tue, 2008-06-10 at 18:40 -0400, Beglin, Brad R wrote:
> > >I am also unable to change my max scaling frequency on my Thinkpad T61.
> > >Interestingly enough, I can change the frequency as long as the new
> > > value is less than 1.2 GHz.  If I try to set the new max frequency
> > > higher than that, the max scaling frequency file reverts to 1.2GHz. 
> > > Here is in example:
> >
> > Well, I did a lot more research, and it seems, at least in my case and
> > probably others, that this is a long-time know bug, as detailed here:
> >
> > http://bugzilla.kernel.org/show_bug.cgi?id=7060
> > http://lkml.org/lkml/2007/1/16/120
> > http://www.thinkwiki.org/wiki/Problem_with_CPU_frequency_scaling
> > http://forums.lenovo.com/lnv/board/message?board.id=T_Series_Thinkpads&th
> >read.id=7420
>
> Be careful, these reports have different causes.
> E.g.:
> ---
> If the battery pack is removed and the laptop is powered by AC only, the
> CPU downclocks to the lowest multiplier and remains locked in low speed
> ---
> Might be a BIOS bug (or even intended?).
>
> > However, I can report, as outlined in the Thinkwiki.org article, that
> > adding
> > "processor.ignore_ppc=1" to the kernel boot parameters fixed the
> > problem for me
> > (with kernel 2.6.25-r4).
> >
> > I hope this helps the others who are having the same problem. mp.
>
> Arkadiusz has provided some interesting debug results.
> He and some others reported cpufreq limitation to the lowest freq on
> some boots. I am pretty sure this is not a BIOS issue as _PPC is always
> 0 there.
>
> Beglin: If you could compile CPU_FREQ_DEBUG in and boot with
> cpufreq.debug=7. If you run into this issue and grep for:
> dmesg |grep -i ppc
> you probably see the same issue than Arkadiusz which probably is not a
> BIOS but a kernel error.
>
> Arkadiusz: If you run into this again can you check whether you have:
> cat /sys/devices/system/cpu/cpu0/cpufreq/ondemand/powersave_bias
> set (if yes, this should only be set when working on battery?).

Was zero there afail. (I did the test some time ago after seeing this mail but 
forgot to reply 8-)

> Another idea:
> Maybe increasing
> /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate
> helps?

Didn't help. I was trying to various values there.

>
> Strange seem to be the duplicate messages and duplicate tries to set the
> same freq over and over again.
>
> Also there seem some frequencies tried to be set which should not exist:
> 152342 kHz, 57142 kHz, 0 kHz

>    Thomas

-- 
Arkadiusz Mi≈õkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/

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