[Bug 12826] cpufreq driver do not expose all data and configuration to /sys

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http://bugzilla.kernel.org/show_bug.cgi?id=12826





------- Comment #7 from anonymous@xxxxxxxxxxxxxxxxxxxx  2009-03-06 18:50 -------
Reply-To: akpm@xxxxxxxxxxxxxxxxxxxx

On Sat, 07 Mar 2009 03:39:31 +0100 Maciej Piechotka <uzytkownik2@xxxxxxxxx>
wrote:

> On Fri, 2009-03-06 at 15:30 -0800, Andrew Morton wrote: 
> > (switched to email.  Please respond via emailed reply-to-all, not via the
> > bugzilla web interface).
> > 
> > On Fri,  6 Mar 2009 05:21:50 -0800 (PST)
> > bugme-daemon@xxxxxxxxxxxxxxxxxxx wrote:
> > 
> > > http://bugzilla.kernel.org/show_bug.cgi?id=12826
> > > 
> > >            Summary: cpufreq driver do not expose all data and configuration
> > >                     to /sys
> > >            Product: Power Management
> > >            Version: 2.5
> > >      KernelVersion: 2.6.29-rc7
> > >           Platform: All
> > >         OS/Version: Linux
> > >               Tree: Mainline
> > >             Status: NEW
> > >           Severity: normal
> > >           Priority: P1
> > >          Component: cpufreq
> > >         AssignedTo: cpufreq@xxxxxxxxxxxxxxx
> > >         ReportedBy: uzytkownik2@xxxxxxxxx
> > > 
> > > 
> > > Latest working kernel version: 2.6.28
> > > Earliest failing kernel version: 2.6.29-rc7 (also -rc5 and -rc6 but tested only
> > > with patchset)
> > > Distribution: Gentoo
> > > Hardware Environment: Thinkpad R51e
> > > Software Environment: Standard stack (although reproduced with only /bin/sh as
> > > init)
> > > Problem Description:
> > > Contrary to documentation there are little files controlling the cpufreq
> > > 
> > > # ls /sys/devices/system/cpu/cpu0/cpufreq/
> > > conservative  stats
> > > # ls /sys/devices/system/cpu/cpu0/cpufreq/conservative 
> > > down_threshold  ignore_nice_load      sampling_rate      sampling_rate_min
> > > freq_step       sampling_down_factor  sampling_rate_max  up_threshold
> > > 
> > > Steps to reproduce:
> > > Boot
> > 
> > I'd say that
> > 
> > commit 8529154ec3f3ac20344c65b7a040c604c7af7651
> > Author: Herton Ronaldo Krzesinski <herton@xxxxxxxxxxxxxxx>
> > Date:   Sat Nov 15 17:02:46 2008 -0200
> > 
> >     [CPUFREQ] Add Celeron Core support to p4-clockmod.
> > 
> > has a good chance of being the cause of this regression?
> 
> Unfortunately I reverted this commit and it had no effect.
> 
> However I found however commit:
> commit e088e4c9cdb618675874becb91b2fd581ee707e6
> Author: Matthew Garrett <mjg@xxxxxxxxxx>
> Date:   Tue Nov 25 13:29:47 2008 -0500
> 
>     [CPUFREQ] Disable sysfs ui for p4-clockmod.
>     
>     p4-clockmod has a long history of abuse.   It pretends to be a CPU
>     frequency scaling driver, even though it doesn't actually change
>     the CPU frequency, but instead just modulates the frequency with
>     wait-states.
>     The biggest misconception is that when running at the lower
> 'frequency'
>     p4-clockmod is saving power.  This isn't the case, as workloads
> running
>     slower take longer to complete, preventing the CPU from entering
> deep C stat
> es.
>     
>     However p4-clockmod does have a purpose.  It can prevent
> overheating.
>     Having it hooked up to the cpufreq interfaces is the wrong way to
> achieve
>     cooling however. It should instead be hooked up to ACPI.
>     
>     This diff introduces a means for a cpufreq driver to register with
> the
>     cpufreq core, but not present a sysfs interface.

eh?  So we deliberately added a regression?

> 
> I guess lack of sysfs ui is the problem  (at lest AFAIU 'sysfs ui').
> However lack of sysfs ui prevents the cpufreq from lowering frequency on
> overheat[1]. I'll try tomorrow (well. today morning) if this commit
> causes it.

Thanks.

> While I understend that the p4-clockmod shouldn't be used no other
> driver is working. p4-clockmod is recommend on thinkwiki[2]. All I found
> is a post from 2006 mentioning there is a patch for speedstep driver
> which the author is going to try in a spare time - but p4-clockmod is
> working. So there are no known replacements for them.
> 
> Regards
> 
> PS, Even if the commit will not be reverted documentation should be
> updated. For example in help of p4-clockmod the change should be
> mentioned.
> 
> [1] I'd find out the problem if the system didn't started to overheat.
> Something is wrong but lowering the 'frequency' drop the temperature
> only by 20 degrees (from 9x to 7x).
> [2] http://www.thinkwiki.org/wiki/Intel_Celeron_M#Speed_Step
> 


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