Re: 3.9.0 + CONFIG_X86_INTEL_PSTATE=y -> ThinkPad T420 with i5 lost ACPI functionality

[Dirk Brandewie <dirk.brandewie@gmail.com>]

On 05/03/2013 12:36 PM, Rafael J. Wysocki wrote:
> On Friday, May 03, 2013 06:55:37 PM Toralf Förster wrote:
>> The following file doesn't exists at my Gentoo Linux
>> /sys/devices/system/cpu/cpufreq/ondemand/ignore_nice_load
>> in 3.9.0 if I activate CONFIG_X86_INTEL_PSTATE=y
>>
>> That means, that a command like
>>
>> $> echo 1 > /sys/devices/system/cpu/cpufreq/ondemand/ignore_nice_load
>>
>> in /etc/rc.local is now no longer working.
>> A high fan +  high temperature are the result, even if just the BOINC client
>> is run with low prio (nice 19) in the back ground.
>>


ignore_nice_load is a feature of the ondemand governor.

The intel_pstate driver is seeing the load presented by the BOINC client and
is adjusting the pstate accordingly.

>> Manually loading the missing module won't work too :
>>
>> $> modprobe acpi_cpufreq
>> modprobe: ERROR: could not insert 'acpi_cpufreq': Device or resource busy
>>
>> Is the behaviour a bug or a feature ?

The intel_pstate drive has already registered as a scaling driver so when
acpi_cpufreq tries to register as a scaling driver the registration fails

>
> The thermal management problem is not an intentional outcome, definitely.
>
>> In the later case: How can I achieve the previous behaviour back ?
>>

If you require the ondemand governor you can remove CONFIG_X86_INTEL_PSTATE
from your configuration or add "intel_pstate=disable" to your kernel command
line.

--Dirk
>> This issue might affect the RH EL kernel too [1] where I observed a similar behaviour.
>>
>>
>> [1] http://elrepo.org/bugs/view.php?id=379
>
> Dirk, is this the problem we were talking about recently or something else?
>
> Rafael
>
>