[SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

jmanes · 2015-01-26 23:06:46

Hello everyone,

First and foremost, I am using a ThinkPad X200 with a Core2Duo P8400 CPU.

I have installed the DKMS phc-intel module as explained here. I also have a few values set up in /etc/default/phc-intel for undervolting. However, there are no phc_intel files found under the /sys/devices/system/cpu/cpu0/cpufreq/ directory. I get this instead:

thinkpad-x200~ % ls /sys/devices/system/cpu/cpu0/cpufreq 
affected_cpus		    freqdomain_cpus		   scaling_governor
bios_limit		    related_cpus		   scaling_max_freq
cpuinfo_cur_freq	    scaling_available_frequencies  scaling_min_freq
cpuinfo_max_freq	    scaling_available_governors    scaling_setspeed
cpuinfo_min_freq	    scaling_cur_freq
cpuinfo_transition_latency  scaling_driver

Is this normal? It seems to indicate to me that the undervolting isn't really taking place. With proper undervolting the X200 can idle at ~8W but I idle at around 10-11W.

Any help is appreciated!

Last edited by jmanes (2015-01-27 15:26:12)

ooo · 2015-01-27 01:52:00

make sure you're using acpi-cpufreq and not intel-pstate driver. phc doesn't work with the latter

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver

jmanes · 2015-01-27 06:01:40

ooo wrote:

make sure you're using acpi-cpufreq and not intel-pstate driver. phc doesn't work with the latter
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver

It looks like everything checks out....

jmanes@thinkpad-x200 [~] % cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
acpi-cpufreq
jmanes@thinkpad-x200 [~] %

ooo · 2015-01-27 07:52:17

In that case you should look for clues in dmesg/journal

dmesg | grep acpi-cpufreq

If phc was working, you should see phc_* files in /sys/devices/system/cpu/cpuN/cpufreq/
Also, it could be a good idea to build the phc modules manually first with 'phc-intel setup' instead of the dkms systemd service, to make sure that they build ok.

jmanes · 2015-01-27 15:25:50

ooo wrote:

In that case you should look for clues in dmesg/journal
dmesg | grep acpi-cpufreq
If phc was working, you should see phc_* files in /sys/devices/system/cpu/cpuN/cpufreq/
Also, it could be a good idea to build the phc modules manually first with 'phc-intel setup' instead of the dkms systemd service, to make sure that they build ok.

Absolutely wonderful information.

I went ahead and compiled the regular phc module and phc-intel setup threw errors saying that I did not have the current headers installed. I installed the headers, rebooted and all was well. phc_* files now show up in /sys/devices/system/cpu/cpuN/cpufreq!

I'll mark this as solved, but as a last question... now that I have this set up to work can I safely re-install the DKMS module?

ooo · 2015-01-27 16:17:23

jmanes wrote:

as a last question... now that I have this set up to work can I safely re-install the DKMS module?

probably yes, but since DKMS is still different than running 'phc-intel setup', you could double check that you can build the phc-intel modules with DKMS manually before enabling a systemd service that does that automatically. But most likely it would work.

the worst thing that could happen if it didn't work, is that you'd miss the undervolting after a kernel update

Arch Linux

#1 2015-01-26 23:06:46

[SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

#2 2015-01-27 01:52:00

Re: [SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

#3 2015-01-27 06:01:40

Re: [SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

#4 2015-01-27 07:52:17

Re: [SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

#5 2015-01-27 15:25:50

Re: [SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

#6 2015-01-27 16:17:23

Re: [SOLVED] No phc_intel file in /sys/devices/system/cpu/cpu0/cpufreq

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