Question

2

intel_pstate driver not being loaded when added to grub file

rated 0 times [ 2] [ 0] / answers: 1 / hits: 2327 / 2 Years ago, fri, may 27, 2022, 12:49:29

I have a

Processor   Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz

Memory  16305MB (2531MB used)

Machine Type    Laptop

Operating System    Ubuntu 20.04.3 LTS

In my /etc/default/grub file I have the line

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=enable"

I did a sudo update-grub after the changes but when I do a
cpupower frequency-info or a cpufreq-info --driver it says the driver used is intel_cpufreq

rt@sys76:~$ cpufreq-info --driver

intel_cpufreq





rt@sys76:~$ cpupower frequency-info



analyzing CPU 0:

  driver: intel_cpufreq

  CPUs which run at the same hardware frequency: 0

  CPUs which need to have their frequency coordinated by software: 0

  maximum transition latency: 20.0 us

  hardware limits: 800 MHz - 3.40 GHz

  available cpufreq governors: conservative ondemand userspace powersave performance schedutil

  current policy: frequency should be within 1.70 GHz and 3.40 GHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency: Unable to call hardware

  current CPU frequency: 798 MHz (asserted by call to kernel)

  boost state support:

    Supported: yes

    Active: yes

rt@sys76:~$

How can I get the cpufreq-info --driver
to use intel_pstate driver?

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lawain

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answered 2 Years ago landarre · Accepted Answer

Your processor, i7-4700MQ, predates HWP (HardWare Pstate) control. The migration path as determined by the kernel power management group, for these Intel processors is to default towards the intel_pstate CPU frequency scaling driver being in passive mode using the schedutil scaling governor. To that end this commit was done:

commit 33aa46f252c703e42c81a76696cd0c240f2281e4 Author: Rafael J.
Wysocki [email protected] Date: Wed Mar 25 15:03:35 2020
+0100

cpufreq: intel_pstate: Use passive mode by default without HWP



After recent changes allowing scale-invariant utilization to be

used on x86, the schedutil governor on top of intel_pstate in the

passive mode should be on par with (or better than) the active mode

"powersave" algorithm of intel_pstate on systems in which

hardware-managed P-states (HWP) are not used, so it should not be

necessary to use the internal scaling algorithm in those cases.



Accordingly, modify intel_pstate to start in the passive mode by

default if the processor at hand does not support HWP of if the driver

is requested to avoid using HWP through the kernel command line.



Among other things, that will allow utilization clamps and the

support for RT/DL tasks in the schedutil governor to be utilized on

systems in which intel_pstate is used.

You are actually using the intel_pstate CPU frequency scaling driver, however it is in passive mode. Try this:

echo active | sudo tee /sys/devices/system/cpu/intel_pstate/status

and then check:

cat /sys/devices/system/cpu/intel_pstate/status

If that works as expected then change your grub line to:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=active"

and see if it boots the way you want.

Note that the CPU Frequency scaling driver intel_cpufreq is just the intel_pstate driver in passive mode.

Example:

doug@s19:~/temp$ grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver

/sys/devices/system/cpu/cpu0/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu10/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu11/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu1/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu2/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu3/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu4/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu5/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu6/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu7/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu8/cpufreq/scaling_driver:intel_cpufreq

/sys/devices/system/cpu/cpu9/cpufreq/scaling_driver:intel_cpufreq



doug@s19:~/temp$ cat /sys/devices/system/cpu/intel_pstate/status

passive

doug@s19:~/temp$ echo active | sudo tee /sys/devices/system/cpu/intel_pstate/status

active



doug@s19:~/temp$ grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver

/sys/devices/system/cpu/cpu0/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu10/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu11/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu1/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu2/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu3/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu4/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu5/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu6/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu7/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu8/cpufreq/scaling_driver:intel_pstate

/sys/devices/system/cpu/cpu9/cpufreq/scaling_driver:intel_pstate