linux: can't set cpu frequency governor with cpupower


Jan 18, 2021
I have a server HPE ProLiant system w
ith AMD Epyc CPU, BIOS A43 v1.20, with Linux kernel 4.19.71. Now, I'm trying to set CPU performance governor:

# cpupower frequency-set -g performance
Setting cpu: 0
Error setting new values. Common errors:
- Do you have proper administration rights? (super-user?)
- Is the governor you requested available and modprobed?
- Trying to set an invalid policy?
- Trying to set a specific frequency, but userspace governor is not available,
for example because of hardware which cannot be set to a specific frequency
or because the userspace governor isn't loaded?

So I begin troubleshooting:

# cpupower frequency-info
analyzing CPU 0:
no or unknown cpufreq driver is active on this CPU
CPUs which run at the same hardware frequency: Not Available
CPUs which need to have their frequency coordinated by software: Not Available
maximum transition latency: Cannot determine or is not supported.
Not Available
available cpufreq governors: Not Available
Unable to determine current policy
current CPU frequency: Unable to call hardware
current CPU frequency: Unable to call to kernel
boost state support:
Supported: yes
Active: yes
Boost States: 0
Total States: 3
Pstate-P0: 2000MHz
Pstate-P1: 1800MHz
Pstate-P2: 1500MHz
# ls /sys/devices/system/cpu/cpufreq/

So, for whatever reason, it thinks that cpufreq drivers are missing. However, the kernel .config has the following enabled:


I did try to disable CONFIG_X86_INTEL_PSTATE and add CONFIG_X86_POWERNOW_K8 (the only AMD-specific in the current kernel), but it didn't seem to help.

So, I took some time to debug the drivers behaviour -- drivers/cpufreq/cpufreq.c and drivers/cpufreq/acpi-cpufreq.c and found that acpi-cpufreq actually fails with message:

ACPI-based processor performance control unavailable

As far as I understand, in acpi_processor_get_performance_info() the driver attempts to read _PCT object from ACPI table and fails, because can't find it. Does this mean that the BIOS has no full support of ACPI, or CPU microcode needs to be updated, or the kernel is missing something?

I would be happy for any advice.
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