On HP ProLiant DL580 G8 hardware "no or unknown cpufreq driver is active on this CPU" messages.

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Environment

SUSE Linux Enterprise Server 12 Service Pack 3 (SLES 12 SP3)

HP ProLiant DL580 Gen8, System ROM - P79: 1.00_01-14-2014 (initial version of the firmware) up
to and including 2.00_02-22-2018 (latest version at the time of writing).

Situation

On HP ProLiant DL580 G8 hardware it may appear as if the utilities in cpufrequtils are not working since no driver is loaded. The command cpupower returns output similar to:

# cpupower frequency-info
analyzing CPU 0:
no or unknown cpufreq driver is active on this CPU
...

Resolution

In such a case it may be that "Processor X2Apic Support" is enabled in the BIOS.

In case it is enabled changing this option to disabled should allow a driver to be loaded if "Collaborative Power Control" is enabled in RBSU (ROM-Based Setup Utility). Depending on the "Power Regulator Setting" option (in iLO or RBSU) either the pcc-cpufreq or the intel_pstate cpufreq driver should be loaded on this platform.

Once the "Power Regulator Setting" is set to "Dynamic Power Savings Mode" the pcc-cpufreq driver should load, ie.

# cpupower frequency-info
analyzing CPU 0:
driver: pcc-cpufreq
...

If the "Power Regulator Setting" is set to "OS Control Mode" the intel_pstate
driver should load, ie.

# cpupower frequency-info
analyzing CPU 0:
driver: intel_pstate
...

Cause

The Linux cpufreq subsystem depends on consistent ACPI (Advanced Configuration and Power Interface) information to associate processor objects with entries in MADT (i.e. Processor local APIC entries, or Processor local x2APIC entries).

When "Processor X2Apic Support" is disabled, MADT (Multiple APIC Description Table) contains Processor Local APIC entries and the provided ACPI processor declarations are sufficient to perform this mapping. When "Processor X2Apic Support" is enabled, MADT contains Processor Local x2APIC entries and the provided ACPI processor declarations are no longer sufficient to perform this mapping. Linux expects UID object values under a processor device to associate it with a Processor Local x2APIC entry in MADT, however this is not provided on the HP ProLiant DL580 Gen8 platform.

Additional Information

Disclaimer

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