EPP write fails with "Device or resource busy" on Intel Core Ultra 7 155H (Arch)

[Z-Mackintosh]

Summary

On my machine, auto-cpufreq works for governor switching, but writing EPP fails consistently.

cpufreqctl.auto-cpufreq --epp --set=performance returns:

/usr/bin/cpufreqctl.auto-cpufreq: line 99: echo: write error: Device or resource busy

The error repeats once per logical CPU (22 times on this machine).

Environment

• Distro: EndeavourOS (Arch-based, rolling)
• Kernel: 6.18.9-arch1-2
• CPU: Intel(R) Core(TM) Ultra 7 155H
• Driver: intel_pstate (active)
• auto-cpufreq: installed as systemd service (auto-cpufreq.service)

What works

• sudo cpufreqctl.auto-cpufreq --governor --set=performance works
• auto-cpufreq.service runs and applies other settings
• power-profiles-daemon is masked/inactive

What fails

• sudo cpufreqctl.auto-cpufreq --epp --set=performance
• same failure even after changing platform profile from low-power to balanced

Reproduction

sudo cpufreqctl.auto-cpufreq --governor --set=performance
sudo cpufreqctl.auto-cpufreq --epp --set=performance

Also tested:

cat /sys/firmware/acpi/platform_profile
cat /sys/firmware/acpi/platform_profile_choices
echo balanced | sudo tee /sys/firmware/acpi/platform_profile
sudo cpufreqctl.auto-cpufreq --epp --set=performance

Additional observations

• EPP choices are present:
  • /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_preferences
  • values: default performance balance_performance balance_power power
• Current EPP across policies remains default
• Error occurs per-core/per-policy write attempt

Expected behavior

If EPP cannot be changed on this hardware/firmware state, auto-cpufreq should gracefully skip EPP writes (or fallback) without flooding logs with repeated errors.

Question

Is this a known limitation for newer Intel Core Ultra + current kernel/firmware combinations, and should EPP be auto-skipped in this case?

[AdnanHodzic]

Changes related to wrong EPP and EBP fallback profiles were merged as part of #925

But this issue seems to be identical to what was reported in #751 and similar things were reported in #724

Since I don't have Intel Core Ultra I can't reproduce this issue, if you or anyone else has any ideas how to resolve it. Please give it a try in implementing this functionality, please give it a try and contribute to the project and you will be credited for your work as part of future release.