Low Power Mode Lost/Stuck After System Suspend and Power Profile Switch

[quevon24]

Environment Details

• Platform/CPU: Core Ultra 7 155H (Meteor Lake)

• Operating System: Manjaro Linux (GNOME Desktop)

• Kernel Version: 6.17.1-0-MANJARO

• intel-lpmd Version: 0.1.0

• Power Management: systemd-logind and power-profiles-daemon (via GNOME)

Description of the Problem

The Intel Low Power Mode Daemon (intel-lpmd) reliably fails to maintain or re-enter the automatic (AUTO) Low Power Mode state after two distinct, common system events. This leads to higher-than-expected active idle power consumption and elevated CPU package temperatures until the daemon is manually reset.

Events Causing the Failure

1. Resume from System Suspend (S3)

After successfully suspending the system (systemctl suspend) and resuming, the intel-lpmd daemon seems to be in a stuck or uninitialized state. Although the system is idle, the expected LP Mode behavior (e.g., P-core isolation) does not activate, and the daemon does not respond to changes in system load.

2. Manual Power Profile Switch

When changing the system's power profile using the Desktop Environment (DE) utility (e.g., switching from "Balanced") to any other (e.g., "Performance" or "Power Saver"), the LP Mode functionality is lost immediately after the profile switch completes.

Actual Behavior

After either event (Suspend/Resume or Profile Switch):

1. Power consumption is noticeably higher than expected (resulting in increased battery drain and heat generation) compared to when LP Mode is correctly active.

2. Checking the daemon status often shows it is running, but it fails to isolate P-cores or enter LP Mode.

3. The system behaves as if intel_lpmd_control OFF was permanently executed, despite the service being active.

Steps to Reproduce

To reproduce Event 1 (Suspend/Resume):

1. Ensure intel-lpmd.service is running and successfully in AUTO mode.

2. Run systemctl suspend.

3. Resume the system.

4. LP Mode will be inactive.

To reproduce Event 2 (Profile Switch):

1. Ensure intel-lpmd.service is running and successfully in AUTO mode.

2. Use the DE (GNOME/KDE) to switch from one profile (e.g., "Balanced") to any other (e.g., "Performance").

3. Switch the profile back to the initial profile (e.g., "Balanced").

4. LP Mode will be inactive.

Critical Workaround / Debugging Information

The only reliable way to restore full LP Mode functionality after either of the above events is by forcing the daemon to turn off, and then forcing it back into automatic mode. This two-step sequence re-establishes the correct state:

sudo intel_lpmd_control OFF
sudo intel_lpmd_control AUTO

[spandruvada]

Thanks for the report. We are debugging.

[maciejwieczorretman]

Hello!
I tried looking into this issue and I found two things:

1. With the default config file the polling seems to get disabled when using WLT proxy. You're welcome to test the patch I wrote on this branch:
   https://github.com/maciejwieczorretman/intel-lpmd/tree/main_issue_106
   In the config file I also enable AUTO when in balanced profile mode which seems to be a dependency of WLT proxy that's used.

2. The simple solution is trying to use the hardware WLT hints and not the WLT proxy that's in the default config file. You can achieve that by finding the config file you're using and commenting out "1". With that I didn't notice the problems you were describing and the mode switching works pretty smooth.

Both of these options worked for me - arguably the first one (using the WLT Proxy) sometimes takes a while to switch back to idle after the suspend/wakeup event - but I believe it was at most 20 seconds and I was compiling the kernel previously just to try different loads, so maybe there have been some leftover perf traces.