Kernel configuration settings not applied by systemd script (making the recommandation of powertop permanent)

Problem statement

I try to make the tuning recommandations provided by PowerTop permanent by writing kernel settings in a script executed in a oneshot systemd service. Scripts contains line such as

[...]

echo 'auto' > '/sys/bus/i2c/devices/i2c-6/device/power/control';

[...]

But for some reason, settings are not applied after startup. Running a systemctl start powertop manually in a terminal after login properly applies the parameters. I cannot figure out why it work after login, but not at startup.

The approach is inspired from How do I make Powertop changes permanent?

Configuration

The definition of the service in /etc/systemd/system/powertop.service is as follow

[Unit]
Description=Power tuning based on PowerTOP

[Service]
Type=oneshot
Environment="TERM=dumb"
RemainAfterExit=true
ExecStart=/home/XXXX/Documents/scripts/powertop/powertune.sh

[Install]
WantedBy=multi-user.target

The script writing the kernel configuation is as folow

#!/bin/bash
echo "power tuning"

whoami

echo 'auto' > '/sys/bus/i2c/devices/i2c-6/device/power/control';
echo 'auto' > '/sys/bus/i2c/devices/i2c-7/device/power/control';
echo 'auto' > '/sys/bus/i2c/devices/i2c-0/device/power/control';
echo 'auto' > '/sys/bus/i2c/devices/i2c-1/device/power/control';
echo 'auto' > '/sys/bus/i2c/devices/i2c-2/device/power/control';

echo 'auto' > '/sys/bus/i2c/devices/i2c-3/device/power/control';

echo 'auto' > '/sys/bus/pci/devices/0000:00:02.0/power/control';
echo 'auto' > '/sys/block/sda/device/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:14.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.4/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.2/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:17.0/ata2/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:17.0/ata3/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1c.5/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:17.0/ata1/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:17.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:14.2/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:16.3/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:00.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.3/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:01:00.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:04.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:02:00.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1c.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.0/power/control';
echo 'auto' > '/sys/bus/pci/devices/0000:00:1f.6/power/control';

echo 'disabled' > '/sys/bus/usb/devices/1-5.1/power/wakeup';

Verification already done

The service has been properly enabled with systemctl enable powertop, and I can verify with a systemctl status powertop that is was indeed exectued at startup.

root@cs0:/etc/systemd/system# systemctl status powertop
● powertop.service - Power tuning based on PowerTOP
     Loaded: loaded (/etc/systemd/system/powertop.service; enabled; vendor preset: enabled)
     Active: active (exited) since Mon 2022-11-14 19:36:00 CET; 9s ago
    Process: 6584 ExecStart=/home/XXXXX/Documents/scripts/powertop/powertune.sh (code=exited, status=0/SUCCESS)
   Main PID: 6584 (code=exited, status=0/SUCCESS)
        CPU: 6ms

Nov 14 19:36:00 cs0 systemd[1]: Starting Power tuning based on PowerTOP...
Nov 14 19:36:00 cs0 powertune.sh[6584]: power tuning
Nov 14 19:36:00 cs0 powertune.sh[6585]: root
Nov 14 19:36:00 cs0 systemd[1]: Finished Power tuning based on PowerTOP.

System

• Ubuntu 22.04.1 LTS
• Linux cs0 5.15.0-52-generic #58-Ubuntu SMP Thu Oct 13 08:03:55 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Any help would really be appreciated.