Dependency on lg_laptop

[mnlipp]

[x] I've read and accepted the Bug Reporting Howto [x] I've provided all required tlp-stat outputs via Gist (see below)

Describe the bug

The kernel includes a module lg_laptop which provides a facility to set the battery charge limit on lg_laptops. This kernel module is loaded automatically (no idea what triggers this) on my LG laptop (running Arch Linux). However, it is loaded after systemd has started tlp.

Loading the module sets the battery charge limit to 100%. As the module is loaded after tlp has strated, this effectively undoes tlp's setting (I have configures tlp to set the limit to 80%).

Expected behavior

I'm not sure how tlp sets the battery charge limit without using lg_laptop. But the startup should be delayed until the module has been loaded.

Additional context

A workaround is to explicitly load lg_module with a file in /etc/modules-load.d. The files there seem to be processed before systemd reached the multi-user.target.

[linrunner]

tlp.service is already run really, really late in the boot process. Additionally waiting for lg_laptop to load at some point - trigged by whatever - is something I want to avoid.

To be clear: TLP sets the charge thresholds via lg_laptop. There is no other way.

[mnlipp]

To be clear: TLP sets the charge thresholds via lg_laptop. There is no other way.

Okay, then I have misinterpreted the log. Using Arch lg_laptop is simply not loaded when tlp runs and therefore tlp does nothing on startup. (Yet later I see tlp reporting the wrong state because something has loaded lg_laptop. If there had been no information, I would have considered that the module is missing.) Adding lg_laptop to /etc/modules-load.d fixes this.

My interpretation was biased because I had Fedora running on the laptop before and although there is no entry in /etc/modules-load.d, lg_laptop is loaded before tlp. Made me assume that it's tlp that loads the module.

[linrunner]

TLP recognizes hardware by the fact that the specific module is loaded. Then it checks if sysfiles for charge thresholds are present.

Plugin for LG: https://github.com/linrunner/TLP/blob/main/bat.d/35-lg

Therefore TLP requires that the appropriate kernel module is already loaded. The OS/kernel usually loads all modules that match the hardware. If not, the user has to enforce via configuration (as in your case).

TLP does not try to load all supported kernel modules for battery care. This would clutter the syslog with failures which is not acceptable.