[PinePhone Thermals] Set lower default thermal trip points
Currently we do not have a thermal management engine (yet) for the PinePhone/PinePhone Pro.
There's something in the works, but that's still far from ready.
To prevent devices from running quite hot during (even under normal load conditions) it's better to lower the current default thermal trip points for the cpu.
This makes thermal throttling of the cpu kick in much earlier, and prevents the phone from becoming a pocket heater.
Current thermal trip points which are used quite often are (45/55/70), which seem quite good.
With these settings phone doesn't feel as hot anymore as before, maybe even comparable to a modern android device.
The thermal trip points can be altered (patched) in the kernel ".dtsi" files, but it's also possible to use a script to lower the defaults at boot time.
Easiest way to do this, is by using SystemD's own tmpfiles.d daemon.
It's a temporary solution after all until a proper thermal management engine has been finished.
If you create a file /etc/tmpfiles.d/throttling.conf, with the following contents:
w /sys/class/thermal/thermal_zone0/trip_point_0_temp - - - - 45000
w /sys/class/thermal/thermal_zone0/trip_point_1_temp - - - - 55000
w /sys/class/thermal/thermal_zone0/trip_point_2_temp - - - - 70000
Please let me know what you think of it.