Fix Linux Suspend Battery Drain

After researching the following links:

https://askubuntu.com/questions/1029474/ubuntu-18-04-dell-xps13-9370-no-longer-suspends-on-lid-close/1036122#1036122 https://www.kernel.org/doc/html/v4.15/admin-guide/pm/sleep-states.html

I had discovered that the Linux Kernel post 5.4 defaults suspend to a hardware agnostic software suspend implementation called s2idle. This is guaranteed to work on all systems, but has the worst power efficiency. The default for devices used to be deep.

To see if your device can support deep suspend state run this command

cat /sys/power/mem_sleep

# Example output
[s2idle] deep

If you see that the selected default is s2idle, you need to add a kernel boot parameter to change the default back to deep.

You need to add this option

mem_sleep_default=deep

On grub, you would add this in the /etc/default/grub file, on systemd-boot, you can add this in the /boot/loader/entries/*.conf file. Finally on PopOS, you must use the built-in boot manager cli tool kernelstub

sudo kernelstub -a "mem_sleep_default=deep"

Finally, check your /etc/systemd/sleep.conf file to ensure that the SuspendState= has mem as the first option. If the commented default indicates this, no changes need to be made.

Restart your computer, and the changes will be applied. Now you can suspend your computer, and to check that it has successfully reached deep suspend, run dmesg.

sudo dmesg | grep suspend

You should get the output

[  261.199248] PM: suspend entry (deep)
[  263.380254] PM: suspend exit