One of the most annoying problems I recently had with Linux notebooks with the “btusb” driver was the disconnect of bluetooth mouse devices. Devices like my Microsoft Bluetooth Mobile Mouse 3600, Xiaomi Mi Portable Mouse or other Bluetooth LE (low energy) mice have had lost their connection when my notebooks ran on battery and a reconnect was possible only after a restart of the Bluetooth stack.
I have been looking for solutions on the internet and tried out many workarounds including disabling the Wifi power management.
What has finally fixed my issue was disabling autosuspend for bluetooth.
An easy way to fix this is to create a modprobe configuration file
/etc/modprobe.d/btusb-autosuspend-disable.confwith the contents:
options btusb enable_autosuspend=0