Why does my display flicker when the power source changes?


This is caused by the radeon driver’s power management. To disable the setting either use




depending on your card/kernel. Refer to Graphics for details.

Kernel message ‘ERROR radeon: ring 0 test failed’ on AC power


Affected hardware: a Lenovo Ideapad 300 (Intel / Radeon hybrid graphics) user reported this issue.

Solution: disable DPM like this


Flickering screen

Nvidia Optimus

Affected hardware: a Dell Latitude 5480 user reported ‘screen flickers at an inconsistent rate, though not that sporadic’.

Solution: disable ASPM on battery in the configuration


Why does my laptop consume so much battery power?

Nvidia Optimus

Laptops with Optimus hybrid graphics contain two graphics units, one from Intel on the processor die (‘integrated’, iGPU) and one from Nvidia (‘discrete’, dGPU). Linux uses the Intel unit by default, but at the same time the unused Nvidia unit might be enabled and using a lot of battery power because no driver is loaded.

TLP can’t do anything about this – Possible solutions are:

  • Disable one of the units in the BIOS setup
  • Use a tool to disable the dGPU (see list below)

Significant loss of energy saving after upgrade to 1.0

Version 1.0 and higher exempt (blacklists) all dGPU’s from runtime power management. For certain hardware/kernel combinations this means that the dGPU is no longer automatically deactivated at system startup.

Solution: remove dGPU’s from the driver blacklist in the configuration


or use a tool (see list below) to disable the dGPU upon boot.

I use PRIME to disable the dGPU, why is it always re-enabled after boot?

Nvidia Optimus

Exclude the dGPU from runtime power management.

Version 1.0 and higher: blacklist the driver(s)


Version 0.9 and before: blacklist the device


Hint: to check whether ‘01:00.0’ matches your Nvidia dGPU, use

lspci -v | perl -ne '/VGA/../^$/ and /VGA|Kern/ and print'

Refer to Runtime Power Management and ASPM too.

Bumblebee fails to re-enable the dGPU

Exclude the dGPU from runtime power management, see the previous section.

See also

Incomplete list of tools to handle hybrid graphics GPU switching:

Also look for solutions already integrated into your Linux distribution or desktop.