There’s this ’new‘ intel graphics feature in Linux kernels called Panel Self-Refresh.
This feature bypasses the GPU drawing cycle if there’s nothing to render on your display, so it’s ought to save certain amount of battery charge, as you can simply take the old drawing buffer contents and stream it to the display hardware.
Unfortunately, this somehow seems to work only on newer hardware, i.e. neither my Lenovo z510 from 2013 nor my even older Samsung N220 Atom netbook.
Symptoms are progressivley whitening screen contents if one doesn’t move the mouse (,so it has to reassemble display contents again) or even an entirely black display when booting up my netbook.
How to disable it?
i915.enable_psr=0 to your kernel boot options, so either e.g. under /boot/refind_linux.conf or your grub config.
[Update: I had PSR disabled for a while now, but it seems they’ve fixed these display issues in recent kernel versions, so no need to apply this fix anymore – nice!]