Comment 6 for bug 971061

I have this same issue on my Series 9 NP900x4b too.

One thing I noticed is that DIRECTLY after doing a "bios" update from windows... things started to work perfectly for a while in Linux. I ended up booting back into windows for a game at some point, and after coming back it has reverted back to working as stated above.

This makes me wonder if perhaps some sort of ACPI corruption is going on. Ive tried to reflash the firmware since then... but it won't let you flash the same version twice. I would love to compare a ACPI DSDT dump from just after flashing to after it has stopped working.

One can do so via:
cat /sys/firmware/acpi/tables/DSDT > dsdt.dat

You can then dissasemble it with iasl
iasl -d dsdt.dat