https://bugzilla.kernel.org/show_bug.cgi?id=64891

--- Comment #22 from Joaquín Aramendía samsagax@gmail.com --- Thanks for the reply, Alex. Adding 'acpiphp.disable=1' to bootloader indeed helps.

Tested on $ uname -r 3.12.6-1-ARCH

Last lines of dmesg shows the Nvidia card is shut down [ 25.473454] hda-intel 0000:01:00.1: Disabling via VGA-switcheroo [ 28.062014] ACPI Warning: _SB_.PCI0.P0P1.PEGP._DSM: Argument #4 type mismatch - Found [Integer], ACPI requires [Package] (20130725/nsarguments-95)

And is confirmed by vgaswitcheroo # cat /sys/kernel/debug/vgaswitcheroo/switch 0:IGD:+:Pwr:0000:00:02.0 1:DIS: :DynOff:0000:01:00.0 2:DIS-Audio: :Off:0000:01:00.1

Then tested powering on/off with prime and it didn't work. It froze when calling: $ DRI_PRIME=1 glxinfo | grep renderer

Couldn't catch the dmesg after that.

Indeed it seems like a duplicate of bug 61891. I can't test the patch proposed there as it's radeon specific.