Nouveau error - trying to get external gpu to work with libreboot/gnuboot

I recently flashed my BIOS chip with either GNUboot and libreboot. But I have not been able to get my external graphics card to work. The only error I could find regarding to nouveau is:

... vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=none

Does anyone know what could cause this error, or in what direction to look? Everything worked before flashing. Now only able to get display with serial cable and on-board graphics.