Description of problem: An external monitor was working fine using rawhide with kernel 4.3 on a optimus laptop with the external monitor output connected only to the nvidia card. However with the kernel 4.5 in latest rawhide that stopped working. xrandr doesn't detect the external monitor and it says that the HDMI is disconnected. DRI_PRIME=1 glxgears works as expected. Additional info: The card is: GeForce GT 520M OpenGL ES 3.0 Mesa 11.2.0-devel Gallium 0.4 on NVD9
Can you please attach dmesg output from both the working and non working kernels?
Doing some pruning, this bug looks to be years old. Please test on a newer kernel and reopen if the problem still exists.