[NVC1][optimus] nouveau black display, only mouse cursor visible when using intel driver for integrated GPU

Submitted by Dominik Mierzejewski @rathann

Assigned to Nouveau Project

Link to original bug (#109187)

Description

Created attachment 142919
Xorg.log with intel+nouveau drivers

I'm getting black output on HDMI-connected display driven by nVidia GeForce GT 525M (GF108M). Mouse cursor is visible on both built-in display and on the external HDMI-connected display. This used to work on Fedora 27. I can see this on Fedora 29, but I can't pinpoint which package update broke it because I haven't checked the external display (a projector) for quite some time. This machine is a Dell XPS 15 L502X with Intel HD3000 integrated graphics and nVidia GeForce GT 525M discrete GPU in Optimus configuration. Here's my xorg.conf snippet:

Section "Monitor"
Identifier "Internal LCD"
DisplaySize 345 195
EndSection

Section "Monitor"
VendorName "Benq"
ModelName "W1100"
Identifier "Projector"
DisplaySize 16900 9400
EndSection

Section "Device"
Identifier "Internal Graphics"
Driver "intel"
Option "Monitor-LVDS1" "Internal LCD"
Option "TearFree" "on"
EndSection

Section "Device"
Identifier "Optimus Graphics"
Driver "nouveau"
Option "Monitor-HDMI-1-2" "Projector"
EndSection

Switching both drivers to "modesetting" makes the issue go away. I'm attaching Xorg logs for both configurations.

Attachment 142919, "Xorg.log with intel+nouveau drivers":
Xorg.0.log-intel+nouveau.txt