G92GLM has black screen after trying to change to lower resolution than native
I'm using the Nouveau driver with an NVIDIA G92GLM [Quadro FX 2800M]. When I updated my Debian installation from 9 to 10, I found that setting resolution to a lower value (1024x768), the screen would stay black.
The Debian kernel that worked was 4.9.0-11 and the new one that has the problem is 4.19.0-6, but I compiled the latest kernel from https://github.com/skeggsb/linux and got the same result.
Through bisection and trying kernel builds, I found the problem first occurred in the 4.14 branch https://github.com/skeggsb/linux/commits/linux-4.14/drivers/gpu/drm/nouveau specifically at commit 0c697fa
The test I run is just this: #!/bin/sh xrandr -s 1024x768 --output LVDS-1 --mode 1024x768 sleep 10
back to normal, this works
xrandr -s 1920x1200 --output LVDS-1 --mode 1920x1200
Attached is the syslog during that time with some debugging enabled nouveau-debug.log