Since I upgraded from 6.5.5 - to any 6.6.x release, I have had issues with only a single monitor displaying PlasmaLogin and desktop content. the 2nd monitor is active (HDMI signal), but nothing displays (i.e. black image only).
ENVIRONMENT:
- Archlinux - 6.19.11-arch1-1
- Dell D3100 USB3.0 hub - with two 1920*1080 60Hz monitors attached via HDMI native (i.e. HDMI to HDMI - no display port conversions etc)
- Dell Optiplex 3050 Micro - with Intel Integrated graphics (UHD630) - with linux i915 kernel module / driver
- DisplayLink 6.2.1 - compiled and installed from ArchLinux AUR - using Synaptics supplied 6.2 drivers
- evdi 1.14.15 - compiled and installed form ArchLinux AUR
I have no additional kernel module parameters on evdi nor i915.
I do not have a separate GPU physically installed (i.e. no other AMD/nvidia) and no nouveau or other drivers/kernel modules installed.
displaylink service starts fine (no systemd/dmesg/journalctl errors)
Both monitors are enabled in Plasma’s display and configuration
PROBLEM:
The 2nd monitor is getting a signal - but is being rendered “black” by Plasma. I know this because I can see my mouse “disappear’ off edge into the 2nd monitor. I can also tell - because from PlasmaLogin - the focus monitor changes to prompt for password when i move the mouse into the “black” monitor (without any picture)
I am getting these errors in the system log whenever the mouse enters the “black” / 2nd monitor:
evdi: [E] evdi_painter_grabpix_ioctl:1128 Failed to map scanout buffer
I am using the latest evdi/displaylink combination so believe they are compatible
WORKAROUND:
I have found the following setting in /etc/environment enables the 2nd monitor, however UI performance seems to degrade
KWIN_DRM_USE_MODIFIERS=0
With the above - the 2nd monitor works, but mouse doesn’t display. I added:
KWIN_FORCE_SW_CURSOR=1
But then mouse is very jittery.
Has there been a regression in 6.6+?
NB: without the KWIN_FORCE_SW_CURSOR=1 setting, the EVDI log error changes.