My workaround is to enable GuC firmware loading and boot without the dock attached.
Kernel 4.15.0.30 Ubuntu 18.04.1 Xorg/Gnome Lenovo 4th gen X1 20FBxxx Skylake i7 Intel built-in video
Looks like this is some kind of race condition related to DisplayPort Multi-Stream mode (DP-MST). This is why multi-monitor docking stations are affected. A race is happening, with system attempting modesetting upon disconnect of the mst dock, which leaves the connector enabled. Error messages upon disconnect:
[drm:intel_dp_start_link_train [i915]] *ERROR* failed to enable link training
[drm:intel_mst_pre_enable_dp [i915]] *ERROR* failed to allocate vcpi
Next connection leads to black screen. Multiple error messages upon connect:
[drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit
My workaround is to enable GuC firmware loading and boot without the dock attached.
Kernel 4.15.0.30 Ubuntu 18.04.1 Xorg/Gnome Lenovo 4th gen X1 20FBxxx Skylake i7 Intel built-in video
Looks like this is some kind of race condition related to DisplayPort Multi-Stream mode (DP-MST). This is why multi-monitor docking stations are affected. A race is happening, with system attempting modesetting upon disconnect of the mst dock, which leaves the connector enabled. Error messages upon disconnect:
[drm:intel_ dp_start_ link_train [i915]] *ERROR* failed to enable link training mst_pre_ enable_ dp [i915]] *ERROR* failed to allocate vcpi
[drm:intel_
Next connection leads to black screen. Multiple error messages upon connect:
[drm:intel_ wait_ddi_ buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit
Related cases I've found:
https:/ /patchwork. kernel. org/patch/ 8603521/ /bugzilla. redhat. com/show_ bug.cgi? id=1470960 /bugs.launchpad .net/ubuntu/ +source/ xserver- xorg-video- intel/+ bug/1552040 /bugs.freedeskt op.org/ show_bug. cgi?id= 73705
https:/
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Workaround:
sudo vi /etc/modprobe. d/i915. conf
options i915 enable_ guc_loading= 1 enable_ guc_submission= 1
sudo update-initramfs -u
sudo reboot
always reboot while disconnected from DP MST dock