A bit of random testing with undocking and docking repeatedly, with sometimes 'killall unity-settings-daemon' to reread monitors.xml and hopefully reset the display mode, shows weird behaviour.
After a docked fresh boot, after undocking i get for xrandr (SNIPs for brevity): Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192 eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 310mm x 174mm 2560x1440 60.00 + 1920x1440 60.00 [SNIP] DP-1 disconnected (normal left inverted right x axis y axis) HDMI-1 disconnected (normal left inverted right x axis y axis) DP-2 disconnected (normal left inverted right x axis y axis) HDMI-2 disconnected (normal left inverted right x axis y axis) DP-3 disconnected (normal left inverted right x axis y axis) HDMI-3 disconnected (normal left inverted right x axis y axis) DP-3-1 connected (normal left inverted right x axis y axis) 1024x768 60.00 800x600 60.32 56.25 848x480 60.00 640x480 59.94 DP-3-2 connected (normal left inverted right x axis y axis) 1024x768 60.00 800x600 60.32 56.25 848x480 60.00 640x480 59.94 DP-3-3 disconnected (normal left inverted right x axis y axis) Redocking and going through a few glitchy stretched display mode changes gets a more promising xrandr: eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 310mm x 174mm 2560x1440 60.00 + 1920x1440 60.00 [SNIP] DP-1 disconnected (normal left inverted right x axis y axis) HDMI-1 disconnected (normal left inverted right x axis y axis) DP-2 disconnected (normal left inverted right x axis y axis) HDMI-2 disconnected (normal left inverted right x axis y axis) DP-3 disconnected (normal left inverted right x axis y axis) HDMI-3 disconnected (normal left inverted right x axis y axis) DP-3-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 518mm x 324mm 1920x1200 59.95 + 1920x1080 50.00 [SNIP] DP-3-2 connected (normal left inverted right x axis y axis) 1920x1200 59.95 + 1920x1080 50.00 [SNIP] DP-3-3 disconnected (normal left inverted right x axis y axis) But that just means the monitors are advertised in System Settings -> Displays, where I can change their position, resolution, etc. but they stay dark. Here's a few log lines after undocking: Dez 20 16:15:31 talas kernel: [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* failed to enable link training Dez 20 16:15:31 talas kernel: [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization Dez 20 16:16:18 talas kernel: [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* failed to enable link training Dez 20 16:16:18 talas kernel: [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization Dez 20 16:17:16 talas kernel: [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* failed to enable link training Dez 20 16:17:16 talas kernel: [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization After docking and various shenanigans I get: Dez 20 16:29:56 talas kernel: [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun Notably the "too many voltage retries" error is missing this time. Again when rebooting everything works fine. Except for un-/redocking of course. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1651454 Title: [Lenovo Thinkpad T460p] Ultra Dock external displays not detected after suspend/resume cycle To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1651454/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
