[Bug 111480] New: i915 monitor connected through dock not working

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111480

            Bug ID: 111480
           Summary: i915 monitor connected through dock not working
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: not set
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: joseph-thommes at gmx.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 145148
  --> https://bugs.freedesktop.org/attachment.cgi?id=145148&action=edit
dmesg connecting dock with monitor and activating it

Bug description:

Monitor connected through HDMI or DP in lenovo-thunderbolt dock causes
[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO
underrun
and after some time
[drm:intel_dp_start_link_train [i915]] *ERROR* Timed out waiting for DP idle
patterns
if enabled in xserver. Just connecting and not using it doesn't do anything.

The monitor shows up as a DP-Monitor even if it is connected through HDMI.
Also my input becomes extremely laggy, windows do not respond and my fan spins
up (not sure if this is related). I do not get any output on the screen, but
resolution etc are determined correctly when checking in xrandr.
After unplugging the monitor, everything is back to normal.

The monitor works with other computers.
All available firmware updates (dock and laptop) have been installed.

System environment:
-- chipset: not sure how to determine
-- system architecture: 64-bit
-- xf86-video-intel: 1:2.99.917+870+g6f4972d5-1
-- xserver: 1.20.5-2
-- mesa: 19.1.4-1
-- libdrm: 2.4.99-1
-- kernel: 5.2.9-arch1-1-ARCH
-- Linux distribution: arch
-- Machine or mobo model: Lenovo Thinkpad T490 (20N2), Ultra Docking Station
Type 40AJ
-- Display connector: HDMI/DP through dock

Reproducing steps:
Power up the laptop and login.
Connect the dock with a Monitor plugged in. (HDMI)
Activate the second screen (with arandr).

Alternative:
Boot with dock and monitor connected and start an X session.

Additional info:
None

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