Fails to detect monitors connected to docking stations

[Thomas Schweikle]

The graphics system fails to detect monitors connected to ports on docking stations. The ports themselves are detected an reported, but stay in state "disconnected" regardless there are monitors connected or not.

Internally the laptop has two Display-Ports, two HDMI-Ports and the build in Display. xrandr reports them:
- eDP-1 (Internal display)
- DP-1 (Internal Display-Port-1)
- DP-2 (Internal Display-Port-2)
- HDMI-1 (Internal HDMI-Port-1)
- HDMI-2 (Internal HDMI-Port-2)

Two of the four ports are wired to the laptop hardware-ports
- DP-1 -> Mini-Display-Port
- HDMI-1 -> HDMI-Port

Within the docking station there are additional hardware ports wired:
- HDMI-1 -> VGA
- DP-1 -> DVI
- DP-1 -> Display-Port-1
- HDMI-2 -> HDMI
- DP-2 -> Display-Port-2

Connecting displays to any of these ports is reported running Windows 10, or Ubuntu 21.04. With Ubuntu 21.10 only displays connected to the Mini-Display-Port are reported. All other hardware ports are ignored and will stay in disconnected state, even if active monitors are connected to them.

This is what xrandr reports if two monitors are connected directly to the laptop, one via HDMI, the other via Mini-Display-Port:
eDP-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 308mm x 173mm
   1920x1080 60.01*+ 60.01 59.97 59.96 59.93
   [...]
   360x202 59.51 59.13
   320x180 59.84 59.32
DP-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 520mm x 330mm
   1920x1200 59.95*+
   [...]
   640x480 75.00 59.94
   720x400 70.08
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)

The monitors connected to the build in HDMI are not recognized, as those connected to both Display-Ports available on this dock.

Connecting monitors only to the Dock only the build in display is recognized, no other.

Seen this on:
- ThinkPad T450s (20BW)
- ThinkPad T460s (20FA)
- ThinkPad T470s (20HF, 20HG)

With ThinkPad Ultra Dock (40A2)

Then:
- ThinkPad T480
- ThinkPad T490
- ThinkPad T14

With ThinkPad Ultra Dock (40AJ)

Same Problem exists with
- Acer TravelMate and Acer-Dock II
- Dell and Dell-Docks

The bug might be within the kernel, graphics subsystems, x11, wayland.
I could verity that going back to Ubuntu 21.04 (hirsute) this bug vanishes. And starts showing up again after upgrading to 21.10 (impish).

ProblemType: Bug
DistroRelease: Ubuntu 21.10
Package: libxrandr2 2:1.5.2-0ubuntu1
ProcVersionSignature: Ubuntu 5.13.0-21.21-generic 5.13.18
Uname: Linux 5.13.0-21-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu71
Architecture: amd64
CasperMD5CheckResult: pass
CompositorRunning: None
Date: Thu Dec 23 10:20:55 2021
DistUpgraded: Fresh install
DistroCodename: impish
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation Skylake GT2 [HD Graphics 520] [8086:1916] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Skylake GT2 [HD Graphics 520] [17aa:2233]
InstallationDate: Installed on 2021-08-18 (127 days ago)
InstallationMedia: Xubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
MachineType: LENOVO 20FAS16K00
ProcKernelCmdLine: BOOT_IMAGE=/BOOT/ubuntu_sxscpx@/vmlinuz-5.13.0-21-generic root=ZFS=rpool/ROOT/ubuntu_sxscpx ro quiet splash vt.handoff=1
SourcePackage: libxrandr
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/30/2016
dmi.bios.release: 1.20
dmi.bios.vendor: LENOVO
dmi.bios.version: N1CET52W (1.20 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20FAS16K00
dmi.board.vendor: LENOVO
dmi.board.version: SDK0J40697 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.9
dmi.modalias: dmi:bvnLENOVO:bvrN1CET52W(1.20):bd11/30/2016:br1.20:efr1.9:svnLENOVO:pn20FAS16K00:pvrThinkPadT460s:rvnLENOVO:rn20FAS16K00:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20FA_BU_Think_FM_ThinkPadT460s:
dmi.product.family: ThinkPad T460s
dmi.product.name: 20FAS16K00
dmi.product.sku: LENOVO_MT_20FA_BU_Think_FM_ThinkPad T460s
dmi.product.version: ThinkPad T460s
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.107-8ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 21.2.2-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.20.13-1ubuntu1.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-2build1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200714-1ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.17-1build1