Hi there! I have a Lenovo Carbon X1 and I use an external HP Z27 4K monitor. I have the monitor connected to the Lenovo laptop using a HDMI cable. I also have the same monitor connected to a Dell desktop computer using a DP cable.
I can change the selected input on the monitor from HDMI (laptop) to DP (desktop). The problem is that when I change it back, both the external monitor AND the laptop screen flicker as if I had physically plugged in the monitor.
Checking dmesg, I'm getting the following messages:
```
[616849.330989] [drm:drm_dp_dual_mode_detect [drm_kms_helper]] *ERROR* Unexpected DP dual mode adaptor ID 50
[616853.593595] [drm:drm_dp_dual_mode_detect [drm_kms_helper]] *ERROR* Unexpected DP dual mode adaptor ID 50
```
Sometimes I get back my desktop, but more often then not the external monitor is stuck as 1920*1080 and I have to use `autorandr` to fix that.
```
lsb_release -rd
Description: Ubuntu 21.04
Release: 21.04
```
```
uname -a
Linux my-laptop 5.11.0-22-generic #23-Ubuntu SMP Thu Jun 17 00:34:23 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
```
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: leo 116787 F.... pulseaudio
CasperMD5CheckResult: pass
CurrentDesktop: KDE
DistroRelease: Ubuntu 21.04
InstallationDate: Installed on 2021-07-12 (42 days ago)
InstallationMedia: Kubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
MachineType: LENOVO 20QD001UUS
Package: linux (not installed)
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.11.0-31-generic root=/dev/mapper/vgkubuntu-root ro quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 5.11.0-31.33-generic 5.11.22
RelatedPackageVersions:
linux-restricted-modules-5.11.0-31-generic N/A
linux-backports-modules-5.11.0-31-generic N/A
linux-firmware 1.197.3
Tags: hirsute
Uname: Linux 5.11.0-31-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 09/11/2019
dmi.bios.release: 1.20
dmi.bios.vendor: LENOVO
dmi.bios.version: N2HET37W (1.20 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20QD001UUS
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: 1.10
dmi.modalias: dmi:bvnLENOVO:bvrN2HET37W(1.20):bd09/11/2019:br1.20:efr1.10:svnLENOVO:pn20QD001UUS:pvrThinkPadX1Carbon7th:rvnLENOVO:rn20QD001UUS:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad X1 Carbon 7th
dmi.product.name: 20QD001UUS
dmi.product.sku: LENOVO_MT_20QD_BU_Think_FM_ThinkPad X1 Carbon 7th
dmi.product.version: ThinkPad X1 Carbon 7th
dmi.sys.vendor: LENOVO
Attached lspci-vnvn.log