Artifacts when connected to an external 4K display

[roland]

I get artifacts when I connect my laptop (Lenovo X1 7th Gen) to an external 4k monitor via usb-c->DP.

See the attached screenshot.

This happened after I upgraded to ubuntu 20.04.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xorg 1:7.7+19ubuntu14
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CasperMD5CheckResult: skip
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Thu Apr 23 22:35:27 2020
DistUpgraded: 2020-04-23 22:04:58,240 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: focal
DistroVariant: ubuntu
DkmsStatus:
 nvidia, 440.64, 5.3.0-48-generic, x86_64: installed
 nvidia, 440.64, 5.4.0-26-generic, x86_64: installed
 v4l2loopback, 0.12.3, 5.3.0-48-generic, x86_64: installed
 v4l2loopback, 0.12.3, 5.4.0-26-generic, x86_64: installed
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
 Intel Corporation UHD Graphics 620 (Whiskey Lake) [8086:3ea0] (rev 02) (prog-if 00 [VGA controller])
   Subsystem: Lenovo UHD Graphics 620 (Whiskey Lake) [17aa:2292]
InstallationDate: Installed on 2019-10-07 (199 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
MachineType: LENOVO 20QDCTO1WW
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-26-generic root=UUID=298d5179-f5b4-410d-aafb-92630b5b48a1 ro quiet splash vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to focal on 2020-04-23 (0 days ago)
dmi.bios.date: 03/18/2020
dmi.bios.vendor: LENOVO
dmi.bios.version: N2HET47W (1.30 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20QDCTO1WW
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.modalias: dmi:bvnLENOVO:bvrN2HET47W(1.30):bd03/18/2020:svnLENOVO:pn20QDCTO1WW:pvrThinkPadX1Carbon7th:rvnLENOVO:rn20QDCTO1WW:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad X1 Carbon 7th
dmi.product.name: 20QDCTO1WW
dmi.product.sku: LENOVO_MT_20QD_BU_Think_FM_ThinkPad X1 Carbon 7th
dmi.product.version: ThinkPad X1 Carbon 7th
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.101-2
version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.4-2ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.20.8-2ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200226-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1

[Sebastien Bacher (seb128)]

Thank you for your bug report. The log has

[ 12.559830] Call Trace:
[ 12.559838] __video_do_ioctl+0x1a7/0x410 [videodev]
[ 12.559844] video_usercopy+0x2b5/0x670 [videodev]
[ 12.559848] ? v4l_s_fmt+0x670/0x670 [videodev]
[ 12.559854] video_ioctl2+0x15/0x20 [videodev]
[ 12.559859] v4l2_ioctl+0x4c/0x60 [videodev]
[ 12.559863] do_vfs_ioctl+0x407/0x670
[ 12.559865] ? putname+0x4a/0x50
[ 12.559866] ksys_ioctl+0x67/0x90
[ 12.559868] __x64_sys_ioctl+0x1a/0x20
[ 12.559870] do_syscall_64+0x57/0x190
[ 12.559873] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Looks like it"s rather a kernel driver issue

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[roland (roland-micite)]

@seb128 I've removed the v4l2 loopback module. That stopped the kernel driver issue you mentioned.
The problem with the artifacts persists. Now it's on my laptop screen without the external display being preset.

Note: This is only when I run on the internal intel GPU. It doesn't happen when X uses my external nvidia one.

[roland (roland-micite)]

Reconfiguring X made this go away

[Daniel van Vugt (vanvugt)]

It's a common complaint/mistake: bug 1867668