My external Diplay Flickers

[Balaji]

I connected a Samsung external monitor to my laptop which runs on Ubuntu 24.04 with intel Iris graphics, the external monitor flickers continuously.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: xorg 1:7.7+23ubuntu3
ProcVersionSignature: Ubuntu 6.8.0-31.31-generic 6.8.1
Uname: Linux 6.8.0-31-generic x86_64
ApportVersion: 2.28.1-0ubuntu2
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CasperMD5CheckResult: pass
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Thu May 9 10:48:41 2024
DistUpgraded: Fresh install
DistroCodename: noble
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation Alder Lake-UP3 GT2 [Iris Xe Graphics] [8086:46a8] (rev 0c) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Alder Lake-UP3 GT2 [Iris Xe Graphics] [17aa:50a6]
InstallationDate: Installed on 2024-05-06 (3 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Release amd64 (20240424)
MachineType: LENOVO 21B4S2L718
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-31-generic root=UUID=a74f0381-c0e0-4163-ae5a-6aa2f5cfa36b ro quiet splash vt.handoff=7
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/23/2024
dmi.bios.release: 1.23
dmi.bios.vendor: LENOVO
dmi.bios.version: R1UET46W (1.23 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21B4S2L718
dmi.board.vendor: LENOVO
dmi.board.version: SDK0T76530 WIN
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.14
dmi.modalias: dmi:bvnLENOVO:bvrR1UET46W(1.23):bd02/23/2024:br1.23:efr1.14:svnLENOVO:pn21B4S2L718:pvrThinkPadL13Gen3:rvnLENOVO:rn21B4S2L718:rvrSDK0T76530WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21B4_BU_Think_FM_ThinkPadL13Gen3:
dmi.product.family: ThinkPad L13 Gen 3
dmi.product.name: 21B4S2L718
dmi.product.sku: LENOVO_MT_21B4_BU_Think_FM_ThinkPad L13 Gen 3
dmi.product.version: ThinkPad L13 Gen 3
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.120-2build1
version.libgl1-mesa-dri: libgl1-mesa-dri 24.0.5-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:21.1.12-1ubuntu1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:22.0.0-1build1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20210115-1build1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.17-2build1

[Resit Sahin (resitsahin)]

I am using a pc with dual monitor. My second monitor with a hdmi cable was flickering with each mouse movement. I have changed its frequency from 60Hz to 50Hz flickering gone. My firs monitor is 4K

[Daniel van Vugt (vanvugt)]

Balaji, please try reducing the screen resolution and/or refresh rate.

[Mario Marinero (mmarinero)]

Same setup as #2 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2065250/comments/2

The failing monitor is 1080p old NEC MustySync EA231EMi
The main monitor is 4K, it has no issues

Lowering resolutions to 1600x900 on failing monitor or 1080p on 4k monitor solves the issue
Lowering refresh to 50 hz on the failing monitor also solves the issue

[Daniel van Vugt (vanvugt)]

If lowering the resolution or refresh rate solves it then most likely you need a higher quality HDMI cable.

I say HDMI cable because those usually have the most quality problems, whereas DisplayPort does not.