Public bug reported:
Summary:
Severe desktop flickering occurs on Kubuntu 24.04.3 LTS when both integrated
TigerLake Iris Xe Graphics and discrete Iris Xe MAX (DG1) GPUs are initialized
by the i915 driver.
The issue disappears immediately when the DG1 is not force-probed.
System Information
Distribution: Kubuntu 24.04.3 LTS (Noble Numbat)
Desktop Environment: KDE Plasma 5.27.12
Kernel: 6.14.0-33-generic
Host: Acer Swift SF314-510G (BIOS V1.13)
CPU: Intel Core i5-1135G7 (Tiger Lake, 4C/8T)
Integrated GPU: Intel Iris Xe Graphics (GT2, Device ID 0x9A49)
Discrete GPU: Intel Iris Xe MAX (DG1, Device ID 0x4905)
Display Server: X11 (KWin compositor)
Driver: i915
Firmware versions (loaded successfully):
i915/tgl_dmc_ver2_12.bin
i915/dg1_dmc_ver2_02.bin
i915/dg1_guc_70.bin
i915/dg1_huc.bin
Steps to Reproduce
Edit /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.force_probe=*
i915.enable_psr=0"
Run:
sudo update-grub
sudo reboot
After boot, both GPUs (iGPU 0x9A49 and DG1 0x4905) are initialized:
[drm] Found tigerlake/uy (device ID 9a49)
[drm] Found dg1 (device ID 4905)
Desktop session starts flickering constantly:
Wallpaper disappears
Right-click menu stops responding
Plasma shell reloads repeatedly
Removing i915.force_probe=* and rebooting fixes the issue completely.
Expected Behavior
System should remain stable with both GPUs initialized, allowing DG1 to
handle compute or rendering workloads.
Actual Behavior
Severe flickering, broken compositor, and unstable desktop when DG1 is
initialized.
Workaround
Boot with DG1 disabled:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_psr=0"
→ Flickering disappears instantly, system remains smooth and stable.
Relevant dmesg Output
i915 0000:03:00.0: [drm] Found dg1 (device ID 4905)
i915 0000:03:00.0: [drm] GT0: GUC: submission enabled
i915 0000:03:00.0: [drm] Cannot find any crtc or sizes
Additional Notes
This system uses a hybrid configuration (TigerLake iGPU + DG1 dGPU).
DG1 firmware loads correctly but does not attach to any display output
(Cannot find any crtc or sizes).
Possibly related to multi-GPU handling regression in i915 for DG1 on
hybrid laptops.
Kernel tainted message appears when DG1 is force-probed:
Force probing unsupported Device ID 4905, tainting kernel
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.14.0-33-generic 6.14.0-33.33~24.04.1
ProcVersionSignature: Ubuntu 6.14.0-33.33~24.04.1-generic 6.14.11
Uname: Linux 6.14.0-33-generic x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: muthi 1783 F.... pipewire
muthi 1785 F.... wireplumber
/dev/snd/controlC1: muthi 1785 F.... wireplumber
/dev/snd/seq: muthi 1783 F.... pipewire
CRDA: N/A
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Tue Oct 28 12:18:25 2025
InstallationDate: Installed on 2025-10-27 (1 days ago)
InstallationMedia: Kubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
MachineType: Acer Swift SF314-510G
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.14.0-33-generic
root=UUID=f44d5586-9aa3-4b44-943f-eac9451e5525 ro quiet splash
i915.force_probe=9a49 i915.enable_psr=0 i915.enable_fbc=0 i915.enable_dc=0
vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-6.14.0-33-generic N/A
linux-backports-modules-6.14.0-33-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.19
SourcePackage: linux-hwe-6.14
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/28/2022
dmi.bios.release: 1.13
dmi.bios.vendor: Insyde Corp.
dmi.bios.version: V1.13
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: Brahma_TL
dmi.board.vendor: TGL
dmi.board.version: V1.13
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: Chassis Version
dmi.ec.firmware.release: 1.13
dmi.modalias:
dmi:bvnInsydeCorp.:bvrV1.13:bd10/28/2022:br1.13:efr1.13:svnAcer:pnSwiftSF314-510G:pvrV1.13:rvnTGL:rnBrahma_TL:rvrV1.13:cvnAcer:ct10:cvrChassisVersion:sku0000000000000000:
dmi.product.family: Swift 3X
dmi.product.name: Swift SF314-510G
dmi.product.sku: 0000000000000000
dmi.product.version: V1.13
dmi.sys.vendor: Acer
** Affects: linux-hwe-6.14 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
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https://bugs.launchpad.net/bugs/2129991
Title:
External monitor flickers when DG1 (Iris Xe MAX) is enabled on Acer
Swift SF314-510G (TigerLake + DG1 hybrid graphics)
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