Public bug reported:
Disclaimer: this bug report was co-authoured with Claude code with
assistance in finding the cause.
Package: linux-image-7.0.0-38-generic (7.0.0-38.38)
Regression from: linux-image-7.0.0-34-generic (7.0.0-34.34), which works
correctly
Release: Ubuntu 26.04 (resolute)
SUMMARY
After upgrading from 7.0.0-34 to 7.0.0-38, horizontal band artifacts appear
across the screen whenever a large part of the display changes, for example
GNOME overview and workspace transitions, or the KDE Plasma logout fade.
Booting 7.0.0-34 with no other changes makes the problem disappear.
HARDWARE
- GPU: AMD Radeon RX 9070 XT (Navi 48, 1002:7550), Sapphire, driver amdgpu
- Monitor: MSI MPG 274U E16M, 3840x2160, connected over DisplayPort (DP-2)
- Mode: 3840x2160 at 160Hz (also affected at 120Hz). 60Hz is clean.
- Mesa 26.0.8, linux-firmware 20260319 (both unchanged between the working
and broken kernels)
SOFTWARE
- GNOME Shell 50.1 on Wayland (Mutter), 1.25x fractional scaling
- KDE Plasma Wayland session also tested (see below)
DISPLAY LINK STATE (7.0.0-38, from /sys/kernel/debug/dri/1/DP-2/)
- dsc_clock_en: 1 (DSC active)
- dsc_slice_width: 480
- dsc_bits_per_pixel: 256 (16 bpp)
- link_settings: 4 lanes, rate 0x1e (HBR3), full speed, no link-training
downgrade
SYMPTOMS
- Horizontal bands of corruption spanning the screen during full-screen
animations.
- Not seen in fullscreen games.
- Not seen at 60Hz (which does not need DSC).
- Reproduces in both GNOME and KDE Plasma, so it is not compositor-specific.
KEY FINDING
With power_dpm_force_performance_level=auto the memory clock idles at 96 MHz
(pp_dpm_mclk level 0) and the artifacts appear. With
echo high > /sys/class/drm/card1/device/power_dpm_force_performance_level
the artifacts disappear in both GNOME and KDE. Switching back to auto brings
them back. This suggests memory clock switching is not completing within the
vblank window on this DSC mode, which does not happen on 7.0.0-34.
REPRODUCE
1. Boot 7.0.0-38 with the 4K 160Hz monitor on DisplayPort.
2. Leave the performance level on auto and let the GPU idle.
3. Open the GNOME overview or switch workspaces.
POSSIBLE CAUSES (from comparing the 7.0.0-34 and 7.0.0-38 changelogs; I have
not read the diffs or bisected)
- drm/amd/display: consolidate DCN vblank/flip handling onto vupdate_no_lock
- drm/amd/display: Fix DTB DTO updates breaking live pixel rate sources
- drm/amd/display: ISM (idle state manager) fixes
- drm/amdgpu: Fix context pstate override handling
WORKAROUNDS
- Boot 7.0.0-34.
- Force power_dpm_force_performance_level=high.
- Use 60Hz.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-38-generic 7.0.0-38.38
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: GNOME
Date: Sun Oct 18 02:53:09 2026
InstallationDate: Installed on 2023-06-15 (1220 days ago)
InstallationMedia: Ubuntu 23.04 "Lunar Lobster" - Release amd64 (20230418)
IwDevWlp5s0Link: Not connected.
MachineType: Gigabyte Technology Co., Ltd. X570 AORUS MASTER
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-38-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-24 (177 days ago)
dmi.bios.date: 01/04/2022
dmi.bios.release: 5.17
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: F35
dmi.board.asset.tag: Default string
dmi.board.name: X570 AORUS MASTER
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: Default string
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 3
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.modalias:
dmi:bvnAmericanMegatrendsInternational,LLC.:bvrF35:bd01/04/2022:br5.17:svnGigabyteTechnologyCo.,Ltd.:pnX570AORUSMASTER:pvr-CF:rvnGigabyteTechnologyCo.,Ltd.:rnX570AORUSMASTER:rvrDefaultstring:cvnDefaultstring:ct3:cvrDefaultstring:skuDefaultstring:pfaX570MB:
dmi.product.family: X570 MB
dmi.product.name: X570 AORUS MASTER
dmi.product.sku: Default string
dmi.product.version: -CF
dmi.sys.vendor: Gigabyte Technology Co., Ltd.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2171312
Title:
amdgpu: horizontal screen corruption on RX 9070 XT at 4K 120/160Hz
(DSC) with 7.0.0-38; 7.0.0-34 is fine
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