Public bug reported:
I am reporting a regression affecting HDMI detection on an AMD Radeon RX
570 (Ellesmere/Polaris, PCI ID 1002:67df) under Kubuntu 26.04.1 LTS.
Hardware:
* GPU: AMD Radeon RX 570
* HDMI monitor: Lenovo G27c-10
* A second monitor is connected via DisplayPort.
Expected behaviour:
Both monitors should be detected and usable.
Actual behaviour:
* With kernel 6.8.0-146-generic and the boot parameter amdgpu.dc=0, both
monitors work correctly.
* With kernel 7.0.0-38-generic and amdgpu.dc=0, no DRM connectors are exposed
and no display output is available.
* With kernel 7.0.0-38-generic and amdgpu.dc=1, DisplayPort works, but HDMI-A-1
reports "disconnected" and its EDID file contains 0 bytes.
* Reconnecting the HDMI cable does not restore detection.
* Kernel logs show successful AMDGPU initialization but no useful HDMI, HPD, or
EDID messages.
The issue appears to be a regression in the AMDGPU display driver
between kernels 6.8.0-146 and 7.0.0-38.
Please investigate HDMI connector detection on Polaris/Ellesmere GPUs
when using the 7.0 kernel.
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
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/controlC0',
'/dev/snd/hwC0D0', '/dev/snd/pcmC0D2c', '/dev/snd/pcmC0D0c',
'/dev/snd/pcmC0D0p', '/dev/snd/by-id', '/dev/snd/by-path',
'/dev/snd/controlC2', '/dev/snd/hwC2D0', '/dev/snd/pcmC2D11p',
'/dev/snd/pcmC2D10p', '/dev/snd/pcmC2D9p', '/dev/snd/pcmC2D8p',
'/dev/snd/pcmC2D7p', '/dev/snd/pcmC2D3p', '/dev/snd/controlC1',
'/dev/snd/pcmC1D0c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CasperMD5CheckResult: unknown
Date: Fri Oct 9 19:45:56 2026
InstallationDate: Installed on 2024-11-01 (707 days ago)
InstallationMedia: Kubuntu 24.04.1 LTS "Noble Numbat" - Release amd64 (20240827)
IwDevWlx90de8032c046Link: Not connected.
MachineType: Micro-Star International Co., Ltd. MS-7C39
ProcFB:
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-38-generic
root=UUID=7bc5eb45-c76b-446e-8342-fc6090f1e1f8 ro quiet splash amdgpu.dc=0
drm_kms_helper.poll=0
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: Aucun
démon PulseAudio en cours d’exécution, ou ne s’exécutant pas dans une session
de type démon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-10-01 (8 days ago)
dmi.bios.date: 06/04/2020
dmi.bios.release: 5.12
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1.30
dmi.board.asset.tag: Default string
dmi.board.name: B365M PRO-VDH(MS-7C39)
dmi.board.vendor: Micro-Star International Co., Ltd.
dmi.board.version: 1.0
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 3
dmi.chassis.vendor: Micro-Star International Co., Ltd.
dmi.chassis.version: 1.0
dmi.modalias:
dmi:bvnAmericanMegatrendsInc.:bvr1.30:bd06/04/2020:br5.12:svnMicro-StarInternationalCo.,Ltd.:pnMS-7C39:pvr1.0:rvnMicro-StarInternationalCo.,Ltd.:rnB365MPRO-VDH(MS-7C39):rvr1.0:cvnMicro-StarInternationalCo.,Ltd.:ct3:cvr1.0:skuDefaultstring:pfaDefaultstring:
dmi.product.family: Default string
dmi.product.name: MS-7C39
dmi.product.sku: Default string
dmi.product.version: 1.0
dmi.sys.vendor: Micro-Star International Co., Ltd.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute third-party-packages
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https://bugs.launchpad.net/bugs/2170380
Title:
[amdgpu] HDMI not detected on Radeon RX 570 with kernel
7.0.0-38-generic
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