[amdgpu + nvidia PCI passthrough] Screen flickering on ultra wide

Bug #1811863 reported by AlexV
12
This bug affects 2 people
Affects Status Importance Assigned to Milestone
xorg-server (Ubuntu)
New
Undecided
Unassigned
xserver-xorg-video-amdgpu (Ubuntu)
New
Undecided
Unassigned

Bug Description

I'm running 18.04 including all updates on an LG 38WK95C at 3840x1600@75. I'm experiencing constant flickering on screen when setting the refresh rate to 75Hz in settings. When I set to refresh rate to 60Hz, the flicking is gone.

When enabeling freesync in the monitor's settings, the 60Hz isn't available and the only choices are 29.99Hz or 75Hz, which again causes flickering.

This looks like the same issue in bug #1749975.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu7.1
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Tue Jan 15 16:43:10 2019
DistUpgraded: Fresh install
DistroCodename: bionic
DistroVariant: ubuntu
DkmsStatus:
 amdgpu, 18.50-708488, 4.15.0-43-generic, x86_64: installed
 nvidia, 415.25, 4.15.0-29-generic, x86_64: installed
 nvidia, 415.25, 4.15.0-43-generic, x86_64: installed
ExtraDebuggingInterest: Yes
GraphicsCard:
 NVIDIA Corporation Device [10de:1f02] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: Micro-Star International Co., Ltd. [MSI] Device [1462:3734]
 Advanced Micro Devices, Inc. [AMD/ATI] Polaris12 [1002:699f] (rev c7) (prog-if 00 [VGA controller])
   Subsystem: Micro-Star International Co., Ltd. [MSI] Lexa PRO [Radeon RX 550] [1462:8a90]
InstallationDate: Installed on 2019-01-02 (12 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-43-generic root=UUID=9ac85046-be6e-411d-a51c-10b221c750d0 ro splash quiet iommu=1 amd_iommu=on vt.handoff=1
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/18/2018
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P1.80
dmi.board.name: B450 Pro4
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.80:bd12/18/2018:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnB450Pro4:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.91-2
version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.5-0ubuntu0~18.04.1
version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.5-0ubuntu0~18.04.1
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4.2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2

Revision history for this message
AlexV (alexver) wrote :
affects: xorg (Ubuntu) → xorg-server (Ubuntu)
summary: - Screen flickering on ultra wide
+ [amdgpu + nvidia PCI passthrough] Screen flickering on ultra wide
tags: added: amdgpu nvidia radeon
Revision history for this message
Daniel van Vugt (vanvugt) wrote :

According to your XorgLog.txt it looks like the choice of 75Hz is coming from the AMDGPU driver:

[ 97.816] (II) AMDGPU(0): Modeline "3840x1600"x75.0 566.25 3840 4016 4104 4400 1600 1607 1617 1716 +hsync -vsync (128.7 kHz eP)

However the AMDGPU driver is also confused by the monitor's aspect ratio, which might be the problem:

[ 97.816] (WW) AMDGPU(0): Output HDMI-A-0: Strange aspect ratio (879/366), consider adding a quirk
[ 97.816] (WW) AMDGPU(0): Output HDMI-A-0: Strange aspect ratio (879/366), consider adding a quirk
[ 97.816] (WW) AMDGPU(0): Output HDMI-A-0: Strange aspect ratio (879/366), consider adding a quirk

Does the same monitor work when plugged into an Intel or Nvidia GPU?

Changed in xorg-server (Ubuntu):
status: New → Incomplete
Changed in xserver-xorg-video-amdgpu (Ubuntu):
status: New → Incomplete
Revision history for this message
AlexV (alexver) wrote :

The monitor works fine when plugged in the Nvidia GPU or when booting the same hardware in Windows 10.

Revision history for this message
Launchpad Janitor (janitor) wrote :

[Expired for xorg-server (Ubuntu) because there has been no activity for 60 days.]

Changed in xorg-server (Ubuntu):
status: Incomplete → Expired
Revision history for this message
Launchpad Janitor (janitor) wrote :

[Expired for xserver-xorg-video-amdgpu (Ubuntu) because there has been no activity for 60 days.]

Changed in xserver-xorg-video-amdgpu (Ubuntu):
status: Incomplete → Expired
Changed in xserver-xorg-video-amdgpu (Ubuntu):
status: Expired → New
Changed in xorg-server (Ubuntu):
status: Expired → New
Revision history for this message
Markus Strenn (markus-strenn) wrote :

I have the flickering problem with 2560x1440 screens, AMD Radeon RX 550.
tried it on two screens: asus and samsung. asus is capable of freesync, samsung not. asus can handle higher frequency, samsung 50Hz only.

On samsung it works without any problems. On asus monitor I have the same flickering problem on 75Hz, switching down to 60Hz solves the problem.

I'm on Ubuntu 18.10, kernel 4.18.0-16. - with very intense flickering.
Upgraded to 5.0.2 kernel manually, seems like flickering is a little bit better.

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