Ubuntu 18.04, all the x, libdrm, kernel, etc. packages up to date. KDE.
When waking the displays from sleep with 4.15 any display not yet fully woken up seem to be reported as disconnected. This happens both when waking the whole computer from sleep (systemctl suspend) or just the displays themselves (due to me not touching mouse+keyboard for a while).
Setup:
Radeon RX 560
Primary display: bottom right, displayport, on
Secondary display 1: left, hdmi, on
Secondary display 2: top right, dvi, off
Video of how it should work, using 4.4.15: https://www.youtube.com/watch?v=h7nMYbm5ZxU
Note how even though the left (secondary) display wakes up first, both instantly display their proper desktops.
Video of how it works with the current default kernel (and 4.16.7 from kernel-ppa/mainline): https://www.youtube.com/watch?v=VdVFNXPszSI
Note how when the left (secondary) display wakes up first, KDE decides that this is probably the only display available, so tries to switch the primary desktop to it, then a split second later the bottom right wakes up and KDE knows *that* should be the primary according to the config, so it switches back.
My interpretation is that KDE thinks the bottom right display slowly waking up is actually off, so it does the reasonable thing and uses the other available one as primary.
One way or the other, that's not how it used to work in older kernels, so as far as I'm concerned it's a regression.
---
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: mmazur 2270 F.... pulseaudio
/dev/snd/controlC1: mmazur 2270 F.... pulseaudio
CurrentDesktop: KDE
DistroRelease: Ubuntu 18.04
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
Package: linux (not installed)
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-20-generic root=UUID=d170afa1-e8de-4480-a0d7-4a4e8e304caf ro amdgpu.dc_log=1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
RelatedPackageVersions:
linux-restricted-modules-4.15.0-20-generic N/A
linux-backports-modules-4.15.0-20-generic N/A
linux-firmware 1.173
RfKill:
1: hci0: Bluetooth
Soft blocked: no
Hard blocked: no
Tags: bionic
Uname: Linux 4.15.0-20-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm bacula cdrom dip docker libvirt libvirtd lpadmin plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 04/29/2016
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P2.10
dmi.board.name: Z97E-ITX/ac
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.:bvrP2.10:bd04/29/2016:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnZ97E-ITX/ac: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.
This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:
apport-collect 1770836
and then change the status of the bug to 'Confirmed'.
If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.
This change has been made by an automated script, maintained by the Ubuntu Kernel Team.