In kernel 4.14.59, monitor resolution is detected correctly. In kernels after that, they are not detected correctly.

[Erik Granger]

 dpkg --list | grep linux-image
ii linux-image-4.15.0-36-generic 4.15.0-36.39 amd64 Signed kernel image generic
ii linux-image-4.15.0-38-generic 4.15.0-38.41 amd64 Signed kernel image generic
ii linux-image-generic 4.15.0.38.40 amd64 Generic Linux kernel image
ii linux-image-unsigned-4.14.59-041459-generic 4.14.59-041459.201807280929 amd64 Linux kernel image for version 4.14.59 on 64 bit x86 SMP

Booting from GRUB into 4.14.59 allows my two monitors to run at their native resolution, 2560x1440. Any newer kernel does not allow my two monitors to run at their native resolution, only allowing up to 1920x1200.

uname -a

Linux blackbox 4.14.59-041459-generic #201807280929 SMP Sat Jul 28 09:32:10 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

[Erik Granger (erikgranger)]

Monitors: L24q-20

Graphics card: AMD RX 560

Let me know what other information I should attach, this is my first bug report.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Cristian Aravena Romero (caravena)]

Did this issue start happening after an update/upgrade? Was there a
prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer
to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest
v4.19 kernel[0].

If this bug is fixed in the mainline kernel, please add the following
tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag:
'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as
"Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.19

[Erik Granger (erikgranger)]

Linux blackbox 4.19.0-041900-generic #201810221809 SMP Mon Oct 22 22:11:45 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

When running this kernel, the bug changes but is still present. In arandr, the 2560x1440 resolution is available, however the monitor interprets the signal as 1280x1440, which makes everything look wonky and unreadable. Is this considered the same bug, and should I market as 'kernel-bug-exists-upstream'?

[Cristian Aravena Romero (caravena)]

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 1799613

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'.

[Erik Granger (erikgranger)]

Attached apport

[Kai-Heng Feng (kaihengfeng)]

Does `amdgpu.dc=0` help?

[Erik Granger (erikgranger)]

Where is that configured?

[Erik Granger (erikgranger)]

I think that fixed it.

To add `amdgpu.dc=0`, you must edit your grub configuration

https://askubuntu.com/questions/1029517/amd-rx480-screen-flicker-after-update-to-18-04#1032198

>To do this, edit the file /etc/default/grub, for example using

>sudoedit /etc/default/grub
>Find the line beginning GRUB_CMDLINE_LINUX_DEFAULT and add the text amdgpu.dc=0 between the double quotes (""). Leave any other parameters as they are. For example, you may end up with a line like this:

>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.dc=0"
>Save the file and exit, and then run

>sudo update-grub
>to write the configuration, and reboot.

After doing this, the resolution is detected correctly and appears normal in the 4.15.0-38-generic kernel.

[Kai-Heng Feng (kaihengfeng)]

Please file an upstream bug at [1], Product: DRI, Component: DRM/amdgpu.

[1] https://bugzilla.freedesktop.org

[Cristian Aravena Romero (caravena)]

Hello,

Open bug in launchpad.net
https://bugs.launchpad.net/bugs/1799613

"Booting from GRUB into 4.14.59 allows my two monitors to run at their native resolution, 2560x1440. Any newer kernel does not allow my two monitors to run at their native resolution, only allowing up to 1920x1200."

Best regards,
--
Cristian Aravena Romero (caravena)

[Cristian Aravena Romero (caravena)]

https://bugzilla.freedesktop.org/show_bug.cgi?id=108554
--
Cristian Aravena Romero (caravena)

[Alexdeucher (alexdeucher)]

Please attach your xorg log and dmesg output. Can you bisect?

[Cristian Aravena Romero (caravena)]

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 -p xorg 1799613

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'.

[Daniel van Vugt (vanvugt)]

Cristian, please stop creating upstream bugs for other people.

Some of your bug reports are invalid, and even the valid ones need to be created by the person who was experiencing the bug. Because they are the ones who will need to answer questions and own the upstream bug.

[Andre Klapper (a9016009)]

No further information provided by reporter, hence unfortunately closing as WORKSFORME.

[Erik Granger (erikgranger)]

Hello, I am still having this issue. Adding amdgpu.dc=0 to the grub config "fixes" it, but with the side-effect that startup text is illegible (for some reason). This would make it hard if I ever had to restore my system after a failed launch of the session manager or something like that. I now have an rx590, but the same monitors.

[Erik Granger (erikgranger)]

Hello,

Every time I re-image my computer, I have to frantically search the internet for this bug report to fix this issue. It is now 5 years after the initial bug report, and it is still unfixed. Since then, I've upgraded my CPU and my RAM and swapped out a new video card (still an AMD but a newer fancier 590 instead of that lowly POS 560). I've also bought a house, and had 2 children with an option on a third, I've experienced major life changes, I've laughed, I've cried, and I've grown. Life is full of changes, some for the better and some for the worse, but change is inevitable, it's built into the very nature of our world, but it is good to know that some things never change.

I don't know if I'm the only person on the planet who runs into it, I don't know what amd.dc=0 means, but to celebrate the release of Plasma 6 I ran this fix again. I hope that, in 2 or 4 or 10 years, if I'm still using these same monitors, I'll still run into this issue, and this belief now binds me, grounds me, humbles me, and keeps me oriented. This bug is my North Star. When I have to re-find this thread in order to remember what it is I have to do to work around this issue, I know that the tempest, for a moment, is o'er, and that I am anchored in bug divine.

Maybe one day I'll learn what amd.dc=0 does, and why it needs to be added to grub, but it is not this day.