DisplayPort on Radeon HD 5770 not working for 3440x1440 display
Submitted by Robin
Assigned to xf86-video-ati maintainers
Created attachment 127797
Output of: journalctl -b _COMM=gdm-x-session
I recently bought a DisplayPort KVM switch to be able to easily alternate between my laptop and desktop when hooked up to a LG 35UC87C monitor.
I had previously been running this without any problems on Fedora 22 using the HDMI connection to my Radeon HD5770. However, I got only a blank screen when I switched to using the DisplayPort connection.
I decided to update to Fedora 24 before doing anything else and ended up doing this as a fresh install on the root drive after somehow messing up the upgrade (home and data disks are separate).
Currently it works correctly if hooked up to the HDMI cable.
It works correctly with the DisplayPort cable under Windows (ie. this is not a hardware fault)
If attached to the DisplayPort it works if I have nomodeset on the kernel line - but of course only at low resolution.
If I put radeon.modeset=1 on the kernel line it blanks almost immediately after booting starts.
If I add a second monitor to the HDMI cable I can see the Xserver starts and is correctly spreading itself across both monitors, just the LG monitor is blank.
The LG monitor is being correctly detected as shown by the output of xrandr:
Screen 0: minimum 320 x 200, current 5360 x 1440, maximum 8192 x 8192
DisplayPort-0 connected primary 3440x1440+1920+0 (normal left inverted right x axis y axis) 800mm x 335mm
3440x1440 59.97*+ 49.99 29.99
1920x1080 60.00 59.94
1280x720 60.00 59.94
720x480 60.00 59.94
640x480 60.00 59.94
HDMI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm
1920x1080 60.00*+ 50.00 59.94
1920x1080i 60.00 50.00 59.94
1280x1024 75.02 60.02
1280x720 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
1440x480 60.00 59.94
800x600 72.19 75.00 60.32 56.25
720x480 60.00 59.94
640x480 75.00 66.67 60.00 59.94
DVI-0 disconnected (normal left inverted right x axis y axis)
DVI-1 disconnected (normal left inverted right x axis y axis)
If I use the "Display Configuration" interface in KDE and lower the resolution to 2560x1080 then it turns on. However I can't find any way of getting it to display at the full resolution of 3440x1440 - it always just blanks and the monitor says it has no signal.
lspci output is:
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Juniper XT [Radeon HD 5770]
/var/log/Xorg.0.log doesn't seem to be up to date so I've attached the output of
journalctl -b _COMM=gdm-x-session
Attachment 127797, "Output of: journalctl -b _COMM=gdm-x-session":