Bug 205987 - Monitor Modeline missing for ACER XB240H
Summary: Monitor Modeline missing for ACER XB240H
Status: RESOLVED DUPLICATE of bug 201497
Alias: None
Product: Other
Classification: Unclassified
Component: Configuration (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: other_configuration@kernel-bugs.osdl.org
Depends on:
Reported: 2019-12-28 15:55 UTC by chriskoch
Modified: 2020-01-03 19:29 UTC (History)
0 users

See Also:
Kernel Version: All Versions >4.15
Regression: No
Bisected commit-id:


Description chriskoch 2019-12-28 15:55:45 UTC
Steps to reproduce:

When using kernels >4.15 the system is booting into 640x480@60hz
xrandr shows no other available modelines.

Actual Results:

Linux can be used, but the resolution cannot be switched.

Expected Results:

The system should boot into the native resolution of the monitor which is 1920x1080. When executing xrandr all possible modelines should be present.
I think there is a communication error. The DisplayPort cannot read the EDID.


AMD Vega 56 GPU
ACER XB240H 1080x1920@144hz connected via DisplayPort

Additional Information on how to temporarily fix it - add modeline manually:

I booted into a Kernel 4.15 and looked up the current working modeline for my monitor in /var/log/Xorg.0.log

then I executed following commands:
xrandr --newmode "1920x1080X"  325.08  1920 1944 1976 2056  1080 1083 1088 1098 +hsync +vsync
xrandr --addmode DisplayPort-0 1920x1080X
(xrandr --output DisplayPort-0 --mode 1920x1080X)
and the right resolution shows up.

How to boot automatically into the new modeline?
I created /usr/share/X11/xorg.conf.d/10-monitor.conf with following content:
Section "Monitor"
    Identifier "DisplayPort-0"
    Modeline "1920x1080X"  325.08  1920 1944 1976 2056  1080 1083 1088 1098 +hsync +vsync
    Option "PreferredMode" "1920x1080X"

Comment 1 chriskoch 2020-01-03 19:29:30 UTC

*** This bug has been marked as a duplicate of bug 201497 ***

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