Bugzilla – Bug 1218732
Lenovo T14 external monitor aliasing at monitor resolution
Last modified: 2024-03-02 12:49:50 UTC
Created attachment 871784 [details] Photo of display issues at 1920x1080 resolution I have a Lenovo Thinkpad T14 and am having trouble displaying properly on a Samsung SyncMaster P2770HD monitor. lspci | grep -i vga 00:02.0 VGA compatible controller: Intel Corporation Alder Lake-UP3 GT2 [Iris Xe Graphics] (rev 0c) The native resolution of the T14 built-in monitor is 1920x1200 (16:10 aspect ratio). The P2770HD is native 1920x1080 (16:9 aspect ratio). I am displaying only on one monitor due to https://bugzilla.opensuse.org/show_bug.cgi?id=1211975 The P2770HD displays fine with 1680x1050 resolution (16:10). When I set the P2770HD to its native 1920x1080 resolution, it looks like I am displaying a 1920x1080 window scaled from a 1920x1200 screen; the bottom of the screen is cutoff and there is aliasing. See attachment. I cannot screen capture this behavior with the KDE Spectacle program. When I screen capture, the result looks normal, not what is actually displayed on screen.
It appears to me rather like a desktop-specific issue, not the kernel / driver problem. Is it a KDE Wayland session?
KDE System Settings says: Graphics Platform: X11
OK, it's X11, then easier to debug. What does xrandr output show up? And what if you choose the resolution manually via xrandr command? Still resulting in the cut-off and/or aliasing?
Created attachment 871985 [details] xrandr output with 1680x1050 resolution
Created attachment 871986 [details] xrandr output with 1920x1080 resolution
Correction: when displaying with 1920x1080 resolution on the external monitor, the screen is cutoff on both the left and the bottom. Choosing resolution with xrandr appears equivalent to changing the KDE settings; the screen is cutoff both on left and bottom, and there is aliasing.
(In reply to Matthew Mah from comment #6) > Correction: when displaying with 1920x1080 resolution on the external > monitor, the screen is cutoff on both the left and the bottom. > > Choosing resolution with xrandr appears equivalent to changing the KDE > settings; the screen is cutoff both on left and bottom, and there is > aliasing. And is the displayed size really 1920x1080, too? That is, the actually displayed isn't 1920x1080? Also, can you try other monitor to see whether it's a monitor-specific problem or not?
> And is the displayed size really 1920x1080, too? That is, the actually displayed isn't 1920x1080? I don't understand the question. I found an LG 27UK650 with 3840x2160 resolution that seems to display fine with either 3840x2160 or 1920x1080 resolution. I know I had a Lenovo laptop running Tumbleweed running able to drive this Samsung SyncMaster P2770HD monitor at native resolution at some point previously. I am not sure whether it was the same laptop hardware.
My question is whether the displayed area really matches with the expectation; i.e. it's 1920x1080 pixels are shown but it doesn't fit to the monitor, or is another size displayed actually? I guess the former, but it's hard to judge. If so, the next step is to identify whether it's a problem of the laptop (and the GPU driver) or it's the problem of the monitor. If you have another machine (with a different GPU) and you can check with this monitor, it'd be helpful. (Or check with another monitor that have the same resolution.) Last but not least, please boot with boot options "drm.debug=0x1e log_buf_len=16M", and get the dmesg output after configuring for the monitor. Compress the output and upload to Bugzilla. It'll show what GPU drivers are trying to do.
I have checked a second monitor, a SyncMaster B2230HD with 1920x1080 resolution, and it displays fine at this resolution. How do I set boot options with UEFI and grub? For this grub interface, there is no direct boot options box, and entering the options into the bottom of the boot script appears to do nothing.
(In reply to Matthew Mah from comment #10) > I have checked a second monitor, a SyncMaster B2230HD with 1920x1080 > resolution, and it displays fine at this resolution. > > How do I set boot options with UEFI and grub? For this grub interface, there > is no direct boot options box, and entering the options into the bottom of > the boot script appears to do nothing. On the GRUB boot, press 'e', and the dialog to edit the GRUB config will appear. Move the cursor via cursor keys and add/remove the options in the line definining "linux /boot/vmlinuz-....". Then continue to boot with ctrl-x or F10 key.
Created attachment 872946 [details] gzipped dmesg This is the requested dmesg log with kernel boot parameters modified. The resolution is initially set to display at 1680x1050, then is set to the 1920x1080 resolution where aliasing occurs.
Thanks. Any chance to get the similar dmesg with the debug option for another good-working monitor (with the same resolution)? Then we may compare what made difference. We may compare the EDID between them, too.
Created attachment 873183 [details] gzipped dmesg for working external 1920x1080 monitor This is the dmesg output for a working (no aliasing) external 1920x1080 Samsung B2230HD monitor.