Raspberry Pi400 limited to 1080p

[vwbusguy]

How did you upgrade to 21.10? (Fresh install / Upgrade) Fresh install

Related Application and/or Package Version (run apt policy $PACKAGE NAME): x11 - xorg 1:7.7+22ubuntu2

Issue/Bug Description: Pop only detects up and allows up to 1080p on a Pi400 when connected to a 1440p monitor. hdmi_enable_4kp60=1 is set in config.txt by default and the higher resolution works with other distros on this monitor. xrandr shows 1920x1028@60 as the highest.

Steps to reproduce (if you know): Fresh install of Pop_OS 21.10 beta, connected to 1440p monitor via hdmi

Expected behavior: Full resolution of monitor up to what the Pi400 and monitor support.

Other Notes:

[vwbusguy]

It appears to be a kernel parameter limiting it:

[    0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=0 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 video=HDMI-A-1:1920x1080M@60 smsc95xx.macaddr=DC:A6:32:DA:EF:22 vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000  dwc_otg.lpm_enable=0 console=tty1 root=LABEL=writable rootfstype=ext4 elevator=deadline rootwait fixrtc

[vwbusguy]

It looks like this might be somehow getting implied incorrectly from the fkms based on https://github.com/raspberrypi/documentation/blob/develop/documentation/asciidoc/computers/configuration/kernel-command-line-config.adoc#display-entries-in-fkms-and-kms-modes

[vwbusguy]

I booted up Ubuntu 21.10 and can confirm that this is a regression for Pop_OS. I get 1440p from Ubuntu 21.10 on the same Pi400 and monitor but only up to 1080p on Pop_OS 21.10 Beta.

[jacobgkau]

It looks like that Ubuntu session is running Wayland. Does Ubuntu have the issue if you choose an Xorg session, and/or does Pop have the issue if you enable Wayland in /etc/gdm3/custom.conf and log into a Wayland session?

[vwbusguy]

I'll try Wayland, but the kernel command line I posted above from dmesg suggests it's an issue before the display server starts. I'll report back after trying x11 on Ubuntu and/or Wayland on Pop.

[vwbusguy]

x11 on Ubuntu 21.10 also works with 1440p:

[vwbusguy]

Wayland didn't make a difference.

In summary, I get 1440p with Wayland and x11 on Ubuntu 21.10. I only get 1080p on Pop_OS with x11 or Wayland.

[vwbusguy]

Good news! I updated recently and now have 1440p.