Set single 6k display on Xorg/Debian with xrandr when not advertised via EDID (example: Dell U3224KB)

6k.sh

#!/bin/bash
# Set up modeline and activate it for DELL U3234KB 6k display
# For a single monitor, easy to modify to set more than one, if you can afford two 6k monitors ...
# Tested on cards capable of 6k @ 60hz using Xorg modesetting and intel drivers
# Set up/etc/X11/xorg.conf.d/20-intel.conf like this per Debian documentation:
#
# Section "Device"
#  Identifier "Intel Graphics"
#  Driver "modesetting"
# EndSection
#
# Optionally, you might use the "intel" driver, or "xe" driver, depending on
# your GPU and your needs
#
#
# Notes
# -----
#   - Specifying -r with cvt is critically important in my case
#   - Specifying --crtc 1 with xrandr is also critically important
#   - Otherwise, nothing special here
#   - It's probably not necessary, but you can also add video=DP-1:6144x3456@60 to grub
#     - Alone, it won't do anything useful
#
# - mzpqnxow
#
# Output
# ------
# $ ./6k
# Getting info from cvt and xrandr ...
#	Current active output:	DP-1
#	Generated new modeline: "6144x3456R"  1344.25  6144 6192 6224 6304  3456 3459 3464 3555 +hsync -vsync
#	New modeline name: "6144x3456R"
#
#  --- Create mode ...
# dry-run: xrandr --newmode "6144x3456R" 1344.25 6144 6192 6224 6304 3456 3459 3464 3555 +hsync -vsync
#  --- Add mode to output DP-1 ...
# dry-run: xrandr --addmode DP-1 "6144x3456R"
#  --- Set mode as active for output DP-1 ...
# dry-run: xrandr --output DP-1 --mode "6144x3456R" --crtc 1
# Success !!
# Resolution set to [email protected] !!
# $
#
set -eu
# Set to 1 to print the commands without running them
DRY_RUN=0
# Monitor parameters for Dell U3224KB 6K display on Intel GPU
hz=60
x=6144
y=3456
crtc=1


if [ $DRY_RUN -ne 0 ]; then
  echo "DRY-RUN MODE !!!"
  xrandr="echo dry-run: xrandr"
else
  xrandr="xrandr"
fi

if [ $(xrandr | grep -c '\sconnected') -ne 1 ]; then
  echo "This only works if you have a single display !!"
  exit 1
fi

printf "Getting info from cvt and xrandr ...\n"

output=$(xrandr | grep '\sconnected' | cut -d ' ' -f 1)
printf "\tCurrent active output:\t%s\n" $output

modeline="$(cvt -r $x $y $hz | grep -Po '^Modeline\s+\K.*')"
printf "\tGenerated new modeline: %s\n" "$modeline"

modename="$(echo $modeline | grep -Po '\".*?\"')"
printf "\tNew modeline name: %s\n\n" $modename

printf " --- Create mode ...\n"
$xrandr --newmode $modeline

printf " --- Add mode to output %s ...\n" "$output"
$xrandr --addmode $output $modename

printf " --- Set mode as active for output %s ...\n" "$output"
$xrandr --output $output --mode $modename --crtc $crtc

if [ $? -eq 0 ]; then
  printf "Success !!\nResolution set to %dx%d@%fhz !!\n" $x $y $hz
else
  printf "Failure !!\nUnable to set resolution to %dx%d@%fhz !!\n" $x $y $hz
fi

In theory you can "simply" generate an EDID blob with a 6k resolution in it, put it into your initramfs, and tell the kernel command-line where to access it. A few problems with that...

1. Few (no?) EDID generation tools support >= 4k resolution, so they produce corrupted output
2. It's really painful looking up exactly how to do this (where exactly to put the blob under /lib/firmware, what kernel commandline parameter to specify, etc.)

Just use xrandr, if it works, count yourself lucky

I went in circles with this for days because of the need for --crtc 1 in xrandr, something I've never had to use before...