[drm] User-defined mode not supported: "3840x2160"

[thetravellor]

On connecting a Dell P21715q monitor to a raspberry pi 4b 4gb model using an "official" HDMI cable, powered by an "official raspberry pi power supply, the display loads at 4k (3840 x 2160) resolution.

Every time the user interacts with the display and also periodiically, the display blinks on and off.

The drm kernel modul produces the following output each time:

[25575.038256] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25635.026883] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25695.051527] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25755.031481] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25815.069912] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25875.532477] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25936.061468] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5
[25996.542699] vc4-drm gpu: [drm] User-defined mode not supported: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x68 0x5

No "user" mode has been knowlingly selected, all I di was plug in an HDMI cable after installing the OS.

 cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"
NAME="Debian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"
VERSION_CODENAME=bullseye
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

This is te 64bit Raspberry Pi OS build.

cat /boot/config.txt
# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Uncomment this to enable infrared communication.
#dtoverlay=gpio-ir,gpio_pin=17
#dtoverlay=gpio-ir-tx,gpio_pin=18

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

# Automatically load overlays for detected cameras
camera_auto_detect=1

# Automatically load overlays for detected DSI displays
display_auto_detect=1

# Enable DRM VC4 V3D driver
dtoverlay=vc4-kms-v3d
max_framebuffers=2

# Run in 64-bit mode
arm_64bit=1

# Disable compensation for displays with overscan
disable_overscan=1

[cm4]
# Enable host mode on the 2711 built-in XHCI USB controller.
# This line should be removed if the legacy DWC2 controller is required
# (e.g. for USB device mode) or if USB support is not required.
otg_mode=1

[all]

[pi4]
# Run as fast as firmware / board allows
arm_boost=1

[all]
dtoverlay=gpio-fan,gpiopin=14,temp=80000
gpu_mem=64