Dietpi Rock Pi 4 B - Screens Not Detected

Troubleshooting
1

Creating a bug report/issue

I have searched the existing open and closed issues and find nothing useful

Required Information

  • DietPi version |
  • G_DIETPI_VERSION_CORE=9
    G_DIETPI_VERSION_SUB=12
    G_DIETPI_VERSION_RC=1
    G_GITBRANCH=‘master’
    G_GITOWNER=‘MichaIng’
  • Distro version | bullseye
  • Kernel version | Linux DietPi 6.12.25-current-rockchip64 #1 SMP PREEMPT Fri Apr 25 08:48:08 UTC 2025 aarch64 GNU/Linux
  • Architecture | arm64
  • SBC model |ROCK 4 (aarch64) [rock pi 4 b, Exactly]
  • Power supply used | Usb Type C cable connected to my pc but it was same when it plugged to powerbank
  • SD card used | SanDisk ultra 32gb

Additional Information (if applicable)

  • Software title |
  • Bug report ID |

Steps to reproduce

  1. Open up SBC
  2. Plug the screen (both 4 inch and 7 inch hdmi screen are not detected)
  3. Nothing happened???

Expected behaviour

  • Should detecting screen and screen should be showing desktop???

Actual behaviour

Screens are not detecting, also when I configure a resolution in dietpi-config (actual screen resolution, 800x480), System don’t care about that and just using standart resolution like 1920x1080 (and screen is just 4 inch, so it not like 1920x1080…)
Interesting thing is I actually look to dietpienv, my screen resoluyion is written here like I writed!
But when I enter dietpi-config and display, it says 1920x1080
So, I think dietpi not reading dietpiEnv screen resolution?

rootdev=UUID=177e9bbe-c7e3-4471-a255-c0e431d81507
rootfstype=ext4

The init system logs to the console defined last.

consoleargs=console=tty1
usbstoragequirks=
extraargs=net.ifnames=0 video=HDMI-A-1:800x480,rotate=90
docker_optimizations=on
overlay_path=rockchip
overlay_prefix=rockchip
overlays=
user_overlays=
dtoverlay=vc4-fkms-v3d (that command was something I see on this forum that solve problem but did absolute nothing, maybe I put this in wrong place)

resim
resim840×325 7.97 KB

Yea, Its both not reading my resolution input and disabled display

Extra details

xrandr command says just “can’t display” No error message, nothing.
We have a problem houston

2

Hey mate. First of all, does it change something whether you plug the HDMI display before boot, or after boot?

Are there other displays listed? There are so many ROCK 4 variants, not sure whether some have 2 HDMI or analogue video output. … ah the ROCK 4C+ has dual HDMI, the ROCK 4B should have not.

The supported resolutions are read from /sys/class/drm/card?-HDMI-A-1/modes (in this case), filled by the driver from information derived from the hardware itself, which should of course not list resolutions not supported. So indeed weird that it offers 1080p for a 800x480 native display. Are there more modes above native shown in the list, respectively when reading that API?

cat /sys/class/drm/card?-HDMI-A-1/modes

So far we assume the first line to be the currently selected resolution. But the API is not well documented, and there are still things we need to find out, hence the beta status of this (new) tool.

However, what might be the actual reason for the black screen is that it is disabled. See bottom option. This is read from:

cat /sys/class/drm/card?-HDMI-A-1/enabled

This is also not reflected in your cmdline entry video=HDMI-A-1:800x480,rotate=90. To disable video device, there would need to be a “d” after the mode, i.e. video=HDMI-A-1:800x480d,rotate=90. If there is none, it should be enabled automatically, if connection is detected. Can you verify that this is detected correctly?

cat /sys/class/drm/card?-HDMI-A-1/status

It should be however not listed at all in dietpi-display if not connected. There is a way to override that autodetection and force it to be enabled. Please try to adjust your /boot/dietpi.txt to add an “e”:

extraargs=net.ifnames=0 video=HDMI-A-1:800x480e,rotate=90

In any case, falsely detected connection state and supported modes indeed means there is a connectivity issue, or the displays give weird data the driver cannot handle correctly.

Please check for kernel errors as well. powering an RK3399 with HDMI screen attached via PC USB or powerbank does not sound reliable. I’d use a proper PSU meant to provide stable voltage to run devices, not for charging. Maybe the kernel is showing related undervoltage warnings:

dmesg -l 0,1,2,3

This is only valid for Raspberry Pi in another config file. It has no effect in /boot/dietpiEnv.txt, at best remove that line again.

For reference, the Linux documentation for setting modes: modedb default video mode support — The Linux Kernel documentation