RPI 4 HDMI video output flickering

Troubleshooting
1

Required Information

  • DietPi version: v8.12.1
  • Distro version: Debian GNU/Linux 11 (bullseye)
  • Kernel version: Linux DietPi 5.15.76-v8+ #1597 SMP PREEMPT Fri Nov 4 12:16:41 GMT 2022 aarch64 GNU/Linux
  • SBC model: RPi 4 Model B (aarch64)
  • Power supply used: 5V 3A
  • SD card used: SanDisk ultra 16 GB

Additional Information (if applicable)

Steps to reproduce

1.Turn on the RPI4
2. Turn on Monitor
3. Flickering screen

Expected behaviour

No flickering

Actual behaviour

the video output started flickering out of the blue. I don’t know if it is a hardware issue, but I suspect it is system related. If I use another SD card that I have with OSMC, it works fine. Monitor is a Samsung 1080p. I tried all 1080p resolution on dietpi-config with not luck. Also tried to add HDMI_BOOST=7 in boot/config.txt. Tried different HDMI cables. Nothing can make it stop the flickering.

2

Does it make a difference when you enable/disable KMS, either via dietpi-config or adding/commenting a line in /boot/config.txt

dtoverlay=vc4-kms-v3d
3

Thank you for your response.
Yes, changing to the vc4-kms-v3d driver make the flickering stop, but also change the resolution. The image look stretched and neofetch shows that the resolution is 1152x864

4

You can try to change the resolution in the Display Option menu with dietpi-config.

1 Like
5

I had tried this before without success. For some reason I don’t know, it worked now. Thanks

6

The problem is that KMS and resolution are currently mixed in the resolution menu, so KMS is always 1080p and everything else is always non-KMS, which ia bad and there is no reason for this. We need to change this, have a dedicated legacy vs fKMS vs KMS toggle and the resolution menu independently of this.

Means for now it’s beat to choose resolution first, then KMS manually, or resolution manually as well.