Screen goes blank some seconds with KMS DRM on boot and with vlc

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#5,367 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
linux, python, raspberry-pi
Domain
computer-graphics, embedded-iot, operating-systems

Research direction

No source file or test is named. Start by reproducing on a Raspberry Pi 4 with 32-bit Raspberry OS Bullseye using KMS/DRM and the VLC configuration described, then compare FKMS and MMAL behavior. Done means identifying and correcting the boot and VLC display blanking, or establishing the missing evidence needed to diagnose it.

Written by the indexing model from the issue text.

Description

Describe the bug

I am using the newest 32bit Raspberry OS with all updates.
When using KMS my screen goes shortly blank on boot. And also on every start and close of vlc player with "--vout=drm_vout" in python.

If i switch to fkms the screen blanking on boot stops.
if i change vlc to ""--vout mmal_vout"" the screen blanking stops with vlc.

Please tell me if you need more details.

Monitor is a 640x480 5 inch chinese Innolux Display connected over HDMi.

Same behaviour happens with the default chinese HDMI2AV Adapters and connected to any analog Video screen.
Here it is not "blanking" but also loosing connection and showing test image stripes from the adapter.

My normal PC Monitors Samsung and LG do not have this problem.

Have tried many config.txt settings but nothing helps. Seems to be something on load of KSM/DRM. I saw there was an old gamma problem with same behaviour, perhaps it is this again.

Edit: Interesting fact i found today is that hdmi safe mode 1 fails on both ( hdmi screen and hdmi2av adapter ) to display console after boot. Theres is no signal.
But setting the safemode parameters manually works. ( but still with blanking )
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
config_hdmi_boost=4
hdmi_group=2
hdmi_mode=4
disable_overscan=0
overscan_left=24
overscan_right=24
overscan_top=24
overscan_bottom=24

Could it be something safemode sets additionally to this parameters that is not described officicially is doing the blanking ?

Steps to reproduce the behaviour

boot rasperry os and start python vlc player with DRM KMS

Device (s)

Raspberry Pi 4 Mod. B

System

32bit Raspberry OS Bullseye LITE - all newest updates

Logs

No response

Additional context

No response

Dominant language
C
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