Pi5: Dual HDMI EDID detection fails during boot - displays work individually but not simultaneously

Start by reproducing the dual-monitor setup on a Raspberry Pi 5 and inspect the DRM EDID paths for HDMI-A-1 and HDMI-A-2 under /sys/class/drm, comparing the result with wlr-randr. Review the supplied boot parameters in /boot/firmware/cmdline.txt and the raspinfo output; done means dual displays are detected at boot with valid EDID data without forcing firmware EDIDs.

Describe the bug

I have an rpi5 (2gb), with latest trixie based rpi os on it.

I wanted to connect two screens to it, but it didn't work. Interestingly: any screen works in any port, but not together.

After long hours of research and trial and error I figured out the solution, but i do think there is a bug somewhere.

So the symptoms are that if both screens connected, the second one wouldn't even show up in wlr-randr, or if you mess around with the video= parameters, you get it up, and reported as connected, but all edid data will be null.

So my solution was this:

• sudo mkdir -p /lib/firmware/edid
• Connect one monitor, extract the edid: sudo cat /sys/class/drm/card1-HDMI-A-2/edid > /lib/firmware/edid/1920x1080.bin
• Add this to /boot/firmware/cmdline.txt: video=HDMI-A-1:1920x1080@60e video=HDMI-A-2:1920x1080@60e drm.edid_firmware=HDMI-A-1:edid/1920x1080.bin,HDMI-A-2:edid/1920x1080.bin

So this seems to bypass all edid related bugging and forces the outputs to be configured according to the specified edid binary.

Steps to reproduce the behaviour

Connect two screens at the same time. I don't know if it has anything to do with me connecting two blackmagick bididrectional sdi converters or not.

Device (s)

Raspberry Pi 5

System

ccpadmin@avpi:~ $ raspinfo | pastebinit
https://pastebin.com/bVu2JTx9
ccpadmin@avpi:~ $ cat /etc/rpi-issue
Raspberry Pi reference 2025-10-01
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7dadcf1fc5ce1648ab09409ab978831690c9a955, stage4
ccpadmin@avpi:~ $ vcgencmd version
2025/05/08 15:13:17
Copyright (c) 2012 Broadcom
version 69471177 (release) (embedded)
ccpadmin@avpi:~ $ uname -a
Linux avpi 6.12.47+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.47-1+rpt1 (2025-09-16) aarch64 GNU/Linux

Logs

No response

Additional context

No response