EDID not loaded on BalenaOS 6.4 and later

[HakanL]

I have a custom board/display for my Raspberry Pi CM4. It’s worked great for the last two years or so, up until and including Linux kernel 6.1.77-v8 in/around Balena OS 6.4.2. Today I tried to upgrade to BalenaOS 6.4.3+rev1 and now the display on my device isn’t working any longer. I have pinpointed it to the updated Linux kernel in 6.12.1-v8 and it’s probably due to the fact that my hardware doesn’t have an EDID EEPROM chip (it’s a driver chip connected directly to the HDMI output on the CM4 and I’ve had to specify a cmdline.txt option to set the video mode). But now with the latest kernel I’m getting this error in dmesg:

[    0.626997] vc4-drm gpu: [drm] *ERROR* Failed to get ddc i2c adapter by node

followed by a ton of:

[    0.895312] vc4-drm gpu: [drm] HDMI Sink doesn't support RGB, something's wrong.

And the display isn’t working. My application starts up, but I can’t see anything. I’ve tried a variety of ways to set the edid with a custom file, but for the life of me I can’t figure it out. I saw this post:

Where to place edid.dat on Raspberry Pi

In order to get my Raspberry Pi to support my monitor on Raspbian I have to put a edid.dat file into the root of the SD card and then it ends up in /boot once the OS boots. Can anyone advise where should I put the edid.dat file in the resin.io SD card so that it gets used during boot? I’ve tried at the root but that didn’t work.

But it’s either out-dated, or it doesn’t work. I’ve tried to put my edid.dat file in various locations, granted it may not actually be there during boot time, but I figured at least it would be in /mnt/boot since that’s where the cmdline.txt is loaded from, but I still get this in dmesg:

[    1.006250] [drm] Initialized vc4 0.0.0 for gpu on minor 0
[    1.006364] vc4-drm gpu: Direct firmware load for /mnt/boot/edid.dat failed with error -2
[    1.006373] vc4-drm gpu: [drm] *ERROR* [CONNECTOR:33:HDMI-A-1] Requesting EDID firmware "/mnt/boot/edid.dat" failed (err=-2)
[    1.007292] vc4-drm gpu: Direct firmware load for /mnt/boot/edid.dat failed with error -2
[    1.007297] vc4-drm gpu: [drm] *ERROR* [CONNECTOR:33:HDMI-A-1] Requesting EDID firmware "/mnt/boot/edid.dat" failed (err=-2)
[    1.008667] vc4-drm gpu: [drm] HDMI Sink doesn't support RGB, something's wrong.

This is what the section in cmdline.txt looks like: drm.edid_firmware=/mnt/boot/edid.dat.

I don’t know if it’s hard-coded in the kernel to only allow a relative path under /lib/firmware, or what could be the issue?

[HakanL]

@HakanL

vc4-drm gpu: [drm] HDMI Sink doesn't support RGB, something's wrong.

I also opened a Github issue for this as it seems to be a regression from earlier versions and possibly related to a load order change (vs actual kernel change): Regression in BalenaOS 6.4.3: drm.edid_firmware Fails with ENOENT (-2) Due to vc4 Load Before Filesystem Mount · Issue #3635 · balena-os/meta-balena · GitHub

[mpous]

Hello @HakanL thanks for all the details you shared.

Let me ping the OS team to see how we can help you more!

Keep us posted on any progress you make!

[HakanL]

Any update? This prevents me from upgrading the OS and unfortunately with no downgrade option it can brick my devices. I noticed nobody tagged the Github issue I created, is that not the correct way to report issues?