[Bug 2128161] Re: pi-kernel VC4-KMS not working with CM5

[Justin Ayers]

Thank you for such a quick response. I have tried your suggestion in
comment 5 above. However, the shortened overlay name (vc4-pi5) did NOT
resolve the issue on my system. I can see on the display if I do a power
cycle that when it reads from the NVME and reads the config.txt file it
does use the shortened vc4-pi5.dtbo

Your bootloader logs show "Loaded overlay 'vc4-pi5'" at 7.27 seconds,
which is great - the overlay loaded from the bootloader's perspective.

Can you verify that you are using Ubuntu Core 24 and the snaps are
stable? Didn't know if maybe you were on an edge version or not

However, after my system boots with dtoverlay=vc4-pi5,cma-128:
- ALL device tree nodes still show status="disabled"
- /dev/dri/ does not exist
- vc4 module loads but never binds (usage count = 0)
- dmesg has ZERO vc4 messages
- ubuntu-frame still fails with "No DRM devices detected"

Questions:
1. On YOUR system with the vc4-pi5 overlay, what does this show?
```
   cat /sys/firmware/devicetree/base/soc/hdmi at 7ef00700/status
   ls -la /dev/dri/
   lsmod | grep vc4
```

2. Does your system actually have working graphics/ubuntu-frame with
this workaround?

3. Is the vc4-kms-v3d-pi5.dtbo file in pi-kernel 1047 known to create
disabled device tree nodes? Should it set status="okay" by default?

Without vclog available on Ubuntu Core, I cannot verify if the
bootloader actually loaded the overlay on my system, but even if it did,
the nodes remain disabled.

Could this be a bug in the overlay file itself, rather than just the
path length issue?

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https://bugs.launchpad.net/bugs/2128161

Title:
  pi-kernel VC4-KMS not working with CM5

Status in canonical-kernel-snaps:
  Invalid
Status in linux-raspi package in Ubuntu:
  Invalid
Status in rpi-eeprom package in Ubuntu:
  New

Bug description:
  Hello!

  After switching from PI4B to CM5 on core24 stopped working vc4 driver.
  PiOS (trixie) working with CM5 too.

  On Raspberry Pi 4B by sudo dmesg | grep vc4:

  [ 3.496362] vc4-drm gpu: bound fe400000.hvs (ops vc4_hvs_ops [vc4])
  [ 3.500184] rc rc0: vc4-hdmi-0 as /devices/platform/soc/fef00700.hdmi/rc/rc0
  [ 3.500322] input: vc4-hdmi-0 as /devices/platform/soc/fef00700.hdmi/rc/rc0/input0
  [ 3.506345] input: vc4-hdmi-0 HDMI Jack as /devices/platform/soc/fef00700.hdmi/sound/card0/input1
  [ 3.507075] vc4-drm gpu: bound fef00700.hdmi (ops vc4_hdmi_ops [vc4])
  [ 3.512241] rc rc1: vc4-hdmi-1 as /devices/platform/soc/fef05700.hdmi/rc/rc1
  [ 3.512368] input: vc4-hdmi-1 as /devices/platform/soc/fef05700.hdmi/rc/rc1/input2
  [ 3.518685] input: vc4-hdmi-1 HDMI Jack as /devices/platform/soc/fef05700.hdmi/sound/card1/input3
  [ 3.518919] vc4-drm gpu: bound fef05700.hdmi (ops vc4_hdmi_ops [vc4])
  [ 3.519244] vc4-drm gpu: bound fe004000.txp (ops vc4_txp_ops [vc4])
  [ 3.519461] vc4-drm gpu: bound fe206000.pixelvalve (ops vc4_crtc_ops [vc4])
  [ 3.519618] vc4-drm gpu: bound fe207000.pixelvalve (ops vc4_crtc_ops [vc4])
  [ 3.519762] vc4-drm gpu: bound fe20a000.pixelvalve (ops vc4_crtc_ops [vc4])
  [ 3.519870] vc4-drm gpu: bound fe216000.pixelvalve (ops vc4_crtc_ops [vc4])
  [ 3.520029] vc4-drm gpu: bound fec12000.pixelvalve (ops vc4_crtc_ops [vc4])
  [ 3.527520] [drm] Initialized vc4 0.0.0 20140616 for gpu on minor 0
  [ 3.528322] vc4-drm gpu: [drm] Cannot find any crtc or sizes
  [ 3.530767] vc4-drm gpu: [drm] Cannot find any crtc or sizes
  [ 3.531094] vc4-drm gpu: [drm] Cannot find any crtc or sizes

  On Compute module 5 vc4 not loading (sudo dmesg | grep vc4 empty, sudo
  dmesg | grep fb):

  [ 7.050579] bcm2708_fb soc:fb: Unable to determine number of FBs. Disabling driver.
  [ 7.058623] bcm2708_fb: probe of soc:fb failed with error -2

  Two boards have (snap list):

  Name Version Rev Tracking Publisher Notes
  console-conf 24.04.1+git45g5f9fae19+g7598200 80 24/stable canonical** -
  core24 20250829 1197 latest/stable canonical** base
  mesa-2404 24.2.8-snap185 917 latest/stable canonical** -
  pi 24-3 151 24/stable canonical** gadget
  pi-kernel 6.8.0-1039.43 1047 24/stable canonical** kernel
  snapd 2.71 25205 latest/stable canonical** snapd
  ubuntu-frame 211-mir2.20.1 12494 24/stable canonical** -

  Linux kernel:

  Linux localhost 6.8.0-1039-raspi #43-Ubuntu SMP PREEMPT_DYNAMIC Tue
  Sep 9 12:15:05 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux

  config.txt:

  dtoverlay=vc4-kms-v3d

  Is there a solution to make VC4-KMS work on core24?

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