[Bug 2099935] Re: PCI initialization failure following kernel panic reboot on Raspberry Pi CM4

[Jürg Häfliger]

** Tags added: kernel-daily-bug

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Title:
  PCI initialization failure following kernel panic reboot on Raspberry
  Pi CM4

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

Bug description:
  Ubuntu Server 24.10 
  Linux ubuntu 6.11.0-1004-raspi #4-Ubuntu SMP PREEMPT_DYNAMIC Fri Sep 27 22:25:34 UTC 2024 aarch64 aarch64 aarch64 GNU/Linux

  We're seeing that following a kernel panic and reboot, the PCI fails
  to initialize correctly and associated  devices (such as Wi-Fi card)
  are not available.

  Issue Description:
  •	On the first boot, everything works correctly.
  •	However, after a Kernel Panic, the device reboots, but PCIe does not reset or re-initialize properly.
  •	When this happens:
  o	The Wi-Fi card is not recognized.
  o	The lspci command shows no PCI devices.
  o	The dmesg log includes the message:

  [    0.591441] brcm-pcie fd500000.pcie: link down

  •	A soft reboot does not fix the issue.
  •	The only way to recover is to completely remove and reconnect power (hard reboot).

  
  We have tried modifying /boot/firmware/config.txt and /boot/firmware/cmdline.txt, which has reduced but not fully resolved the issue.

  How to Reproduce The Problem:
  1.	Power up the hardware
  2.	Run ‘lspci’ – observe the result includes the PCI Bridge and Wi-Fi card
  3.	Trigger a kernel panic with the command ‘echo c | sudo tee /proc/sysrq-trigger’, causing a reboot
  4.	Run ‘lspci’ – observer the output is now empty

  
  The same issue does not occur on Raspberry Pi OS - it seems to be specific to Ubuntu.

  Any assistance/guidance on how to troubleshoot this would be much
  appreciated!

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