From the logs and the code, the driver times out after 200ms waiting for
the PCIe link to come up. We could extend that time but I doubt that's
going to help given that when the link does come up it comes up fairly
quickly, long before the timeout.

BAD:
[    0.361545] pci_bus 0000:01: supply vpcie12v not found, using dummy regulator
[    0.606763] brcm-pcie fd500000.pcie: link down

GOOD:
[    0.347484] pci_bus 0000:01: supply vpcie12v not found, using dummy regulator
[    0.451325] brcm-pcie fd500000.pcie: clkreq-mode set to default
[    0.453464] brcm-pcie fd500000.pcie: link up, 5.0 GT/s PCIe x1 (SSC)

It's possible that the driver violates the PCI spec. I need to dig
through the reset sequence. There are also some settings that change the
reset behavior that we could explore. Not sure if that helps or matters.
Also, maybe it's possible to limit the link to 2.5 GT/s to check if that
makes it more stable.

Can you attach the output of `sudo lspci -vvv` for a good and a bad
state to the bug?

And what's the output of `sudo vcgencmd bootloader_config`?

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https://bugs.launchpad.net/bugs/2099935

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

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