Re: [Bug 215925] New: PCIe regression on Raspberry Pi Compute Module 4 (CM4) breaks booting

[Bjorn Helgaas <bjorn.helgaas@gmail.com>]

On Sat, Apr 30, 2022 at 2:53 PM <bugzilla-daemon@kernel.org> wrote:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=215925
>
>             Bug ID: 215925
>            Summary: PCIe regression on Raspberry Pi Compute Module 4 (CM4)
>                     breaks booting
>            Product: Drivers
>            Version: 2.5
>     Kernel Version: v5.17-rc1
>           Hardware: ARM
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: PCI
>           Assignee: drivers_pci@kernel-bugs.osdl.org
>           Reporter: kibi@debian.org
>         Regression: No
>
> Catching up with latest kernel releases in Debian, it turned out that my
> Raspberry Pi Compute Module 4, mounted on an official Compute Module 4 IO
> Board,
> and booting from an SD card, no longer boots: this means a black screen on the
> HDMI output, and no output on the serial console.
>
> Trying various releases, I confirmed that v5.16 was fine, and v5.17-rc1 was the
> first (pre)release that wasn't.
>
> After some git bisect, it turns out the cause seems to be the following commit
> (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=830aa6f29f07a4e2f1a947dfa72b3ccddb46dd21):
>
> ```
> commit 830aa6f29f07a4e2f1a947dfa72b3ccddb46dd21
> Author: Jim Quinlan <jim2101024@gmail.com>
> Date:   Thu Jan 6 11:03:27 2022 -0500
>
>     PCI: brcmstb: Split brcm_pcie_setup() into two funcs
> ```
>
> Starting with this commit, the kernel panics early (before 0.30 seconds), with
> an `Asynchronous SError Interrupt`. The backtrace references various
> `brcm_pcie_*` functions; I can share a picture or try and transcribe it
> manually if that helps (nothing on the serial console…).
>
> This commit is part of a branch that was ultimately merged as
> d0a231f01e5b25bacd23e6edc7c979a18a517b2b; starting with this commit, there's
> not even a backtrace anymore, the screen stays black after the usual “boot-up
> rainbow”, and there's still nothing on the serial console.
>
> I confirmed that 88db8458086b1dcf20b56682504bdb34d2bca0e2 (on the master side)
> was still booting properly, and that 87c71931633bd15e9cfd51d4a4d9cd685e8cdb55
> (from the branch being merged into master) is the last commit showing the
> panic.
>
> Since d0a231f01e5b25bacd23e6edc7c979a18a517b2b is a merge commit that includes
> conflict resolutions in drivers/pci/controller/pcie-brcmstb.c, I suppose this
> could be consistent with the initial panic being “upgraded” into an even more
> serious issue.
>
> I've also verified that latest master (v5.18-rc4-396-g57ae8a492116) is still
> affected by this issue.
>
> The regular Raspberry Pi 4 B doesn't seem to be affected by this issue: the
> exact same image on the same SD card (with latest master) boots fine on it.