[Bug 256264] Devices behind PEX 8664 PCIe Switch not detected since 11.0-RELEASE

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256264

            Bug ID: 256264
           Summary: Devices behind PEX 8664 PCIe Switch not detected since
                    11.0-RELEASE
           Product: Base System
           Version: 13.0-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: chris@acsi.ca

Hello,

 SUMMARY:

 I have not been able to upgrade past FreeBSD 10.3 as since versions 11.0 ->
13.0 devices behind my fileserver's PCIe Switch are not detected. The switch
itself is detected, which is a PEX 8664 PCIe Switch, link below. 

 --

 I'm using a Dell M610x blade server, which has a PEX/Broadcom 8664 Switch in
it to provide 2 PCIe slots, which I use to run SAS controllers to a drive
array.

 This arrangement has worked perfectly since the early days of 7/8.0, and I've
pretty much ran each version of FreeBSD since then, until 11.0 came out.

 This is when I could no longer see/detect devices plugged into the PCIe slots.
Things were busy, FreeBSD 10.2 worked well, so it was just left this way for
years.

 Now I do need to upgrade software-wise to 13.0, so I've invested some time
tracking down what is happening, with the hopes that a knowledgeable person can
fix this up. 

 - I have confirmed with 10.3-RELEASE and a 11.0-RELEASE mini-iso boot that the
problem starts in 11.0, and I can confirm it's still an issue in 12.0 and 13.0.
I also boot into a 10.2-RELEASE because I happen to have that handy. 
Everything works/detects fine in 10.3 or lower. 

 - These are GENERIC kernels, fresh from the iso/img I boot from, nothing
custom. 

 - I currently have a 10.2 (or 10.3) boot and a 13.0 boot ready to swap back
and forth to try and isolate / probe info. I'll attach a few lspci dumps after
this message. 

 - The card in question is a LSI 2008 Chipset, mps0 - But it's nothing do do
with that card/brand/config. I have also installed an Intel X540 Network card
in the PCIe slots and find the same issue - There's nothing behind the PEC 8664
in FreeBSD 13.0, and no problems in 10.2. I have also confirmed that 13.0 boots
up and detects the mps0 without issue when I use a different system without the
PEX 8664

 - At some point in my research I came across a similar issue where the
developer mentioned that for some reason they were not scanning behind the
switch. It was a different chipset and issue, and  I don't have that thread
handy at the moment, I will post if I come across it again. 

Ref:
https://www.broadcom.com/products/pcie-switches-bridges/pcie-switches/pex8664

I'm rusty, but fairly knowledgeable and useful if you need me to compile
something, install patches, etc. I could give SSH access, but sending me a
patch to test may be quicker. 

lspci dumps in the next message.

Thanks.

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