PCI extended tags regression: 3ware 9650SE-2LP RAID controller not working on AMD Ryzen system

[Bjorn Helgaas]

See https://bugzilla.kernel.org/show_bug.cgi?id=202425.

Robert bisected a problem with a 3ware 9650SE-2LP controller to
60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported") and
verified that reverting it solves the problem.

We have found issues in the past where Root Ports don't handle
extended tags correctly and have added quirks to avoid use of them:

  1b30dfd376e2 ("PCI: Mark Broadcom HT1100 and HT2000 Root Port Extended Tags as broken")
  62ce94a7a5a5 ("PCI: Mark Broadcom HT2100 Root Port Extended Tags as broken")

I don't know yet what Root Ports Robert has, but maybe we need a
similar quirk?

I'm pretty sure Root Ports that don't handle extended tags are out of
spec, so it would be ideal if we could get the manufacturer to provide
an erratum as documentation.

Bjorn