On Thu, May 20, 2021 at 05:40:54PM +0000, Deucher, Alexander wrote:

It doesn't really have anything to do with PCI.  The PCI link is just a proxy
for specific AMD platforms.  It's platform firmware behavior we are catering
to.  This was originally posted as an nvme quirk, but during the review it
was recommended to move the quirk into PCI because the quirk is not specific
a particular NVMe device, but rather a set of AMD platforms.  Lots of other
platforms seems to do similar things in the nvme driver based on ACPI or DMI
flags, etc.  On our hardware this nvme flag is required for all cezanne and
renoir platforms.

The quirk was initially presented as specific to the pci root. Does it make
more sense for nvme to recognize the limitation from querying a different
platform component instead of the pci bus?