Re: [PATCH v4 1/2] usb: xhci-pci: add AMD Promontory 21 PCI glue

[Jihong Min <hurryman2212@icloud.com>]

On 5/9/26, Mario Limonciello wrote:
 > Promontory 21 is only on AMD platforms and AMD platforms are only x86.
 > I think the Kconfig should be conditional on AMD CPU support being
 > enabled and X86 architecture so that we don't bloat other architectures
 > with dead code that will never run.

I agree with limiting this to x86, and I changed the current branch in that
direction.

One detail I would like to double-check is whether CPU_SUP_AMD should 
also be
part of the dependency, or whether X86 alone would be more accurate for the
PCI glue.

The PROM21 xHCI function is still a PCI device. I found one public 
example of
a B650/PROM21-based PCIe add-in card design which is reported to work in 
both
AMD and Intel systems:

https://www.tomshardware.com/pc-components/chipsets/pcie-card-unlocks-amd-chipset-power-on-intel-motherboards-or-you-can-turn-any-b650-motherboard-into-an-x670-one

That is clearly a niche/community hardware case, not a normal AMD platform,
and I do not want to over-weight it. But it made me wonder if:

   depends on X86

would be the more accurate dependency than:

   depends on X86 && CPU_SUP_AMD

for a PCI-attached PROM21 xHCI controller. The option would still use:

   default USB_XHCI_PCI

and the hwmon sensor driver would still stay behind its own
SENSORS_PROM21_XHCI option.

I am fine keeping CPU_SUP_AMD if you prefer; I just wanted to check before
locking that part in for v5.

Sincerely,
Jihong Min