Re: [PATCH] PCI/ASPM: Should not report ASPM support to BIOS if FADT indicates ASPM is unsupported

Matthew Garrett
2022-07-15T08:29:56Z

On Fri, Jul 15, 2022 at 03:40:36PM +0800, Manyi Li wrote:

> Please see the details of this issus:
> https://bugzilla.kernel.org/show_bug.cgi?id=216245

Hmm. The only case where changing aspm_support_enabled to false should
matter is in pcie_aspm_init_link_state(), where it looks like we'll
potentially rewrite some registers even if aspm_disabled is true. I
think in theory we shouldn't actually modify anything as a result, and
the lspcis from the bug don't show any ASPM values having changed, but I
don't trust Realtek hardware in the general case so maybe it gets upset
here? If the proposed patch is to just set aspm_support_enabled to false
when we see the FADT bit set then I think this is fine.