[PATCH v2 2/4] PCI/ASPM: Add pcie_aspm_remove_cap() to override advertised link states

[Maciej W. Rozycki]

On Wed, 12 Nov 2025, Bjorn Helgaas wrote:

> > > +	pci_info(pdev, "ASPM:%s%s removed from Link Capabilities to avoid device defect\n",
> > > +		 lnkcap & PCI_EXP_LNKCAP_ASPM_L0S ? " L0s" : "",
> > > +		 lnkcap & PCI_EXP_LNKCAP_ASPM_L1 ? " L1" : "");
> > 
> > I think this gives a false impression that the ASPM CAPs are being
> > removed from the LnkCap register. This function is just removing it
> > from the internal cache and the LnkCap register is left unchanged.
> 
> Very true, this is confusing since we're not actually changing the
> LnkCap register, so lspci etc will still show these states as
> supported.  The quirk needs to work for arbitrary devices, and there's
> no generic way to change LnkCap, so the quirk can't do that.

 There's no way to poke at hw, but that is only relevant for x86 I believe 
and not the default access method for `lspci' anyway.  For sysfs we do it 
already for things such as fixing the device class; cf. `quirk_isa_bridge'
(arch/alpha/kernel/pci.c), so why is it a problem here?  Unless we want to 
keep it for `lspci' actually.

  Maciej