[+cc Michael]
On Thu, Dec 28, 2023 at 04:31:12PM -0600, Bjorn Helgaas wrote:
> On Wed, Dec 20, 2023 at 05:12:50PM -0800, David E. Box wrote:
> ...
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 55bc3576a985..3c4b2647b4ca 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1579,7 +1579,7 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
> > {
> > ...
> > + So we restore here only the
> > + * LNKCTL register with the ASPM control field clear. ASPM will
> > + * be restored in pci_restore_aspm_state().
> > + */
> > + val = cap[i++] & ~PCI_EXP_LNKCTL_ASPMC;
> > + pcie_capability_write_word(dev, PCI_EXP_LNKCTL, val);
>
> When CONFIG_PCIEASPM is not set, we will clear ASPMC here and never
> restore it. I don't know if this ever happens. Do we need to worry
> about this? Might firmware restore ASPMC itself before we get here?
> What do we want to happen in this case?
>
> Since ASPM is intertwined with the PCIe Capability, can we call
> pci_restore_aspm_state() from here instead of from
> pci_restore_state()?
>
> Calling it here would make it easier to see the required ordering
> (LNKCTL with ASPMC cleared, restore ASPM L1SS, restore ASPMC) and
> it would be obvious that none of the other stuff in
> pci_restore_state() is relevant (PASID, PRI, ATS, VC, etc).
>
> If that could be done, I think it would make sense to do the same with
> pci_save_aspm_state() even though it's a little more independent.
The lspci output in Michael's report at
https://lore.kernel.org/r/76c61361-b8b4-435f-a9f1-32b716763d62@xxxxxxxxxxx
reminded me that LTR is important for L1.2, and we currently have
this:
pci_restore_state
pci_restore_ltr_state
pci_restore_pcie_state
I wonder if pci_restore_ltr_state() should be called from
pci_restore_pcie_state() as well? It's intimately connected to ASPM,
and that connection isn't very clear in the current code.
Bjorn
