Re: [PATCH V1] PCI/ASPM: Skip L1SS save/restore if not already enabled

[Wysocki, Rafael J]

On 1/19/2023 3:21 PM, Kai-Heng Feng wrote:
> Hi Vidya,
>
> On Thu, Jan 19, 2023 at 5:49 PM Vidya Sagar <vidyas@xxxxxxxxxx> wrote:
> > Skip save and restore of ASPM L1 Sub-States specific registers if they
> > are not already enabled in the system. This is to avoid issues observed
> > on certain platforms during restoration process, particularly when
> > restoring the L1SS registers contents.
> >
> > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=216782
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > ---
> >   drivers/pci/pcie/aspm.c | 19 ++++++++++++++++++-
> >   1 file changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index 53a1fa306e1e..5d3f09b0a6a9 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -757,15 +757,29 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
> >                                  PCI_L1SS_CTL1_L1SS_MASK, val);
> >   }
> >
> > +static bool skip_l1ss_restore;
> Maybe move it inside "struct pci_dev"?

Yes, it can be different for different devices, so it cannot be static IMV.


> > +
> >   void pci_save_aspm_l1ss_state(struct pci_dev *dev)
> >   {
> >          struct pci_cap_saved_state *save_state;
> >          u16 l1ss = dev->l1ss;
> > -       u32 *cap;
> > +       u32 *cap, val;
> >
> >          if (!l1ss)
> >                  return;
> >
> > +       /*
> > +        * Skip save and restore of L1 Sub-States registers if they are not
> > +        * already enabled in the system
> > +        */
> > +       pci_read_config_dword(dev, l1ss + PCI_L1SS_CTL1, &val);
> > +       if (!(val & PCI_L1SS_CTL1_L1SS_MASK)) {
> > +               skip_l1ss_restore = 1;
> > +               return;
> > +       }
> > +
> > +       skip_l1ss_restore = 0;
> > +
> >          save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> >          if (!save_state)
> >                  return;
> > @@ -784,6 +798,9 @@ void pci_restore_aspm_l1ss_state(struct pci_dev *dev)
> >          if (!l1ss)
> >                  return;
> >
> > +       if (skip_l1ss_restore)
> > +               return;
> > +
> >          save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> >          if (!save_state)
> >                  return;
> > --
> > 2.17.1