On Fri, Aug 2, 2024 at 8:04 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> On Thu, May 30, 2024 at 04:52:27PM +0800, Kai-Heng Feng wrote:
> > Intel SoC cannot reach lower power states when mapped VMD PCIe bridges
> > and NVMe devices don't have ASPM configured.
> >
> > So set aspm_os_control attribute to let OS really enable ASPM for those
> > devices.
> >
> > Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
>
> I assume f492edb40b54 was tested and worked at the time. Is the
> implication that newer Intel SoCs have added more requirements for
> getting to low power states, since __pci_enable_link_state() would
> have warned and done nothing even then?
>
> Or maybe this is a new system that sets ACPI_FADT_NO_ASPM, and
> f492edb40b54 was tested on systems that did *not* set
> ACPI_FADT_NO_ASPM?
I believe it's the case here. Vendors may or may not set
ACPI_FADT_NO_ASPM, so f492edb40b54 works on some systems but not
others.
Kai-Heng
>
> > Link: https://lore.kernel.org/linux-pm/218aa81f-9c6-5929-578d-8dc15f83dd48@xxxxxxxxx/
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > ---
> > drivers/pci/controller/vmd.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> > index 87b7856f375a..1dbc525c473f 100644
> > --- a/drivers/pci/controller/vmd.c
> > +++ b/drivers/pci/controller/vmd.c
> > @@ -751,6 +751,8 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> > if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> > return 0;
> >
> > + pdev->aspm_os_control = 1;
> > +
> > pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
> >
> > pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> > --
> > 2.43.0
> >
