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?
> 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
>
