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    SubjectRe: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain
    Hi,

    On Fri, Aug 21, 2020 at 08:32:20PM +0800, Kai-Heng Feng wrote:
    > New Intel laptops with VMD cannot reach deeper power saving state,
    > renders very short battery time.
    >
    > As BIOS may not be able to program the config space for devices under
    > VMD domain, ASPM needs to be programmed manually by software. This is
    > also the case under Windows.
    >
    > The VMD controller itself is a root complex integrated endpoint that
    > doesn't have ASPM capability, so we can't propagate the ASPM settings to
    > devices under it. Hence, simply apply ASPM_STATE_ALL to the links under
    > VMD domain, unsupported states will be cleared out anyway.
    >
    > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
    > ---
    > drivers/pci/pcie/aspm.c | 3 ++-
    > drivers/pci/quirks.c | 11 +++++++++++
    > include/linux/pci.h | 2 ++
    > 3 files changed, 15 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
    > index 253c30cc1967..dcc002dbca19 100644
    > --- a/drivers/pci/pcie/aspm.c
    > +++ b/drivers/pci/pcie/aspm.c
    > @@ -624,7 +624,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
    > aspm_calc_l1ss_info(link, &upreg, &dwreg);
    >
    > /* Save default state */
    > - link->aspm_default = link->aspm_enabled;
    > + link->aspm_default = parent->dev_flags & PCI_DEV_FLAGS_ENABLE_ASPM ?
    > + ASPM_STATE_ALL : link->aspm_enabled;
    >
    > /* Setup initial capable state. Will be updated later */
    > link->aspm_capable = link->aspm_support;
    > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
    > index bdf9b52567e0..2e2f525bd892 100644
    > --- a/drivers/pci/quirks.c
    > +++ b/drivers/pci/quirks.c
    > @@ -5632,3 +5632,14 @@ static void apex_pci_fixup_class(struct pci_dev *pdev)
    > }
    > DECLARE_PCI_FIXUP_CLASS_HEADER(0x1ac1, 0x089a,
    > PCI_CLASS_NOT_DEFINED, 8, apex_pci_fixup_class);
    > +
    > +/*
    > + * Device [8086:9a09]
    > + * BIOS may not be able to access config space of devices under VMD domain, so
    > + * it relies on software to enable ASPM for links under VMD.
    > + */
    > +static void pci_fixup_enable_aspm(struct pci_dev *pdev)
    > +{
    > + pdev->dev_flags |= PCI_DEV_FLAGS_ENABLE_ASPM;
    > +}
    > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a09, pci_fixup_enable_aspm);
    > diff --git a/include/linux/pci.h b/include/linux/pci.h
    > index 835530605c0d..66a45916c7c6 100644
    > --- a/include/linux/pci.h
    > +++ b/include/linux/pci.h
    > @@ -227,6 +227,8 @@ enum pci_dev_flags {
    > PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10),
    > /* Don't use Relaxed Ordering for TLPs directed at this device */
    > PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
    > + /* Enable ASPM regardless of how LnkCtl is programmed */
    > + PCI_DEV_FLAGS_ENABLE_ASPM = (__force pci_dev_flags_t) (1 << 12),

    I wonder if instead of dev_flags this should have a bit field in struct
    pci_dev? Not sure which one is prefered actually, both seem to include
    quirks as well ;-)

    > };
    >
    > enum pci_irq_reroute_variant {
    > --
    > 2.17.1

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