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    SubjectRe: [PATCH AUTOSEL 4.14 15/31] PCI: PM: Avoid possible suspend-to-idle issue
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    On 6/8/2019 1:46 PM, Sasha Levin wrote:
    > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
    >
    > [ Upstream commit d491f2b75237ef37d8867830ab7fad8d9659e853 ]
    >
    > If a PCI driver leaves the device handled by it in D0 and calls
    > pci_save_state() on the device in its ->suspend() or ->suspend_late()
    > callback, it can expect the device to stay in D0 over the whole
    > s2idle cycle. However, that may not be the case if there is a
    > spurious wakeup while the system is suspended, because in that case
    > pci_pm_suspend_noirq() will run again after pci_pm_resume_noirq()
    > which calls pci_restore_state(), via pci_pm_default_resume_early(),
    > so state_saved is cleared and the second iteration of
    > pci_pm_suspend_noirq() will invoke pci_prepare_to_sleep() which
    > may change the power state of the device.
    >
    > To avoid that, add a new internal flag, skip_bus_pm, that will be set
    > by pci_pm_suspend_noirq() when it runs for the first time during the
    > given system suspend-resume cycle if the state of the device has
    > been saved already and the device is still in D0. Setting that flag
    > will cause the next iterations of pci_pm_suspend_noirq() to set
    > state_saved for pci_pm_resume_noirq(), so that it always restores the
    > device state from the originally saved data, and avoid calling
    > pci_prepare_to_sleep() for the device.
    >
    > Fixes: 33e4f80ee69b ("ACPI / PM: Ignore spurious SCI wakeups from suspend-to-idle")
    > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    > Reviewed-by: Keith Busch <keith.busch@intel.com>
    > Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
    > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > ---
    > drivers/pci/pci-driver.c | 17 ++++++++++++++++-
    > include/linux/pci.h | 1 +
    > 2 files changed, 17 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
    > index ea69b4dbab66..f5d66335fe53 100644
    > --- a/drivers/pci/pci-driver.c
    > +++ b/drivers/pci/pci-driver.c
    > @@ -726,6 +726,8 @@ static int pci_pm_suspend(struct device *dev)
    > struct pci_dev *pci_dev = to_pci_dev(dev);
    > const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
    >
    > + pci_dev->skip_bus_pm = false;
    > +
    > if (pci_has_legacy_pm_support(pci_dev))
    > return pci_legacy_suspend(dev, PMSG_SUSPEND);
    >
    > @@ -799,7 +801,20 @@ static int pci_pm_suspend_noirq(struct device *dev)
    > }
    > }
    >
    > - if (!pci_dev->state_saved) {
    > + if (pci_dev->skip_bus_pm) {
    > + /*
    > + * The function is running for the second time in a row without
    > + * going through full resume, which is possible only during
    > + * suspend-to-idle in a spurious wakeup case. Moreover, the
    > + * device was originally left in D0, so its power state should
    > + * not be changed here and the device register values saved
    > + * originally should be restored on resume again.
    > + */
    > + pci_dev->state_saved = true;
    > + } else if (pci_dev->state_saved) {
    > + if (pci_dev->current_state == PCI_D0)
    > + pci_dev->skip_bus_pm = true;
    > + } else {
    > pci_save_state(pci_dev);
    > if (pci_power_manageable(pci_dev))
    > pci_prepare_to_sleep(pci_dev);
    > diff --git a/include/linux/pci.h b/include/linux/pci.h
    > index 59f4d10568c6..430f3c335446 100644
    > --- a/include/linux/pci.h
    > +++ b/include/linux/pci.h
    > @@ -346,6 +346,7 @@ struct pci_dev {
    > D3cold, not set for devices
    > powered on/off by the
    > corresponding bridge */
    > + unsigned int skip_bus_pm:1; /* Internal: Skip bus-level PM */
    > unsigned int ignore_hotplug:1; /* Ignore hotplug events */
    > unsigned int hotplug_user_indicators:1; /* SlotCtl indicators
    > controlled exclusively by

    This has been reported to be problematic, I wouldn't recommend taking it
    for -stable at this point.


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