PCI: PM: Avoid possible suspend-to-idle issue

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>

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index cae630f..5eadbc3 100644 (file)
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -734,6 +734,8 @@ 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);
 
@@ -827,7 +829,20 @@ 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 4a5a84d..dd436da 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -344,6 +344,7 @@ 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