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PCI: PM: Skip devices in D0 for suspend-to-idle

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Commit d491f2b752 ("PCI: PM: Avoid possible suspend-to-idle issue")
attempted to avoid a problem with devices whose drivers want them to
stay in D0 over suspend-to-idle and resume, but it did not go as far
as it should with that.

Namely, first of all, the power state of a PCI bridge with a
downstream device in D0 must be D0 (based on the PCI PM spec r1.2,
sec 6, table 6-1, if the bridge is not in D0, there can be no PCI
transactions on its secondary bus), but that is not actively enforced
during system-wide PM transitions, so use the skip_bus_pm flag
introduced by commit d491f2b752 for that.

Second, the configuration of devices left in D0 (whatever the reason)
during suspend-to-idle need not be changed and attempting to put them
into D0 again by force is pointless, so explicitly avoid doing that.

Fixes: d491f2b752 ("PCI: PM: Avoid possible suspend-to-idle issue")
Reported-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
This commit is contained in:
Rafael J. Wysocki 2019-06-13 23:59:45 +02:00
parent d1fdb6d8f6
commit 3e26c5feed
1 changed files with 35 additions and 12 deletions
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47
drivers/pci/pci-driver.c
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@ -524,7 +524,6 @@ static void pci_pm_default_resume_early(struct pci_dev *pci_dev)
pci_power_up(pci_dev);
pci_restore_state(pci_dev);
pci_pme_restore(pci_dev);
pci_fixup_device(pci_fixup_resume_early, pci_dev);
}
/*
@ -831,18 +830,16 @@ static int pci_pm_suspend_noirq(struct device *dev)
if (pci_dev->skip_bus_pm) {
/*
* The function is running for the second time in a row without
* Either the device is a bridge with a child in D0 below it, or
* 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.
* suspend-to-idle in a spurious wakeup case. The device should
* be in D0 at this point, but if it is a bridge, it may be
* necessary to save its state.
*/
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 {
if (!pci_dev->state_saved)
pci_save_state(pci_dev);
} else if (!pci_dev->state_saved) {
pci_save_state(pci_dev);
if (pci_power_manageable(pci_dev))
pci_prepare_to_sleep(pci_dev);
@ -851,6 +848,22 @@ static int pci_pm_suspend_noirq(struct device *dev)
dev_dbg(dev, "PCI PM: Suspend power state: %s\n",
pci_power_name(pci_dev->current_state));
if (pci_dev->current_state == PCI_D0) {
pci_dev->skip_bus_pm = true;
/*
* Per PCI PM r1.2, table 6-1, a bridge must be in D0 if any
* downstream device is in D0, so avoid changing the power state
* of the parent bridge by setting the skip_bus_pm flag for it.
*/
if (pci_dev->bus->self)
pci_dev->bus->self->skip_bus_pm = true;
}
if (pci_dev->skip_bus_pm && !pm_suspend_via_firmware()) {
dev_dbg(dev, "PCI PM: Skipped\n");
goto Fixup;
}
pci_pm_set_unknown_state(pci_dev);
/*
@ -898,7 +911,16 @@ static int pci_pm_resume_noirq(struct device *dev)
if (dev_pm_smart_suspend_and_suspended(dev))
pm_runtime_set_active(dev);
pci_pm_default_resume_early(pci_dev);
/*
* In the suspend-to-idle case, devices left in D0 during suspend will
* stay in D0, so it is not necessary to restore or update their
* configuration here and attempting to put them into D0 again may
* confuse some firmware, so avoid doing that.
*/
if (!pci_dev->skip_bus_pm || pm_suspend_via_firmware())
pci_pm_default_resume_early(pci_dev);
pci_fixup_device(pci_fixup_resume_early, pci_dev);
if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_resume_early(dev);
@ -1194,6 +1216,7 @@ static int pci_pm_restore_noirq(struct device *dev)
}
pci_pm_default_resume_early(pci_dev);
pci_fixup_device(pci_fixup_resume_early, pci_dev);
if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_resume_early(dev);