PCI: PM: Skip devices in D0 for suspend-to-idle
Commitd491f2b752
("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 commitd491f2b752
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>
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@ -524,7 +524,6 @@ static void pci_pm_default_resume_early(struct pci_dev *pci_dev)
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pci_power_up(pci_dev);
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pci_restore_state(pci_dev);
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pci_pme_restore(pci_dev);
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pci_fixup_device(pci_fixup_resume_early, pci_dev);
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}
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/*
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@ -831,18 +830,16 @@ static int pci_pm_suspend_noirq(struct device *dev)
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if (pci_dev->skip_bus_pm) {
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/*
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* The function is running for the second time in a row without
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* Either the device is a bridge with a child in D0 below it, or
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* the function is running for the second time in a row without
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* going through full resume, which is possible only during
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* suspend-to-idle in a spurious wakeup case. Moreover, the
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* device was originally left in D0, so its power state should
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* not be changed here and the device register values saved
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* originally should be restored on resume again.
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* suspend-to-idle in a spurious wakeup case. The device should
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* be in D0 at this point, but if it is a bridge, it may be
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* necessary to save its state.
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*/
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pci_dev->state_saved = true;
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} else if (pci_dev->state_saved) {
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if (pci_dev->current_state == PCI_D0)
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pci_dev->skip_bus_pm = true;
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} else {
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if (!pci_dev->state_saved)
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pci_save_state(pci_dev);
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} else if (!pci_dev->state_saved) {
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pci_save_state(pci_dev);
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if (pci_power_manageable(pci_dev))
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pci_prepare_to_sleep(pci_dev);
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@ -851,6 +848,22 @@ static int pci_pm_suspend_noirq(struct device *dev)
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dev_dbg(dev, "PCI PM: Suspend power state: %s\n",
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pci_power_name(pci_dev->current_state));
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if (pci_dev->current_state == PCI_D0) {
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pci_dev->skip_bus_pm = true;
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/*
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* Per PCI PM r1.2, table 6-1, a bridge must be in D0 if any
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* downstream device is in D0, so avoid changing the power state
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* of the parent bridge by setting the skip_bus_pm flag for it.
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*/
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if (pci_dev->bus->self)
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pci_dev->bus->self->skip_bus_pm = true;
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}
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if (pci_dev->skip_bus_pm && !pm_suspend_via_firmware()) {
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dev_dbg(dev, "PCI PM: Skipped\n");
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goto Fixup;
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}
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pci_pm_set_unknown_state(pci_dev);
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/*
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@ -898,7 +911,16 @@ static int pci_pm_resume_noirq(struct device *dev)
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if (dev_pm_smart_suspend_and_suspended(dev))
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pm_runtime_set_active(dev);
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pci_pm_default_resume_early(pci_dev);
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/*
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* In the suspend-to-idle case, devices left in D0 during suspend will
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* stay in D0, so it is not necessary to restore or update their
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* configuration here and attempting to put them into D0 again may
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* confuse some firmware, so avoid doing that.
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*/
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if (!pci_dev->skip_bus_pm || pm_suspend_via_firmware())
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pci_pm_default_resume_early(pci_dev);
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pci_fixup_device(pci_fixup_resume_early, pci_dev);
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if (pci_has_legacy_pm_support(pci_dev))
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return pci_legacy_resume_early(dev);
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@ -1194,6 +1216,7 @@ static int pci_pm_restore_noirq(struct device *dev)
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}
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pci_pm_default_resume_early(pci_dev);
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pci_fixup_device(pci_fixup_resume_early, pci_dev);
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if (pci_has_legacy_pm_support(pci_dev))
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return pci_legacy_resume_early(dev);
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