Commit 3e26c5fe authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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



Commit d491f2b7 ("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 d491f2b7 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: d491f2b7 ("PCI: PM: Avoid possible suspend-to-idle issue")
Reported-by: default avatarKai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: default avatarKai-Heng Feng <kai.heng.feng@canonical.com>
parent d1fdb6d8

drivers/pci/pci-driver.c

+35 −12
Original line number Diff line number Diff line
@@ -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);



	/*
@@ -898,8 +911,17 @@ static int pci_pm_resume_noirq(struct device *dev) 
	if (dev_pm_smart_suspend_and_suspended(dev))

		pm_runtime_set_active(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);

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