From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit 3e26c5feed2add218046ecf91bab3cfa9bf762a6 ]
Commit d491f2b75237 ("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 d491f2b75237 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: d491f2b75237 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/pci-driver.c | 47 ++++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 12 deletions(-)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 5c9873fcbd08..e69af9b8361d 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -526,7 +526,6 @@ 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); }
/* @@ -833,18 +832,16 @@ 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); @@ -853,6 +850,22 @@ 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);
/* @@ -900,7 +913,16 @@ 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); @@ -1201,6 +1223,7 @@ 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);