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

BugLink: https://bugs.launchpad.net/bugs/1808957
Patchwork: https://patchwork.kernel.org/patch/10993697/

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>
(cherry picked from commit 3e26c5feed2add218046ecf91bab3cfa9bf762a6)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Timo Aaltonen <tjaalton@ubuntu.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 2a35d16959be02c5fe463f920fd2967b516be427..54c1bbac301f767a9dcec4019a1c98baac8722d6 100644 (file)
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -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);
 }
 
 /*
@@ -819,18 +818,16 @@ 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);
@@ -839,6 +836,22 @@ 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);
 
        /*
@@ -886,7 +899,16 @@ 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);
@@ -1180,6 +1202,7 @@ 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);