Merge branch 'pm-pci'

Merge a PCI power management regression fix.

* pm-pci:
  PCI / ACPI / PM: Resume bridges w/o drivers on suspend-to-RAM

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 65113b6eed14..89ee6a2b6eb8 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -629,6 +629,18 @@ static bool acpi_pci_need_resume(struct pci_dev *dev)
 {
         struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
 
+        /*
+         * In some cases (eg. Samsung 305V4A) leaving a bridge in suspend over
+         * system-wide suspend/resume confuses the platform firmware, so avoid
+         * doing that, unless the bridge has a driver that should take care of
+         * the PM handling.  According to Section 16.1.6 of ACPI 6.2, endpoint
+         * devices are expected to be in D3 before invoking the S3 entry path
+         * from the firmware, so they should not be affected by this issue.
+         */
+        if (pci_is_bridge(dev) && !dev->driver &&
+            acpi_target_system_state() != ACPI_STATE_S0)
+                return true;
+
         if (!adev || !acpi_device_power_manageable(adev))
                 return false;