diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 90d070ec1026..2870cd36e3e0 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -893,7 +893,9 @@ EXPORT_SYMBOL_GPL(__pci_complete_power_transition);
  * -EINVAL if the requested state is invalid.
  * -EIO if device does not support PCI PM or its PM capabilities register has a
  * wrong version, or device doesn't support the requested state.
+ * 0 if the transition is to D1 or D2 but D1 and D2 are not supported.
  * 0 if device already is in the requested state.
+ * 0 if the transition is to D3 but D3 is not supported.
  * 0 if device's power state has been successfully changed.
  */
 int pci_set_power_state(struct pci_dev *dev, pci_power_t state)