Merge branch 'pci/pm'

- Only read PCI_PM_CTRL register when available, to avoid reading the wrong
  register and corrupting dev->current_state (Feiyang Chen)

* pci/pm:
  PCI/PM: Only read PCI_PM_CTRL register when available

Author: bjorn-helgaas

drivers/pci/pci.c

@@ -1226,6 +1226,10 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
  *
  * On success, return 0 or 1, depending on whether or not it is necessary to
  * restore the device's BARs subsequently (1 is returned in that case).
+ *
+ * On failure, return a negative error code.  Always return failure if @dev
+ * lacks a Power Management Capability, even if the platform was able to
+ * put the device in D0 via non-PCI means.
  */
 int pci_power_up(struct pci_dev *dev)
 {
@@ -1242,9 +1246,6 @@ int pci_power_up(struct pci_dev *dev)
 		else
 			dev->current_state = state;
 
-		if (state == PCI_D0)
-			return 0;
-
 		return -EIO;
 	}
 
@@ -1302,8 +1303,12 @@ static int pci_set_full_power_state(struct pci_dev *dev)
 	int ret;
 
 	ret = pci_power_up(dev);
-	if (ret < 0)
+	if (ret < 0) {
+		if (dev->current_state == PCI_D0)
+			return 0;
+
 		return ret;
+	}
 
 	pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
 	dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;