PCI PM: Introduce __pci_[start|complete]_power_transition() (rev. 2)

The radeonfb driver needs to program the device's PMCSR directly due
to some quirky hardware it has to handle (see
http://bugzilla.kernel.org/show_bug.cgi?id=12846 for details) and
after doing that it needs to call the platform (usually ACPI) to
finish the power transition of the device.  Currently it uses
pci_set_power_state() for this purpose, however making a specific
assumption about the internal behavior of this function, which has
changed recently so that this assumption is no longer satisfied.
For this reason, introduce __pci_complete_power_transition() that may
be called by the radeonfb driver to complete the power transition of
the device.  For symmetry, introduce __pci_start_power_transition().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.c

@@ -539,6 +539,53 @@ void pci_update_current_state(struct pci_dev *dev, pci_power_t state)
 	}
 }
 
+/**
+ * pci_platform_power_transition - Use platform to change device power state
+ * @dev: PCI device to handle.
+ * @state: State to put the device into.
+ */
+static int pci_platform_power_transition(struct pci_dev *dev, pci_power_t state)
+{
+	int error;
+
+	if (platform_pci_power_manageable(dev)) {
+		error = platform_pci_set_power_state(dev, state);
+		if (!error)
+			pci_update_current_state(dev, state);
+	} else {
+		error = -ENODEV;
+		/* Fall back to PCI_D0 if native PM is not supported */
+		pci_update_current_state(dev, PCI_D0);
+	}
+
+	return error;
+}
+
+/**
+ * __pci_start_power_transition - Start power transition of a PCI device
+ * @dev: PCI device to handle.
+ * @state: State to put the device into.
+ */
+static void __pci_start_power_transition(struct pci_dev *dev, pci_power_t state)
+{
+	if (state == PCI_D0)
+		pci_platform_power_transition(dev, PCI_D0);
+}
+
+/**
+ * __pci_complete_power_transition - Complete power transition of a PCI device
+ * @dev: PCI device to handle.
+ * @state: State to put the device into.
+ *
+ * This function should not be called directly by device drivers.
+ */
+int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state)
+{
+	return state > PCI_D0 ?
+			pci_platform_power_transition(dev, state) : -EINVAL;
+}
+EXPORT_SYMBOL_GPL(__pci_complete_power_transition);
+
 /**
  * pci_set_power_state - Set the power state of a PCI device
  * @dev: PCI device to handle.
@@ -575,31 +622,17 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 	if (dev->current_state == state)
 		return 0;
 
-	if (state == PCI_D0) {
-		/*
-		 * Allow the platform to change the state, for example via ACPI
-		 * _PR0, _PS0 and some such, but do not trust it.
-		 */
-		int ret = platform_pci_power_manageable(dev) ?
-			platform_pci_set_power_state(dev, PCI_D0) : 0;
-		if (!ret)
-			pci_update_current_state(dev, PCI_D0);
-	}
+	__pci_start_power_transition(dev, state);
+
 	/* This device is quirked not to be put into D3, so
 	   don't put it in D3 */
 	if (state == PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
 		return 0;
 
 	error = pci_raw_set_power_state(dev, state);
 
-	if (state > PCI_D0 && platform_pci_power_manageable(dev)) {
-		/* Allow the platform to finalize the transition */
-		int ret = platform_pci_set_power_state(dev, state);
-		if (!ret) {
-			pci_update_current_state(dev, state);
-			error = 0;
-		}
-	}
+	if (!__pci_complete_power_transition(dev, state))
+		error = 0;
 
 	return error;
 }

include/linux/pci.h

@@ -689,6 +689,7 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size);
 /* Power management related routines */
 int pci_save_state(struct pci_dev *dev);
 int pci_restore_state(struct pci_dev *dev);
+int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state);
 int pci_set_power_state(struct pci_dev *dev, pci_power_t state);
 pci_power_t pci_choose_state(struct pci_dev *dev, pm_message_t state);
 bool pci_pme_capable(struct pci_dev *dev, pci_power_t state);