PCI: Make pci_wakeup_bus() & pci_bus_set_current_state() public

There are PCI devices which are power-manageable by a nonstandard means,
such as a custom ACPI method.  One example are discrete GPUs in hybrid
graphics laptops, another are Thunderbolt controllers in Macs.

Such devices can't be put into D3cold with pci_set_power_state() because
pci_platform_power_transition() fails with -ENODEV.  Instead they're put
into D3hot by pci_set_power_state() and subsequently into D3cold by
invoking the nonstandard means.  However as a consequence the cached
current_state is incorrectly left at D3hot.

What we need to do is walk the hierarchy below such a PCI device on
powerdown and update the current_state to D3cold.  On powerup the PCI
device itself and the hierarchy below it is in D0uninitialized, so we
need to walk the hierarchy again and wake all devices, causing them to
be put into D0active and then letting them autosuspend as they see fit.

To this end make pci_wakeup_bus() & pci_bus_set_current_state() public
so PCI drivers don't have to reinvent the wheel.

Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://patchwork.freedesktop.org/patch/msgid/2962443259e7faec577274b4ef8c54aad66f9a94.1520068884.git.lukas@wunner.de

drivers/pci/pci.c

@@ -800,7 +800,7 @@ static int pci_wakeup(struct pci_dev *pci_dev, void *ign)
  * pci_wakeup_bus - Walk given bus and wake up devices on it
  * @bus: Top bus of the subtree to walk.
  */
-static void pci_wakeup_bus(struct pci_bus *bus)
+void pci_wakeup_bus(struct pci_bus *bus)
 {
 	if (bus)
 		pci_walk_bus(bus, pci_wakeup, NULL);
@@ -850,11 +850,11 @@ static int __pci_dev_set_current_state(struct pci_dev *dev, void *data)
 }
 
 /**
- * __pci_bus_set_current_state - Walk given bus and set current state of devices
+ * pci_bus_set_current_state - Walk given bus and set current state of devices
  * @bus: Top bus of the subtree to walk.
  * @state: state to be set
  */
-static void __pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state)
+void pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state)
 {
 	if (bus)
 		pci_walk_bus(bus, __pci_dev_set_current_state, &state);
@@ -876,7 +876,7 @@ int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state)
 	ret = pci_platform_power_transition(dev, state);
 	/* Power off the bridge may power off the whole hierarchy */
 	if (!ret && state == PCI_D3cold)
-		__pci_bus_set_current_state(dev->subordinate, PCI_D3cold);
+		pci_bus_set_current_state(dev->subordinate, PCI_D3cold);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(__pci_complete_power_transition);

include/linux/pci.h

@@ -1147,6 +1147,8 @@ void pci_pme_wakeup_bus(struct pci_bus *bus);
 void pci_d3cold_enable(struct pci_dev *dev);
 void pci_d3cold_disable(struct pci_dev *dev);
 bool pcie_relaxed_ordering_enabled(struct pci_dev *dev);
+void pci_wakeup_bus(struct pci_bus *bus);
+void pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state);
 
 /* PCI Virtual Channel */
 int pci_save_vc_state(struct pci_dev *dev);