PCI: Add helper functions pci_get[put]_host_bridge_device()

Add helper functions to get/put the root bus's host bridge device.

Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com> (AMD Seattle)
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: Grant Likely <grant.likely@linaro.org>
CC: Rob Herring <robh+dt@kernel.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Arnd Bergmann <arnd@arndb.de>

drivers/pci/host-bridge.c

@@ -23,6 +23,20 @@ static struct pci_host_bridge *find_pci_host_bridge(struct pci_bus *bus)
 	return to_pci_host_bridge(root_bus->bridge);
 }
 
+struct device *pci_get_host_bridge_device(struct pci_dev *dev)
+{
+	struct pci_bus *root_bus = find_pci_root_bus(dev->bus);
+	struct device *bridge = root_bus->bridge;
+
+	kobject_get(&bridge->kobj);
+	return bridge;
+}
+
+void  pci_put_host_bridge_device(struct device *dev)
+{
+	kobject_put(&dev->kobj);
+}
+
 void pci_set_host_bridge_release(struct pci_host_bridge *bridge,
 				 void (*release_fn)(struct pci_host_bridge *),
 				 void *release_data)

include/linux/pci.h

@@ -510,6 +510,9 @@ static inline struct pci_dev *pci_upstream_bridge(struct pci_dev *dev)
 	return dev->bus->self;
 }
 
+struct device *pci_get_host_bridge_device(struct pci_dev *dev);
+void pci_put_host_bridge_device(struct device *dev);
+
 #ifdef CONFIG_PCI_MSI
 static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev)
 {