PCI: Setup disabled bridges even if buses are added

This patch sets up disabled bridges even if buses have already been
added.

pci_assign_unassigned_resources is called after buses are added.
pci_assign_unassigned_resources calls pci_bus_assign_resources.
pci_bus_assign_resources calls pci_setup_bridge to configure BARs of
bridges.

Currently pci_setup_bridge returns immediately if the bus have already
been added. So pci_assign_unassigned_resources can't configure BARs of
bridges that were added in a disabled state; this patch fixes the issue.

On logical hot-add, we need to prevent the kernel from re-initializing
bridges that have already been initialized. To achieve this,
pci_setup_bridge returns immediately if the bridge have already been
enabled.

We don't need to check whether the specified bus is a root bus or not.
pci_setup_bridge is not called on a root bus, because a root bus does
not have a bridge.

The patch adds a new helper function, pci_is_enabled. I made the
function name similar to pci_is_managed. The codes which use
enable_cnt directly are changed to use pci_is_enabled.

Acked-by: Alex Chiang <[e-mail]>
Signed-off-by: Yuji Shimada <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

drivers/pci/bus.c

···
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->subordinate) {
-			if (atomic_read(&dev->enable_cnt) == 0) {
+			if (!pci_is_enabled(dev)) {
 				retval = pci_enable_device(dev);
 				pci_set_master(dev);
 			}

drivers/pci/pci-sysfs.c

···
 		return -EPERM;
 
 	if (!val) {
-		if (atomic_read(&pdev->enable_cnt) != 0)
+		if (pci_is_enabled(pdev))
 			pci_disable_device(pdev);
 		else
 			result = -EIO;

drivers/pci/pci.c

···
  */
 int pci_reenable_device(struct pci_dev *dev)
 {
-	if (atomic_read(&dev->enable_cnt))
+	if (pci_is_enabled(dev))
 		return do_pci_enable_device(dev, (1 << PCI_NUM_RESOURCES) - 1);
 	return 0;
 }
···
  */
 void pci_disable_enabled_device(struct pci_dev *dev)
 {
-	if (atomic_read(&dev->enable_cnt))
+	if (pci_is_enabled(dev))
 		do_pci_disable_device(dev);
 }
 

drivers/pci/setup-bus.c

···
 	struct pci_bus_region region;
 	u32 l, bu, lu, io_upper16;
 
-	if (!pci_is_root_bus(bus) && bus->is_added)
+	if (pci_is_enabled(bridge))
 		return;
 
 	dev_info(&bridge->dev, "PCI bridge, secondary bus %04x:%02x\n",

include/linux/pci.h

···
 int __must_check pcim_enable_device(struct pci_dev *pdev);
 void pcim_pin_device(struct pci_dev *pdev);
 
+static inline int pci_is_enabled(struct pci_dev *pdev)
+{
+	return (atomic_read(&pdev->enable_cnt) > 0);
+}
+
 static inline int pci_is_managed(struct pci_dev *pdev)
 {
 	return pdev->is_managed;