PCI: Delay enabling bridges until they're needed

We currently enable PCI bridges after scanning a bus and assigning
resources.  This is often done in arch code.

This patch changes this so we don't enable a bridge until necessary, i.e.,
until we enable a PCI device behind the bridge.  We do this in the generic
pci_enable_device() path, so this also removes the arch-specific code to
enable bridges.

[bhelgaas: changelog]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e37fea6e178d..44a1a8a0ad7b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1145,6 +1145,24 @@ int pci_reenable_device(struct pci_dev *dev)
         return 0;
 }
 
+static void pci_enable_bridge(struct pci_dev *dev)
+{
+        int retval;
+
+        if (!dev)
+                return;
+
+        pci_enable_bridge(dev->bus->self);
+
+        if (pci_is_enabled(dev))
+                return;
+        retval = pci_enable_device(dev);
+        if (retval)
+                dev_err(&dev->dev, "Error enabling bridge (%d), continuing\n",
+                        retval);
+        pci_set_master(dev);
+}
+
 static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
 {
         int err;
@@ -1165,6 +1183,8 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
         if (atomic_inc_return(&dev->enable_cnt) > 1)
                 return 0;               /* already enabled */
 
+        pci_enable_bridge(dev->bus->self);
+
         /* only skip sriov related */
         for (i = 0; i <= PCI_ROM_RESOURCE; i++)
                 if (dev->resource[i].flags & flags)