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>

5 files changed, 23 insertions, 28 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index b1ff02ab4f13..fc1b74013743 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -216,24 +216,6 @@ void pci_bus_add_devices(const struct pci_bus *bus)
         }
 }
 
-void pci_enable_bridges(struct pci_bus *bus)
-{
-        struct pci_dev *dev;
-        int retval;
-
-        list_for_each_entry(dev, &bus->devices, bus_list) {
-                if (dev->subordinate) {
-                        if (!pci_is_enabled(dev)) {
-                                retval = pci_enable_device(dev);
-                                if (retval)
-                                        dev_err(&dev->dev, "Error enabling bridge (%d), continuing\n", retval);
-                                pci_set_master(dev);
-                        }
-                        pci_enable_bridges(dev->subordinate);
-                }
-        }
-}
-
 /** pci_walk_bus - walk devices on/under bus, calling callback.
  *  @top      bus whose devices should be walked
  *  @cb       callback to be called for each device found
@@ -301,4 +283,3 @@ EXPORT_SYMBOL(pci_bus_put);
 EXPORT_SYMBOL(pci_bus_alloc_resource);
 EXPORT_SYMBOL_GPL(pci_bus_add_device);
 EXPORT_SYMBOL(pci_bus_add_devices);
-EXPORT_SYMBOL(pci_enable_bridges);
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 59df8575a48c..52dee9d31e1c 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -723,7 +723,6 @@ static int __ref enable_device(struct acpiphp_slot *slot)
         acpiphp_sanitize_bus(bus);
         acpiphp_set_hpp_values(bus);
         acpiphp_set_acpi_region(slot);
-        pci_enable_bridges(bus);
 
         list_for_each_entry(dev, &bus->devices, bus_list) {
                 /* Assume that newly added devices are powered on already. */
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)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 46ada5c098eb..85c114cd91cc 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1979,7 +1979,6 @@ unsigned int __ref pci_rescan_bus(struct pci_bus *bus)
 
         max = pci_scan_child_bus(bus);
         pci_assign_unassigned_bus_resources(bus);
-        pci_enable_bridges(bus);
         pci_bus_add_devices(bus);
 
         return max;
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 4d9ebb4ce015..8f86be13678f 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1440,7 +1440,7 @@ again:
 
         /* any device complain? */
         if (list_empty(&fail_head))
-                goto enable_and_dump;
+                goto dump;
 
         if (tried_times >= pci_try_num) {
                 if (enable_local == undefined)
@@ -1449,7 +1449,7 @@ again:
                         dev_info(&bus->dev, "Automatically enabled pci realloc, if you have problem, try booting with pci=realloc=off\n");
 
                 free_list(&fail_head);
-                goto enable_and_dump;
+                goto dump;
         }
 
         dev_printk(KERN_DEBUG, &bus->dev,
@@ -1482,10 +1482,7 @@ again:
 
         goto again;
 
-enable_and_dump:
-        /* Depth last, update the hardware. */
-        pci_enable_bridges(bus);
-
+dump:
         /* dump the resource on buses */
         pci_bus_dump_resources(bus);
 }
@@ -1556,7 +1553,6 @@ enable_all:
         if (retval)
                 dev_err(&bridge->dev, "Error reenabling bridge (%d)\n", retval);
         pci_set_master(bridge);
-        pci_enable_bridges(parent);
 }
 EXPORT_SYMBOL_GPL(pci_assign_unassigned_bridge_resources);