PCI: Assign resources before drivers claim devices (pci_scan_bus())

Previously, pci_scan_bus() created a root PCI bus, enumerated the devices
on it, and called pci_bus_add_devices(), which made the devices available
for drivers to claim them.

Most callers assigned resources to devices after pci_scan_bus() returns,
which may be after drivers have claimed the devices.  This is incorrect;
the PCI core should not change device resources while a driver is managing
the device.

Remove pci_bus_add_devices() from pci_scan_bus() and do it after any
resource assignment in the callers.

[bhelgaas: changelog, check for failure in mcf_pci_init()]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Geert Uytterhoeven <geert@linux-m68k.org>
CC: Guan Xuetao <gxt@mprc.pku.edu.cn>
CC: Richard Henderson <rth@twiddle.net>
CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
CC: Matt Turner <mattst88@gmail.com>

2 files changed, 6 insertions, 3 deletions

diff --git a/drivers/pci/hotplug/ibmphp_core.c b/drivers/pci/hotplug/ibmphp_core.c
index 96c5c729cdbc..15302475f5b7 100644
--- a/drivers/pci/hotplug/ibmphp_core.c
+++ b/drivers/pci/hotplug/ibmphp_core.c
@@ -738,7 +738,7 @@ static void ibm_unconfigure_device(struct pci_func *func)
  */
 static u8 bus_structure_fixup(u8 busno)
 {
-        struct pci_bus *bus;
+        struct pci_bus *bus, *b;
         struct pci_dev *dev;
         u16 l;
 
@@ -765,7 +765,11 @@ static u8 bus_structure_fixup(u8 busno)
                                         (l != 0x0000) && (l != 0xffff)) {
                         debug("%s - Inside bus_structure_fixup()\n",
                                                         __func__);
-                        pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
+                        b = pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
+                        if (!b)
+                                continue;
+
+                        pci_bus_add_devices(b);
                         break;
                 }
         }
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8d2f400e96cb..88604f29d140 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2123,7 +2123,6 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
         b = pci_create_root_bus(NULL, bus, ops, sysdata, &resources);
         if (b) {
                 pci_scan_child_bus(b);
-                pci_bus_add_devices(b);
         } else {
                 pci_free_resource_list(&resources);
         }