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

Previously, pci_scan_root_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_root_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_root_bus() and do it after any
resource assignment in the callers.

Note that ARM's pci_common_init_dev() already called pci_bus_add_devices()
after pci_scan_root_bus(), so we only need to remove the first call:

  pci_common_init_dev
    pcibios_init_hw
      pci_scan_root_bus
        pci_bus_add_devices        # first call
    pci_bus_assign_resources
    pci_bus_add_devices            # second call

[bhelgaas: changelog, drop "root_bus" var in alpha common_init_pci(),
return failure earlier in mn10300, add "return" in x86 pcibios_scan_root(),
return early if xtensa platform_pcibios_fixup() fails]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
CC: Matt Turner <mattst88@gmail.com>
CC: David Howells <dhowells@redhat.com>
CC: Tony Luck <tony.luck@intel.com>
CC: Michal Simek <monstr@monstr.eu>
CC: Ralf Baechle <ralf@linux-mips.org>
CC: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Chris Metcalf <cmetcalf@ezchip.com>
CC: Chris Zankel <chris@zankel.net>
CC: Max Filippov <jcmvbkbc@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/mn10300/unit-asb2305/pci.c b/arch/mn10300/unit-asb2305/pci.c
index 613ca1e55b4b..3dfe2d31c67b 100644
--- a/arch/mn10300/unit-asb2305/pci.c
+++ b/arch/mn10300/unit-asb2305/pci.c
@@ -342,6 +342,7 @@ static int __init pcibios_init(void)
 {
         resource_size_t io_offset, mem_offset;
         LIST_HEAD(resources);
+        struct pci_bus *bus;
 
         ioport_resource.start   = 0xA0000000;
         ioport_resource.end     = 0xDFFFFFFF;
@@ -371,11 +372,14 @@ static int __init pcibios_init(void)
 
         pci_add_resource_offset(&resources, &pci_ioport_resource, io_offset);
         pci_add_resource_offset(&resources, &pci_iomem_resource, mem_offset);
-        pci_scan_root_bus(NULL, 0, &pci_direct_ampci, NULL, &resources);
+        bus = pci_scan_root_bus(NULL, 0, &pci_direct_ampci, NULL, &resources);
+        if (!bus)
+                return 0;
 
         pcibios_irq_init();
         pcibios_fixup_irqs();
         pcibios_resource_survey();
+        pci_bus_add_devices(bus);
         return 0;
 }