PCI: workaround hard-wired bus number V2

Fixes PCI device detection on IBM xSeries IBM 3850 M2 / x3950 M2
when using ACPI resources (_CRS).
This is default, a manual workaround (without this patch)
would be pci=nocrs boot param.

V2: Add dev_warn if the workaround is hit. This should reveal
how common such setups are (via google) and point to possible
problems if things are still not working as expected.
-> Suggested by Jan Beulich.

Cc: stable@vger.kernel.org
Tested-by: garyhade@us.ibm.com
Signed-off-by: Yinghai Lu <yinghai.lu@oracle.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/probe.c

@@ -651,6 +651,11 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 	dev_dbg(&dev->dev, "scanning [bus %02x-%02x] behind bridge, pass %d\n",
 		secondary, subordinate, pass);
 
+	if (!primary && (primary != bus->number) && secondary && subordinate) {
+		dev_warn(&dev->dev, "Primary bus is hard wired to 0\n");
+		primary = bus->number;
+	}
+
 	/* Check if setup is sensible at all */
 	if (!pass &&
 	    (primary != bus->number || secondary <= bus->number)) {