[ 05/72] PCI: workaround hard-wired bus number V2

[Greg KH]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yinghai Lu <yinghai.lu@xxxxxxxxxx>

commit 71f6bd4a23130cd2f4b036010c5790b1295290b9 upstream.

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.

Tested-by: garyhade@xxxxxxxxxx
Signed-off-by: Yinghai Lu <yinghai.lu@xxxxxxxxxx>
Signed-off-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/pci/probe.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -651,6 +651,11 @@ int __devinit pci_scan_bridge(struct pci
 	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)) {


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