3.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
commit 7a0b33d4a45d30b9a838fba4efcd80b7b57d4d16 upstream.
This reverts commit fc1b253141b3 ("PCI: Don't scan random busses in
pci_scan_bridge()") because it breaks CardBus on some machines.
David tested a Dell Latitude D505 that worked like this prior to
fc1b253141b3:
pci 0000:00:1e.0: PCI bridge to [bus 01]
pci 0000:01:01.0: CardBus bridge to [bus 02-05]
Note that the 01:01.0 CardBus bridge has a bus number aperture of
[bus 02-05], but those buses are all outside the 00:1e.0 PCI bridge bus
number aperture, so accesses to buses 02-05 never reach CardBus. This is
later patched up by yenta_fixup_parent_bridge(), which changes the
subordinate bus number of the 00:1e.0 PCI bridge:
pci_bus 0000:01: Raising subordinate bus# of parent bus (#01) from #01 to #05
With fc1b253141b3, pci_scan_bridge() fails immediately when it notices that
we can't allocate a valid secondary bus number for the CardBus bridge, and
CardBus doesn't work at all:
pci 0000:01:01.0: can't allocate child bus 01 from [bus 01]
I'd prefer to fix this by integrating the yenta_fixup_parent_bridge() logic
into pci_scan_bridge() so we fix the bus number apertures up front. But
I don't think we can do that before v3.17, so I'm going to revert this to
avoid the problem while we're working on the long-term fix.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=83441
Link: http://lkml.kernel.org/r/1409303414-5196-1-git-send-email-david.henningsson@xxxxxxxxxxxxx
Reported-by: David Henningsson <david.henningsson@xxxxxxxxxxxxx>
Tested-by: David Henningsson <david.henningsson@xxxxxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/pci/probe.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -838,16 +838,12 @@ int pci_scan_bridge(struct pci_bus *bus,
goto out;
}
- if (max >= bus->busn_res.end) {
- dev_warn(&dev->dev, "can't allocate child bus %02x from %pR\n",
- max, &bus->busn_res);
- goto out;
- }
-
/* Clear errors */
pci_write_config_word(dev, PCI_STATUS, 0xffff);
- /* The bus will already exist if we are rescanning */
+ /* Prevent assigning a bus number that already exists.
+ * This can happen when a bridge is hot-plugged, so in
+ * this case we only re-scan this bus. */
child = pci_find_bus(pci_domain_nr(bus), max+1);
if (!child) {
child = pci_add_new_bus(bus, dev, max+1);
--
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