From 7a0b33d4a45d30b9a838fba4efcd80b7b57d4d16 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Fri, 19 Sep 2014 10:56:06 -0600 Subject: [PATCH] Revert "PCI: Don't scan random busses in pci_scan_bridge()" 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@canonical.com Reported-by: David Henningsson Tested-by: David Henningsson Signed-off-by: Bjorn Helgaas CC: stable@vger.kernel.org # v3.15+ --- drivers/pci/probe.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index e3cf8a2e6292..7c8ca351beae 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -838,16 +838,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass) 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);