[PATCH] pci: fixup parent subordinate busnr

I believe the change that broke things is introduction of
pci_fixup_parent_subordinate_busnr().

The patch here does two things:
- hunk #1 should fix the problems you've seen when you boot without
  additional "pci" kernel options;
- hunk #2 supposedly fixes boot with "pci=assign-busses" option which
  otherwise hangs Acer TM81xx machines as reported.

Please try this with and without "pci=assign-busses". If it boots,
I'd like to see 'lspci -vvx' for both cases.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 1 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index c77d5b1bbff6..005786416bb5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -402,6 +402,12 @@ static void pci_enable_crs(struct pci_dev *dev)
 static void __devinit pci_fixup_parent_subordinate_busnr(struct pci_bus *child, int max)
 {
         struct pci_bus *parent = child->parent;
+
+        /* Attempts to fix that up are really dangerous unless
+           we're going to re-assign all bus numbers. */
+        if (!pcibios_assign_all_busses())
+                return;
+
         while (parent->parent && parent->subordinate < max) {
                 parent->subordinate = max;
                 pci_write_config_byte(parent->self, PCI_SUBORDINATE_BUS, max);
@@ -478,8 +484,18 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev * dev, int max
                  * We need to assign a number to this bus which we always
                  * do in the second pass.
                  */
-                if (!pass)
+                if (!pass) {
+                        if (pcibios_assign_all_busses())
+                                /* Temporarily disable forwarding of the
+                                   configuration cycles on all bridges in
+                                   this bus segment to avoid possible
+                                   conflicts in the second pass between two
+                                   bridges programmed with overlapping
+                                   bus ranges. */
+                                pci_write_config_dword(dev, PCI_PRIMARY_BUS,
+                                                       buses & ~0xffffff);
                         return max;
+                }
 
                 /* Clear errors */
                 pci_write_config_word(dev, PCI_STATUS, 0xffff);