[U-Boot-Users] Pci multi bridge bug

[Philippe Simal <philippe.simal@ba-elec.com>]

Hello,

I'm running u-boot-1.0.0 on a IBM PPC440GP.
I have a custom made board with 2 pci-to-pci bridge Intel 21154BE and
several devices behind it. (* PCI bus layout)
On boot-up, u-boot immediately recognizes the 2 bridges and 1 device on bus
0.
It also has no problem for enumirating all the devices on bus 1, but u-boot
can't find any device on bus 2.
When I look at the bridge configuration using the 'pci 0 long' command, I
see that the secondary bus address field of bridge 1 is set to 1.
This should be 2. I also see that on bridge 1 but also on bridge 0 the
subordinate bus address field always is filled with a 0.

First of all I already implemented the type1 configuration cycle bug fix at
(..\drivers\Pci_indirect.c).

To work this kind of PCI configuration, I changed the following lines:
1. The problem with the secondary bus address is fixed by changing
     pci_hose_write_config_byte(hose, dev, PCI_SECONDARY_BUS, sub_bus + 1);
    to
    pci_hose_write_config_byte(hose, dev, PCI_SECONDARY_BUS,
hose->current_busno);
    in
   (file: '..\drivers\Pci_auto.c';   function: 'static void
pciauto_prescan_setup_bridge())
2. The problem with the subordinate bus address is solved by swapping the
code lines from
     pciauto_postscan_setup_bridge(hose, dev, sub_bus);
     sub_bus = hose->current_busno;
     to
     sub_bus = hose->current_busno;
     pciauto_postscan_setup_bridge(hose, dev, sub_bus);
    (file: '..\drivers\Pci_auto.c';   function: int pciauto_config_device())

I'm not sure if this fix is fully failed proof but it works fine for this
design.

I hope my findings can be a contribution to the u-boot project.

* PCI bus layout.

   BUS0
         |
         |
         |     /-------\  BUS1
         |---|            |--------       -> 7 PCI devices
         |     \-------/
         |   Bridge 0
         |
         |
         |     /-------\  BUS2
         |---|            |--------     -> 7 PCI devices
         |     \-------/
         |   Bridge 1
         |
         |
         |--- 1 PCI device

Greetings,
Philippe