PPC405EX PCI CPU vs bus address mapping question

I have a Kilauea board with one custom PCIE card plugged into the PCIE1 slot. The custom card contains four PCI devices which are connected via a PCIE-PCI bridge to the Kilauea.

These devices need to communicate directly with each other. This is done by telling each device the PCI bus address of its partners.

I tried using pci_resource_start() to get the bus address, but that apparently gives me the cpu address.

Specifically, pci_resource_start() returns the following addresses for the four devices:

0x0000000090000000, 0x0000000094000000,
0x0000000098000000, and 0x000000009c000000.

However, if I look at the BAR registers in config space, they are set to 80000000, 84000000, 88000000, and 8c000000.

During boot, I see:

PCI host bridge /plb/pciex@0c0000000 (primary) ranges:
MEM 0x0000000090000000..0x000000009fffffff -> 0x0000000080000000

And that does correspond to the "ranges" line in my dts file.

So there is clearly an offset of 0x10000000 between the CPU and bus address.

My question is: What is the correct way for the driver to learn of this offset, so that it can tell the devices where to find their partners?

I see in pci_process_bridge_OF_ranges() that hose->pci_mem_offset is calculated. That is probably the value I want, but I don't see a "clean" way to access it.

Steve