Oops while assigning PCI resources

From: Russell King (rmk@arm.linux.org.uk)
Date: Thu Dec 07 2000 - 14:22:24 EST


Hi,

Kernel is 2.4.0-test12-pre7

I'm seeing an oops while assigning PCI resources on an ARM board. This
board as a PCI to PCI bridge on board without any devices on the second
bus.

Trace is:

Trace; c0013ac0 <pbus_assign_resources+0/e4>
Trace; c0013ba4 <pci_assign_unassigned_resources+0/98>
Trace; c0009f34 <pcibios_init+0/68>
Trace; c0012db4 <pci_init+0/44>
Trace; c00089ec <do_basic_setup+0/54>

The place which is causing the oops is in drivers/pci/setup-bus.c:

        for (ln=bus->children.next; ln != &bus->children; ln=ln->next) {
                struct pci_bus *b = pci_bus_b(ln);

                vvvvvvvvvvvvvvvvvvvvv
                b->resource[0]->start = ranges->io_start = ranges->io_end;
                ^^^^^^^^^^^^^^^^^^^^^
                b->resource[1]->start = ranges->mem_start = ranges->mem_end;

                pbus_assign_resources(b, ranges);

The reason is because b->resource is NULL. Looking at drivers/pci/pci.c,
when we hit a non-cardbus bridge, we never set b->resource[*] to point to
anything. We call "pci_add_new_bus" from pci_scan_bridge, but neither
pci_add_new_bus nor pci_scan_bridge sets up the resources.

Unfortunately, the PCI bus code (in drivers/pci/setup-bus.c) seems to
assume that someone somewhere has allocated these resources.
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