Bjorn Helgaas wrote:
> On Mon, 2009-10-26 at 14:23 -0700, Yinghai Lu wrote:
>
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/setup-bus.c
>> +++ linux-2.6/drivers/pci/setup-bus.c
>> @@ -322,33 +322,54 @@ static void pci_bridge_check_ranges(stru
>> }
>> }
>>
>> -/* Helper function for sizing routines: find first available
>> - bus resource of a given type. Note: we intentionally skip
>> - the bus resources which have already been assigned (that is,
>> - have non-NULL parent resource). */
>> -static struct resource *find_free_bus_resource(struct pci_bus *bus, unsigned long type)
>> +void pci_bridge_release_not_used_res(struct pci_bus *bus)
>> {
>> int i;
>> struct resource *r;
>> unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
>> IORESOURCE_PREFETCH;
>>
>> - for (i = 0; i < PCI_BUS_NUM_RESOURCES; i++) {
>> + /* for pci bridges res only */
>> + for (i = 0; i < 3; i++) {
>
> I think the "i = 0; i < 3" part is to check the bridge apertures, i.e.,
> the I/O base/limit, the memory base/limit, and the prefetchable memory
> base/limit. Right? We need some way to indicate that more clearly than
> using a hard-coded "3".
yes. the 0x1c, 0x20, and 0x28
>
>> r = bus->resource[i];
>> - if (r == &ioport_resource || r == &iomem_resource)
>> - continue;
>> - if (r && (r->flags & type_mask) == type) {
>> + if (r && (r->flags & type_mask)) {
>> if (!r->parent)
>> - return r;
>> + continue;
>> /*
>> * if there is no child under that, we should release
>> * and use it. don't need to reset it, pbus_size_* will
>> * set it again
>> */
>> if (!r->child && !release_resource(r))
>
> We got this resource pointer out of a struct pci_bus, and we release it
> here. We must have previously done a request_resource(),
> allocate_resource(), or similar. Where does that happen? Are the
> requests and releases nested correctly?
>
> I would think that somewhere, we would be doing a request_resource() and
> assigning the resource to pci_bus->resource[x]. But there are very few
> assignments to the pci_bus resources:
> setup_resource (only for "pci=use_crs")
> pci_read_bridge_bases (just a copy from upstream bus resources)
> pci_alloc_child_bus (copy from upstream bridge resources)
> pci_create_bus (set to &ioport_resource or &iomem_resource)
>
> My guess is that this release_resource() releases something we copied
> from the bridge in pci_alloc_child_bus(). But that doesn't seem right,
> because we aren't changing the bridge programming here.
in arch/x86/pci/i386.c::
pcibios_resource_survey() ==> pcibios_allocate_bus_resources()
YH
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