>> When PCI probe flag PCI_REASSIGN_ALL_RSRC has been passed into PCI
>> core, it's hoped that all resources to be reassigned by PCI core.
>> As to particular P2P (PCI-to-PCI) bridge, the size of the corresponding
>> BAR (I/O, MMIO, prefetchable MMIO) is calculated by the resources
>> required by the PCI devices behind the P2P bridge. That means that
>> the information like start/end address retrieved from the hardware
>> registers of the P2P bridge is meainingless in the case. However,
>> we still count that in and the BARs might have been configured by
>> firmware with non-zero size. That leads to space waste.
>>
>> The patch explicitly sets the size of P2P bridge BARs to zero in
>> case that resource reassignment is expected with PCI probe flag
>> PCI_REASSIGN_ALL_RSRC. In the result, it will save overall resource
>> required by the system without waste.
>
>Hrm... there was a reason I wasn't doing that .... but I can't
>remember what it was, it's possible it no longer applies. I'll
>have to make sure this patch is tested on various 4xx and FSL
>configs.
>
Ok. Thanks, Ben. By the way, I've tested it on Firebird-L machine
while passing PCI_REASSIGN_ALL_RSRC into PCI core. Everything looks
fine :-)
>Cheers,
>Ben.
Thanks,
Gavin
>
>> Signed-off-by: Gavin Shan <sha...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/kernel/pci-common.c | 16 ++++++++++++----
>> 1 file changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/pci-common.c
>> b/arch/powerpc/kernel/pci-common.c
>> index 8e78e93..0fe214d 100644
>> --- a/arch/powerpc/kernel/pci-common.c
>> +++ b/arch/powerpc/kernel/pci-common.c
>> @@ -966,13 +966,14 @@ static void __devinit pcibios_fixup_bridge(struct
>> pci_bus *bus)
>> if (i >= 3 && bus->self->transparent)
>> continue;
>>
>> - /* If we are going to re-assign everything, mark the resource
>> - * as unset and move it down to 0
>> + /* If we're going to reassign everything, we can
>> + * shrink the P2P resource to have size as being
>> + * of 0 in order to save space.
>> */
>> if (pci_has_flag(PCI_REASSIGN_ALL_RSRC)) {
>> res->flags |= IORESOURCE_UNSET;
>> - res->end -= res->start;
>> res->start = 0;
>> + res->end = -1;
>> continue;
>> }
>>
>> @@ -1234,7 +1235,14 @@ void pcibios_allocate_bus_resources(struct pci_bus
>> *bus)
>> pr_warning("PCI: Cannot allocate resource region "
>> "%d of PCI bridge %d, will remap\n", i, bus->number);
>> clear_resource:
>> - res->start = res->end = 0;
>> + /* The resource might be figured out when doing
>> + * reassignment based on the resources required
>> + * by the downstream PCI devices. Here we set
>> + * the size of the resource to be 0 in order to
>> + * save more space.
>> + */
>> + res->start = 0;
>> + res->end = -1;
>> res->flags = 0;
>> }
>>
>
>
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