Problem with PCI bus rescan on 460EX
Kenji Kaneshige
kaneshige.kenji at jp.fujitsu.com
Wed Mar 17 12:03:05 EST 2010
Felix Radensky wrote:
> Hello, Kenji-san
>
> Kenji Kaneshige wrote:
>>
>> I misunderstood the problem.
>> My understanding was memory resource was not enabled even though Linux
>> set
>> the Memory Space bit in the command register. But it was not correct. The
>> bridge memory window was marked unused and Linux didn't try to set Memory
>> Space bit in the command register. Current my understanding is as
>> follows.
>> Please correct me if I'm still misunderstanding something.
>>
>> 1) Your BIOS doesn't assign any resource to the bridge if its child PCI
>> hot-plug slot is not occupied.
>>
>> 2) At the boot time, pci_assign_unassigned_resources() try to assign
>> memory resouces to the bridge using pci_bus_assign_resource(), but
>> it was disabled because there are no devices require memory resource.
>>
>> 3) And then pci_assign_unassigned_resouces() calls pci_enable_bridge(),
>> but Memory Space bit in the command register was not set because no
>> memory resource are assigned to the bridge. At the same time,
>> pci_dev->enable_cnt was incremented.
>>
>> 4) At the rescan time, pci_setup_bridge() and pci_enable_bridge() doesn't
>> work because the bridge is already marked "enabled" (i.e.
>> pci_dev->enable_cnt is not zero).
>>
>> I don't have any concrete idea how to fix that so far, but I can say
>> my idea
>> (pcibios_enable_device() should return an error) was wrong.
>>
>>
> I was wandering if setting is_hotplug_bridge property for this bridge
> (e.g. via
> header quirk) can be an acceptable solution. This will allow passing
> hpmemsize
> kernel parameter, to specify the amount of memory to assign to the bridge.
> I've tested this approach and it seems to work.
Looks good to me.
By the way, I think Yinghai's bridge resource reallocation patch series
might help you. It is in Jesse's PCI tree. Please take a look.
Thanks,
Kenji Kaneshige
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