Re: [Bug #15124] PCI host bridge windows ignored (works with pci=use_crs)

Yinghai Lu
2010-01-26T18:21:29Z

On 01/26/2010 10:16 AM, Linus Torvalds wrote:
>
>
> On Tue, 26 Jan 2010, Bjorn Helgaas wrote:
>>
>> which IS big enough, and we know the bridge is in fact forwarding the
>> [mem 0xd0000000-0xdfffffff 64bit pref] region, because the Radeon works
>> when Jeff boots with "pci=use_crs".
>
> I bet it's a subtractive decode thing. Sure, it could be just another
> undocumented range register (does anybody have the datasheet for that
> thing?) but Intel tends to often have subtractive decode.
>
> That system in question has three PCI express root ports, but two of them
> have IO and memory disabled according to the lspci info. So maybe it's as
> simple as that "I/O Hub PCI Express Root Port 7" just catching anything
> that nobody else does, and the single IOH host chip doing the same?
>
>> I think we should remove intel_bus.c before .33. It's breaking boxes
>> and we don't know how to fix it. Even if we do find out how to fix it,
>> I think we should move toward using _CRS instead, because that's what
>> Windows uses and it's an easy way for the firmware to tell us about
>> platform quirks.
>
> I suspect that for 33 it is indeed best to just revert. But somebody is
> bound to have information on how the actual hardware works. Yinghai?

I have asked intel if there is any bit that could be enabled the routing.
there is no info about for their documentations.

Yinghai