Re: Regression: bug 85491: radeon 0000:01:00.0: Fatal error during GPU init

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Fri, Dec 05, 2014 at 09:59:37PM +1100, Benjamin Herrenschmidt wrote:
>On Thu, 2014-12-04 at 14:06 -0800, Yinghai Lu wrote:
>> > I'm considering reverting 5b28541552ef (assuming that would fix this radeon
>> > regression) because I think the radeon problem is worse than the 74151
>> > problem and I think we can solve 74151 in a different way.
>> >

Commit 5b28541552ef affects PowerPC PCI greatly. Without the commit, those
adapters requesting large BAR would fail and can't work properly. Another
related thing is SRIOV support. Currently, VF BARs are covered by 64-bits
prefetch windows and we expect VF BARs allocated from 64-bits prefetchable
windows. If we're going to revert commit 5b28541552ef, too much things are
affected. I think it's more reasonable to find a solution for bug#85491 if
that's not too hard.

Looking at bug#85491 and the logs from Marek, BIOS didn't configure windows
and BARs for PCI bridge and adapters properly, which forces the kernel to
reassign those BARs/windows failing to be claimed previously. If I'm correct,
we need a way to reassign the bridge's non-prefetchable window and with it,
find_free_bus_resource() needn't check on "!r->parent".

Another way to fix it would be to returning error from pbus_size_mem() for
64-bits-prefetchable case so that prefetchable BARs will be assigned from
prefetchable windows (64-bits flag will be ignored). I guss Yinghai will
have more comments on this.

>> > Guo, Ben, this would affect you!  It's too late to revert 5b28541552ef for
>> > v3.18, but we really need to work on this for v3.19.
>> >
>> > FOr 85491 (the radeon problem), we might be able to work around it by
>> > fixing the bridge window, but I'm not sure we could even get that done
>> > before v3.18.  I'll work on that today.
>> 
>> shrink bridge mmio pref range instead of reject it?
>
>Guo unfortunately doesn't work for us anymore. Gavin, Richard, can
>you handle this please ?
>

Thanks,
Gavin

>Cheers,
>Ben.
>
>