[PATCH] powerpc/pci: Only do fixed PHB numbering on powernv

[Michael Ellerman]

"Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com> writes:
> On 08/08/2016 09:32 PM, Michael Ellerman wrote:
>> "Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com> writes:
>>>
>>> (i) What is the specific issue? Do you have some logs or at least a
>>> "high-level" description of the problem in Xorg? I took a look in its
>>> code and PCI domain is coded as u16, which is correct/expected. So it
>>> seems a subtle bug we should investigate and hopefully fix.
>>
>> It was reported here:
>>
>>    https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-August/147062.html
>>
>> It seems xorg just has a hard coded limit of 256 domains.
>
> Thanks for the link Michael. I guess Xorg _had_ this limit in the 
> "past", since the function that was logged on error - xf86MapLegacyIO() 
> - was removed by a commit of 2014:
>
> https://lists.x.org/archives/xorg-devel/2014-July/043224.html

Aha, nice work.

In fact it seems to be better than that, the array of domains was
removed in 2011 in:

  https://cgit.freedesktop.org/xorg/xserver/commit/?id=858fbbb40d7c69540cd1fb5315cebf811c6e7b3f

Which is officially ancient history as far as I'm concerned.

>>> (ii) Why is it related to the absence of pseries check?! You said this
>>> was your bad, but as far as I understand, Xorg runs in pSeries too so
>>> the issue should also be there heheh
>>
>> Well yes I guess it would, if anyone had tested Xorg on pseries :)
>
> We use to test Xorg on pSeries regularly; in fact, I made a quick test 
> today:
>
> http://imgur.com/a/l1lP8
>
> I forced the domain to be 0xffff as in the above image, and everything 
> worked fine.

Awesome.

>> I think for now I'm going to apply this, and we'll work out something
>> else later.
>
> OK, I guess your solution is fine and solves the pasemi issue quickly, 

No given the above info on xorg I'll drop this, and merge just the
endian fix.

cheers