[coreboot] PCI MMCONF on amdfam10

Stefan Reinauer stefan.reinauer at coreboot.org
Mon Dec 16 20:18:04 CET 2013

* Kyösti Mälkki <kyosti.malkki at gmail.com> [131213 11:29]:
> Yet we have had commit 032c23db for 5 months:
>   intel/i945: Use MMCONF_SUPPORT_DEFAULT
>   Change all PCI configuration accesses to MMIO on all boards
>   with i945 chipset. To enable MMIO style access, add explicit
>   PCI IO config write in the bootblock.
> I remember a week or so after this was merged you made that comment
> about i945 on a related change. I requested literature reference or
> a test case to see if I should revert. I got neither and the revert
> never took place.

Unfortunately I can not provide literature references; I worked on that
chipset 5+ years ago. Here are some of the reasons..

 - I never actually saw this behavior _documented_ anywhere
 - I received documentation under NDA
 - I have since changed jobs and had to destroy all documentation
   received through my previous employer
You should be able to use any i945 board to test that, however. For the
reasons above, I also don't have access to that hardware anymore, so I
can't do the testing for you.

> Until you are  more specific on your statement, I am reading it as follows:
>   Stefan added 'select MMCONF_SUPPORT_DEFAULT' on a mainboard with i945
>   and the board did not boot.

It might even boot but it will be missing half of the hardware setup
since the device probing mechanism won't see the devices.
> I am not saying yout statement is incorrect, but how about some
> argumentation?

It's really purely something I saw on hardware and I remembered. So I
shared it. If you need proof, we will need to wait and see if anybody
is actually still using this chipset in the future. I'm also not sure
if that behavior was specific to the model of the i945 chipset used in
those systems back then (Kontron 986LCD-M iirc, but it might have been
the getac or roda, too where I ran those tests)

Hope this helps.


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