[coreboot] HT3 for AMD boards

Marc Jones marcj303 at gmail.com
Tue Oct 26 05:09:24 CEST 2010

On Mon, Oct 25, 2010 at 2:53 PM, Scott Duplichan <scott at notabs.org> wrote:
> Hello,
> An HT configuration change is needed to allow the southbridge link
> to run at HT3 frequencies on supported hardware. AMD family 10h
> processors support HT3, as do many AMD motherboards. When the
> southbridge runs at the default settings of 8-bit, 200 MHz, the
> throughput is insufficient for supporting high resolution graphics.
> I have the needed changes ready but can test only the mahogany_fam10
> project. The change involves the buid swap list, which is also used
> by projects supporting the previous generation AMD processor (family 0Fh).
> The change may also allow family 0Fh boards to use improved SB link
> settings.
> Here is my proposal. If it seems OK, I will submit a patch.
> 1) Add an option for HT_MANUAL_SWAP_LIST to amdfam10/kconfig and
>   amdk8/kconfig. The default is zero, which means it has no effect
>   unless overridden.
> 2) Modify ht_wrapper.c to use HT_MANUAL_SWAP_LIST as the swap list,
>   if non-zero.
> 3) In mainboard/amd/mahogany_fam10/Kconfig, override HT_MANUAL_SWAP_LIST
>   with the value that is known to allow HT3 to work.
> 4) Possibly do the same for mainboard/amd/mahogany/Kconfig and test
>   using a family 0Fh processor (I think I can find one).
> 5) Modify amdht/comlib.h so that if a critical HT initialization error
>   occurs, it is no longer ignored. It will now log a message such as:
>   === Failure at line 1145 of file src/northbridge/amd/amdht/h3finit.c ===,
>   though execution will continue for backwards compatibility.
> The idea is that nothing changes by default, except for the one or two
> projects I can test on real hardware. For other boards, owners of the
> hardware can add the HT_MANUAL_SWAP_LIST override to their mainboard
> kconfig and tweak it until it works.

Hi Scott,

I think that this seems reasonable. We will try to get others to test
some more platforms too.



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