[coreboot] HT_CHAIN_* woes

[Marc Jones]

On Wed, Sep 29, 2010 at 2:12 PM, Arne Georg Gleditsch
<arne.gleditsch at numascale.com> wrote:
> Marc Jones <marcj303 at gmail.com> writes:
>> Yes, This stuff is a mess.
>
> Thank you, then I'm not mad. :)
>
>> I don't completly understand it and couldn't document it.  The
>> swaplist is really a place holder. I am not sure how the fields really
>> work. Part of the problem is the use of the same early ht init for sb
>> decode etc from K8, and then the later real ht init based on the AMD
>> code.  The requirement of the CONFIG_HT_CHAIN_UNITID_BASE setting for
>> the BUIDSwaplist may be wrong.
>>
>> The SB_ setting refers to the the last device in the chain, like the
>> sb600 or sb700.
>
> Hm, ok.  That helps a bit.

Sorry. I mis-spoke. The 780 is the last HT device, sb700 is a Alink
(PCI like) device.

>
>> Can you point what you are looking at in 780.c that is hard-coding the
>> HT address?
>
> In rs780.c
>
>  277        nb_dev = dev_find_slot(0, PCI_DEVFN(0, 0));
>  278        if (!nb_dev) {
>  279                die("rs780_enable: CAN NOT FIND RS780 DEVICE, HALT!\n");
>
> appears to assume that the rs780 exists as device 0.

Ah, ok. I see.

http://www.hypertransport.org/docs/tech/HTC20051222-0046-0008-Final-4-21-06.pdf
See section 7.2.2 to start.



>
>> There is a non-patch that may address this, check this email thread:
>> http://patchwork.coreboot.org/patch/1053/
>
> Right, I remember seeing that go by...  Reading the patch, it would
> appear to be addressing the same issue.  After digging a bit into this
> today, I now believe I can make things behave relatively sane by simply
> passing something like
>
> static BOOL ht_swaplist(u8 node, u8 link, u8 **List)
> {
>        static u8 swaplist[] = { 0x0, 0xff, 0xff };
>        if ((node == 0) && (link == 2)) {
>                *List = swaplist;
>                return 1;
>        }
>        return 0;
> }
>
> as the swaplist callback for this particular mainboard.  If we can come
> up with a way of doing that in a reasonably clean manner, I think I
> prefer that to more magic based on the HT_CHAIN-variables.
>
> Hm.  However, I also notice that of the boards calling the
> amd_ht_init-wrapper, the only other ones with HT_CHAIN_UNITID_BASE ==
> 0x0 are tilapia and mahogany, both rs780-based.  And mahogany apparently
> needs patches to h3finit.c to work.  Does tilapia_fam10 work
> as-is?
>

I don't think it does, I think that we need the patch, which is why I
acked it. We haven't received any more clarification from Zheng.

> Perhaps I should just work the above into the general swaplist callback
> for these cases?

If you can figure it out, please do. I didn't really look at the
swaplist contents and how it works.

Marc


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