[coreboot] PC Engines apu2 boot regression

[Kyösti Mälkki]

On Fri, May 4, 2018 at 8:22 PM, Aaron Durbin <adurbin at google.com> wrote:
> On Fri, May 4, 2018 at 11:16 AM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
>> On Fri, May 4, 2018 at 7:19 PM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
>>> On Fri, May 4, 2018 at 6:37 PM, Aaron Durbin <adurbin at google.com> wrote:
>>>>>
>>>>> Any idea what can be result of such weird behavior?
>>>>
>>
>> My current guess is AP CPUs do not see initialised memory for
>> _car_region_start .. _end. That region is set up using fixed MTRRs in
>> low memory and probably not synced between cores so early in romstage.
>>
>
> Ugh.  Why do we allow the APs to run through all these stages? Is this
> for parallel node memory training? Can we ring fence where the APs
> actually run better?
>

I have to check closer, but for apu2 this would be in AMD_INIT_EARLY
already, so AP CPUs run way before (the only) memory controller is
configured. I believe there is microcode updates and some CPU
registers that are also synced during AMD_INIT_EARLY. So it is doing
more than just bringing an idle AP task engine.

I find it particularly hard to be civil on your first question, so
trying with sarcasm instead. After 5000 or so development hours and
direct support from AMD, is the boot sequence for soc/stoneyridge
prototypes equally bad, that is, AP CPUs execute through bootblock and
verstage?

Kyösti