[coreboot] PC Engines apu2 boot regression

Aaron Durbin adurbin at google.com
Sat May 5 23:17:21 CEST 2018


On Fri, May 4, 2018 at 8:49 PM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
> 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?

They currently jump to where they are told at the moment. See
bootblock_c_entry() in src/soc/amd/stoneyridge/bootblock/bootblock.c.
There is no running through multiple stages within coreboot.

I think you are right that guarding things w/ boot_cpu() would work.
Is CONFIG_SQUELCH_EARLY_SMP set for all those types of boards? Or do
we have a weird mix? Or should we have a Kconfig that says 'CAR' is
not symmetric across cpus thus can't be used?



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