[coreboot] PC Engines apu2 boot regression

[Aaron Durbin]

On Sat, May 5, 2018 at 4:26 PM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
> On Sun, May 6, 2018 at 12:17 AM, Aaron Durbin <adurbin at google.com> wrote:
>>> 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 CAR_GLOBAL equally fails with soc/amd/stoneyridge if you had
> SoC with multiple compute units where MTRRs are not shared, thus setup
> becomes asymmetric between some cores. Marshall's experiments support
> this happens.

Agreed. That's a concern w/ running APs through all the stages and not
having a symmetric view of the address space.

>
>> 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?
>
> I would rather grant AP CPUs access to CAR_GLOBALs by manipulating the
> MTRR setup.
>
> Kyösti