[coreboot] PC Engines apu2 boot regression

[Kyösti Mälkki]

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.

> 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