[coreboot] PC Engines apu2 boot regression

[Piotr Król]

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On 05/05/2018 11:53 AM, Kyösti Mälkki wrote:
> On Sat, May 5, 2018 at 3:06 AM, Marshall Dawson 
> <marshalldawson3rd at gmail.com> wrote:
>>> 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.
>> 
>> 
>> Kyosti, I haven't kept a close watch on CAR changes in the other
>> AMD systems, however in experimenting with CZ using ST source I
>> found that 4 cores had a problem using CAR globals, so I think
>> you're on the right track. AMD's CAR setup code assumes each core
>> only needs fixed MTRRs configured for their own particular region
>> of storage -- they all don't get access to 100% of the CAR area.
>> Going from 2 cores (ST) to 4 cores (CZ), the higher two cores
>> could no longer access the CAR globals at the bottom of the
>> region. Try this hack and see if it improves for you:
>> 
> 
> Hi Marshall
> 
> Thanks, your suggested MTRR change seems to solve the regression.
> It was definetely about CAR_GLOBALs failing for AP CPUs in general.
> We just had not hit this case before for typical builds, as use of 
> POSTCAR_STAGE barely avoided the error from triggering.
> 
> So did you hit problems with CAR_GLOBAL in agesa_get_dispatcher(), 
> when experimeting CZ vs ST? I don't see why this code works even
> for dual-core ST but I did not evaluate CAR layout. Documentation
> part for fixed MTRRs in gcccar.inc appears to be same.
> 
> Now, does this MTRR change have potential to actually become _the_ 
> fix? I don't see why it could not. It's pretty much all that we can
> do with binaryPI, anything else touches the blobs.

Hi Marshall, Kyösti,
also confirm that this patch fix regression on recent master. Will you
sent patch?

Best Regards,
- -- 
Piotr Król
Embedded Systems Consultant
https://3mdeb.com | @3mdeb_com
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