[coreboot-gerrit] Change in coreboot[master]: soc/intel: skl,cnl,icl: rely on TOLUM as cbmem_top returned by FSP

[Arthur Heymans (Code Review)]

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/36136 )

Change subject: soc/intel: skl,cnl,icl: rely on TOLUM as cbmem_top returned by FSP
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Patch Set 15:

Some thoughts: Some things do not need to be guessed an can be directly read from hardware registers (SA_BASE, TSEG, BDSM, GSM, ...) other things rely on guessing what the FSP did. Why not keep the calculation for things that are most certainly valid (hardware registers) and use the FSP HOB information to fill in gaps for things that cannot be read back (PRMRR?)? That allows to properly know the memory map, while still provide a correct result wrt the top of usable lower memory.

I'm not so familiar with the FSP interfaces, so IDK if that's just the worst of both worlds...