Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/42453 )
Change subject: soc/intel/jasperlake: Add the SkipCpuReplacementCheck configuration ......................................................................
Patch Set 4:
(1 comment)
https://review.coreboot.org/c/coreboot/+/42453/4/src/soc/intel/jasperlake/ch... File src/soc/intel/jasperlake/chip.h:
https://review.coreboot.org/c/coreboot/+/42453/4/src/soc/intel/jasperlake/ch... PS4, Line 293: uint8_t SkipCpuReplacementCheck;
I believe that setting this UPD means MRC training is skipped even if there is no cached training da […]
No, this isn't possible. One can't skip memory training and successfully boot when there's no training data at all. This is about reusing existing memory training data when the CPU might have been replaced.
The CPU replacement check is something MRC does before reusing training data. On SKL, it consists of asking the ME/CSE about it. If the CPU has been replaced, then MRC will discard the training data and force a full memory training. SPS on SKL does not support CPU replacement Check, so Kabylake FSP forces a full memory retrain on such platforms.
I think a similar story happens with CSE Lite, but I've no idea. In any case, it's pretty useless for soldered-on platforms, as one does not simply swap BGA chips back and forth.