Change in coreboot[master]: mb/google/puff: add a region to cache SPD data

[Kane Chen (Code Review)]

Kane Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/40415 )

Change subject: mb/google/puff: add a region to cache SPD data
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Patch Set 4:

(1 comment)
> Patch Set 4:
>
> Just curious about MRC rule, if case 1. remove one dimm case 2. swap both dimm. We still need retrain again, right?

1. yes, remove one dimm, MRC should retrain.

2.
if the 2 dimms are same, we couldn't find a way to detect a dimm swap.  
if 2 dimms are different, the MRC should retrain if 2 dimms are swapped.

https://review.coreboot.org/c/coreboot/+/40415/2/src/mainboard/google/hatch/... 
File src/mainboard/google/hatch/romstage_spd_smbus.c:

https://review.coreboot.org/c/coreboot/+/40415/2/src/mainboard/google/hatch/... 
PS2, Line 102: time
last system boot