TSEG is not accessible in ring 0 after it is locked in ramstage, in
contrast with cbmem which remains accessible. Assuming SMM does not
touch the cache this is a good region to cache stages.
Tested on Lenovo thinkpad X200: on cold boot the external stage cache
gets created and the cached ramstage gets successfully used on the S3
resume path.
Change-Id: I642f7d6ae5523a35904c8e1f029027565a364d26
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/25604
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
c3e9ba03b6