[coreboot-gerrit] Change in coreboot[master]: ec/google/wilco: Set minimum UCSI_ACPI region length

[Mathew King (Code Review)]

Mathew King has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/38414 )

Change subject: ec/google/wilco: Set minimum UCSI_ACPI region length
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Patch Set 4: Code-Review+2

(1 comment)
> Patch Set 4:
>
> (1 comment)

https://review.coreboot.org/c/coreboot/+/38414/4//COMMIT_MSG 
Commit Message:

https://review.coreboot.org/c/coreboot/+/38414/4//COMMIT_MSG@10 
PS4, Line 10: we set minimum UCSI_ACPI length to be located outside of IMD small region.
> where is it placed then? […]

The UCSI kernel driver maps the ACPI memory as not cached. Cache mapping is set on page boundaries and all IMD small is within the same page. If another driver maps the memory as write-back before the UCSI driver is loaded then the UCSI driver will fail to map the memory as not cached. By forcing the UCSI memory out of the IMD small it can map the memory correctly because it is in it's own page.

Bernardo, will you add some more detail to the commit message?