Jasper Lake: Commit 21e61847 (ramtop caching) causes FSP-M to fail with EFI_UNSUPPORTED

[Matt DeVillier]

I already pushed a revert: https://review.coreboot.org/c/coreboot/+/78091

Intel stated they have no intention of releasing a public FSP for JSL
unfortuantely

On Fri, Sep 22, 2023 at 10:01 AM Jonathon Hall 
wrote:
> For Librem 11 (Intel N5100, Jasper Lake), I had to revert 21e61847 [1] in
> order for FspMemoryInit to succeed for second and later boots.
>
> If the MTRR is set in early_ramtop_enable_cache_range(), all JSL FSPs I
> tested fail FspMemoryInit with EFI_UNSUPPORTED.  Since there is no public
> FSP release for JSL, I tested the FSP binaries from a number of Chromebooks
> buggzy, cret, boten, storo.
>
> Before submitting a revert patch I wanted to discuss whether this should
> be conditionally enabled or reverted.  @Sean, I saw you authored this
> change, does it work for you?  Are there other FSP binaries available where
> this might work?
>
> CC Matt DeVillier, as this will probably affect 4.21 releases of the
> MrChromebox UEFI firmware for JSL devices.
>
> Thanks,
> Jonathon
>
> [1] https://review.coreboot.org/c/coreboot/+/74518