[coreboot-gerrit] [S] Change in coreboot[main]: drivers/intel/fsp2_0: Support FSP-M execution from CBFS cache

[Jérémy Compostella (Code Review)]

Attention is currently required from: Andrey Petrov, Arthur Heymans, Bora Guvendik, Chen, Gang C, Dinesh Gehlot, Eran Mitrani, Jakub Czapiga, Kapil Porwal, Paul Menzel, Ronak Kanabar, Shuo Liu, Subrata Banik, Tarun.

Jérémy Compostella has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/81212?usp=email )

Change subject: drivers/intel/fsp2_0: Support FSP-M execution from CBFS cache
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Patch Set 7:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/81212/comment/0c46aecc_b8ffda68 :
PS6, Line 42:  2 MB
> > The goal is not to offer a one configuration fit all solution. […]

This commit goal is to offer an alternative to `FSP_M_ADDR` solution allowing the use FSP-M compression. The commit message also provides some information on the impact when used on particular board design for illustration. With this scope in mind, what would you suggest to add to this commit to help with your point ?

File src/drivers/intel/fsp2_0/Kconfig:

https://review.coreboot.org/c/coreboot/+/81212/comment/43ae905f_6f1aff37 :
PS3, Line 221: FSP_EXECUTE_FROM_CBFS_CACHE
> Having an assertion can avoid the device to run into the actual issue but I don't  see an option about how one would mitigate the SPI size limitation and able to boot to OS with lower cache with this proposal?

I had it as an assert at some points but went back to a WARNING to align with what is done for other non-booting images within the same Makefile.

This commit has no vocation to provide any mitigation if FSP-M cannot fit in CAR. This feature should only be use if it can fit as stated in the Kconfig.

I totally agree that working on reducing the footprint is the way to go to minimize the occupation of the SPINOR in general as it yields better results. The point of this commit is not to force any decision for any particular design but to offer an extra way to reduce the SPINOR occupation by leveraging existing code in a more flexible way.