soc/intel/alderlake: Implement MultiPhase SI Init Index 2 callback

The details about how the CPU multiprocessor init (MP) has migrated
from coreboot to FSP can be found in
https://doc.coreboot.org/soc/intel/mp_init/mp_init.html.

The major reason behind this migration is to support the Intel
proprietary and restricted CPU feature programming which can't be
performed if coreboot sets the BIOS_DONE or BIOS Reset CPL as part
of coreboot MP Init flow (prior to calling FSP-S). Hence, the new
flow introduced with Tiger Lake platform forced having monolithic
MP Init peformed by FSP (using coreboot MP PPI wrapper code).

The last 3-4 years of FSP doing MP Init has demonstrated ample
issues during platform bringup which is specific to UEFI MP Service
implementation and not relevant to open source coreboot. This new
flow makes the debug and validation aspect complicated where
any FSP MP Init code changes should have been validated with coreboot
MP PPI wrapper else might cause some failure, unfortunately,
the validation commitment has never been met, hence, issue debugging
is the only solution that remains in practice.

Most importantly, the restricted feature programming which demanded
closed source MP Init (for features like SGX and C6DRAM) has never
been enabled in coreboot (starting with Alder Lake, the SGX feature
has been dropped).

This patch attempts to decouple FSP-S doing MP Init from the rest
of the FSP-S silicon init and introduces 2nd MultiPhase SI init
which allows bootloader to perform the mandatory SoC programming
before FSP-S has done with PM programming (a.k.a set the reset CPL).

The core/uncore BWG suggests the minimum SoC programming before
BIOS Reset CPL is set. coreboot uses the MultiPhaseSI Init Index 2
to perform the required CPU programming before enabling the BIOS
Reset CPL.

This implementation would allow us to get rid of FSP running CPU
feature programming and additionally make several EDK2 MP service
modules optional (those are packed to create FSP-S blob).

In summary, this change would allow coreboot to utilize open source
MP init without running into FSP-S related code blocks.

Note: At present, Intel Alder Lake FSP doesn't have support for
MultiPhase SI Init, Index 2 (submitted a FSP code changes over
chrome-internal to enable this feature to decouple MP Init from
FSP-S init).

BUG=b:233199592
TEST=Build and boot google/taeko to ChromeOS.
Perform several thousands cycles of suspend test and power cycle
without running into any issue.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I314c63c917ef6fdd32f364b2c60bae22486b8b74
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64979
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>

0 files changed, 0 insertions, 0 deletions