soc/amd/common/psp_smi: implement P2C mailbox handling

When the PSP wants to access the SPI flash during runtime, but isn't the
owner of the SPI flash controller, it sends an SMI to the x86 side. The
corresponding SMI handler then checks the P2C (PSP to core) mailbox for
the command and data, processes the command, and if needed puts the
requested data into the P2C buffer.

The P2C mailbox is a memory region in TSEG aka SMM memory. Both location
and size are communicated to the PSP via the PSP SMM info mailbox
command which is sent right after mpinit is done.

This commit adds the code to access the P2C mailbox to the PSP SMI
handler code, but the handling of the actual mailbox commands the PSP
sends to the SMI handler is added in later patches to keep the patch
size manageable.

This patch is a heavily reworked version of parts of CB:65523.

Document #55758 Rev. 2.04 was used as a reference.

Test=When selecting SOC_AMD_COMMON_BLOCK_PSP_SMI, Mandolin still builds

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Signed-off-by: Ritul Guru <ritul.bits@gmail.com>
Change-Id: I50479bed2332addae652026c6818460eeb6403af
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83740
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>

0 files changed, 0 insertions, 0 deletions