soc/intel/p2sb: Refactor `p2sb_execute_sideband_access` function

This patch refactors p2sb_execute_sideband_access() to be able to
handle SBI operations in both SMM and non-SMM scenarios.

Prior to FSP-S operation being done, the IOE P2SB device will be
visible on the PCI bus hence, performing the SBI operation using IOE
P2SB doesn't involve unhide/hide operation.

Post FSP-S, the IOE P2SB device is hidden.

Additionally, SBI operations can't be performed as is. The only
possible way to send SBI is inside SMM mode and to do that, coreboot
needs to unhide the P2SB device prior to sending the SBI and hide
it post sending SBI.

As a result, the p2sb_execute_sideband_access() function has been
refactored to manage these cases seamlessly without users of the
p2sb_execute_sideband_access() actually being bothered about the
calling mode.

BUG=b:239806774
TEST=Able to perform p2sb_execute_sideband_access() function call in
both SMM and non-SMM mode without any hang/die.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: Iafebd5190deb50fd95382f17bf0248fcbfb23cb8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66950
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

0 files changed, 0 insertions, 0 deletions