[M] Change in coreboot[master]: soc/intel/cmn/cse: Create another config for sending CSE EOP cmd late

[Subrata Banik (Code Review)]

Subrata Banik has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/69976 )

Change subject: soc/intel/cmn/cse: Create another config for sending CSE EOP cmd late
......................................................................

soc/intel/cmn/cse: Create another config for sending CSE EOP cmd late

Presently, coreboot supports two instances of sending EOP cmd to
the Intel CSE.

1. Sending EOP cmd to CSE during `.final` operation from cse pci driver.
2. Starting with Alder Lake, the recommendation was to send EOP to CSE
earlier than CSE `.final` operation. Since then it's referred to as
`Sending EOP Early`. This method helped to save the CSE EOP response
time significantly.

During Meteor Lake platform, CSE EOP response time has become
non-deterministic and we have figured that sending EOP command later
than CSE .final operation is actually helping to optimize the boot time
significantly (around ~150ms savings compared to sending from `.final`
ops and ~5sec compared to sending CSE early).

Hence, this patch intended to create yet another kconfig for sending
CSE late (specifically after `.final` operation). The idea for this
newer config is to use the boot state machine for sending CSE EOP cmd.

The patch train in this series would add the specific changes to allow
sending EOP late and perform other essential operations required prior
booting to OS as coreboot decided to skip calling into FSP Notify phase.

The current plan is that Intel Meteor Lake platform will select this
newer config from SoC code.

BUG=none
TEST=Able to send EOP command successfully for Google/Taeko.

Signed-off-by: Subrata Banik 
Change-Id: Iea512cd5b79d61dd5d5a962079baf525027c831f
---
M src/soc/intel/common/block/cse/Kconfig
1 file changed, 50 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/76/69976/1

diff --git a/src/soc/intel/common/block/cse/Kconfig b/src/soc/intel/common/block/cse/Kconfig
index 55a2b49..cdc4db4 100644
--- a/src/soc/intel/common/block/cse/Kconfig
+++ b/src/soc/intel/common/block/cse/Kconfig
@@ -54,6 +54,17 @@
      In later stages, CSE might be busy and might require more time to process EOP command.
      SoC can use this Kconfig to send EOP earlier by itself.

+config SOC_INTEL_CSE_SEND_EOP_LATE
+	bool
+	depends on SOC_INTEL_COMMON_BLOCK_CSE
+	help
+	  Use this config to send End Of Post (EOP) late (even after CSE `final` operation)
+	  using boot state either `BS_PAYLOAD_BOOT` or `BS_PAYLOAD_LOAD` from common code
+	  in order to reduce time required to send EOP and getting CSE response.
+	  It has been observed that CSE might be busy and might require more time to
+	  process the EOP command.
+	  SoC can use this Kconfig to send EOP later by itself.
+
 config SOC_INTEL_CSE_LITE_SKU
    bool
    default n