[M] Change in coreboot[master]: mb/google/rex: Update Debug Flash Layout to fit WP_RO within 4MB

[Subrata Banik (Code Review)]

Attention is currently required from: Tarun Tuli, Kapil Porwal.

Subrata Banik has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/74253 )

Change subject: mb/google/rex: Update Debug Flash Layout to fit WP_RO within 4MB
......................................................................

mb/google/rex: Update Debug Flash Layout to fit WP_RO within 4MB

This patch updates the Rex debug flash layout to optimize WP_RO to 4MB.

Changes for chromeos.fmd:

SI_BIOS:
     RW_SECTION_A/B: Increase to 7.5MB.
     RW_LEGACY: Introduce with 1MB.
     RW_MISC: Increased to 1MB.
     RW_UNUSED: 2MB (reserved)
     WP_RO: Reduce to 4MB

Additionally, ensure RW_SECTION_B region starts at 16MB boundary in the
SPI Flash.

BUG=b:277143384
TEST=Able to build and boot google/rex with FSP release and debug image.

Signed-off-by: Subrata Banik 
Change-Id: I4ab69eb24937d58c8bc5d3c0a6e5cb70b843a1ae
---
M src/mainboard/google/rex/chromeos-debug-fsp.fmd
1 file changed, 50 insertions(+), 15 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/53/74253/1

diff --git a/src/mainboard/google/rex/chromeos-debug-fsp.fmd b/src/mainboard/google/rex/chromeos-debug-fsp.fmd
index bd250f5f..c3c1336 100644
--- a/src/mainboard/google/rex/chromeos-debug-fsp.fmd
+++ b/src/mainboard/google/rex/chromeos-debug-fsp.fmd
@@ -4,37 +4,45 @@
    	SI_ME
    }
    SI_BIOS 23M {
-		RW_SECTION_A 7604K {
+		RW_SECTION_A 7680K {
    		VBLOCK_A 8K
    		FW_MAIN_A(CBFS)
    		RW_FWID_A 64
    		ME_RW_A(CBFS) 4400K
    	}
-		RW_MISC 152K {
-			RW_ELOG(PRESERVE) 4K
-			RW_SHARED 4K {
-				SHARED_DATA 4K
-			}
-			RW_VPD(PRESERVE) 8K
-			RW_NVRAM(PRESERVE) 8K
-			UNIFIED_MRC_CACHE(PRESERVE) 128K {
-				RECOVERY_MRC_CACHE 64K
-				RW_MRC_CACHE 64K
-			}
-		}
    	# This section starts at the 16M boundary in SPI flash.
    	# MTL does not support a region crossing this boundary,
    	# because the SPI flash is memory-mapped into two non-
    	# contiguous windows.
-		RW_SECTION_B 7604K {
+		RW_SECTION_B 7680K {
    		VBLOCK_B 8K
    		FW_MAIN_B(CBFS)
    		RW_FWID_B 64
    		ME_RW_B(CBFS) 4400K
    	}
+		RW_MISC 1M {
+			UNIFIED_MRC_CACHE(PRESERVE) 128K {
+				RECOVERY_MRC_CACHE 64K
+				RW_MRC_CACHE 64K
+			}
+			RW_ELOG(PRESERVE) 16K
+			RW_SHARED 16K {
+				SHARED_DATA 8K
+				VBLOCK_DEV 8K
+			}
+			# The RW_SPD_CACHE region is only used for rex variants that use DDRx memory.
+			# It is placed in the common `chromeos.fmd` file because it is only 4K and there
+			# is free space in the RW_MISC region that cannot be easily reclaimed because
+			# the RW_SECTION_B must start on the 16M boundary.
+			RW_SPD_CACHE(PRESERVE) 4K
+			RW_VPD(PRESERVE) 8K
+			RW_NVRAM(PRESERVE) 24K
+		}
+		RW_LEGACY(CBFS) 1M
+		RW_UNUSED 2M
    	# Make WP_RO region align with SPI vendor
    	# memory protected range specification.
-		WP_RO 8M {
+		WP_RO 4M {
    		RO_VPD(PRESERVE) 16K
    		RO_GSCVD 8K
    		RO_SECTION {