modules: trusted-firmware-m: Add STM32_FLASH_LAYOUT_BEGIN_OFFSET

Add TF-M directive STM32_FLASH_LAYOUT_BEGIN_OFFSET needed to specify
the gap needed by external boot stage resources at flash beginning.
The offset tells STM32 TF-M firmware the base offset in the flash
where the several TF-M and non-secure image areas shall be located.

The CMake directive was introduced mainline TF-M commit [1] and merged
in Zephyr TF-M repository [2].

Link: TrustedFirmware-M/trusted-firmware-m@fc035b8 [1]
Link: zephyrproject-rtos/trusted-firmware-m@954dc80 [2]
Signed-off-by: Etienne Carriere <[email protected]>

Author: etienne-lms

modules/trusted-firmware-m/CMakeLists.txt

@@ -281,6 +281,12 @@ if (CONFIG_BUILD_WITH_TFM)
     list(APPEND TFM_CMAKE_ARGS -DETHOS_DRIVER_PATH=${CONFIG_TFM_ETHOS_DRIVER_PATH_LOCAL})
   endif()
 
+  if(CONFIG_TFM_STM32_FLASH_LAYOUT_BEGIN_OFFSET)
+    list(APPEND TFM_CMAKE_ARGS
+      -DSTM32_FLASH_LAYOUT_BEGIN_OFFSET=${CONFIG_TFM_STM32_FLASH_LAYOUT_BEGIN_OFFSET}
+    )
+  endif()
+
   file(MAKE_DIRECTORY ${TFM_BINARY_DIR})
   add_custom_target(tfm_cmake
     DEPENDS ${TFM_BINARY_DIR}/CMakeCache.txt

modules/trusted-firmware-m/Kconfig.tfm

@@ -517,4 +517,14 @@ config TFM_EXCEPTION_INFO_DUMP
 	  On fatal errors in the secure firmware, capture info about the exception.
 	  Print the info if the SPM log level is sufficient.
 
+config TFM_STM32_FLASH_LAYOUT_BEGIN_OFFSET
+	int "Offset gap at beginning of flash layout"
+	depends on SOC_FAMILY_STM32
+	default 0
+	help
+	  Set an offset at the beginning of the STM32 platform flash
+	  layout above which TF-M resources location start. The platform uses
+	  this gap for platform specific reason, as for example when a
+	  bootloader that is external to TF-M is used.
+
 endif # BUILD_WITH_TFM