sysbuild: Add firmware loader application type support

Adds support for setting up a firmware loader image in a build,
which can also optionally automatically configure MCUboot and the
application image to be able to boot the firmware loader image
using the retention subsystem

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

share/sysbuild/cmake/modules/sysbuild_extensions.cmake

@@ -216,7 +216,7 @@ endfunction()
 #                             and debugging.
 #
 function(ExternalZephyrProject_Add)
-  set(app_types MAIN BOOTLOADER)
+  set(app_types MAIN BOOTLOADER FIRMWARE_LOADER)
   cmake_parse_arguments(ZBUILD "" "APPLICATION;BOARD;BOARD_REVISION;SOURCE_DIR;APP_TYPE;BUILD_ONLY" "" ${ARGN})
 
   if(ZBUILD_UNPARSED_ARGUMENTS)

share/sysbuild/image_configurations/BOOTLOADER_image_default.cmake

@@ -29,10 +29,17 @@ elseif(SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP OR SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP_WI
   set(bootmode CONFIG_BOOT_DIRECT_XIP)
 elseif(SB_CONFIG_MCUBOOT_MODE_RAM_LOAD)
   set(bootmode CONFIG_BOOT_RAM_LOAD)
-elseif(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER)
-  set(bootmode CONFIG_BOOT_FIRMWARE_LOADER)
 elseif(SB_CONFIG_MCUBOOT_MODE_SINGLE_APP_RAM_LOAD)
   set(bootmode CONFIG_SINGLE_APPLICATION_SLOT_RAM_LOAD)
+elseif(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER)
+  set(bootmode CONFIG_BOOT_FIRMWARE_LOADER)
+
+  if(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER_BOOT_MODE_ENTRANCE)
+    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETAINED_MEM y)
+    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETENTION y)
+    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETENTION_BOOT_MODE y)
+    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_BOOT_FIRMWARE_LOADER_BOOT_MODE y)
+  endif()
 endif()
 
 foreach(loopbootmode ${bootmodes})

share/sysbuild/image_configurations/FIRMWARE_LOADER_image_default.cmake

@@ -0,0 +1,22 @@
+# Copyright (c) 2025 Nordic Semiconductor
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# This sysbuild CMake file sets the sysbuild controlled settings as properties
+# on a firmware updater image.
+
+set_config_bool(${ZCMAKE_APPLICATION} CONFIG_BOOTLOADER_MCUBOOT "${SB_CONFIG_BOOTLOADER_MCUBOOT}")
+set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_SIGNATURE_KEY_FILE
+                  "${SB_CONFIG_BOOT_SIGNATURE_KEY_FILE}"
+)
+set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_ENCRYPTION_KEY_FILE
+                  "${SB_CONFIG_BOOT_ENCRYPTION_KEY_FILE}"
+)
+
+if("${SB_CONFIG_SIGNATURE_TYPE}" STREQUAL "NONE")
+  set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_GENERATE_UNSIGNED_IMAGE y)
+else()
+  set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_GENERATE_UNSIGNED_IMAGE n)
+endif()
+
+set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER y)

share/sysbuild/image_configurations/MAIN_image_default.cmake

@@ -39,9 +39,16 @@ if(SB_CONFIG_BOOTLOADER_MCUBOOT)
     set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_BOOTLOADER_MODE_RAM_LOAD y)
     set_config_bool(${ZCMAKE_APPLICATION} CONFIG_XIP n)
     set_config_int(${ZCMAKE_APPLICATION} CONFIG_FLASH_SIZE 0)
-  elseif(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER)
-    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER y)
   elseif(SB_CONFIG_MCUBOOT_MODE_SINGLE_APP_RAM_LOAD)
     set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP_RAM_LOAD y)
+  elseif(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER)
+    set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER y)
+
+    if(SB_CONFIG_MCUBOOT_MODE_FIRMWARE_UPDATER_BOOT_MODE_ENTRANCE)
+      set_config_bool(${ZCMAKE_APPLICATION} CONFIG_REBOOT y)
+      set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETAINED_MEM y)
+      set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETENTION y)
+      set_config_bool(${ZCMAKE_APPLICATION} CONFIG_RETENTION_BOOT_MODE y)
+    endif()
   endif()
 endif()

share/sysbuild/images/CMakeLists.txt

@@ -12,6 +12,7 @@ ExternalZephyrProject_Add(
 
 # This allows for MCUboot to be included.
 sysbuild_add_subdirectory(bootloader)
+sysbuild_add_subdirectory(firmware_loader)
 
 # Include zephyr modules generated sysbuild CMake file.
 foreach(SYSBUILD_CURRENT_MODULE_NAME ${SYSBUILD_MODULE_NAMES})

share/sysbuild/images/Kconfig

@@ -3,3 +3,4 @@
 # SPDX-License-Identifier: Apache-2.0
 
 rsource "bootloader/Kconfig"
+rsource "firmware_loader/Kconfig"

share/sysbuild/images/bootloader/Kconfig

@@ -141,6 +141,14 @@ config MCUBOOT_MODE_SINGLE_APP_RAM_LOAD
 
 endchoice
 
+config MCUBOOT_MODE_FIRMWARE_UPDATER_BOOT_MODE_ENTRANCE
+	bool "Firmware updater retention boot mode entrance"
+	depends on MCUBOOT_MODE_FIRMWARE_UPDATER
+	help
+	  Will enable retained memory, retention and the boot mode module in MCUboot and the main
+	  application so that it can be used to force booting the firmware loader application
+	  image. This needs the ``zephyr,boot-mode`` chosen node to be correctly configured.
+
 config SIGNATURE_TYPE
 	string
 	default "NONE" if BOOT_SIGNATURE_TYPE_NONE

share/sysbuild/images/firmware_loader/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Copyright (c) 2025 Nordic Semiconductor
+#
+# SPDX-License-Identifier: Apache-2.0
+
+if(SB_CONFIG_FIRMWARE_LOADER_IMAGE_PATH)
+  ExternalZephyrProject_Add(
+    APPLICATION ${SB_CONFIG_FIRMWARE_LOADER_IMAGE_NAME}
+    SOURCE_DIR ${SB_CONFIG_FIRMWARE_LOADER_IMAGE_PATH}
+    APP_TYPE FIRMWARE_LOADER
+  )
+endif()

share/sysbuild/images/firmware_loader/Kconfig

@@ -0,0 +1,37 @@
+# Copyright (c) 2025 Nordic Semiconductor
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config SUPPORT_FIRMWARE_LOADER_SMP_SVR
+	bool
+	default y
+
+choice FIRMWARE_LOADER
+	prompt "Firmware loader image"
+	default FIRMWARE_LOADER_IMAGE_NONE
+	depends on MCUBOOT_MODE_FIRMWARE_UPDATER
+
+config FIRMWARE_LOADER_IMAGE_NONE
+	bool "None"
+	help
+	  Do not Include a firmware loader image in the build.
+
+config FIRMWARE_LOADER_IMAGE_SMP_SVR
+	bool "smp_svr"
+	depends on SUPPORT_FIRMWARE_LOADER_SMP_SVR
+	help
+	  Include the MCUmgr ``smp_svr`` sample as the firmware loader image to use.
+
+endchoice
+
+config FIRMWARE_LOADER_IMAGE_NAME
+	string
+	default "smp_svr" if FIRMWARE_LOADER_IMAGE_SMP_SVR
+	help
+	  Name of firmware loader image.
+
+config FIRMWARE_LOADER_IMAGE_PATH
+	string
+	default "${ZEPHYR_BASE}/samples/subsys/mgmt/mcumgr/smp_svr" if FIRMWARE_LOADER_IMAGE_SMP_SVR
+	help
+	  Source directory of firmware loader image.