mcuboot: Kconfig options for single app slot RAM loading mode

MCUboot has a configuration for single application slot RAM loading, in
which the single loader (or a hook thereof) can load an application from
an arbitrary flash location to RAM. Applications that are to be loaded
in this way need to specify, in their mcuboot header, the load address
in RAM they are meant to be loaded.

This patch adds a new Kconfig for this mode. The load address used comes
from devicetree chosen property "mcuboot,ram-load-dev", if it exists,
and if not, "zephyr,sram".

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>

cmake/mcuboot.cmake

@@ -95,7 +95,8 @@ function(zephyr_mcuboot_tasks)
 
   # If single slot mode, or if in firmware updater mode and this is the firmware updater image,
   # use slot 0 information
-  if(NOT CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP AND (NOT CONFIG_MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER OR CONFIG_MCUBOOT_APPLICATION_FIRMWARE_UPDATER))
+  if(NOT CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP AND (NOT CONFIG_MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER OR CONFIG_MCUBOOT_APPLICATION_FIRMWARE_UPDATER)
+      AND NOT CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP_RAM_LOAD)
     # Slot 1 size is used instead of slot 0 size
     set(slot_size)
     dt_nodelabel(slot1_flash NODELABEL "slot1_partition" REQUIRED)
@@ -138,6 +139,15 @@ function(zephyr_mcuboot_tasks)
     set(imgtool_args --align 1 --load-addr ${chosen_ram_address} ${imgtool_args})
     set(imgtool_args_alt_slot ${imgtool_args} --hex-addr ${slot1_partition_address})
     set(imgtool_args ${imgtool_args} --hex-addr ${slot0_partition_address})
+  elseif(CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP_RAM_LOAD)
+    dt_chosen(ram_load_dev PROPERTY "mcuboot,ram-load-dev")
+    if(DEFINED ram_load_dev)
+      dt_reg_addr(load_address PATH ${ram_load_dev})
+    else()
+      dt_chosen(chosen_ram PROPERTY "zephyr,sram")
+      dt_reg_addr(load_address PATH ${chosen_ram})
+    endif()
+    set(imgtool_args --align 1 --load-addr ${load_address} ${imgtool_args})
   else()
     set(imgtool_args --align ${write_block_size} ${imgtool_args})
   endif()

doc/build/dts/api/api.rst

@@ -462,3 +462,8 @@ device.
        WS2812 GPIO driver
    * - zephyr,touch
      - touchscreen controller device node.
+   * - mcuboot,ram-load-dev
+     - When a Zephyr application is built to be loaded to RAM by MCUboot, with
+       :kconfig:option:`CONFIG_MCUBOOT_BOOTLOADER_MODE_SINGLE_APP_RAM_LOAD`,
+       this property is used to tell MCUboot the load address of the image, which
+       will be the ``reg`` of the chosen node.

modules/Kconfig.mcuboot

@@ -254,6 +254,21 @@ config MCUBOOT_BOOTLOADER_MODE_FIRMWARE_UPDATER
 	  a dedicated firmware updater application used to update the slot0_partition
 	  application.
 
+config MCUBOOT_BOOTLOADER_MODE_SINGLE_APP_RAM_LOAD
+	bool "MCUboot has been configured in single app RAM load mode"
+	select MCUBOOT_BOOTLOADER_MODE_HAS_NO_DOWNGRADE
+	select MCUBOOT_BOOTLOADER_NO_DOWNGRADE
+	help
+	  MCUboot can load the image to RAM from an arbitrary location. In this mode,
+	  MCUboot will copy the image to RAM and begin execution from there. The image
+	  must be linked to execute from RAM, the address that it is copied to is
+	  specified using the load-addr argument when running imgtool.
+	  Note that while not used directly, a slot0_partition must be defined in the
+	  DT, as it is used to get information about size of the image to be loaded.
+	  This option automatically selects MCUBOOT_BOOTLOADER_NO_DOWNGRADE as it is
+	  not possible to swap back to older version of the application. In fact, none
+	  of the swap operations are supported in this mode.
+
 endchoice # MCUBOOT_BOOTLOADER_MODE
 
 config MCUBOOT_BOOTLOADER_MODE_HAS_NO_DOWNGRADE