samples: Fix FOTA for nRF54LM20

- Removed a wrong DTS configuration that changes the ROM/RAM sizes.
- Modified Mcuboot files to support compression and internal-rom
only.
- Aligned sysbuild to support compression and internal-rom only
for nRF54LM20 target.
- Added readme note.

Signed-off-by: Arkadiusz Balys <arkadiusz.balys@nordicsemi.no>

Author: ArekBalysNordic

samples/light_switch/Kconfig.sysbuild

@@ -45,6 +45,16 @@ endif # SOC_SERIES_NRF53X
 if BOARD_NRF54LM20DK
 
 config PM_OVERRIDE_EXTERNAL_DRIVER_CHECK
+	default n
+
+config PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY
+	default n
+
+choice MCUBOOT_MODE
+	default MCUBOOT_MODE_OVERWRITE_ONLY
+endchoice
+
+config MCUBOOT_COMPRESSED_IMAGE_SUPPORT
 	default y
 
 endif # BOARD_NRF54LM20DK

samples/light_switch/README.rst

@@ -125,7 +125,8 @@ For example, when building from the command line, use the following command:
 Alternatively, you can :ref:`configure Zigbee FOTA manually <ug_zigbee_configuring_components_ota>`.
 
 .. note::
-   You can use the :file:`prj_fota.conf` file only with a development kit that contains the nRF52840, nRF5340, nRF54L15 or nRF54L10 SoC.
+   You can use the :file:`prj_fota.conf` file only with a development kit that contains the nRF52840, nRF5340, nRF54L15, nRF54L10 or nRF54LM20 SoC.
+   For nRF54LM20 SoC, the external flash is not used, all the images are stored in the internal flash with the compression enabled.
 
 To activate the Multiprotocol Bluetooth LE extension, set :makevar:`EXTRA_CONF_FILE` to the :file:`overlay-multiprotocol_ble.conf`.
 For example, when building from the command line, use the following command:

samples/light_switch/boards/nrf54lm20dk_nrf54lm20a_cpuapp_fota.overlay

@@ -13,7 +13,6 @@
 		zephyr,zigbee-timer = &timer24;
 		zephyr,code-partition = &slot0_partition;
 		zephyr,ieee802154 = &ieee802154;
-		nordic,pm-ext-flash = &mx25r64;
 	};
 
 	pwmleds {
@@ -46,19 +45,6 @@
 	};
 };
 
-/* Restore full RRAM and SRAM */
-&cpuapp_rram {
-	reg = <0x0 DT_SIZE_K(2036)>;
-};
-
-&cpuapp_sram {
-	reg = <0x20000000 DT_SIZE_K(512)>;
-};
-
 &timer24 {
 	status = "okay";
 };
-
-&mx25r64 {
-	status = "okay";
-};

samples/light_switch/sysbuild/mcuboot/boards/nrf54lm20dk_nrf54lm20a_cpuapp.conf

@@ -7,13 +7,24 @@
 CONFIG_HW_STACK_PROTECTION=n
 CONFIG_BOOT_WATCHDOG_FEED=n
 
-# nRF54LM20DK uses SPI NOR external flash
-CONFIG_GPIO=y
-CONFIG_SPI=y
-CONFIG_SPI_NOR=y
-CONFIG_SPI_NOR_SFDP_DEVICETREE=y
-CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096
-CONFIG_PM_OVERRIDE_EXTERNAL_DRIVER_CHECK=y
+# Disable all debug features
+CONFIG_ASSERT_VERBOSE=n
+CONFIG_ASSERT_NO_FILE_INFO=y
+CONFIG_PRINTK=n
+
+# Bootloader size optimization to fit into 28 KB partition.
+# These options can be safely disabled because in this configuration,
+# the secondary slot resides in the internal RRAM, so features
+# needed to handle the external flash are not needed.
+CONFIG_SPI_NOR=n
+CONFIG_SPI=n
 
 # Increase the maximum number of sectors to 512 to fit the big image size (> 1024 kB).
 CONFIG_BOOT_MAX_IMG_SECTORS=512
+
+# Currently, without tickless kernel, the SYSCOUNTER value after the software
+# reset is not set properly and due to that the first system interrupt is not called
+# in the proper time - the SYSCOUNTER value is set to the value from before
+# reset + 1. Hence, the reboot time increases more and more.
+# To avoid it enable tickles kernel for mcuboot.
+CONFIG_TICKLESS_KERNEL=y

samples/light_switch/sysbuild/mcuboot/boards/nrf54lm20dk_nrf54lm20a_cpuapp.overlay

@@ -4,12 +4,10 @@
  * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
  */
 
-/ {
-	chosen {
-		nordic,pm-ext-flash = &mx25r64;
-	};
-};
-
+/* Disable the external flash, as it's not needed
+ * for the configuration with secondary slot residing
+ * in the internal RRAM.
+ */
 &mx25r64 {
-	status = "okay";
+	status = "disabled";
 };

samples/light_switch/sysbuild/mcuboot/prj.conf

@@ -4,42 +4,39 @@
 # SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 #
 
-CONFIG_PM=n
 
 CONFIG_MAIN_STACK_SIZE=10240
-CONFIG_MBEDTLS_CFG_FILE="mcuboot-mbedtls-cfg.h"
 
 CONFIG_BOOT_SWAP_SAVE_ENCTLV=n
-CONFIG_BOOT_ENCRYPT_IMAGE=n
-
-CONFIG_BOOT_UPGRADE_ONLY=n
 CONFIG_BOOT_BOOTSTRAP=n
-
-### mbedTLS has its own heap
-# CONFIG_HEAP_MEM_POOL_SIZE is not set
-
-### We never want Zephyr's copy of tinycrypt.  If tinycrypt is needed,
-### MCUboot has its own copy in tree.
-# CONFIG_TINYCRYPT is not set
-# CONFIG_TINYCRYPT_ECC_DSA is not set
-# CONFIG_TINYCRYPT_SHA256 is not set
+CONFIG_PM=n
 
 CONFIG_FLASH=y
 CONFIG_FPROTECT=y
 
-### Various Zephyr boards enable features that we don't want.
-# CONFIG_BT is not set
-# CONFIG_BT_CTLR is not set
-# CONFIG_I2C is not set
-
-CONFIG_LOG=y
-CONFIG_LOG_MODE_MINIMAL=y # former CONFIG_MODE_MINIMAL
-### Ensure Zephyr logging changes don't use more resources
-CONFIG_LOG_DEFAULT_LEVEL=0
-### Use info log level by default
-CONFIG_MCUBOOT_LOG_LEVEL_INF=y
-### Decrease footprint by ~4 KB in comparison to CBPRINTF_COMPLETE=y
+# Bootloader size optimization
 CONFIG_CBPRINTF_NANO=y
-CONFIG_NRF_RTC_TIMER_USER_CHAN_COUNT=0
-### Use the minimal C library to reduce flash usage
-CONFIG_MINIMAL_LIBC=y
+CONFIG_PRINTK=n
+CONFIG_CONSOLE=n
+CONFIG_SERIAL=n
+CONFIG_UART_CONSOLE=n
+CONFIG_USE_SEGGER_RTT=n
+CONFIG_GPIO=n
+
+CONFIG_BOOT_MAX_IMG_SECTORS=256
+
+CONFIG_LOG=n
+CONFIG_CONSOLE_HANDLER=n
+CONFIG_BOOT_BANNER=n
+CONFIG_NCS_BOOT_BANNER=n
+CONFIG_TIMESLICING=n
+CONFIG_RESET_ON_FATAL_ERROR=n
+CONFIG_MULTITHREADING=n
+CONFIG_TICKLESS_KERNEL=n
+CONFIG_TIMEOUT_64BIT=n
+CONFIG_NRF_ENABLE_ICACHE=n
+CONFIG_SIZE_OPTIMIZATIONS=y
+
+# Activate LTO
+CONFIG_LTO=y
+CONFIG_ISR_TABLES_LOCAL_DECLARATION=y