nRF Desktop: nRF54LM20: execute the app code from RAM #25661

kapi-no · 2025-11-19T08:19:28Z

Side PRs:

Proposed a potential improvement to automatically set the Kconfig options CONFIG_BOOT_IMAGE_EXECUTABLE_RAM_START and CONFIG_BOOT_IMAGE_EXECUTABLE_RAM_SIZE according to the DTS description:
[nrf noup] boot: zephyr: support code-sram label to define exe region sdk-mcuboot#575

Other potential improvements:

Create and finalise a PR moving the main linker script nrf_desktop.ld to the newly created linker directory so that we can have all linker scripts in one place

NordicBuilder · 2025-11-19T08:22:54Z

CI Information

^{To view the history of this post, click the 'edited' button above}
Build number: 4

Inputs:

Sources:

sdk-nrf: PR head: e4d08c06c05b6817b33717c97a9e1dd0904ab1c4

more details

sdk-nrf:

PR head: e4d08c06c05b6817b33717c97a9e1dd0904ab1c4
merge base: 15efef3f4f99bd43cc7b7dcba28d1db5ead7eeb6
target head (main): 8c57fe56d393c39bd9af8944787f55181b02760c
Diff

Github labels

Enabled	Name	Description
	ci-disabled	Disable the ci execution
	ci-all-test	Run all of ci, no test spec filtering will be done
	ci-force-downstream	Force execution of downstream even if twister fails
	ci-run-twister	Force run twister
	ci-run-zephyr-twister	Force run zephyr twister

List of changed files detected by CI (19)

applications
│  ├── nrf_desktop
│  │  ├── CMakeLists.txt
│  │  ├── configuration
│  │  │  ├── nrf54lm20dk_nrf54lm20a_cpuapp
│  │  │  │  ├── app_common.dtsi
│  │  │  │  ├── images
│  │  │  │  │  ├── mcuboot
│  │  │  │  │  │  ├── app.overlay
│  │  │  │  │  │  ├── prj.conf
│  │  │  │  │  │  ├── prj_llvm.conf
│  │  │  │  │  │  │ prj_release.conf
│  │  │  │  ├── memory_map.dtsi
│  │  │  │  ├── pm_static.yml
│  │  │  │  ├── pm_static_llvm.yml
│  │  │  │  ├── pm_static_release.yml
│  │  │  │  ├── prj.conf
│  │  │  │  ├── prj_llvm.conf
│  │  │  │  ├── prj_release.conf
│  │  │  │  ├── sysbuild.conf
│  │  │  │  ├── sysbuild_llvm.conf
│  │  │  │  │ sysbuild_release.conf
│  │  ├── linker
│  │  │  │ config_channel_dfu_ram_load.ld
│  │  ├── src
│  │  │  ├── modules
│  │  │  │  ├── Kconfig.config_channel
│  │  │  │  │ dfu.c

Outputs:

Toolchain

Version: df3cc9d822
Build docker image: docker-dtr.nordicsemi.no/sw-production/ncs-build:df3cc9d822_e595b21c39

Test Spec & Results: ✅ Success; ❌ Failure; 🟠 Queued; 🟡 Progress; ◻️ Skipped; ⚠️ Quarantine

◻️ Toolchain - Skipped: existing toolchain is used
✅ Build twister
- sdk-nrf test count: 49
✅ Integration tests
- ✅ desktop52_verification

Disabled integration tests

- test-fw-nrfconnect-nrf_lrcs_positioning
- test_ble_nrf_config
- test-fw-nrfconnect-apps
- test-fw-nrfconnect-ble_mesh
- test-fw-nrfconnect-ble_samples
- test-fw-nrfconnect-chip
- test-fw-nrfconnect-fem
- test-fw-nrfconnect-nfc
- test-fw-nrfconnect-nrf-iot_libmodem-nrf
- test-fw-nrfconnect-nrf-iot_lwm2m
- test-fw-nrfconnect-nrf-iot_samples
- test-fw-nrfconnect-nrf-iot_thingy91
- test-fw-nrfconnect-nrf-iot_zephyr_lwm2m
- test-fw-nrfconnect-nrf_crypto
- test-fw-nrfconnect-ps-main
- test-fw-nrfconnect-rpc
- test-fw-nrfconnect-rs
- test-fw-nrfconnect-tfm
- test-fw-nrfconnect-thread-main
- test-low-level
- test-sdk-audio
- test-sdk-dfu
- test-sdk-find-my
- test-sdk-mcuboot
- test-sdk-wifi
- test-secdom-samples-public

Note: This message is automatically posted and updated by the CI

github-actions · 2025-11-19T09:02:20Z

You can find the documentation preview for this PR here.

Preview links for modified nRF Connect SDK documents:

https://ncsdoc.z6.web.core.windows.net/PR-25661/nrf/applications/nrf_desktop/doc/dfu.html

NordicBuilder · 2025-11-19T09:09:15Z

Memory footprint analysis revealed the following potential issues

applications.nrf_desktop.zdebug.uart[nrf54lm20dk/nrf54lm20a/cpuapp]: RAM size increased by 344725[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zdebug[nrf52833dk/nrf52820]: ROM size increased by 540[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zdebug_dongle.uart[nrf54h20dk@0.9.0/nrf54h20/cpuapp]: ROM size increased by 752[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease.usb_next[nrf52840dk/nrf52840]: ROM size increased by 768[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf52840dongle/nrf52840]: ROM size increased by 1632[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf52840gmouse/nrf52840]: ROM size increased by 1064[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf5340dk/nrf5340/cpuapp]: ROM size increased by 1820[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf54h20dk@0.9.0/nrf54h20/cpuapp]: ROM size increased by 804[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf54l15dk/nrf54l15/cpuapp]: ROM size increased by 724[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf54lm20dk/nrf54lm20a/cpuapp]: RAM size increased by 247397[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease[nrf54lm20dk/nrf54lm20a/cpuapp]: ROM size increased by 3789[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)
applications.nrf_desktop.zrelease_dongle[nrf54h20dk@0.9.0/nrf54h20/cpuapp]: ROM size increased by 1396[B] in comparison to the main[3524638] branch. - link (cc: @nrfconnect/ncs-si-bluebagel)

Note: This message is automatically posted and updated by the CI (latest/sdk-nrf/PR-25661/4)

nordicjm · 2025-11-20T08:20:47Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+
+&cpuapp_rram {
+	/* Application does not use cpuflpr core. Assign whole RRAM to cpuapp. */
+	reg = < 0x0 DT_SIZE_K(2036) >;


<value value> style, no space after < and before >

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/images/mcuboot/app.overlay

kapi-no · 2025-11-20T13:50:25Z

Pushed an update with the following additions:

KMU support.
Removal of the CONFIG_BOOT_MAX_IMG_SECTORS Kconfig, which throws a warning and is not necessary when using DTS for partitioning.

nordicjm · 2025-11-21T11:43:00Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+			 * RAM due to the dependency on the nrfutil device tool and its KMU
+			 * provisioning functionality.
+			 */
+			nrf_kmu_reserved_push_area: memory@0 {


reserved memory is for hardware only, so KMU usage is fine, DMA usage is fine...

nordicjm · 2025-11-21T11:43:32Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+			 * both the MCUboot image and the application code. Currently, it is used
+			 * to share the image metadata between the bootloader and the application.
+			 */
+			cpuapp_sram_retained_mem_region: memory@400 {


this though is not, this is normal RAM, it needs to be a child of the sram node, see the retention doc in zephyr for an example

nordicjm · 2025-11-21T11:43:46Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+				#address-cells = <1>;
+				#size-cells = <1>;
+				ranges = <0x0 0x7a400 DT_SIZE_K(20)>;
+			};


so it can be moved here

MarekPieta · 2025-11-21T08:22:30Z

applications/nrf_desktop/CMakeLists.txt

                                  SYMBOLS __start_config_channel_modules __stop_config_channel_modules
                                  KEEP SORT NAME)
+  if(CONFIG_DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_RAM_LOAD)
+    zephyr_linker_sources(RODATA linker/config_channel_dfu_ram_load.ld)


Should we add zephyr_linker_section/zephyr_iterable_section too? This commit suggests that it's needed for IAR: b937d94

I don't think we have to, as we just perform validation as part of this linker section without creating any new symbols

Could you please check if the assertion is properly triggered for LLVM? (to ensure no silent errors in the future)

MarekPieta · 2025-11-21T08:24:27Z

applications/nrf_desktop/src/modules/Kconfig.config_channel

+	  validate if the executable RAM region of the application image does not overlap with
+	  the RAM region of the MCUboot image.
+
+config DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_UNSPECIFIED


Consider listing the swap mode explicitly too. Then we might e.g. emit an error/warning log in case MCUboot mode unsupported by the module is selected

MarekPieta · 2025-11-21T09:52:16Z

applications/nrf_desktop/src/modules/Kconfig.config_channel


+config DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_RAM_LOAD
+	bool "Adjust the DFU module to be compatible with the RAM load mode of MCUboot"
+	depends on USE_DT_CODE_PARTITION


Dependency on disabled Partition Manager might be even more relevant here (we might need a build assert here)

btw. Would it work also for other platforms (e.g. nRF52)? We might limit support to nRF54LM20 (temporarily) if needed

MarekPieta · 2025-11-21T09:59:41Z

applications/nrf_desktop/src/modules/Kconfig.config_channel

+	prompt "Adjust the DFU module to be compatible with the specific mode of MCUboot"
 	depends on BOOTLOADER_MCUBOOT
-	default y if MCUBOOT_BOOTLOADER_MODE_DIRECT_XIP
+	default DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_DIRECT_XIP if MCUBOOT_BOOTLOADER_MODE_DIRECT_XIP


Consider using depends on for bootloader modes instead of setting default (that should allow to skip the newly introduced build asserts)

Or maybe we could even use MCUBOOT_BOOTLOADER_MODE_XYZ options directly?

MarekPieta · 2025-11-21T10:02:20Z

applications/nrf_desktop/src/modules/dfu.c

+ * Currently, the revert feature is only supported by the MCUboot bootloader that
+ * is not configured for the standard direct-xip or RAM load mode.
+ */
+#define DFU_REVERT_FEATURE_IS_SUPPORTED                            \


MCUBOOT_REVERT_FEATURE_IS_SUPPORTED (as we refer to MCUboot's revert feature)

Or maybe even MCUBOOT_IMAGE_CONFIRM_NEEDED (to indicate that we need to confirm the image after it's uploaded)

We also need to set the test bit with the boot_request_upgrade API

I will stick to the REVERT variant, it is easily associated with most mcuboot modes

CONFIG_MCUBOOT_BOOTLOADER_MODE_DIRECT_XIP_WITH_REVERT
CONFIG_MCUBOOT_BOOTLOADER_MODE_RAM_LOAD_WITH_REVERT

MarekPieta · 2025-11-21T12:27:48Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+			 */
+			cpuapp_sram_retained_mem_region: memory@400 {
+				compatible = "zephyr,memory-region", "mmio-sram";
+				reg = <0x400 DT_SIZE_K(1)>;


Can we explain why we have a gap between nrf_kmu_reserved_push_area and RetainedMem?

Also: maybe we could set size to 0x100 for now and expand when needed (currently part of the retained RAM seems unused)

MarekPieta · 2025-11-21T12:42:13Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+			 * this region, but the ROM section of the application image must never
+			 * fill this region. This DTS node must be assigned to the MCUboot image
+			 * as its chosen SRAM DTS node. The usage of this SRAM region should not
+			 * be close to the maximum size of this region (100%), as the System Heap


Would be good to check what it the System Heap used for in MCUboot. Maybe we could simply disabled it: CONFIG_COMMON_LIBC_MALLOC=n?

Similarly for the application image (nRF Desktop relies on k_malloc)

MarekPieta · 2025-11-21T12:54:29Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/memory_map.dtsi

+
+		slot0_partition: partition@c000 {
+			label = "image-0";
+			reg = <0xc000 DT_SIZE_K(984)>;


Does it make sense to use partition size greater than DK_SIZE_K(489) here? Maybe we could leave part of the memory unused (as it would not be possible to boot bigger image from SRAM anyway)?

Discussed offline, lowering partition size here would not trigger build errors related to partition memory overflows anyway (build system reports FLASH usage of 0).

MarekPieta · 2025-11-21T13:06:41Z

applications/nrf_desktop/linker/config_channel_dfu_ram_load.ld

@@ -0,0 +1,3 @@
+/* Validate that the executable RAM region does not overlap with the MCUboot RAM region. */
+ASSERT(__rom_region_end <= CONFIG_DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_RAM_LOAD_MCUBOOT_RAM_START_ADDR,


I am worried that the assertion might not always be valid (e.g. if user specifies MCUboot's RAM earlier in memory).

Can we at least add a brief comment explaining our assumptions, please?

MarekPieta · 2025-11-21T13:16:50Z

applications/nrf_desktop/src/modules/Kconfig.config_channel

+config DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_RAM_LOAD
+	bool "Adjust the DFU module to be compatible with the RAM load mode of MCUboot"
+	depends on USE_DT_CODE_PARTITION
+	depends on $(dt_nodelabel_exists,cpuapp_sram_mcuboot_ram_region)


Consider using BUILD_ASSERT instead of dependency here (now you might end up with accidentally set CONFIG_DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_UNSPECIFIED)

MarekPieta · 2025-11-24T08:55:52Z

applications/nrf_desktop/src/modules/Kconfig.config_channel

+	bool "Adjust the DFU module to be compatible with the RAM load mode of MCUboot"
+	depends on USE_DT_CODE_PARTITION
+	depends on $(dt_nodelabel_exists,cpuapp_sram_mcuboot_ram_region)
+	select EXPERIMENTAL


Reminder: Make sure that some sort of experimental warning is emitted to the end-user if we remove these app-specific options.

applications/nrf_desktop/src/modules/Kconfig.config_channel

alstrzebonski · 2025-11-24T13:00:55Z

applications/nrf_desktop/configuration/nrf54lm20dk_nrf54lm20a_cpuapp/sysbuild.conf


 SB_CONFIG_BOOTLOADER_MCUBOOT=y
-SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP=y
+SB_CONFIG_MCUBOOT_MODE_RAM_LOAD=y


I wonder if we shouldn't leave one configuration that uses SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP to have both DFU methods support for nRF54LM20. Thanks to that we could have configuration that is not "experimental" (but has report rate issues in USB HS mode).

We can discuss it offline

Added support for the RAM load mode of the MCUboot bootloader to the nRF Desktop application DFU module. Added a linker script with the assert statement that prevents the executable RAM region of the application image to overflow the standard RAM region of the MCUboot image. Ref: NCSDK-35506 Signed-off-by: Kamil Piszczek <Kamil.Piszczek@nordicsemi.no>

Updated the nRF54LM20 DK configuration in the nRF Desktop application to increase the USB High Speed performance by executing application code from RAM. Due to this change, the application can now consistently maintain the 8000Hz report rate in the mouse release configuration. To execute code from RAM, the MCUboot mode has been changed from the direct-xip mode to the RAM load mode. The bootloader now copies the newer application image from one of two RRAM slots into the RAM region and then it starts the application from RAM. To support RAM load mode of the MCUboot bootloader, the partitioning method has been changed from the Partition Manager (PM) to devicetree (DTS). Currently, the PM is not properly supported in the RAM load mode. Ref: NCSDK-35506 Signed-off-by: Aleksander Strzebonski <aleksander.strzebonski@nordicsemi.no> Signed-off-by: Kamil Piszczek <Kamil.Piszczek@nordicsemi.no>

alstrzebonski

LGTM - one comment to discuss tomorrow.

kapi-no requested review from a team as code owners November 19, 2025 08:19

NordicBuilder added the changelog-entry-required Update changelog before merge. Remove label if entry is not needed or already added. label Nov 19, 2025

kapi-no force-pushed the nrf_desktop_nrf54lm20dk_ram_load branch from 25781ba to 8daea40 Compare November 19, 2025 08:23

nordicjm reviewed Nov 20, 2025

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kapi-no force-pushed the nrf_desktop_nrf54lm20dk_ram_load branch from 8daea40 to 729480a Compare November 20, 2025 11:17

kapi-no force-pushed the nrf_desktop_nrf54lm20dk_ram_load branch from 729480a to e4d08c0 Compare November 20, 2025 14:09

nordicjm requested changes Nov 21, 2025

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MarekPieta requested changes Nov 21, 2025

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MarekPieta reviewed Nov 24, 2025

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alstrzebonski reviewed Nov 24, 2025

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kapi-no force-pushed the nrf_desktop_nrf54lm20dk_ram_load branch 2 times, most recently from b0749a4 to f7436ee Compare November 24, 2025 15:33

kapi-no requested a review from a team as a code owner November 24, 2025 15:33

kapi-no added 2 commits November 24, 2025 16:33

NordicBuilder added the doc-required PR must not be merged without tech writer approval. label Nov 24, 2025

kapi-no requested review from MarekPieta, alstrzebonski and nordicjm November 24, 2025 15:34

divipillai approved these changes Nov 24, 2025

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alstrzebonski reviewed Nov 24, 2025

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		@@ -0,0 +1,3 @@
		/* Validate that the executable RAM region does not overlap with the MCUboot RAM region. */
		ASSERT(__rom_region_end <= CONFIG_DESKTOP_CONFIG_CHANNEL_DFU_MCUBOOT_RAM_LOAD_MCUBOOT_RAM_START_ADDR,

nRF Desktop: nRF54LM20: execute the app code from RAM #25661

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nRF Desktop: nRF54LM20: execute the app code from RAM #25661

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CI Information

Inputs:

Sources:

Github labels

Outputs:

Toolchain

Test Spec & Results: ✅ Success; ❌ Failure; 🟠 Queued; 🟡 Progress; ◻️ Skipped; ⚠️ Quarantine

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Memory footprint analysis revealed the following potential issues

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kapi-no commented Nov 20, 2025

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kapi-no commented Nov 19, 2025 •

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