Reducing startup time with MCUBoot in nRF Desktop

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Thu, 13 Feb 2025 17:49:10 GMT

No.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Thu, 13 Feb 2025 15:14:43 GMT

Ok, in that case I will need to drop xip. Does it need any changes to partition manager?

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Thu, 13 Feb 2025 14:06:22 GMT

No, it's not a bug. swap modes always boot from slot 0, direct XIP boots from the highest version, and no state is stored, so you need to determine which image is valid and has the highest version, and the only way to do that is to validate at startup. Therefore, Currently, CONFIG_BOOT_VALIDATE_SLOT0 and Direct-XIP is not a combination we support.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Wed, 12 Feb 2025 17:35:17 GMT

Ok, is that a bug? I’d like to keep direct xip

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Wed, 12 Feb 2025 16:56:53 GMT

You can disable the direct xip in mcuboot mode (SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP), then CONFIG_BOOT_VALIDATE_SLOT0=n takes effect.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Tue, 11 Feb 2025 08:15:23 GMT

Does that mean I can’t disable signature verification at boot?

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Mon, 10 Feb 2025 19:31:59 GMT

Because RSA is mbedtls which is slower, please try to use ecdsa which is tinycrypt.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Fri, 07 Feb 2025 23:16:44 GMT

Yes, that is where I set it, as described in my original post. And like you found, it is not set in .config. But the 920ms delay still persists.

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Fri, 07 Feb 2025 20:22:03 GMT

[quote user="nrbrook"] it seems CONFIG_BOOT_VALIDATE_SLOT0 isn't disabling it, how can it be disabled (while still validating during DFU)?[/quote]

How do you add CONFIG_BOOT_VALIDATE_SLOT0?

I add CONFIG_BOOT_VALIDATE_SLOT0=n in the nrf_desktop/configuration/nrf52840dk_nrf52840/images/mcuboot/prj_fast_pair.conf, and CONFIG_BOOT_VALIDATE_SLOT0 is not set in the .config under build/mcuboot/zephyr.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Fri, 07 Feb 2025 17:37:59 GMT

I only want signature verification at DFU. After that, I don't need it every boot. But it seems CONFIG_BOOT_VALIDATE_SLOT0 isn't disabling it, how can it be disabled (while still validating during DFU)?

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Fri, 07 Feb 2025 13:57:34 GMT

52832 has no hardware crypto. Having some sort of signature is a must for you?

RSA is mbedtls which is slower than a tortoise, and ecdsa is tinycrypt.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Thu, 06 Feb 2025 14:33:35 GMT

I had to generate a key using

python ../../../../../../../bootloader/mcuboot/scripts/imgtool.py keygen -k mcuboot_private_ed.pem -t ecdsa-p256

from the mcuboot directory, because the key you specified didn't exist.

Then it started in 120ms – much better! But why is RSA so much slower given CONFIG_BOOT_VALIDATE_SLOT0=n

Furthermore, my real application is on nrf52832, which has smaller flash, and I recall ecdsa requires much more space in the bootloader.

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Thu, 06 Feb 2025 13:39:31 GMT

Could you try the following and let me know?

--- a/applications/nrf_desktop/configuration/nrf52840dk_nrf52840/sysbuild_fast_pair.conf
+++ b/applications/nrf_desktop/configuration/nrf52840dk_nrf52840/sysbuild_fast_pair.conf
@@ -8,5 +8,6 @@
SB_CONFIG_BT_FAST_PAIR=y
SB_CONFIG_BOOTLOADER_MCUBOOT=y
SB_CONFIG_MCUBOOT_MODE_DIRECT_XIP=y
-SB_CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
-SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="\${APPLICATION_CONFIG_DIR}/images/mcuboot/mcuboot_private_fast_pair.pem"
+SB_CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=y
+SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="\${APPLICATION_CONFIG_DIR}/images/mcuboot/mcuboot_private_ed.pem"

cp ../../nrf52840gmouse_nrf52840/images/mcuboot/mcuboot_private.pem mcuboot/mcuboot_private_ed.pem

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Wed, 05 Feb 2025 18:57:20 GMT

That is what I was testing with. With base configuration I get no delay. With fast pair I get 1s.

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Wed, 05 Feb 2025 17:47:55 GMT

Could you test with nRF52840DK? We got virtually no delay between button presses and led the operation.

RE: Reducing startup time with MCUBoot in nRF Desktop

nrbrook — Tue, 04 Feb 2025 15:22:41 GMT

No, it is just the same.

RE: Reducing startup time with MCUBoot in nRF Desktop

Amanda Hsieh — Tue, 04 Feb 2025 15:06:46 GMT

Hi,

Could you also add CONFIG_NRFX_CLOCK_LFXO_TWO_STAGE_ENABLED=n to images/mcuboot/prj_fast_pair.conf? Does it help?

Regards,
Amanda H.