Reduce MCUBoot startup time

RE: Reduce MCUBoot startup time

Vidar Berg — Fri, 23 Dec 2022 09:46:03 GMT

I cannot think of any major drawbacks with selecting RCOSC clock source for this application. The average sleep current will increase slightly since the RCOSC source requires periodic calibration against the HFXO source (~1.5 uA), but I assume the bulb is mains powered. The RCOSC is also less accurate as you can see from the el. spec. here: Low frequency RC oscillator (LFRC).

RE: Reduce MCUBoot startup time

Yeccc — Fri, 23 Dec 2022 07:38:41 GMT

The first configuration, it seems to reduce more startup time.
Does this modify have other effects?

RE: Reduce MCUBoot startup time

Vidar Berg — Wed, 21 Dec 2022 11:18:53 GMT

Which configuration did you want to use, the one with LFXO or LFRC?

RE: Reduce MCUBoot startup time

Yeccc — Wed, 21 Dec 2022 08:52:17 GMT

Could you confirm it?
Does this modify have other effects?

RE: Reduce MCUBoot startup time

Yeccc — Tue, 20 Dec 2022 10:11:43 GMT

Thanks for your support.

Does this have any other impact?

RE: Reduce MCUBoot startup time

Vidar Berg — Tue, 20 Dec 2022 09:58:16 GMT

Thank you for explaining the reason you are looking to reduce the startup time. This is valuable feedback which I will relay to the developers.

I was able to significantly reduce the startup time now by disabling boot validation that takes place on every reboot by default, and by changing the default clock configuration.

Here are my results:

#1 with RCOSC as LF clock source

Settings added to MCUBoot build:

- CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

- CONFIG_BOOT_VALIDATE_SLOT0=n

In light bulb app:

- CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

#2 with LFXO as LF clock source

Settings added to MCUBoot build:

- CONFIG_SYSTEM_CLOCK_WAIT_FOR_STABILITY=n

- CONFIG_BOOT_VALIDATE_SLOT0=n

In light bulb app:

- CONFIG_SYSTEM_CLOCK_WAIT_FOR_STABILITY=n

You may also consider using the SYS_INIT() macro for functions that may benefit from being run before main().

RE: Reduce MCUBoot startup time

Yeccc — Tue, 20 Dec 2022 00:54:09 GMT

The bulb device needs to be on soon after being powered on;

In addition, our bulb device is restored to factory settings through multiple power on/off sequences, and too long startup time will also affect the user experience.

I really hope you can solve this issue. Thanks a lot.

RE: Reduce MCUBoot startup time

Vidar Berg — Mon, 19 Dec 2022 13:05:55 GMT

Thanks for confirming. I measure 1.1 second here with the original sample project between systeminit() in MCUBoot and app main(). I am checking internally if there is a way to optimize this.

Edit: for me to better understand the problem, could you say something about how this delay affects your application? For instance, if your app requires frequent reboots?

RE: Reduce MCUBoot startup time

Yeccc — Mon, 19 Dec 2022 08:55:49 GMT

Our project is based on the light_bulb.
It's a matter over thread project.

We output GPIO high level in Main application, and then use oscilloscope to check the time difference between 3.3V power supply and GPIO.

RE: Reduce MCUBoot startup time

Vidar Berg — Mon, 19 Dec 2022 08:08:46 GMT

Hi,

What SDK sample is your project based on? Is it Matter, Homekit, or something else? And how do you measure the startup time?

RE: Reduce MCUBoot startup time

Yeccc — Mon, 19 Dec 2022 01:02:04 GMT

Thank you for your help.
RNG is set by default in the nrf52840dk_nrf52840.overlay.

And the signature type is ECDSA_P256, it's also set by default on the nrfConnect SDK of 2.1.1 version.

We expect the startup time to be reduced to 500ms,

this is very important for our bulb product. Please help solve it as soon as possible. Thanks a lot.

# MCUBoot settings
#
# CONFIG_SINGLE_APPLICATION_SLOT is not set
# CONFIG_BOOT_SIGNATURE_TYPE_NONE is not set
# CONFIG_BOOT_SIGNATURE_TYPE_RSA is not set
CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=y

RE: Reduce MCUBoot startup time

Vidar Berg — Fri, 16 Dec 2022 12:21:40 GMT

Hi,

Please try to select the RNG — Random number generator as the entropy source instead of using the CRYPTOCELL — ARM TrustZone CryptoCell 310 (default) by adding the following to your board DT file (or in an overlay):

	chosen {
		zephyr,entropy = &rng;
		};

This accounts for about 400 ms of the startup time according to the thread here: High Current 400ms+ Startup Delay BLE Beacon Using RC Oscillator

What signature type have you selected for MCUBoot, RSA or ECDSA_P256?

Best regards,

Vidar