RE: NCS MCUboot and NVS

Bryan — Wed, 19 Apr 2023 18:26:11 GMT

Hieu,

I retested and confirmed that I do NOT have to keep the dts file in sync. That makes much more sense. My mistake.

Thank you for the detailed information. That will be a very useful post to others.

RE: NCS MCUboot and NVS

Hieu — Wed, 19 Apr 2023 14:02:50 GMT

Hi Bryan,

[quote user=""]Can someone give a thorough explanation of "how" NVS is managed when MCUboot is enabled and how it should be properly configured?[/quote]

To my understanding, NVS works the same way it always does. It is the partition that NVS will be initialized on that would be changed, which I understand is what you are asking by "how it should be properly configured."

From this point on, I will explain with information from NCS v2.3.0. The same details for older version of NCS should be the same or inferable from that.

The way the partitions are created is detailed in the Partition Manager documentation:
Link: Partition Manager — nRF Connect SDK 2.3.0 documentation (nordicsemi.com)

When the Partition Manager is active, it overrides the partitions defined in DTS automatically. This is done by replacing Zephyr macros' implementations based on DTS with that based on Partition Manager.
Refer: https://github.com/nrfconnect/sdk-zephyr/blob/v3.2.99-ncs2/include/zephyr/storage/flash_map.h#L260-L262.

By default, when created automatically, a partition named nvs_storage is always created.
Refer: https://github.com/nrfconnect/sdk-nrf/blob/v2.3.0/subsys/partition_manager/pm.yml.nvs.

In the macro implementation replacement mentioned above, the default name of the storage partition in Zephyr is also replaced with "nvs_storage."
Refer: https://github.com/nrfconnect/sdk-nrf/blob/v2.3.0/include/flash_map_pm.h#L36-L39

The size of this partition is configurable with CONFIG_PM_PARTITION_SIZE_NVS_STORAGE, the default size is 0x6000.
Refer:
Default size: https://github.com/nrfconnect/sdk-nrf/blob/v2.3.0/subsys/partition_manager/Kconfig#L71-L76.
Kconfig definition: https://github.com/nrfconnect/sdk-nrf/blob/v2.3.0/subsys/partition_manager/Kconfig.template.partition_config

It is a little weird that you said you need to keep #2. DTS file in sync with #1. Project Config and #3. Code. Are you certain that if you desync DTS with the rest, the setup will break?

[quote user=""]This does not seem to be the case for NVS storage. I want to limit the size of NVS to as small as possible so as much flash can be used MCUboot as possible. I was told in another devzone post that the smallest number of flash pages that can be used is two (each page is 4096 bytes). One for data and one for swap.

devzone.nordicsemi.com/.../quote]

This is right, please keep that in mind when tuning with CONFIG_PM_PARTITION_SIZE_NVS_STORAGE.

Hieu

[/quote]