boards: frdm_mcxn947: Fix MCUBoot support.

[butok]

• Set MCUBoot "upgrade only" method, as the program size is 128B (>32B).
• Set slot sizes to the same value, required by the MCUBoot "upgrade only" method.

[danieldegrasse]

Set MCUBoot "upgrade only" method, as the program size is 128B (>32B).

Just to be clear, this is a case similar to the LPC55Sxx flash where the program size alignment is too large for MCUBoot to support swapping with upgrades?

[butok]

Set MCUBoot "upgrade only" method, as the program size is 128B (>32B).

Just to be clear, this is a case similar to the LPC55Sxx flash where the program size alignment is too large for MCUBoot to support swapping with upgrades?

Yes, this is the same case.

[mmahadevan108]

@butok , this flash supports 16 bytes write. Why do we need this change?

[mmahadevan108]

Need clarification on this change.

[butok]

@butok , this flash supports 16 bytes write. Why do we need this change?

Hi @mmahadevan108

The MCXN947 FLASH ROM API used by the Zephyr Flash driver does not support 16 byte writes.
It supports 128Bytes only (page size) checked by me on practiced and confirmed by the RM documentation.
That is why the MCUBoot firmware update does not work now. Also, it means that nobody tests FLASH and MCUBoot functionality for NPIs!
BTW: I have heard that the ROM API was fixed for MCXA,

[butok]

Need clarification on this change.

Hi @mmahadevan108
BTW FYI:
(3Jan25) before the PR submit, I asked the SDK team to implement a "[MCXNx4x] Flash Memory Unit (FMU) Driver". Once it's ready, we'll be able to add a workaround (not via the Flash ROM API) to support the 16-byte programming . So far, we have to live with 128 bytes.