'west flash' rebuilds after successful build when enabling SB_CONFIG_BOOTLOADER_MCUBOOT in sysbuild.conf

[aartmulder]

I'm running into a bit of an annoying situation every time i run 'west flash --build-dir ./build' in the command line. It rebuilds always after a successful build i set when SB_CONFIG_BOOTLOADER_MCUBOOT=y in sysbuild.conf. The build command i use is `west build --build-dir ./build . --board xiao_nrf54l15/nrf54l15/cpuapp --sysbuild -- -DBOARD_ROOT="/home/$USER/platform-seeedboards/zephyr"` and i'm working in Ubuntu with VSCode. It is just such a waste of time with a project that starts to grow.

I have tried with and without deleting the build folder as well as with and without the `--pristine` option, no difference.

Any idea's what i can do to change this behaviour

[aartmulder]

Looking into build.ninja i suspect that it has to do with the line starting with: build build.ninja: RERUN_CMAKE | ...

Commenting it out solves the problem (temporarily). Somehow it detects a change in some file and starts to rebuild. If i call west flash a second time it does not rebuild so something is off when the mcuboot part is added.

[Priyanka]

Hi,

Thank you for the updates. I am looking into this and will get back to you soon with a solution.

-Priyanka

[Priyanka]

Hi,

Could you take a look into this PR: https://github.com/nrfconnect/sdk-nrf/pull/24619 

-Priyanka

[aartmulder]

Hi Priyanka,

To be honest I have no experience with pull requests and don't really know what to look at.

aart

[aartmulder]

Is there a possibility to find out which file triggers the rebuild in the next command?

build build.ninja: RERUN_CMAKE | ... 

[Priyanka]

Hi,

So basically what happened is that, this was a known issue in the previous SDK/Zephyr version.

With sysbuild + multiple images (like MCUboot + app), a CMake step that imports DTS/EDT configuration always rewrote a helper .cmake file. Even when the contents didn’t change, the file’s timestamp changed, so CMake/Ninja thought that an input changed and then starts to rebuild everything again.

That’s why every west flash looked like a full rebuild.

So what you can do is, update to the latest Zephyr and nRF Connect SDK versions. This issue has been fixed in the newer versions.

Or else, you could also implement the changes manually in your current version, as show in the PR (this could be a bit complicated):

https://github.com/nrfconnect/sdk-zephyr/pull/3287/files 

-Priyanka

[aartmulder]

That solved it. Thanks a lot Priyanka!

[rlk0]

I am using NCS v3.2.2 and am having the same issue. Has it crept back in to newer versions?