nrf_audio sample with FOTA enabled exceeds ipc_radio FLASH partition

[Benno Trutmann]

Hi.

I try to build the nrf_audio sample as BIS headset with enabled FOTA and NCS2.7.0 and get the following link error for the ipc_radio image:

FAILED: zephyr/zephyr_pre0.elf zephyr/zephyr_pre0.map nrf5340_audio/build/sink-fota/ipc_radio/zephyr/zephyr_pre0.map
ld.bfd.exe: region `FLASH' overflowed by 2976 bytes

The b0n bootloader links fine with this output:

Memory region         Used Size  Region Size  %age Used
           FLASH:       23874 B      34176 B     69.86%
             RAM:        3528 B        64 KB      5.38%

As you can see there is 10KiB unused space in the b0n partition. Therefore I tried to reduce the size of this partition from 0x7800 to 0x6800. I tried to set the config variables CONFIG_PM_PARTITION_SIZE_B0_IMAGE in the corresponding sysbuild conf files (sysbuild/b0n/proj_fota.conf and sysbuild/ipc_radio/proj_fota.conf) or in sysbuild_fota.conf (with SB_ prefix), but my setting is ignored or there is a cmake configure error.

How can I reduce the b0n partition size?

[Amanda Hsieh]

Hi, 

Could you build for the release version: -DFILE_SUFFIX=release?

How do you build the nrf_audio sample as BIS headset with enabled FOTA? Using command or VS code? Could you provide the command or build configuration of VS code? Please provide more clear information to help reproduce the issue. 

Regards,
Amanda H.

[Benno Trutmann]

Hi Amanda.

I used the west command:

$ west build -d build/test -p -b nrf5340_audio_dk/nrf5340/cpuapp --sysbuild -- -DFILE_SUFFIX=fota -DEXTRA_CONF_FILE=broadcast_sink.conf

whereas broadcast_sink.conf contains the following:

CONFIG_TRANSPORT_BIS=y
CONFIG_AUDIO_DEV=1

Here is the build log:

4807.build.zip

[Amanda Hsieh]

You can create a prj_fota.conf under nrf5340_audio\sysbuild\b0n to include CONFIG_PM_PARTITION_SIZE_B0_IMAGE, but I don't think that is a good solution and will not recommend that. 

[Benno Trutmann]

1. Why is reducing the b0n partition not a good solution?

2. I tried a nrf5340_audio/sysbuild/b0n/prj_fota.conf with set CONFIG_PM_PARTITION_SIZE_B0_IMAGE=0x6800 already. It had no effect on the size of the allocated b0n partition.

[Amanda Hsieh]

We don't think this will work due to locking granularity in nRF5340 devices (the SPU flash regions are 16kb each). The SPU also controls write protection, and b0n needs to be write-protected to be immutable. 

[Benno Trutmann]

My reply is not accepted by the system, I always get "An error occurred. Please try again or contact your administrator."

[Benno Trutmann]

I tried to build a FOTA variant now with a nrf5340_audio/sysbuild/ipc_radio/prj_fota.conf copied from prj_release.conf with the following disabled:

CONFIG_DEBUG=n
CONFIG_ASSERT=n
CONFIG_STACK_USAGE=n
CONFIG_THREAD_MONITOR=n
CONFIG_SERIAL=n
CONFIG_CONSOLE=n
CONFIG_PRINTK=n
CONFIG_UART_CONSOLE=n
CONFIG_BOOT_BANNER=n
CONFIG_NCS_BOOT_BANNER=n


With that config I managed to link the ipc_radio image, but only in a tiny margin:
Memory region         Used Size  Region Size  %age Used
           FLASH:      226592 B       222 KB     99.68%
             RAM:       55652 B        64 KB     84.92%

Is there more I can disable? I fear for the future, when the softdevice controller grows only a little in size then there is no space anymore.

[Benno Trutmann]

When the build comes to the signing steps I get the following error:

FAILED: signed_by_mcuboot_and_b0_ipc_radio.bin C:/nrf5340_audio/build/sink-fota/signed_by_mcuboot_and_b0_ipc_radio.bin

...

Usage: imgtool.py sign [OPTIONS] INFILE OUTFILE
Try 'imgtool.py sign -h' for help.
Error: Image size (0x37920) + trailer (0x630) exceeds requested size 0x37800

How can I solve this problem?

[Benno Trutmann]

Here is the full build log:

build3.zip