Reducing size of mcuboot_secondary breaks FOTA

[KarlF]

I have enabled mcuboot and have two boot partitions: primary and secondary. I'm using a static flash configuration. I want to start using the settings subsystem for persistently storing configurations in flash. To make room on the flash for the settings, I have reduced the size of the mcuboot_secondary from 491kbytes to 483kb bytes. My app_update.bin is 410kb, so it still fits within the partition.

I have 3 fw versions:

v10: old flash layout

v11: new flash layout

v12: same as v11, but higher fw version.

For fota I'm using the download_client. I have flashed v10 and starting fota with v11. This works fine and the new image boots correct. The problem arises when trying to do fota the second time. I'm now running v11 and want to do fota with v12. This image will download correctly, but when rebooting it will start up v11, and not v12.

For all versions up to v10, fota works fine. If I first flash v11, then do fota with v12 and so on, everything works fine. The only change from v10 to v11 is the static flash configuration, there is no other change in there.

What am I doing wrong? Since I want to start using settings subsystem, I need to reserve some space for it on the flash. Anyone having some experience with this problem? 

BTW: manually flashing the new sw is not an option since we have products already delivered to customers.

The difference between the two static configurations looks like this:

I have also attached the static configurations for the two different layouts.

Fullscreen 8535.pm_static_v1.txt Download

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
app:
  address: 0x20200
  end_address: 0x88000
  region: flash_primary
  size: 0x67e00
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0x10000
  end_address: 0x10200
  placement:
    align:
      start: 0x8000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0x10000
  end_address: 0x88000
  orig_span: &id001
  - mcuboot_pad
  - app
  - spm
  region: flash_primary
  sharers: 0x1
  size: 0x78000
  span: *id001
mcuboot_primary_app:
  address: 0x10200
  end_address: 0x88000
  orig_span: &id002
  - app
  - spm
  region: flash_primary
  size: 0x77e00
  span: *id002
mcuboot_secondary:
  address: 0x88000
  end_address: 0x100000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x8000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x78000
nrf_modem_lib_ctrl:
  address: 0x20010000
  end_address: 0x200104e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - spm_sram
    - start
  region: sram_primary
  size: 0x4e8
nrf_modem_lib_rx:
  address: 0x200124e8
  end_address: 0x200144e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_tx
  region: sram_primary
  size: 0x2000
nrf_modem_lib_sram:
  address: 0x20010000
  end_address: 0x200144e8
  orig_span: &id003
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x44e8
  span: *id003
nrf_modem_lib_tx:
  address: 0x200104e8
  end_address: 0x200124e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_ctrl
  region: sram_primary
  size: 0x2000
otp:
  address: 0xff8108
  end_address: 0xff83fc
  region: otp
  size: 0x2f4
spm:
  address: 0x10200
  end_address: 0x20200
  inside:
  - mcuboot_primary_app
  placement:
    before:
    - app
  region: flash_primary
  size: 0x10000
spm_sram:
  address: 0x20000000
  end_address: 0x20010000
  inside:
  - sram_secure
  placement:
    after:
    - start
  region: sram_primary
  size: 0x10000
sram_nonsecure:
  address: 0x20010000
  end_address: 0x20040000
  orig_span: &id004
  - sram_primary
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x30000
  span: *id004
sram_primary:
  address: 0x200144e8
  end_address: 0x20040000
  region: sram_primary
  size: 0x2bb18
sram_secure:
  address: 0x20000000
  end_address: 0x20010000
  orig_span: &id005
  - spm_sram
  region: sram_primary
  size: 0x10000
  span: *id005

Fullscreen 4426.pm_static_v2.txt Download

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
app:
  address: 0x20200
  end_address: 0x88000
  region: flash_primary
  size: 0x67e00
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0x10000
  end_address: 0x10200
  placement:
    align:
      start: 0x8000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0x10000
  end_address: 0x88000
  orig_span: &id001
  - mcuboot_pad
  - app
  - spm
  region: flash_primary
  sharers: 0x1
  size: 0x78000
  span: *id001
mcuboot_primary_app:
  address: 0x10200
  end_address: 0x88000
  orig_span: &id002
  - app
  - spm
  region: flash_primary
  size: 0x77e00
  span: *id002
mcuboot_secondary:
  address: 0x88000
  end_address: 0xfe000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x8000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x76000
nrf_modem_lib_ctrl:
  address: 0x20010000
  end_address: 0x200104e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - spm_sram
    - start
  region: sram_primary
  size: 0x4e8
nrf_modem_lib_rx:
  address: 0x200124e8
  end_address: 0x200144e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_tx
  region: sram_primary
  size: 0x2000
nrf_modem_lib_sram:
  address: 0x20010000
  end_address: 0x200144e8
  orig_span: &id003
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x44e8
  span: *id003
nrf_modem_lib_tx:
  address: 0x200104e8
  end_address: 0x200124e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_ctrl
  region: sram_primary
  size: 0x2000
otp:
  address: 0xff8108
  end_address: 0xff83fc
  region: otp
  size: 0x2f4
settings_storage:
  address: 0xfe000
  end_address: 0x100000
  placement:
    before:
    - end
  region: flash_primary
  size: 0x2000
spm:
  address: 0x10200
  end_address: 0x20200
  inside:
  - mcuboot_primary_app
  placement:
    before:
    - app
  region: flash_primary
  size: 0x10000
spm_sram:
  address: 0x20000000
  end_address: 0x20010000
  inside:
  - sram_secure
  placement:
    after:
    - start
  region: sram_primary
  size: 0x10000
sram_nonsecure:
  address: 0x20010000
  end_address: 0x20040000
  orig_span: &id004
  - sram_primary
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x30000
  span: *id004
sram_primary:
  address: 0x200144e8
  end_address: 0x20040000
  region: sram_primary
  size: 0x2bb18
sram_secure:
  address: 0x20000000
  end_address: 0x20010000
  orig_span: &id005
  - spm_sram
  region: sram_primary
  size: 0x10000
  span: *id005

[Hung Bui]

Hi Karl, 
As far as I know the size of the secondary slot and the primary slot need to match. Have you tried to also reduce the size of the primary slot ? You may need to move the secondary slot up. 

Also have you added B0 bootloader into it so that the MCUBoot can be updated ? I'm not sure if you only update the application or you also update the bootloader. 
If you modify the flash layout you would need to update the MCUBoot. 

[KarlF]

Thanks for your input. I tried to also reduce the size of the primary slot, but it didn't help.

Regarding the B0 bootloader. I'm downloading the app_update.bin file. But i'm not entirely sure if that also contains the B0 bootloader. I've looked around to try and figure out which file is the B0 bootloader, but I can't figure it out. Can you point me to the correct file?

When I'm flashing, I'm flashing the merged.hex file, which does contain the bootloader. But I can't figure out which binary file to download using fota for the bootloader.

[Hung Bui]

Hi Karl, 

If you search on Google for "B0 bootloader" you can find this: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bootloader/README.html

You can read more about the secure bootloader chain and how to test it here.

So most likely when you updating from v10 to v11, you were not updating the MCUBoot in your setup and it still have the previous memory layout. 

If you flash v11 directly then the new MCUBoot will be flashed and the new layout will be used. 

[KarlF]

Hi,

I found that I haven't added B0 bootloader ( CONFIG_SECURE_BOOT is not set). Can you confirm that it is not possible to update the MCUBoot if B0 bootloader is not included?

[Hung Bui]

Hi Karl, 
Yes you are correct. It's not possible for MCUBoot to update itself without a B0.