For add custom board with TF-M support, the purpose of nrf/modules/tfm directory in SDK?

[WenjieXiong]

As I search through in the nRF Connect SDK, I can't find any docs about this directory, but I guess it's for override the code inTF-M.

The question is, if I want to add custom board to support TF-M, should I add the board definations in "modules/tee/tf-m/trusted-firmware-m/platform/ext/target/nordic_nrf" or this directory?

Can you give me more explanations to these files in "nrf/modules/tfm"? Thks!

[WenjieXiong]

BTW, the SDK version is 2.2.0.

[Michal]

Hello,

The question is, if I want to add custom board to support TF-M, should I add the board definations in "modules/tee/tf-m/trusted-firmware-m/platform/ext/target/nordic_nrf" or this directory?

No, that shouldn't be necessary. Please just make a standard board file based on the DK. Those TF-M files should added automatically based on the MCU used, not the board. Probably a bit of an unfortunate word usage there.

Best regards,

Michal

[WenjieXiong]

Thank you for your reply.

I have a custom board use nrf5340 with CLAA package and difference pin usages from DK. So I add custom soc dir in zephyr (for CLAA, just copy from QKAA), and custom board dir (for pin usages) with dts and Kconfig in my project dir. The board is test to be OK, so I'm trying to add TF-M configs.

As your reply, I found I can remapping uart pins with 

CONFIG_TFM_UART0_TXD_PIN,..., but I'm not sure I can do all the way to be right. for example, the flash and SRAM layout, the mcu bootloader, are they be overrided?

[Michal]

Why are you adding a custom soc dir? You should be able to just override anything you want in your board files I think?

[WenjieXiong]

You are right, without that custom soc dir is OK.

And as 'zephyr/modules/trusted-firmware-m/Kconfig.tfm' said, I just need to specify:

CONFIG_TFM_BOARD = "nordic_nrf/nrf5340dk_nrf5340_cpuapp"

for my custom board difinations.

Thanks!