Weird flash usage report while using TF-M

[caspar.friedrich]

Hi!

If I build my project with TF-M I noticed that at least the flash usage report differs dramatically compared to the original firmware:

Original:

Memory region | Used Size | Region Size | %age Used
        FLASH:   206060 B      409088 B      50.37%
         SRAM:    83760 B      178968 B      46.80%

With TF-M enabled:

Memory region | Used Size | Region Size | %age Used
        FLASH:   193676 B        208 KB      90.93%
         SRAM:    79024 B      178968 B      44.16%

The actual firmware size makes sense so far and both variants boot fine. My expectation was that the sections should be more or less identical.

Regards

Caspar

[Carl Richard]

Hi, Caspar!

The TF-M partitions the flash regions differently compared to Zephyr resulting in your application using occupying a larger %age of the dedicated non-secure region. As mentioned in the Zephyr documentation on the nRF9160 DK you can adjust the size and start address of the flash image using DTS overlays. There are some samples for TF-M in Zephyr that may be worth checking out.

Best regards,
Carl Richard

[caspar.friedrich]

Okay, thanks. I'll look into that.

[Carl Richard]

Great! Please let me know if you face any other issues.

Best regards,
Carl Richard