[TF-A] Is NS_BL1U necessary to do FWU ?

Hi,

In ARM TBBR, there is a requirement “R0100_TBBR_AFM_FLASHING” (The AP firmware must switch to the Non-Trusted world for executing the SoC firmware loader), But there is no requirement for secure boot as long as I finish chain if ROT verification.

So, can I implement FWU in BL2 which is verified and load from BL1 (ROM)? For example, BL1(ROM) -> Load and verify BL2U with new image from SD to secure RAM -> execute BL2U in Secure RAM then write new image to NAND flash

Best regards, Jun