Hard Processor System Remote System Update User Guide: Agilex™ 5 SoCs

ID 852610
Date 4/18/2025
Public
Document Table of Contents

5.3. U-Boot RSU Support

U-Boot provides the following RSU-related features:

  • Enables you to access the RSU functionality from the U-Boot source code, using an interface similar to LIBRSU
  • Enables you to access the RSU functionality from the U-Boot command line

U-Boot runs at EL1, and it uses the Secure Monitor Call (SMC) handler provided by ATF(which runs at EL3) to access the SDM commands. U-Boot also accesses the QSPI flash to implement the RSU functionality.

Note: Using the U-Boot as the SMC handler is currently only supported for experimental purposes such as bringing up a new board. It allows convenient access to all HPS registers from the U-Boot command line, but comes with reduced security and functionality. All new features are implemented only in ATF.