Intel Agilex® 7 Hard Processor System Remote System Update User Guide

ID 683184
Date 2/23/2024
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 U-Boot source code, using an interface similar with LIBRSU.
  • Enables you to access the RSU functionality from U-Boot command line

U-Boot runs at EL1, and it uses the SMC (Secure Monitor Call) 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: Prior to branch socfpga_v2020.07, U-Boot was running at EL3 and was the provider of the SMC handler for the rest of the HPS software. In branch socfpga_v2020.07 there was the option to have either U-Boot or ATF to implement the SMC handler. Starting with branch socfpga_v2020.10 only the ATF provides the SMC handler. Using the U-Boot as the SMC handler is now only supported for experimental purposes such as bringing up a new board, as it allows convenient access to all HPS registers from U-Boot command line, at the expense of reduced security and functionality. All new features are implemented in ATF only.