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

ID 683184
Date 2/23/2024
Document Table of Contents

6.1. Decision Firmware

The decision firmware is extremely important, as it is executed first when the device powers up, to select and load the highest priority application image. It is also executed each time another application image or the factory image needs to be loaded.

There are four copies of the decision firmware, stored at address zero in QSPI flash. The decision firmware is protected by SHA checksums. If the SDM BootROM detects that the first copy is corrupted, it tries the second copy, then the third and fourth copies.

The index of the currently used decision firmware copy is reported to the HPS through the version field of the RSU_STATUS. U-Boot uses this index to compare the currently used decision firmware copy with the other copies in flash, and reports the ones which do not match as corrupted. The information is also reported to Linux, to be used by LibRSU.

Once you see that one or more copies of the decision firmware are corrupted, you can run either a factory update image or a decision firmware update image to recover. Both options update the decision firmware and the decision firmware data, while the factory update image also updates the factory image.