The HPS SSBL location dropdown in the HPS Boot source section on the FPGA Interfaces tab of the Hard Processor System Intel® Stratix® 10 FPGA IP is new for 18.1. Its purpose is to allow the user to choose where the HPS first stage bootloader should load the second stage boot loader from. However, changing this dropdown does not affect HPS behavior, as the information is only passed from Quartus to Secure Device Manager firmware. The setting is not observed by U-Boot, and thus appears to have no effect.
In order to change the HPS SSBL location, the U-Boot source code needs to be changed. The setting is configured in the function spl_boot_device() from the file arch/arm/mach-socfpga/spl_s10.c. For an example of how to change the HPS SSBL location to the SDM QSPI flash, use the instructions available here: Stratix10SoCSingleQspiFlashBoot
This feature is expected to be fully supported in a future release of U-Boot-socfpga.
