Preloader uboot SPL

Hi,

We have a custom Cyclone V board that runs vxWorks. All boot images are coming from the QSPI with preloader separated from uboot. Preloader starts @ 0x0 location, u-boot @ 0x60000.

I'm not trying to have Linux work on this board but i'm currently stuck with making the pre-loader and u-boot to work. I followed the instructions from Rocketboards for (Cycone V Soc - Boot from QSPI) using Ubuntu22.04 on a VM on how to generate the preloader and u-boot.

https://www.rocketboards.org/foswiki/Documentation/BuildingBootloaderCycloneVAndArria10#Introduction

I managed to compile/generate the u-boot-with-spl.sfp file using the socfpga_cyclone5_qspi_defconfig in the procedure, assuming that the generated file should at least show some boot messages on the serial port.

But at power up, our custom board isn't showing any boot messages on the serial port. Not even garbage text.

I then tried following the Mainline u-Boot for SocFPGA procedure to create a defconfig for our custom board but it's not compiling waiting for user input/decision.

https://www.rocketboards.org/foswiki/Documentation/MainlineUBootForSoCFPGA

So my questions are:

- can i just write the u-boot-with-spl.sfp directly to the QSPI? Considering the system already works with pre-loader and u-boot separated.

- is there a guide on how to generate a preloader and uboot for a custom board?

- for the custom defconfig, is there document that describes what each lines in the file mean?

I am currently enrolled to Intel® SoC FPGA Basics this coming May 25th. I'd appreciate if you can share new materials that can help me get familiarized with using embedded Linux on a Cyclone V system.

Thanks!