New ContributorQuestions regarding the HPS GSRD User Guide for the Agilex™ 5
Hello
In U-Boot and Linux there are some files that allow you to indicate if you need to build a driver or not. These are the configs. For example for agilex 5 we have these:
Linux: https://github.com/altera-fpga/linux-socfpga/blob/socfpga-6.12.19-lts/arch/arm64/configs/defconfig
If a CONFIG is set to 'y' it means that the corresponding driver will be built and integrated into the Linux kernel. If it's set to 'm', the driver will be build but be created as an independent module that you need to load using the insmod command. If it's set to 'n', then the driver is not built and won't be available to the Linux kernel.
In the GSRD page, Yocto is the one that updates the device tree along to CONFIGS and other things. Yocto is very powerful but difficult to use. What I understand about the Yocto flow is that it gets the content of the Linux/ATF/U-Boot repo with a specific branch indicated in a recipe, and then executes recipes that update device trees and CONFIGS and also apply patches (to fix an issue or support any specific functionality). You need to create or modify these recipes to do what you want. Once that the repo is updated this is built and generates the Linux/ATF/U-Boot binaries. Then also Yocto has recipes to build Linux file system, libraries and applications that are copied into the file system. When it gets all components already built, Yocto also integrates these in you final binaries that could be a SD card image, a .rpd or .jic image to boot from QSPI, etc. But to update the recipes is it needed to have certain level of knowledge about Yocto. The good thing is that this is popular and there are many resources in the web.
Again, if you are starting with our devices and you don't have much experience with Linux, I suggest you to start with https://altera-fpga.github.io/rel-25.1/embedded-designs/agilex-5/e-series/premium/boot-examples/ug-linux-boot-agx5e-premium/.
Also we have a very nice simulator for our Agilex 5 device that could help you to ramp up on this, in case you don't have a dev kit:
https://www.altera.com/products/development-tools/simics-virtual-platform
