Building the Bootloader (U-boot) under Quartus Pro 21.3 20240205¶
1. Prerequisites 2. Building the FPGA Image 3. Building the Bootloader 4. Building the Filesystem 5. Building the SD Card
- Table of contents
- Building the Bootloader (U-boot) under Quartus Pro 21.3 20240205
Introduction¶
The main boot loader for the MitySOM-A10S is Das U-Boot. This boot loader is used to configure the pin mux, DDR, program the FPGA, and launch the next stage application/OS. Critical Link started from Intel's port of Das U-Boot and made the following modifications:
- Reading the MAC address from the on board EEPROM (part of the factoryconfig command)
- Optionally programming the external PLL chips, U14 and U15, if PLL configuration file is provided
The v2023.07 version of the u-Boot, recommended for use with Quartus Pro versions greater than 19.3, transitions from a single bootloader image running in SRAM to 2 boot images. The first image is the secondary program loader (SPL), which runs in the on-board HPS SRAM. The SPL is responsible for loading the peripheral bitstream into the FPGA, configuring the HPS EMIF memory interfaces and loading the tertiary program loader, u-Boot, into DDR4 for final boot execution. The default configuration for the MitySOM-A10S is to load from the SD MMC card. However, support is included for booting from the on-board eMMC device.
These instructions have been tested with Quartus Pro 21.3
Repository¶
| Description | Repository | Branch | U-Boot Version |
| U-Boot Source | https://git.criticallink.com/git/u-boot-socfpga.git | socfpga_v2023.07 | v2023.07 |
Development Kit Pre-built Outputs¶
| Description | Link |
| 270 KLE U-boot & environment | a10s-p8-bootloaders-20240205.zip |
| 480 KLE U-boot & environment | a10s-p9-bootloaders-20240205.zip |
Pre-Requisites¶
ARM GCC Toolchain¶
Launch a terminal and run a NIOS2 Command Shell. Execute the following commands to download and install the ARM gcc toolchain.
cd wget https://developer.arm.com/-/media/Files/downloads/gnu-a/10.2-2020.11/binrel/\ gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf.tar.xz tar xf gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf.tar.xz export PATH=`pwd`/gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf/bin:$PATH
NOTE: the last command adds the compiler to your PATH. If you launch a new shell, you will need to re-add it to your path by changing directories to your download location and re-running the last command.
Linux Packages¶
You will need the following packages (this list is for Ubuntu 22.04 LTS):
sudo apt-get install gawk wget git-core diffstat unzip texinfo \ gcc-multilib build-essential chrpath socat cpio python python3 \ python3-pip python3-pexpect xz-utils debianutils iputils-ping \ python3-git python3-jinja2 libegl1-mesa libsdl1.2-dev pylint3 xterm \ libncurses-dev gawk flex bison openssl libssl-dev
Quick steps used reference project¶
The Makefile included in the development kit reference project includes a bootloader target, which will perform the steps outlined in the next section. From a NIOS2 Embedded Shell, simply run the following command at the top level directory of the reference project:
make uboot
Detailed steps to Building U-Boot¶
Note: Building uBoot requires a completed FPGA build directory on your host machine.
In this example, TOP_FOLDER is the top directory of your FPGA project area.
- Launch a terminal and run a NIOS2 Command Shell.
- Fetch the u-Boot source code.
mkdir -p software/bootloader cd software/bootloader/ git clone https://git.criticallink.com/git/u-boot-socfpga.git cd u-boot-socfpga git checkout -b socfpga_v2023.07 origin/socfpga_v2023.07
- Convert hps.xml handoff file to include file to be used by the device tree:
cd $TOP_FOLDER/software/bootloader/u-boot-socfpga ./arch/arm/mach-socfpga/qts-filter-a10.sh \ ../../../hps_isw_handoff/hps.xml \ arch/arm/dts/socfpga_mitysom_a10s_handoff.h
- Configure and build U-Boot and the SPL:
cd $TOP_FOLDER/software/bootloader/u-boot-socfpga CROSS_COMPILE=arm-none-linux-gnueabihf- make socfpga_mitysom_a10s_dsc_defconfig make -j 48
- Create the FIT image with the FPGA programmimng files, used by SPL to configure the FPGA:
cd $TOP_FOLDER/software/bootloader/u-boot-socfpga ln -s ../../../output_files/mitysom_a10s.core.rbf . ln -s ../../../output_files/mitysom_a10s.periph.rbf . tools/mkimage -E -f board/cl/mitysom-a10s-dsc/fit_spl_fpga.its fit_spl_fpga.itb
- Create the default u-Boot environment (note: environment text file may be customized for your application)
cd $TOP_FOLDER/software/bootloader/u-boot-socfpga tools/mkenvimage -s 8192 -o ubootenv.bin ../ubootenv.txt
Outputs¶
| Description | Location |
| Bootable image, with four SPL binaries, in the format required by BootROM | $TOP_FOLDER/software/bootloader/u-boot-socfpga/spl/u-boot-splx4.sfp |
| U-Boot image | $TOP_FOLDER/software/bootloader/u-boot-socfpga/u-Boot.img |
| U-Boot Environment Binary | $TOP_FOLDER/software/bootloader/u-boot-socfpga/ubootenv.bin |
Customizing U-Boot¶
Customization through updating the U-boot environment¶
Most U-Boot customization for a carrier board can be done by adjusting the scripts/macros in the U-boot environment. This includes changing the name of the core FPGA image (RBF), Kernel, or device tree block (DTB). The U-boot environment is stored in the SD Card, 512 Bytes from the beginning of the SD Card. It can also be updated inside of U-boot by using the editenv, setenv, and saveenv commands. Please see the U-Boot documentation in Further Reading for more usages.
The U-Boot environment binary is built through the FPGA project, it's source is the ubootenv.txt
FAQ¶
When should I rebuild my bootloader?¶
Your bootloader should be rebuilt anytime the settings in the HPS block in Platform Designer is changed. This includes but not limited to: changing the HPS pin mux, changing any of the clocks generated by the HPS, enabling/changing and the FPGA bridges (Light Weight HPS-to-FPGA, HPS-to-FPGA, FPGA-to-HPS, FPGA-to-SDRAM). When in doubt rebuilt and reflash U-Boot.
Further Read¶
1. Prerequisites 2. Building the FPGA Image 3. Building the Bootloader 4. Building the Filesystem 5. Building the SD Card
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