Building the project

In order to build and test the project, we need a couple of ingridients. The ingridients have been added as git submodules:

branch: rpi-6.9.y-mcfg-quirk, remote: https://github.com/9elements/linux/ branch: main, remote: https://github.com/u-root/u-root.git branch: master, remote: https://github.com/9elements/u-boot-acpi

It is expected by the reader, that he/she has already installed the neccessary toolchain (aarch64-linux-gnu). This can be as easy as installing it using your package manager of choice. It is also required that the go toolchain is installed as well as some typical system binaries that Linux needs in order to compile.

Building u-root

cd u-root
go build .
GOARCH=arm64 ./u-root -defaultsh gosh -o initramfs.cpio boot coreboot-app ./cmds/core/* ./cmds/boot/*
cd -

Building Linux kernel

cd linux
export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-gnu-
make bcm2711_defconfig
./scripts/kconfig/merge_config.sh .config ../acpi.conf ../uroot_initramfs.conf
make Image -j$(nproc)
make dtbs -j$(nproc)
cd -

Building u-boot

cd u-boot
ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- make rpi_4_acpi_defconfig
ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- make -j$(nproc)
cd -

Build u-boot enviroment

cd u-boot
./tools/mkimage -A arm64 -O linux -T script -C none -d ../boot_cmd.txt boot.scr
cd -

Flash contents to sdcard

Your SD card should have at least one partition: 512M FAT32 EFI partition

mount your sd card and copy all ingridients onto the SD Card

mount /dev/mmcblk0p0 /mnt
cp linux/arch/arm64/boot/Image /mnt
cp linux/arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb /mnt
cp u-boot/u-boot.bin /mnt
cp u-boot/boot.scr /mnt
cp config.txt /mnt
cp bootcode.bin /mnt
cp start4.elf /mnt
unmount /mnt

Now plug out the SD card and put it into the raspberry PI 4 B

Workflow

Testing in QEMU:

Starting with QEMU 9.0 you can run the RPI 4 in qemu:

Update boot_cmd.txt:

fatload mmc 1:1 ${kernel_addr_r} Image
fatsize mmc 1:1 Image
#setenv bootargs "console=ttyS0,115200 console=tty1"
bootefi ${kernel_addr_r}:${filesize} -

To run u-boot and boot from MMC run:

qemu-system-aarch64 -machine raspi4b -kernel u-boot/u-boot.bin -cpu cortex-a72 -smp 4 -m 2G -drive file=raspbian.img,format=raw,index=0 -dtb linux/arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb -nographic

Note: Assumes you have Image copied into the raspbian.img image.