Odroid-C2

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(Parts of this page are WIP, still incomplete and some might be incorrect.)

Introduction

The Odroid-C2 single board computer is not very well supported by Alpine/Linux. However the "Generic ARM (aarch64)" build contains almost everything we need !

What do we need ?

• kernel : provided kernel by the Alpine team does not boot
• u-boot : provided u-boot does not autoboot without serial
• system files : everything is okay

On the hardware side:

• Odroid-C2
• Official PSU or just a micro-SD cable (notes : the barrel plug (inner(positive) diameter 0.8mm and outer(negative) diameter 2.5mm) is recommended, without the J1 jumper)
• micro-SD (or eMMC)
• USB to TTL (official or CP2102 chipset or an old rpi)

Required environement and toolchain

Using GNU/Linux is recommended and this guide and here are the required dependencies: Example on debian :

apt install bc bison flex make gcc gcc-aarch64-linux-gnu libncurses-dev git

Environement variables

export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-gnu

Build u-boot from source

git clone --depth 1 https://source.denx.de/u-boot/u-boot.git -b v2022.01 u-boot-denx.de
cd u-boot-denx.de
export ARCH=arm64 && export CROSS_COMPILE=aarch64-linux-gnu-
make mrproper && make odroid-c2_defconfig

Change boot options: TODO : remove lines < # CONFIG_AUTOBOOT_KEYED is not set < # CONFIG_AUTOBOOT_USE_MENUKEY is not set

Patch default configuration:

sed -i -e 's/.*CONFIG_SD_BOOT.*/CONFIG_SD_BOOT=y/' .config
echo "CONFIG_AUTOBOOT_KEYED=y" >> .config
echo "CONFIG_AUTOBOOT_FLUSH_STDIN=y" >> .config
echo "CONFIG_AUTOBOOT_PROMPT="Press quickly 'Enter' twice to stop autoboot: %d\n"" >> .config
echo "# CONFIG_AUTOBOOT_ENCRYPTION is not set" >> .config
echo "CONFIG_AUTOBOOT_DELAY_STR=""" >> .config
echo "CONFIG_AUTOBOOT_STOP_STR="\xd\xd"" >> .config
echo "CONFIG_AUTOBOOT_KEYED_CTRLC=y" >> .config

Build time:

time make -j$(nproc)

Build the latest LTS kernel from source

git clone --depth 1 git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git -b linux-5.154.y linux-stable
cd linux-stable
make mrproper && make defconfig

We need to adapt the default arm64 generated by defconfig

sed -i -e 's/.*CONFIG_SQUASHFS_XZ.*/CONFIG_SQUASHFS_XZ=y/' .config
sed -i -e 's/.*CONFIG_UEVENT_HELPER.*/CONFIG_UEVENT_HELPER=y/' .config
sed -i -e 's/.*CONFIG_BLK_DEV_RAM.*/CONFIG_BLK_DEV_RAM=y/' .config
echo CONFIG_UEVENT_HELPER_PATH=\"/sbin/hotplug\" >> .config
echo CONFIG_BLK_DEV_RAM_COUNT=16 >> .config
echo CONFIG_BLK_DEV_RAM_SIZE=4096 >> .config

Build the kernel:

time make -j$(nproc) Image dtbs modules

Create modloop:

rm -rf installed-modules && mkdir installed-modules
INSTALL_MOD_PATH=installed-modules make modules_install
find installed-modules -type l -delete
rm -f modloop
mksquashfs installed-modules/lib/ modloop -b 1048576 -comp xz -Xdict-size 100% -all-root
rm -rf installed-modules

Assembly

Work in progress

Booting

Work in progress

Troubleshooting

Work in progress