ODROID-C2 Gentoo Overlay

Introduction

This is a Gentoo overlay for additional tools neccessary for running Gentoo Linux on the Hardkernel ODROID C2 single board computer. More information about the ODROID c2 can be found here.

At the moment this overlay provides:

Package Name	Description
dev-embedded/meson-tools	meson-tools, alternative to aml_encrypt_gxb
dev-embedded/odroidc2-fip	fip_create and Hardkernel's ARM Trusted Firmware binaries from their repository
dev-embedded/u-boot-odroidc2	Mainline U-Boot

Some Notes

At this moment all that is described in here will give you a headless setup, without any multimedial features, such as graphics (don't even think of accelerated graphics as of yet) nor sound via hdmi. Despite the mainline kernel having gained some support for hdmi, it is of no use at this present moment.

Please refer to the mainlinening project at http://linux-meson.com.

Installation

Obviously, if you already know what an Gentoo overlay is and how to use one, detailed instructions on how to bring Gentoo onto the C2 are not needed. You've clearly the expertise.

Layman

wget "https://raw.githubusercontent.com/nxmyoz/c2-overlay/master/overlays.xml" -O /etc/layman/overlays/odroidc2.xml
layman -f -a ODROID-C2

make.conf

The most important stuff:

CFLAGS="-O2 -pipe -march=armv8-a+crc+fp+simd -mabi=lp64 -mcpu=cortex-a53+crc+fp+simd -ftree-vectorize --param l1-cache-size=16 --param l1-cache-line-size=64 --param l2-cache-size=512"
CXXFLAGS="${CFLAGS}"
CHOST="aarch64-unknown-linux-gnu"
MAKEOPTS="-j4"
CPU_FLAGS_ARM="edsp neon thumb vfp vfpv3 vfpv4 vfp-d32 crc32 v4 v5 v6 v7 v8 thumb2"

llvm won't build with MAKEOPTS="-j4", so a workaround is needed, like per package env, setting the MAKEOPTS to -j2, as well as boost, which may lead to a hangup of the C2:

# cat /etc/portage/package.env
sys-devel/llvm makeopts-j2
dev-libs/boost makeopts-j2

# cat /etc/portage/env/makeopts-j2
MAKEOPTS="-j2"

U-Boot

Mainline U-Boot support, with booting from the mmc & sd is available starting with 2017.05.

You will need to install dev-embedded/u-boot-tools should you desire to generate your own boot.scr boot script.

The ebuilds provided in this overlay aim to make life simpler by providing all that is needed to build a working U-Boot.

Howto U-Boot with Gentoo

1. Use this overlay
2. emerge -av meson-tools odroidc2-fip u-boot-odroidc2

Note: When building u-boot, make sure your default Python is set to 2.7 (via eselect python ..., or else the build will fail.

odroidc2-fip will provide the following files:

/usr/bin/fip_create
/usr/share/odroidc2-fip/bl1.bin.hardkernel
/usr/share/odroidc2-fip/bl2.package
/usr/share/odroidc2-fip/bl30.bin
/usr/share/odroidc2-fip/bl301.bin
/usr/share/odroidc2-fip/bl31.bin
/usr/share/odroidc2-fip/sd_fusing.sh

while u-boot-odroidc2 will just build the u-boot image with using the odroid-c2_defconfig, and install the resulting image in /usr/share/u-boot-odroidc2/u-boot-${PV}.bin, e.g. for dev-embedded/u-boot-odroidc2-2017.05 it would be /usr/share/u-boot-odroidc2/u-boot-2017.05.bin.

You now can simply generate u-boot in the neccessary format by, as described in u-boot sources, however without the invocation of aml_encrypt_gxb:

PV="2017.05"
DIR=~/.
FDIR=/usr/share/odroidc2-fip

fip_create  --bl30 $FDIR/bl30.bin \
            --bl301 $FDIR/bl301.bin \
            --bl31 $FDIR/bl31.bin \
            --bl33 /usr/share/u-boot-odroidc2/u-boot-${PV}.bin \
            $DIR/fip.bin

fip_create --dump $DIR/fip.bin
cat $FDIR/bl2.package $DIR/fip.bin > $DIR/boot_new.bin
amlbootsig $DIR/boot_new.bin $DIR/u-boot.img
dd if=$DIR/u-boot.img of=$DIR/u-boot.gxbb bs=512 skip=96

Now write it to your boot device (mmc or sd):

DEV=/dev/mmcblk0
BL1=$FDIR/bl1.bin.hardkernel
dd if=$BL1 of=$DEV conv=fsync bs=1 count=442
dd if=$BL1 of=$DEV conv=fsync bs=512 skip=1 seek=1
dd if=$DIR/u-boot.gxbb of=$DEV conv=fsync bs=512 seek=97

That should work.

Kernel (gentoo-sources)

gentoo-sources-4.11

A minimal (at least from my perspective) kernel config for >=sys-kernel/gentoo-sources-4.11 can be found in this repository here.

gentoo-sources-4.19

There is a working kernel config to be found here.

Building The Kernel

Here are the steps in building the kernel:

cd /usr/src/linux
make mrproper clean
wget "https://raw.githubusercontent.com/nxmyoz/c2-overlay/master/c2.config" -O .config

make -j4 Image
make -j4 modules
make -j4 dtbs

rm -rf /lib/modules/*

make modules_install

cp -rf arch/arm64/boot/Image /boot/Image
cp -rf arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dtb /boot/meson-gxbb-odroidc2.dtb

Booting

Create and adjust as needed a /boot/boot.cmd:

setenv loadaddr "0x20000000"
setenv dtb_loadaddr "0x01000000"
setenv initrd_high "0xffffffff"
setenv fdt_high "0xffffffff"
setenv kernel_filename boot/Image
setenv fdt_filename boot/meson-gxbb-odroidc2.dtb
setenv bootargs "root=/dev/mmcblk0p1 rootfstype=ext4 rootwait rw"
setenv bootcmd "ext4load mmc 0:1 '${loadaddr}' '${kernel_filename}'; ext4load mmc 0:1 '${dtb_loadaddr}' '${fdt_filename}'; booti '${loadaddr}' - '${dtb_loadaddr}'"
boot

Then run:

mkimage -C none -A arm -T script -d boot.cmd boot.scr

U-Boot should now be able to find and use boot.scr.