Odroid XU-4 board with Samsung Exynos 5422 SoC

Introduction
------------

The Odroid XU 4 board is developed and shipped by Hrdkernel (hardkernel.com). It
uses the Samsung Exynos 5422 Soc.

Odroid boot process
-------------------

The odroid boot process requires three stages of boot plus trust zone:

    boot level 1

        |
        V

    boot level 2

        |
        V

     u-boot

and they need to be raw copied to the SD card in the following order:

    +----------------+----------------+
    | boot level 1   | 1 block        |
    +----------------+----------------+
    | boot level 2   | 31 block       |
    +----------------+----------------+
    | u-boot         | 63 block       |
    +----------------+----------------+
    | trust zone     | 2111 block     |
    +----------------+----------------+
    | boot partition | 4096 block     |
    +----------------+----------------+
    | rootfs         |                |
    +----------------+----------------+

How to build buildroot
----------------------

Forst of all configure the buildroot environment:

 $ make odroid-xu4_defconfig

If needed personalize the build

 $ make menuconfig

then hit

 $ make

At the end of the build you should get in the output/images directory the
following files:

 - bl1.bin.hardkernel
	Level 1 boot loader

 - bl2.bin.hardkernel.1mb_uboot
	Level 2 boot loader

 - exynos5422-odroidxu4.dtb
	Linux Kernel Device Tree blop

 - rootfs.tar
	Compressed root file system image

 - tzsw.bin.hardkernel
	ARM Truzt Zone

 - u-boot.bin
	u-boot image

 - zImage
	Linux Kernel Image

Set up the bootloader
---------------------

I will assume you will use an sd card which will have as mount point /dev/sdb.
The above images need to be flashed to the SD card to specific addresses, as
follows:

 # dd if=bl1.bin.hardkernel of=/dev/sdb seek=1 bs=512
 # dd if=bl2.bin.hardkernel.1mb_uboot of=/dev/sdb seek=31 bs=512
 # dd if=u-boot.bin of=/dev/sdb seek=63 bs=512
 # dd if=tzsw.bin.hardkernel of=/dev/sdb seek=2111 bs=512

With the above we should be able to boot up to the u-boot bootloader.

Set up the SD card
------------------

The SD card will need to partitions, which you can make with your favourite
partitioner. At the end it should look like this:

Device         Boot  Start      End  Sectors  Size Id Type
/dev/sdb1             4096   135167   131072   64M  b W95 FAT32
/dev/sdb2           135168 15523839 15388672  7.3G 83 Linux

IMPORTANT: Please note that the first partition starts at the block 4096 instead
of the default 2048. This is due to the sizes of the binaries we flased earlier,
which go over the 2048 block, therefore, you need to start the first partition
at a further location, e.g. 4096.

Now format the two partitions, the first as vfat FS type, the second as EXT3 or
EXT4:

 # mkfs.vfat /dev/sdb1
 # mkfs.ext4 /dev/sdb2

Finalize the SD card
--------------------

Now it's time to move Kernel and File System to the SD card. We will start from
the Kernel partition.

First mount it:

 # mount /dev/sdb1/ /mnt/

and copy kernel and dtb

 # cp <buildroot>/output/images/zImage /mnt/
 # cp <buildroot>/output/images/exynos5422-odroidxu4.dtb /mnt/

umount the partition

 # sync
 # umount /dev/sdb1

Mount the rootfs partition:

 # mount /dev/sdb2 /mnt/
 # tar
 # cp <buildroot>/output/images/rootfs.tar -C /mnt/

Umount the partition

 # sync
 # umount /dev/sdb2

The SD card is ready, you can boot now your Odroid XU-4.

Automate u-boot commands
------------------------

In order to avoid customizing u-boot from the u-boot system at boot time, you
can use the boot.cmd file in board/odroid-xu4.

Jut run

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

the output is an u-boot readable binary which needs to be copied in the first
partition of the SD card:

 # mount /dev/sdb1 /mnt/
 # cp boot.scr /mnt/sdb1
 # sync
 # umount /dev/sdb1