This article illustrates how to generate a bootable Linux Kernel 3.11.6 image for CORE9G25

Hardware requirements:

• an Ubuntu Linux PC (we used an Ubuntu 13.10)
• an CORE9G25 with base board CORE9G25-CON
• a 2 GByte (or bigger) microSD card
• a Debug Serial Port Interface

Installing the toolchain:

Install the cross compiler and the toolchain required on your PC following this article:

• Install the ARM9 cross toolchain to compile the Linux Kernel and AT91Bootstrap

Prepare the Kernel sources and build it:

Copy the CORE9G25 Linux-3.11.6.tar.bz2 from the CD to the tmp folder, then do the follow command to uncompress it:

~$ cd ~
~$ tar xvf /tmp/linux-3.11.6.tar.bz2 -C .

then move in the linux-3.11.6 folder:

~$ cd linux-3.11.6
~/linux-3.11.6$
~/linux-3.11.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- at91-ariag25_defconfig

then compile it to generate a device tree blob file (.dtb) by typing:

~/linux-3.11.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- at91-ariag25.dtb

This file will be used by the Linux Kernel at startup time to configure the initial state of your hardware.

Customize the default Linux Kernel configuration:

If you need customize the Kernel configuration by using menuconfig type:

~/linux-3.11.6$ make ARCH=arm menuconfig

Running the Kernel compilation

To compile the Linux Kernel type:

~/linux-3.11.6$ make -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
...
Kernel: arch/arm/boot/zImage is ready

Copying the binary files generated in the bootable microSD

Create now from arch/arm/boot/zImage file a suitable file that the At91Bootstrap bootloader can load from microSD card by typing:

~/linux-3.11.6$ mkimage -A arm -O linux -C none -T kernel -a 20008000 -e 20008000 -n linux-3.11.6 -d arch/arm/boot/zImage image.bin
Image Name:   linux-3.11.6
Created:      Mon Oct 21 09:58:40 2013
Image Type:   ARM Linux Kernel Image (uncompressed)
Data Size:    1709032 Bytes = 1668.98 kB = 1.63 MB
Load Address: 20008000
Entry Point:  20008000

Insert a formatted microSD and copy the bootable Linux image.bin file and the hardware description file at91-CORE9G25.dtb in the first microSD partition:

~/linux-3.11.6$ cp arch/arm/boot/dts/at91-ariag25.dtb /media/$USER/kernel/at91-ariag25.dtb
~/linux-3.11.6$ cp image.bin /media/$USER/kernel/

Compile the Kernel modules

The image generated contains the Linux Kernel and all the built-in device drivers (option [*] in menuconfig) compiled with it.

Al the drivers compiled as external modules (option [M] in menuconfig) need to be compiled and saved in the rootfs /lib directory on the second partition of the microSD. To compile them type:

~/linux-3.11.6$ make modules -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
~/linux-3.11.6$ make modules_install INSTALL_MOD_PATH=./modules ARCH=arm

Copy the kernel modules on the microSD:

~/linux-3.11.6$ sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

At the first access to the CORE9G25 board command line update the module dependencies by typing this command:

~# depmod -a

Use the new Kernel with EmDebian 7.1 Wheezy Grip

Follow this article:

• Build an Embedded Debian Grip 7.2 root filesystem

Quick and dirty test

If you want to try the new Kernel quickly use the binary available on:

• MicroSD card repository

Related links

• Kernel.org
• Linux changes
• Linux Kernel mailing list archives
• Kernel documentation for device trees