Compiling Linux Kernel 4.2.6

This article illustrates how to generate a bootable class='acmetable' Linux Kernel image for Acqua A5, Aria G25 and Arietta G25 boards

Notes

• This procedure was tested on a Linux PC with Ubuntu 15.04
• More info about this Kernel version are available here
• It is advisable to have a Debug Port Interface during the Kernel bootstrap
• Before following this step by step procedure install these packages

Step-by-step Kernel cross-compilation procedure:

Download and save in your home directory the Linux Kernel sources:

• linux-4.2.6.tar.xz

Extract the Kernel sources from the compressed file by typing:

~$ tar xvfJ linux-4.2.6.tar.xz
...

Move inside the new folder:

~$ cd linux-4.2.6
~/linux-4.2.6$

At this point I suggest to create a your own personal branch of Linux Kernel sources with git to keep a trace of any changes from the Kernel mainline using these commands.

~/linux-4.2.6$ git init
~/linux-4.2.6$ git add .
~/linux-4.2.6$ git commit -m "Linux vanilla"
~/linux-4.2.6$ git branch acme
~/linux-4.2.6$ git checkout acme

Download this patch file from GitHub:

• linux-4.2.6.patch

and apply it by typing:

~/linux-4.2.6$ patch -p1 < linux-4.2.6.patch

Then select the right Linux configuration for your board by typing one of these commands:

Acqua A5

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-acqua_defconfig

Arietta G25

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-arietta_defconfig

Aria G25

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-aria_defconfig

Customize the default Linux Kernel configuration:

If you need to customize the Kernel configuration or you just want to take a look around the Kernel setup type:

~/linux-4.2.6$ make ARCH=arm menuconfig

and navigate inside the Kernel configuration using the arrow keys and following the help provided by the menuconfig interface.

Generate the Device Tree Blob file (.dtb)

Now compile the the device tree file requested by your board by typing one of these commands:

Acqua A5

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-acqua.dtb

Arietta G25

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-arietta.dtb

Aria G25

~/linux-4.2.6$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-aria.dtb

Compile the Kernel image

Compile the Linux Kernel sources and generate the binary compressed image file to save in the first partition of microSD card.

~/linux-4.2.6$ make -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- zImage
...
  Image arch/arm/boot/zImage is ready

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. We didn't use any [M] flag in our defconfig so this procedure is not requested but. in case you add something. these are the commands to use to compile them:

~/linux-4.2.6$ make modules -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
...
~/linux-4.2.6$ make modules_install INSTALL_MOD_PATH=./modules ARCH=arm
...

Copy the boot files into the first microSD partition

• Local write
• Remote write

~/linux-4.2.6$ cp arch/arm/boot/dts/acme-acqua.dtb /media/$USER/boot/at91-sama5d3_acqua.dtb
~/linux-4.2.6$ cp arch/arm/boot/zImage /media/$USER/boot
~/linux-4.2.6$ sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

~/linux-4.2.6$ cp arch/arm/boot/dts/acme-arietta.dtb /media/$USER/boot/acme-arietta.dtb
~/linux-4.2.6$ cp arch/arm/boot/zImage /media/$USER/boot
~/linux-4.2.6$ sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

~/linux-4.2.6$ cp arch/arm/boot/dts/acme-aria.dtb /media/$USER/boot/at91-ariag25.dtb
~/linux-4.2.6$ cp arch/arm/boot/zImage /media/$USER/boot
~/linux-4.2.6$ sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

~/linux-4.2.6$ scp arch/arm/boot/dts/acme-acqua.dtb root@ip address:/boot/at91-sama5d3_acqua.dtb
~/linux-4.2.6$ scp arch/arm/boot/zImage root@ip address:/boot
~/linux-4.2.6$ rsync -avc modules/lib/. root@ip address:/lib/.

~/linux-4.2.6$ scp arch/arm/boot/dts/acme-arietta.dtb root@192.168.10.10:/boot/acme-arietta.dtb
~/linux-4.2.6$ scp arch/arm/boot/zImage root@192.168.10.10:/boot
~/linux-4.2.6$ rsync -avc modules/lib/. root@192.168.10.10:/lib/.

~/linux-4.2.6$ scp arch/arm/boot/dts/acme-aria.dtb root@ip address:/media/mmc_p1/at91-ariag25.dtb
~/linux-4.2.6$ scp arch/arm/boot/zImage root@ip address:/media/mmc_p1
~/linux-4.2.6$ rsync -avc modules/lib/. root@ip address:/lib/.

After the first boot

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

~# depmod -a