Acqua technical documentation

Compiling Linux Kernel 5.15.32 LTS for Acqua

This article illustrates how to generate a bootable Linux Kernel image for Acqua SOM starting from the Linux Kernel sources available on the The Linux Kernel Archives

Prerequisite

A Linux PC in required to cross compile the Kernel image.

This procedure has been tested on:

  • Ubuntu 18.04.4 LTS (amd64)

Follow this article to install the Toolchain requested to compile the sources:

It is advisable to have a Debug Port Interface like DPI or USB-3V-SER to check the error messages during the Kernel bootstrap

Step-by-step procedure

Open a terminal on your Linux PC and download the Linux Kernel sources from the main stream repository:

wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.32.tar.xz

extract the Kernel sources from the compressed file by typing:

tar xvfJ linux-5.15.32.tar.xz

move inside the folder created:

cd linux-5.15.32

copy the basic kernel defconfig file suggested from us

wget https://www.acmesystems.it/www/acqua_compile_kernel_5_15/acme-acqua_defconfig -O arch/arm/configs/acme-acqua_defconfig

Set the defconfig:

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-acqua_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:

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)

Download the Acqua device tree file:

wget https://www.acmesystems.it/www/acqua_compile_kernel_5_15/at91-sama5d3_acqua.dts -O arch/arm/boot/dts/at91-sama5d3_acqua.dts

Now compile the device tree file:

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- at91-sama5d3_acqua.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.

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:

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

Copy the boot files into the first microSD partition

Insert a formatted microSD with the boot loader (at91bootstrap) and the rootfs contents already created in your Linux PC and copy on it these files:

Write the Linux Kernel image and the device tree blob in the first microSD partition:

sudo cp arch/arm/boot/zImage /media/$USER/boot
sudo cp arch/arm/boot/dts/at91-sama5d3_acqua.dtb /media/$USER/boot/at91-sama5d3_acqua.dtb

Write the Linux Kernel modules inside the second microSD partition:

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

After the first boot

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

depmod -a

Create a defconfig of your own Kernel configuration

make ARCH=arm savedefconfig

The file defconfig contains your configuration. You could rename and copy it in arch/arm/configs/

cp defconfig arch/arm/configs/my_defconfig

Links

Sergio Tanzilli
Systems designer, webmaster of www.acmesystems.it and founder of Acme Systems srl

Personal email: tanzilli@acmesystems.it
Web pages: https://www.acmesystems.it --- https://www.acmestudio.it
Github repositories: https://github.com/tanzilli --- https://github.com/acmesystems
Telegram group dedicated to the Acme Systems boards: https://t.me/acmesystemssrl

Acqua technical documentation