Roadrunner technical documentation

Compiling Linux Kernel 5.15 LTS for RoadRunner

This article illustrates how to generate a bootable Linux Kernel image for RoadRunner SOM

The contents of this article are mainly derived from the official Microchip reference page available on this link:

Prerequisite

Step-by-step Kernel cross-compilation procedure:

Kernel sources download

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

wget https://github.com/linux4microchip/linux/archive/refs/heads/linux-5.15-mchp.zip
unzip linux-5.15-mchp.zip
cd linux-linux-5.15-mchp

Compile the Kernel image

Download the Roadrunner Kernel config and generate the Kernel bootable image:

wget https://www.acmesystems.it/www/roadrunner_compile_kernel_5_15/roadrunner_defconfig -O arch/arm/configs/roadrunner_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- roadrunner_defconfig

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

make -j4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage
...
Image arch/arm/boot/zImage is ready

Generate the Device Tree Blob file (.dtb)

Download our example of device tree source by typing:

wget https://www.acmesystems.it/www/roadrunner_compile_kernel_5_15/acme-roadrunner.dts -O arch/arm/boot/dts/acme-roadrunner.dts

Now compile the device tree file requested by your board by selecting one of the following commands:

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- acme-roadrunner.dtb

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 -j4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-
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 (zImage) and the device tree blob (acme-roadrunner.dtb) inside the first microSD partition:

sudo cp arch/arm/boot/dts/acme-roadrunner.dtb /media/$USER/boot
sudo cp arch/arm/boot/zImage /media/$USER/boot

Copy also the Linux kernel command file cmdline.txt

wget https://www.acmesystems.it/www/roadrunner_compile_kernel_5_15/cmdline.txt
sudo cp cmdline.txt /media/$USER/boot

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

Links

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.

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

File used in this article

Roadrunner technical documentation