Build Linux from source code¶

Toolchain installation for out of Flexbuild builds¶

To install the toolchain, follow the Debian Flexbuild Toolchain installation guide.

Setup the environment:¶

Set up a working directory

$ export WORKDIR=~/imx95-var-dart-linux
$ mkdir ${WORKDIR}

Define the cross-compiler and the architecture:

$ export CROSS_COMPILE=aarch64-linux-gnu-
$ export ARCH=arm64

Build Linux out of Yocto tree¶

Fetch linux-imx source code:¶

$ cd $WORKDIR
$ git clone https://github.com/varigit/linux-imx.git -b lf-6.12.y_6.12.20-2.0.0_var01

Build Kernel, Modules, and DTBs:¶

Clean and prepare the kernel:

$ cd ${WORKDIR}/linux-imx
$ make mrproper
$ make imx8_var_defconfig

Customize the kernel configuration (optional step):
$ make menuconfig

Build kernel parts:

Build everything:
$ make -j$(nproc)

Build Image.gz only:
$ make -j$(nproc)  Image.gz

Build modules only:
$ make -j$(nproc)  modules

Build device trees only:
$ make -j$(nproc) dtbs

Build only the device tree for DART-MX95 on DT8MCustomBoard:
$ make -j4 freescale/imx95-var-dart-dt8mcustomboard.dtb

Install kernel modules to temporary directory¶

Create a temporary directory to install the modules:

Optional: delete any old installation from previous builds:
$ rm -rf $WORKDIR/rootfs

Create new directory:
$ mkdir -p $WORKDIR/rootfs

Install the modules to the temporary rootfs:

$ cd ${WORKDIR}/linux-imx && \
  make ARCH=arm64 \
    INSTALL_MOD_STRIP=1 \
    INSTALL_MOD_PATH=$WORKDIR/rootfs \
    modules_install

Build external modules¶

Build and install iw61x wifi driver support to temporary rootfs¶

External kernel modules must be compiled against the exact kernel version (commit ID) that is deployed on the target. Follow the steps below to compile and install the mandatory external drivers for the imx95-var-dart.

NXP Wi-Fi linux Driver

Follow the steps below to compile and install the driver for the NXP iw61x chipset.

Fetch the driver:

$ cd $WORKDIR
$ git clone https://github.com/nxp-imx/mwifiex -b lf-6.12.20_2.0.0 mwifiex
$ cd mwifiex && \
  git checkout 7a8beaa1605cb0870dc7ba3312c76df91cb0d6cf && \
  cd ../

Build the driver:

$ cd ${WORKDIR}/mwifiex && 
  make -j$(nproc) KERNELDIR=$WORKDIR/linux-imx

Install the driver to the temporary modules directory:

$ make -j$(nproc) \
    KERNELDIR=${WORKDIR}/linux-imx \
    -C ${WORKDIR}/linux-imx \
    M=${WORKDIR}/mwifiex \
    INSTALL_MOD_PATH=${WORKDIR}/rootfs \
    INSTALL_MOD_STRIP=1 \
    modules_install

Notes:

If you replace the kernel image (Image.gz) on your system, you also need to reinstall the kernel modules, and vice versa.

If you just want to make a change in the device tree, you can compile and replace it without replacing the kernel image and modules.

Install the built kernel images, modules, and device trees on an SD card¶

Copy the Image.gz and device trees to the SD card boot partition, and install the modules in the SD card rootfs partition.
Assuming the rootfs partition is mounted on /media/user/root:

Install the kernel image and modules:
$ cd ${WORKDIR}/linux-imx
$ kver=$(strings arch/arm64/boot/Image | grep -i "Linux version" | awk 'NR==1 {print $3}')
$ sudo cp arch/arm64/boot/Image.gz /media/user/root/boot/Image.gz-${kver}
$ sudo ln -fs Image.gz-${kver} /media/user/root/boot/Image.gz
$ sudo rsync -Kra $WORKDIR/rootfs/* /media/user/root

Install the device trees:
$ sudo cp arch/arm64/boot/dts/freescale/*imx*var*.dtb /media/user/root/boot/

Install the built kernel images, modules, and device trees using SSH on a running target¶

The example below uses ssh to install the kernel on a running device.

First, export a variable with the ip address of your target device:

$ export TARGET_IP=192.168.0.205

Then, copy the kernel image and device trees to the temporary directory, send them to the target using ssh, and install them with the correct user permissions:

$ mkdir -p $WORKDIR/rootfs/boot && \
  cp ${WORKDIR}/linux-imx/arch/arm64/boot/dts/freescale/*imx*var*.dtb $WORKDIR/rootfs/boot && \
  cp ${WORKDIR}/linux-imx/arch/arm64/boot/Image.gz $WORKDIR/rootfs/boot/ && \
  ssh root@${TARGET_IP} 'mkdir /tmp/rootfs' && \
  tar czf - -C $WORKDIR/rootfs . | ssh root@${TARGET_IP} 'tar xzf - -C /tmp/rootfs && \
  chown -R root:root /tmp/rootfs && cp -a /tmp/rootfs/boot/* /boot/ && cp -a /tmp/rootfs/lib/* /lib/ && \
  rm -r /tmp/rootfs'