Coral from Google - Camera Drivers - How to recompile kernel
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Now you can install the kernel, first create a directory to download the python script used to download the source code
mkdir -p <PATH_SCRIPT> export PATH=$PATH:PATH_SCRIPT curl https://storage.googleapis.com/git-repo-downloads/repo > PATH_SCRIPT/repo chmod a+x PATH_SCRIPT/repo
Now go to where the script was downloaded and run the repo script to initialize the code
cd PATH_SCRIPT repo init -u https://coral.googlesource.com/manifest repo sync -j$(nproc)
Automatic kernel compilation
Install the dependencies to build the kernel
sudo apt-get install qemu-user-static sudo apt-get install docker.io sudo adduser $USER docker sudo apt-get install android-tools-adb android-tools-fastboot sudo apt-get install build-essential qemu-user-static bc
Now use the source and build the kernel
source build/setup.sh m docker-linux-imx
If the following error comes up:
wget -O debbootstrap.deb http://ftp.us.debian.org/debian/pool/main/d/debootstrap/debootstrap_1.0.89_all.deb --2023-05-04 17:47:41-- http://ftp.us.debian.org/debian/pool/main/d/debootstrap/debootstrap_1.0.89_all.deb Resolving ftp.us.debian.org (ftp.us.debian.org)... 64.50.236.52, 64.50.233.100, 208.80.154.139, ... Connecting to ftp.us.debian.org (ftp.us.debian.org)|64.50.236.52|:80... connected. HTTP request sent, awaiting response... 404 Not Found 2023-05-04 17:47:42 ERROR 404: Not Found.
Replace the debootsrap URL with a working mirror in the build/prereqs.mk file, for example:
sed -i 's,http://ftp.us.debian.org/debian/pool/main/d/debootstrap/debootstrap_1.0.89_all.deb,http://mirror.nus.edu.sg/Debian/pool/main/d/debootstrap/debootstrap_1.0.89_all.deb,g' build/prereqs.mk
After that, rebuild the kernel:
m docker-linux-imx
You are going to see in the output of the process the following lines, these are the packages that you can install on the board.
dpkg-deb: building package 'linux-headers-4.14.98-imx' in '../linux-headers-4.14.98-imx_12-4_arm64.deb'. dpkg-deb: building package 'linux-kbuild-4.14.98-imx-dbgsym' in '../linux-kbuild-4.14.98-imx-dbgsym_12-4_arm64.deb'. dpkg-deb: building package 'linux-kbuild-4.14.98-imx' in '../linux-kbuild-4.14.98-imx_12-4_arm64.deb'. dpkg-deb: building package 'linux-image-4.14.98-imx' in '../linux-image-4.14.98-imx_12-4_arm64.deb'.
To install the new kernel you can run the following commands
j product cd packages/bsp/ mdt install linux-image-4.14.98-imx_12-4_arm64.deb && \ mdt install linux-kbuild-4.14.98-imx_12-4_arm64.deb && \ mdt install linux-headers-4.14.98-imx_12-4_arm64.deb
Now your driver should be installed in the system
Manual kernel compilation
The process described above is very straight forward for deployment; however, it is not ideal for development since it is very time consuming and not incremental at all. Making a very small change in a file results in a 30min compilation process.
For development purposes it is recommended to use the following approach for a more efficient workflow.
This approach will also allow you to compile other versions of the kernel if you'd like since the coral uses an old version (4.14.98) of the kernel. Keep in mind that updating the kernel might affect compatibility with other modules required by the coral for hardware acceleration and such. Find the instructions below:
1. Getting the toolchain:
For the kernel crosscompilation we need an arm64 toolchain. Feel free to use any you like, in this wiki we use the Linaro toolchain.
Download the pre-built toolchain binaries from: http://releases.linaro.org/components/toolchain/binaries/7.3-2018.05/aarch64-linux-gnu/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu.tar.xz
wget http://releases.linaro.org/components/toolchain/binaries/7.3-2018.05/aarch64-linux-gnu/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu.tar.xz
Execute the following commands to extract the toolchain:
mkdir $HOME/linaro-gcc cd $HOME/linaro-gcc tar xf gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu.tar.xz
2. Compiling the kernel:
cd linux-imx export ARCH=arm64; export CROSS_COMPILE=/$HOME/linaro-gcc/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-; export LOCALVERSION=-imx make O=build defconfig make O=build menuconfig make O=build -j8 Image dtbs make O=build -j8 modules
During the menuconfig stage make sure that the local version auto generation is disabled and that the local version prefix is set to -imx
3. Using the new kernel:
To use the new kernel and dtb you can just replace the old ones with the new ones, for the coral those are
/boot/Image -> /boot/vmlinuz-4.14.98-imx /boot/fsl-imx8mq-phanbell.dtb
You can find the new ones under:
linux-imx/build/arch/arm64/boot/Image linux-imx/build/arch/arm64/boot/dts/freescale/fsl-imx8mq-phanbell.dtb
4. Kernel modules:
When developing a driver, it is useful to only update the driver module. For this move the .ko you need to the board and install it manually.
insmod <module>.ko
Making changes to the dtb or the kernel module should now only require minimal compilation time and moving the .dtb or .ko respectively, significantly accelerating the development time.
If you have the sources as part of a git repository and have uncommited changes, compilation will tag the build with -dirty at the end of the local version, resulting in possible mismatch between the modules and the image or dtb if only one is updated; to avoid this you can simply create a draft commit.
