Compile, Install, and Update Linux Kernel

Obtain Debian Version

Download the latest Debian operating system.
Flash the latest operating system to the micro-SD card. For details, see Flash OS to a Micro-SD Card.

Set up Software Environment

To set up the software environment for the Linux kernel compilation:

Execute the following command to install the essential tools and libraries required to compile the Linux kernel.

$ sudo apt-get install build-essential linux-source bc kmod cpio flex libncurses5-dev libelf-dev libssl-dev dwarves bison git gcc-riscv64-linux-gnu g++-riscv64-linux-gnu vim tree

Execute the following command to check out the source code:
```
$ git clone https://github.com/starfive-tech/linux.git
```
See the Debian release information, find and switch the kernel source code to the corresponding version. The following command example switches to the Debian 202403 branch.
```
$ git checkout JH7110_VF2_515_v5.11.3
```
Execute the following command to set the default configuration of compiling Linux kernel:
```
make <Configuration_File> CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv
```
where, Configuration_File is starfive_visionfive2_defconfig.
(Optional) Modify the configuration file.
```
$ make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- menuconfig
```
For example, to change the CPUFreq governor from ondemand to performance, under Devices Drivers > SPU Frequency scaling, change the Default CPUFreq governor from ondemand to performance and uncheck the ondemand option.
Figure 1. Performance

Compile and Install Kernel Components as a Whole

You can compile and install all kernel components at a time, including kernel configuration file (config), symbol table (System.map), compressed kernel image (vmlinuz), device tree files (dtb), and kernel modules.

You can choose between local and cross compile and install, depending on your compilation environment.

Local compile and install

Use bindeb-pkg to create the Debian kernel install package.

cd linux/
cp arch/riscv/configs/starfive_visionfive2_defconfig .config
make ARCH=riscv olddefconfig
make ARCH=riscv -j$(nproc) bindeb-pkg

Install the kernel to the operating system.
```
dpkg -i *.deb
```

Cross compile and install

Execute the following command to set the default configuration of compiling the kernel:
```
make <Configuration_File> CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv
```
where, Configuration_File is starfive_visionfive2_defconfig.
Execute the following command to compile the kernel image and header files, and then package them as Debian packages:
```
$ nice make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- bindeb-pkg -j$(nproc)  
KDEB_COMPRESS=xz LOCALVERSION=’local_version’
```
Tip: local_version is the version of the kernel, which sets to -performance in this example.
```
$ nice make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- bindeb-pkg -j$(nproc)  
KDEB_COMPRESS=xz LOCALVERSION=-performance
```
After compilation, the following deb files and dtb files are generated in the upper directory:
Figure 2. Compiled Files
Transfer the compiled files through network (SCP) or portable storage medium (USB) to VisionFive 2. The following figure shows an example output of file transfer over the network:

Execute the following command to install the kernel.

$ dpkg -i linux-headers-5.15.0-performance_5.15.0-performance-1_riscv64.deb
$ dpkg -i linux-image-5.15.0-performance_5.15.0-performance-1_riscv64.deb
$ dpkg -i linux-libc-dev_5.15.0-performance-1_riscv64.deb

After installation, the files under /boot are updated.

Compile and Install Kernel Components Individually

You can compile and install kernel components individually. Choose the kernel components you want to install or update.

To compile and install the kernel files and device tree file:

Execute the following command to set the default configuration of compiling the Debian kernel:
```
make <Configuration_File> CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv
```
where, Configuration_File is starfive_visionfive2_defconfig.
After setting up the software environment, execute the following command to compile the source code:
```
$ make CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv -j$(nproc)
```
Execute the following command to create a directory where the kernel files are to be stored.
```
$ mkdir <compiled_kernel_file_dirctory>
```
Execute the following command to cross-compile the Linux kernel and install the kernel files such as config, system.map, and vmlinuz in the specified directory.
```
$ make CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv INSTALL_PATH=<compiled_kernel_file_dirctory> zinstall -j$(nproc)
```
The following figure is an example output where the kernel files are installed in the compiled directory.

Copy the device tree (dtb) files to the <compiled_kernel_file_directory>.

$ cp arch/riscv/boot/dts/starfive/jh7110-visionfive-v2.dtb <compiled_kernel_file_dirctory>

To compile and install the kernel modules:

Execute the following command to compile the kernel modules and install them in the <compiled_kernel_file_dirctory>. The driver files are stored in the lib/modules directory.

$ make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- INSTALL_MOD_PATH=../<compiled_kernel_file_dirctory> modules_install

Note: If the new kernel does not involve changes to the driver module, you can skip this step and the default kernel driver module is used.

The following figure is an example output:

Update Kernel

You can update the kernel components by reinstalling them as a whole or by reinstalling the target components and placing the new files in the corresponding directory.

Place the new Linux kernel files System.map, config, and vmlinuz under the /boot path.
Place the new device tree file jh7110 visionfive v2.dtb in a path corresponding to the kernel version. For example, /boot/dtbs performance/5.15.0/starfive
Place the new kernel module files in the /lib/modules directory.
Generate an initramfs file for the new kernel under the /boot path.
```
update-initramfs -c -k 5.15.0 -b /boot
```
Figure 5. initrd.img

Add Boot Option for New Kernel

Modify the extlinux/extlinux.cn file to add an boot option for the new kernel:

Figure 6. Modify extlinux/extlinux.conf file

Note: If the new kernel does not change the driver module, the default initrd.img-5.15.0-starfive is used. Change initrd.img-5.15.0 to initrd.img-5.15.0-starfive.

After powering on, the new boot option should be available in the U-Boot menu.