This post introduces native Linux kernel built on the Nvidia Jetson TX1 dev board. The scripts are based on the jetsonhacks/buildJetsonTX1Kernel tools. Our target is JetPack 3.3 (the latest SDK supporting TX1 by the time of writing). All the scripts are available at [2]. Have fun~

1. Kernel build on TX1

Nvidia devtalk has some general information about kernel build for TX1 [3], including both native build and cross compile (e.g., from a TFTP server). Here we focus on the native build. The procedure roughly follows a) installing dependencies, b) downloading the kernel src, c) generating config, d) making build, and e) installing the new kernel image.

Unlike a typical kernel build on x86-64 architecture, the most confusing part would be to figure out the right kernel version supported by the board. TX1 uses Nvidia L4T [5], which is a customized kernel for the Tegra SoC. Depending on the JetPack version running on your TX1 board, different L4T version is needed. As you can tell, there are a lot of prepairations needed to be done before we could kick off the build.

2. buildJetsonTX1Kernel

JetsonHacks provides a bunch of scripts to ease and automate differen steps mentioned above, called buildJetsonTX1Kernel [1]. By detecting the tegra chip id (sysfs) and tegra release note (/etc), these scripts can figure out the model of the board (e.g., TX1) and the version of JetPack installed (e.g., 3.2), thus download the right version of L4T kernel source. Please refer to [4] for a detailed usage of these scripts.

3. One-click build

The buildJetsonTX1Kernel scripts are great and useful, but somehow I realized that my TX1 setup was different and I needed some customizations to make my life (hopefully yours too) easier [2]. The first issue was the usage of JetPack 3.3. I have submitted a patch to JetsonHacks for JetsonUtilities to correctly detect this latest JetPack version supported by TX1. Unfortunately, buildJetsonTX1Kernel scripts still only support up to JetPack 3.2. Things get more complicated when both JetPack 3.2 and 3.3 use the same L4T kernel version.

The original scripts assume the usage of eMMC to hold all the kernel build artifacts, which does not hold in my TX1 environment where a 64G SD card is mounted. Accordingly, I have updated all the scripts to use my SD card instead of the default /usr/src/ directory.

I have also created a one-click build script (kbuild.sh) to automate the whole process within one script. Simply running ./kbuild.sh would generate a new kernel image ready to reboot. I have also replaced xconfig with menuconfig since I use SSH to connect with TX1. A simple hello world kernel module is also included as a starting point for module development.

References:

[1] https://github.com/jetsonhacks/buildJetsonTX1Kernel
[2] https://github.com/daveti/buildJetsonTX1Kernel
[3] https://devtalk.nvidia.com/default/topic/762653/-howto-build-own-kernel-for-jetson-tk1/
[4] https://www.jetsonhacks.com/2018/04/21/build-kernel-and-modules-nvidia-jetson-tx1/
[5] https://developer.nvidia.com/embedded/linux-tegra