相关文档：
https://docs.nvidia.com/jetson/archives/r35.1/DeveloperGuide/text/SD/Kernel/KernelCustomization.html
第一步，首先要学习编译内核，参考文档入上所示。用它们的手动下载源码的方式Manually Downloading and Expanding Kernel Sources，否则自动编译的文件是没有的。
这个过程是：
删除
sudo rm -rf $JETPACK/kernel/Image
sudo rm -rf $JETPACK/kernel/dtb
编译
./nvbuild.sh -o $PWD/kernel_out
拷贝
cp $kernel_out/arch/arm64/boot/Image $JETPACK/kernel/
cp -r $kernel_out/arch/arm64/boot/dts/nvidia $JETPACK/kernel/dtb
编译前，需要修改三点：
1.
kernel/kernel-5.10/arch/arm64/configs/tegra_defconfig
CONFIG_PPS=y
CONFIG_PPS_DEBUG=y
CONFIG_PPS_CLIENT_KTIMER=y
CONFIG_PPS_CLIENT_GPIO=y
2. hardware/nvidia/platform/t23x/concord/kernel-dts/tegra234-p3701-0000-p3737-0000.dts
pps {
compatible = "pps-gpio";
assert-falling-edge;
gpios = <&tegra_main_gpio TEGRA234_MAIN_GPIO(Q, 6) GPIO_ACTIVE_LOW>;
status = "okay";
};
3.kernel/kernel-5.10/drivers/pps/clients/pps-gpio.c
ret = pps_gpio_setup(pdev);
if (ret)
return ret;//-EINVAL;
第三点不加就会找不到/dev/pps1
4. 可能用到的安装
sudo apt install wget lbzip2 build-essential bc zip libgmp-dev libmpfr-dev libmpc-dev vim-common
sudo apt-get install libncurses5-dev
sudo apt-get install -y pkg-config
sudo apt-get install libssl-dev
