1，我的硬件

jetson nano b001，就是官方16G emmc的模块，+ 国产图为科技的底板

2，我的目的:

要安装linux preempt rt实时补丁，所以需要重新编译内核源码

3，说明：

jetson nano从r35开始，官方已经带preempt的补丁配置程序了，但是没有编译，没有安装，所以默认你能看到下面信息，但是实际上RT没有运行，没有安装

~$ uname -a
Linux ubuntu 4.9.253-tegra #1 SMP PREEMPT Wed Apr 20 14:25:12 PDT 2022 aarch64 aarch64 aarch64 GNU/Linux

4，开始步骤：

0，重点说明

全程按照下面操作，不要改目录，容易弄错

下面操作内容是在PC电脑的ubuntu上进行的，不是在jetson板子里面。

1，编译需要

# Install required packages
sudo apt-get update 
sudo apt-get install libncurses5-dev 
sudo apt-get install build-essential bc 
sudo apt-get install lbzip2
sudo apt-get install qemu-user-static

2，程序包下载

# L4T Jetson Driver Package
wget https://developer.nvidia.com/embedded/l4t/r32_release_v7.1/t210/jetson-210_linux_r32.7.1_aarch64.tbz2
# L4T Sample Root File System
wget https://developer.nvidia.com/embedded/l4t/r32_release_v7.1/t210/tegra_linux_sample-root-filesystem_r32.7.1_aarch64.tbz2
# L4T Sources:
wget https://developer.nvidia.com/embedded/l4t/r32_release_v7.1/sources/t210/public_sources.tbz2
# GCC Tool Chain for 64-bit BSP
#使用浏览器下载得到gcc开头压缩包
https://developer.nvidia.com/embedded/dlc/l4t-gcc-7-3-1-toolchain-64-bit

3，打补丁

# Create build folder
mkdir $HOME/jetson_nano 
cd $HOME/jetson_nano 

# Extract files
sudo tar xpf jetson-210_linux_r32.7.1_aarch64.tbz2 
cd Linux_for_Tegra/rootfs/ 
sudo tar xpf ../../tegra_linux_sample-root-filesystem_r32.7.1_aarch64.tbz2
cd ../../ 
tar -xvf gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu.tar.xz
sudo tar -xjf public_sources.tbz2
tar -xjf Linux_for_Tegra/source/public/kernel_src.tbz2

# Apply PREEMPT-RT patches
cd kernel/kernel-4.9/ 
./scripts/rt-patch.sh apply-patches

4，编译

# Compile kernel
TEGRA_KERNEL_OUT=jetson_nano_kernel 
mkdir $TEGRA_KERNEL_OUT 
export CROSS_COMPILE=$HOME/jetson_nano/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-
make ARCH=arm64 O=$TEGRA_KERNEL_OUT tegra_defconfig 
make ARCH=arm64 O=$TEGRA_KERNEL_OUT menuconfig

保证如下两条正确

# This option should already be selected: Kernel Features -> Preemption Model: Fully Preemptible Kernel (RT)

# You can modify other options for your kernel, like the timer frequency (or anything you need): Kernel Features -> Timer frequency: 1000 HZ

# After saving the configuration and exiting, start the kernel compilation
make ARCH=arm64 O=$TEGRA_KERNEL_OUT -j16

# Copy results
sudo cp jetson_nano_kernel/arch/arm64/boot/Image $HOME/jetson_nano/Linux_for_Tegra/kernel/Image 
sudo cp -r jetson_nano_kernel/arch/arm64/boot/dts/* $HOME/jetson_nano/Linux_for_Tegra/kernel/dtb/ 
sudo make ARCH=arm64 O=$TEGRA_KERNEL_OUT modules_install INSTALL_MOD_PATH=$HOME/jetson_nano/Linux_for_Tegra/rootfs/ 
cd $HOME/jetson_nano/Linux_for_Tegra/rootfs/ 
sudo tar --owner root --group root -cjf kernel_supplements.tbz2 lib/modules 
sudo mv kernel_supplements.tbz2  ../kernel/ 

# Apply binaries
cd .. 
sudo ./apply_binaries.sh

5，烧写

（1）如果是sd卡的jetson nano，执行如下

cd tools

#可以打开这个sh文件，看参数介绍
sudo ./jetson-disk-image-creator.sh -o jetson_nano.img  -b jetson-nano -r 100

（2）如果是emmc 16G的jetson nano，执行如下

断电jetson nano
先连jetson nano usb到PC Ubuntu电脑（可以是虚拟机）
然后短接jetson nano板子的REC-GND
然后上电

cd $HOME/jetson_nano/Linux_for_Tegra
sudo ./flash.sh jetson-nano-emmc mmcblk0p1

5，延迟测试

sudo apt-get install rt-tests

运行cyclictest程序进行实时性测试：

sudo cyclictest -t 5 -p 80 -n #运行五个线程，线程优先级为80

b@jetson:~uname -a
Linux jetson 4.9.253-rt168 #1 SMP PREEMPT RT Fri Oct 28 09:36:04 CST 2022 aarch64 aarch64 aarch64 GNU/Linux

b@jetson:~$ sudo cyclictest -t 5 -p 80 -n
[sudo] password for b:
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.16 0.16 0.23 1/621 19140

T: 0 (19046) P:80 I:1000 C:  15300 Min:      5 Act:    6 Avg:    7 Max:      20
T: 1 (19047) P:80 I:1500 C:  10200 Min:      5 Act:    6 Avg:    6 Max:      25
T: 2 (19048) P:80 I:2000 C:   7650 Min:      5 Act:    6 Avg:    6 Max:      19
T: 3 (19049) P:80 I:2500 C:   6120 Min:      5 Act:    6 Avg:    7 Max:      24
T: 4 (19050) P:80 I:3000 C:   5100 Min:      5 Act:    7 Avg:    6 Max:      18

参考链接：

https://forums.developer.nvidia.com/t/preempt-rt-patches-for-jetson-nano/72941/25

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本文地址: jetson nano编译kernel内核源码，打preempt rt补丁，烧写