澳门新葡亰App「主页」·欢迎您

    <optgroup id="yjqgf"></optgroup>

  1. <optgroup id="yjqgf"></optgroup>
    1. 技术文章

      当前页面: 首页 >技术文章 >RT-Linux在IMX8上的使用

      RT-Linux在IMX8上的使用

      供稿:韬睿(上海)计算机科技有限公司 2020/10/29 14:16:55

      0 人气:4

      • 关键词: iMX8 ARM Linux
      • 摘要:Real-time Linux 是指在普通 Linux 内核打上 PREEMPT_RT补丁后使内核满足实时要求。下面我们将使用 Apalis iMX8QM 介绍如何开启 Linux 5.4 的实时功能。

      By Toradex胡珊逢

       

      Real-time Linux 是指在普通 Linux 内核打上 PREEMPT_RT补丁后使内核满足实时要求。下面我们将使用 Apalis iMX8QM 介绍如何开启 Linux 5.4 的实时功能。

       

      首先需要下载适用于 Apalis iMX8QM 模块的最新 Linux 内核源码。

      git clone -b toradex_5.4-2.1.x-imx     git://git.toradex.cn/linux-toradex.git

       

      在源码根目录下打开 Makefile 文件查看内核版本,这里我们看到是5.4.47

      $ head Makefile

      # SPDX-License-Identifier: GPL-2.0

      VERSION = 5

      PATCHLEVEL = 4

      SUBLEVEL = 47

      EXTRAVERSION =

      NAME = Kleptomaniac Octopus

       

      下载对应版本的 PREEMPT_RT补丁,解压后放到源码根目录下。

      https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patch-5.4.47-rt28.patch.gz

       

      执行下面命令为 5.4.47 内核打上补丁。

      $ patch -p1     < patch-5.4.47-rt28.patch

       

      根据这里的说明完成内核以及驱动模块编译。

      $ make     defconfig

      $ make     menuconfig

       

      开启 > General setup > [*] Configure standard kernel features

       > General setup > reemption Model 中选择 Fully Preemptible Kernel (Real-Time)

      image001.png

      为了获得更好的实时性能,我们将关闭显示功能以及部分音频功能。在 > Device Drivers > Graphics support 中取消相关显示接口。

      image002.png

       

       > Device Drivers > Sound card support > Advanced Linux Sound Architecture > ALSA for SoC audio support > SoC Audio for Freescale CPUs 中取消 AUDIO TO HDMI TX module support  XCVR 支持。

      image003.png

       

      保存配置后退出,开始编译内核。

      $ make     Image.gz 2>&1 | tee build.log

      $ make -j3     modules

      $ mkdir     modules

      $ export     INSTALL_MOD_PATH=modules

      $ make     modules_install

       

       arch/arm64/boot  modules/lib/modules 目录分别是内核文件 Image.gz 和驱动模块。将其复制到 Apalis iMX8QM 模块的 /media/mmcblk0p1  /lib/modules/。然后执行重启命令。

      root@apalis-imx8:~# sync

      root@apalis-imx8:~# reboot

       

      启动后可以查看目前运行的内核配置情况。

      root@apalis-imx8:~#     zcat /proc/config.gz |grep PREEMPT                                                                                                                        CONFIG_HAVE_PREEMPT_LAZY=y                                                                                                                                                    CONFIG_PREEMPT_LAZY=y                                                                                                                                                         #     CONFIG_PREEMPT_NONE is not set                                                                                                                                              # CONFIG_PREEMPT_VOLUNTARY is not set                                                                                                                                         # CONFIG_PREEMPT is not set                                                                                                                                                   CONFIG_PREEMPT_RT=y                                                                                                                                                           CONFIG_PREEMPT_COUNT=y                                                                                                                                                    CONFIG_PREEMPTION=y                                                                                                                                                           CONFIG_PREEMPT_RCU=y                                                                                                                                                          CONFIG_PREEMPT_NOTIFIERS=y

       

       Apalis iMX8QM 上的两个 A72  四个 A53 核心的时钟都设置到最高。

      root@apalis-imx8:~# echo performance >     /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor

      root@apalis-imx8:~# echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

      root@apalis-imx8:~# cpufreq-info |grep current

            current policy: frequency should be within 600 MHz and 1.20 GHz.

            current CPU frequency is 1.20 GHz (asserted by call to hardware).

            current policy: frequency should be within 600 MHz and 1.20 GHz.

            current CPU frequency is 1.20 GHz (asserted by call to hardware).

            current policy: frequency should be within 600 MHz and 1.20 GHz.

            current CPU frequency is 1.20 GHz (asserted by call to hardware).

        current     policy: frequency should be within 600 MHz and 1.20 GHz.

            current CPU frequency is 1.20 GHz (asserted by call to hardware).

            current policy: frequency should be within 600 MHz and 1.60 GHz.

            current CPU frequency is 1.60 GHz (asserted by call to hardware).

            current policy: frequency should be within 600 MHz and 1.60 GHz.

            current CPU frequency is 1.60 GHz (asserted by call to hardware).

       

      执行 cyclictest 工具查看内核实时性能。

      root@apalis-imx8:~# cyclictest -n m -S -p 99     --policy=fifo -i 431 -H 300

      # /dev/cpu_dma_latency set to 0us

      policy: fifo: loadavg: 0.42 0.31 0.13 2/399     834         

       

      T: 0 (      829) P:99 I:431 C:  59963     Min:      6 Act:    8 Avg:    9 Max:      24

      T: 1 (      830) P:99 I:431 C:  59962     Min:      5 Act:    5 Avg:    6 Max:      26

      T: 2 (      831) P:99 I:431 C:  59962     Min:      5 Act:    7 Avg:    6 Max:      20

      T: 3 (      832) P:99 I:431 C:  59962     Min:      5 Act:    6 Avg:    6 Max:      21

      T: 4 (      833) P:99 I:431 C:  59962     Min:      4 Act:    5 Avg:    6 Max:      20

      T: 3 (      832) P:99 I:431 C:  60517     Min:      5 Act:    7 Avg:    6 Max:      21

      T: 4 (      833) P:99 I:431 C:  60517     Min:      4 Act:    7 Avg:    6 Max:      17

      T: 5 (      834) P:99 I:431 C:  60517     Min:      3 Act:    5 Avg:    4 Max:      12

      下面链接是我们提供的包含实时内核的 BSP,可用于评估和测试。

      ftp://ftp.toradex.cn/Documents/ApplicationNote/resources/RT-Linux/Apalis-iMX8_Reference-Minimal-Image-rt-Tezi_5.0.0-devel-20201028085956+build.0.zip

       

       

      总结

      使用 Toradex Linux BSP 可以很方便集成 PREEMPT-RT 补丁,实现 real-time Linux。为了获得更好的实时性能,除了调整 Linux 内核配置,还需要关注文件系统,通常一个精简的文件系统,由于加载的应用软件或者驱动较少,可以避免占用 CPU 资源。在类似 Apalis iMX8 这种异构多核架构的处理器上会有额外的 Cortex-M4 核心,其可以运行 FreeRTOS提供硬实时能力。具体使用方法可以参考文末链接。

       

       

       

       

       

       

       

       

      参考:

      https://developer.toradex.cn/knowledge-base/real-time-linux

      https://blog.savoirfairelinux.com/en-ca/2020/linux-for-real-time-systems-evaluation-and-security-considerations/

      https://www.toradex.cn/blog/nxp-imx8-m4he-xinfreertos-rpmsg-ying-yong-shi-li

      审核编辑(王静)
      更多内容请访问 韬睿(上海)计算机科技有限公司(http://c.gongkong.com/?cid=16879)

      手机扫描二维码分享本页

      工控网APP下载安装

       

      我来评价

      评价:
      一般
      澳门新葡亰App