By Toradex秦海
1). 简介
NXP iMX8是NXP去年底发布的基于Cortex-A72/A53和Coretex-M4异构多核架构的ARM处理器，作为NXP i.MX系列最新性能也最为强大的处理器，升级了从iMX6 SoloX开始到iMX7的异构双核架构（如下框图），使得不同架构核心的使用更加方便稳定，本文就演示iMX8 Cortex-A和Coretx-M核心之间通过Rpmsg来进行通讯的示例。
本文所演示的ARM平台来自于Toradex 基于NXP iMX8QM ARM处理器的Apalis iMX8QM ARM嵌入式平台。
2). 准备
a). Apalis iMX8QM ARM核心版配合Apalis Evaluation Board载板，连接调试串口UART1（载板X29）到开发主机方便调试。
b). Apalis iMX8 M40和M41分别使用独立的调试UART，在Apalis Evaluation Board进行跳线将M4对应的调试UART连接到开发主机的方式请参考这里。
c). Apalis iMX8 Cortex-A核心安装Toradex Ycoto Linux Console image V3.04版本，详细信息请参考这里。
d). 由于M4s调试UART所用到的管脚和Cortex-A核心Linux系统device tree中管脚配置有冲突，需要修改device tree并重新编译部署
./ device tree 修改patch文件请参考如下，下载Linux kernel源代码以及编译部署方法请参考这里。
https://github.com/simonqin09/Apalis_iMX8_M4_Rpmsg/blob/master/apalis_imx8_m4s_uart.patch
3). M4 FreeRTOS SDK部署
a). 根据这里的说明从NXP MCUXpresso网站下载对应iMX8QM的SDK，当前的最新版本为2.5.2。下载界面如下图所示，在这个页面同时也可以下载到关于SDK的一些说明文档。下载好的SDK文件为 ”SDK_2.5.2_MIMX8QM6xxxFF.tar.gz”
b). 下载Toolchain
./ 根据SDK文档建议使用 gcc-arm 7 2018q2版本，下载地址如下：
https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads/7-2018-q2-update
./ 解压下载好的Toolchain文件到
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# 解压
$ cd
$ tar xvf gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2
# 测试
$ gcc-arm-none-eabi-7-2018-q2-update/bin/arm-none-eabi-gcc --version
arm-none-eabi-gcc (GNU Tools for Arm Embedded Processors 7-2018-q2-update) 7.3.1 20180622 (release) [ARM/embedded-7-branch revision 261907]
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# 可能需要安装额外的工具供后续编译使用，以Ubuntu为例
$ sudo apt-get install make cmake
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c). 编译Helloworld测试应用
./ 解压步骤a下载的SDK文件到
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$ cd
$ tar xvf SDK_2.5.2_MIMX8QM6xxxFF.tar.gz
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./ 导出toolchain路径
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$ export ARMGCC_DIR=
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./ 编译M40 Helloworld应用
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# SDK中包含的示例代码均在 /boards/mekmimx8qm/ 目录
# M40 Helloworld demo 编译
$ cd
$ armgcc/build_all.sh
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./ 编译好的二进制文件位于 armgcc 目录下的 debug/release、ddr_debug/ddr_release、flash_debug/flash_release 目录。默认M4应用从TCM加载，ddr和flash分别对应ddr和flash加载模式，本文不做讨论。另外，Apalis iMX8的memory 区域分配请参考这里。
d). 部署测试M40 Helloworld示例应用
./ 由于目前Apalis iMX8 uboot版本（U-Boot 2018.03-toradex_imx_v2018.03_4.14.78_1.0.0_ga-bringup+g92d0497781）暂时还不支持ELF格式镜像，因此我们将生成的二进制文件m4_image.bin 复制到FAT32分区的SD卡根目录，然后将SD卡连接到Apalis Evaluation Board X19 4bit SD卡插槽
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# Apalis iMX8 上电开机，Cortex-A 核心调试串口UART1 串口终端按住空格键进入uboot
U-Boot 2018.03-toradex_imx_v2018.03_4.14.98_2.3.0_bringup+gd626574ba1 (Apr 17 2020 - 19:28:04 +0000)
CPU: Freescale i.MX8QM revB A53 at 1200 MHz at 25C
DRAM: 4 GiB
MMC: FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... OK
In: serial
Out: serial
Err: serial
Model: Toradex Apalis iMX8 QuadMax 4GB Wi-Fi / BT IT V1.0B, Serial# 06548514
BuildInfo:
- SCFW b929edfe, SECO-FW 27167ff2, IMX-MKIMAGE d7f9440d, ATF bb209a0
- U-Boot 2018.03-toradex_imx_v2018.03_4.14.98_2.3.0_bringup+gd626574ba1
switch to partitions #0, OK
mmc0(part 0) is current device
flash target is MMC:0
Net: eth0: ethernet@5b040000
Fastboot: Normal
Normal Boot
Hit any key to stop autoboot: 0
Apalis iMX8 #
# 查看SD卡image
Apalis iMX8 # ls mmc 2
…
# 加载Helloworld程序并运行
Apalis iMX8 # fatload mmc 2 ${loadaddr} m4_image.bin && dcache flush && bootaux ${loadaddr} 0
9032 bytes read in 20 ms (440.4 KiB/s)
## Starting auxiliary core at 0x80280000 ...
Power on M4 and MU
Copy M4 image from 0x80280000 to TCML 0x34fe0000
Start M4 0
bootaux complete
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./ 运行后，在M40 调试UART对应的串口终端可以看到 ”hello world” 打印输出，然后应用程序可以接收并打印键盘输入，比如这里输入了” this is input before linux boot up” 字符串。
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hello world.
this is input before linux boot up
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./ 此时切换到UART1 调试串口终端，执行下面命令继续启动Linux
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Apalis iMX8 # run bootcmd
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./ 再切换到M40调试串口终端，键盘输入测试
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hello world.
this is input before linux boot up this is input after linux boot up
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./ 对于M41，操作方式类似，只是加载的时候将将命令最后0替换为1
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Apalis iMX8 # fatload mmc 2 ${loadaddr} m4_1_image.bin && dcache flush && bootaux ${loadaddr} 1
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4). M4 FreeRTOS Rpmsg 示例程序测试
a). 根据章节三同样的方法编译 M40/M41 Rpmsg 示例程序，分为两个：
./ rpmsg_lite_str_echo_rtos
./ rpmsg_lite_pingpong_rtos
./ 相关demo的说明请参考对应项目下的readme.txt文件，因为M40和M41的测试结果都一致，本文下面就只用M40做演示示例
b). str_echo 示例程序测试
./ 使用章节3测试中同样方法从SD卡加载str_echo 示例程序 “m4_image.bin” 执行
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# UART1 调试串口终端
Apalis iMX8 # fatload mmc 2 ${loadaddr} m4_image.bin && dcache flush && bootaux ${loadaddr} 0
20112 bytes read in 21 ms (934.6 KiB/s)
## Starting auxiliary core at 0x80280000 ...
Power on M4 and MU
Copy M4 image from 0x80280000 to TCML 0x34fe0000
Start M4 0
bootaux complete
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./ M40 调试串口终端输出
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RPMSG String Echo FreeRTOS RTOS API Demo...
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./ 启动linux
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# UART1 调试串口终端
Apalis iMX8 # run bootcmd
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./ M40 调试串口终端输出
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
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./ 加载Linux下Rpmsg tty驱动建立rpmsg链接
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# UART1 调试串口终端
root@apalis-imx8:~# modprobe imx_rpmsg_tty
[ 539.316502] imx_rpmsg_tty virtio1.rpmsg-virtual-tty-channel.-1.30: new channel: 0x400 -> 0x1e!
[ 539.325355] Install rpmsg tty driver!
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./ M40 调试串口终端输出
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
Get Message From Master Side : "hello world!" [len : 12]
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./ 发送数据测试，如果是M41，则对应虚拟串口为 /dev/ttyRPMSG31
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root@apalis-imx8:~# echo "this is a test from toradex" > /dev/ttyRPMSG30
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./ M40 调试串口终端输出
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
Get Message From Master Side : "hello world!" [len : 12]
Get Message From Master Side : "this is a test from toradex" [len : 27]
Get New Line From Master Side
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c). pingpong 示例程序测试，测试流程和str_echo基本一致，这里简单罗列对应串口打印输出
./ UART1 调试串口终端
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# 在M41上运行Rpmsg pingpong 示例程序
Apalis iMX8 # fatload mmc 2 ${loadaddr} m4_image_pingpong.bin && dcache flush && bootaux ${loadaddr} 0
20696 bytes read in 21 ms (961.9 KiB/s)
## Starting auxiliary core at 0x80280000 ...
Power on M4 and MU
Copy M4 image from 0x80280000 to TCML 0x34fe0000
Start M4 0
bootaux complete
# 启动Linux
Apalis iMX8 # run bootcmd
# 加载Pinpong驱动
root@apalis-imx8:~# modprobe imx_rpmsg_pingpong
[ 34.508241] imx_rpmsg_pingpong virtio1.rpmsg-openamp-demo-channel.-1.30: new channel: 0x400 -> 0x1e!
root@apalis-imx8:~# [ 34.520657] get 1 (src: 0x1e)
[ 34.525069] get 3 (src: 0x1e)
[ 34.529515] get 5 (src: 0x1e)
……
[ 34.738211] get 99 (src: 0x1e)
[ 34.742665] get 101 (src: 0x1e)
[ 34.745865] imx_rpmsg_pingpong virtio1.rpmsg-openamp-demo-channel.-1.30: goodbye!
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./ M40 调试串口终端输出
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# pingpong 程序启动后输出
RPMSG Ping-Pong FreeRTOS RTOS API Demo...
RPMSG Share Base Addr is 0x90010000
# Linux启动后输出
Link is up!
Nameservice announce sent.
# Pingpong 驱动加载后输出
Waiting for ping...
Sending pong...
……
Waiting for ping...
Sending pong...
Ping pong done, deinitializing...
Looping forever...
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5). M4s Firmware配置开机自动加载执行测试
a). 上面的测试都是通过Uboot命令从SD卡加载M4 Firmware进行加载运行，下面我们通过str_echo示例程序演示将M40和M41的固件存放在Apalis iMX8 eMMC Flash空间内，并开机自动加载运行
b). 首先进入Linux系统，分别将之前编译好的存放在SD卡上面的M40和M41的 str_echo程序Firmware复制到Flash vfat分区，也就是存放Linux kernel和device tree等文件的分区
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# UART1 调试串口终端
root@apalis-imx8:~# cd /media/mmcblk0p1/
root@apalis-imx8:/media/mmcblk0p1# ls
Image dpfw.bin fsl-imx8qm-apalis-eval.dtb.bak fsl-imx8qm-apalis-v1.1-eval.dtb
boot.scr fsl-imx8qm-apalis-eval.dtb fsl-imx8qm-apalis-ixora-v1.1.dtb hdmitxfw.bin
# 从SD卡挂载路径复制M4s Str_echo 示例程序固件
root@apalis-imx8:/media/mmcblk0p1# cp /media/mmcblk2p1/m4_image.bin .
root@apalis-imx8:/media/mmcblk0p1# cp /media/mmcblk2p1/m4_1_image.bin .
root@apalis-imx8:/media/mmcblk0p1# ls
Image fsl-imx8qm-apalis-eval.dtb fsl-imx8qm-apalis-v1.1-eval.dtb m4_image.bin boot.scr fsl-imx8qm-apalis-eval.dtb.bak hdmitxfw.bin dpfw.bin fsl-imx8qm-apalis-ixora-v1.1.dtb m4_1_image.bin
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c). 重启进入uboot，配置环境变量
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# UART1 调试串口终端
# 分别指定M4s固件名称
Apalis iMX8 # setenv m4_0_image 'm4_image.bin'
Apalis iMX8 # setenv m4_1_image 'm4_1_image.bin'
# 设置启动顺序，分别启动M40，M41以及Linux
Apalis iMX8 # setenv bootcmd 'run m4boot_0 && run m4boot_1 && run distro_bootcmd'
Apalis iMX8 # saveenv && reset
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d). 配置好重启后可以看到在Linux启动过程中 M40和M41的调试串口都分别打印了相关程序输出
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# UART1 调试串口终端
U-Boot 2018.03-toradex_imx_v2018.03_4.14.98_2.3.0_bringup+gd626574ba1 (Apr 17 2020 - 19:28:04 +0000)
……
Normal Boot
Hit any key to stop autoboot: 0
20112 bytes read in 13 ms (1.5 MiB/s)
## Starting auxiliary core at 0x80280000 ...
Power on M4 and MU
Copy M4 image from 0x80280000 to TCML 0x34fe0000
Start M4 0
bootaux complete
61488 bytes read in 13 ms (4.5 MiB/s)
## Starting auxiliary core at 0x80280000 ...
Power on M4 and MU
Copy M4 image from 0x80280000 to TCML 0x38fe0000
Start M4 1
bootaux complete
……
Scanning mmc 0:1...
Found U-Boot script /boot.scr
……
Starting kernel ...
……
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./ M40 调试串口终端
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
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./ M41 调试串口终端
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
app_srtm: AUTO and I2C service registered
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e). Linux端加载Rpmsg tty驱动并进行发送测试
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# UART1 调试串口终端
# 加载驱动
root@apalis-imx8:~# modprobe imx_rpmsg_tty
[ 34.795096] imx_rpmsg_tty virtio1.rpmsg-virtual-tty-channel.-1.30: new channel: 0x400 -> 0x1e!
[ 34.803985] Install rpmsg tty driver!
[ 34.807934] imx_rpmsg_tty virtio3.rpmsg-virtual-tty-channel-1.-1.31: new channel: 0x400 -> 0x1f!
[ 34.817031] Install rpmsg tty driver!
# 发送信息
root@apalis-imx8:~# echo "this is a message from apalis imx8 linux to m4 0" > /dev/ttyRPMSG30
root@apalis-imx8:~# echo "this is a message from apalis imx8 linux to m4 1" > /dev/ttyRPMSG31
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./ M40 调试串口终端
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RPMSG String Echo FreeRTOS RTOS API Demo...
Nameservice sent, ready for incoming messages...
Get Message From Master Side : "hello world!" [len : 12]
Get Message From Master Side : "this is a message from apalis imx8 linux to m4 0" [len : 48]
Get New Line From Master Side
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./ M41 调试串口终端
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RPMSG String Echo FreeRTOS RTOS API Demo...
Namapp_srtm: AUTO and I2C service registered
eservice sent, ready for incoming messages...
Get Message From Master Side : "hello world!" [len : 12]
Get Message From Master Side : "this is a message from apalis imx8 linux to m4 1" [len : 48]
Get New Line From Master Side
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6). 总结
本文基于NXP iMX8示例了其多核异构架构下Cortex-A核心Linux通过Rpmsg驱动和Cortex-M4核心通讯的示例