本文将详细介绍如何通过使用 RPMSG ( Remote Processor Messaging ), 在 Linux 与 RT-Thread 操作系统之间进行多核异构核间通信。目的是帮助用户掌握 RPMSG 模块的使用流程。

RPMSG

RPMSG（ Remote Processor Messaging ）是一种基于共享内存的进程间通信（IPC） 机制，它允许在非对称多处理（ AMP ） 系统中的不同处理器核心之间进行通信。 这些核心通常运行着完全独立的操作系统（例如，一个核心运行 Linux，另一个运行实时操作系统如 RT-Thread 或裸机程序

硬件连接

AMP 下 rtt 终端串口为 uart9

核心示例代码

AMP 示例相关 API

• rt_device_open(rpmsg, RT_DEVICE_OFLAG_OPEN);：以可读可写的方式打开 rpmsg 设备；
• rt_device_control(rpmsg, RT_DEVICE_CTRL_CONFIG, &rpmsg_remote_echo)：设置 rpmsg 的源目的地址
• rt_thread_create("rpmsg_echo", rpmsg_echo_thread, RT_NULL, THREAD_STACK_SIZE, THREAD_PRIORITY, THREAD_TIMESLICE);：创建 rpmsg_echo 线程
• rt_thread_startup(thread)：启动 rpmsg_echo 线程

• 初始化和操作 rpmsg

applications/rpmsg_echo.c

int rpmsg_echo()
{
    uint32_t ret = RT_EOK;
    rpmsg = rt_device_find("rpmsg");
    if (rpmsg == RT_NULL)
    {
        rt_kprintf("Unable to find rpmsg device.\r\n");
        return RT_ERROR;
    }

    rt_device_open(rpmsg, RT_DEVICE_OFLAG_OPEN); // 打开 rpmsg 设备
    rt_device_control(rpmsg, RT_DEVICE_CTRL_CONFIG, &rpmsg_remote_echo); // 设置 rpmsg 源目的地址

    static rt_thread_t thread = RT_NULL;
    // 创建 rpmsg_echo 线程
    thread = rt_thread_create("rpmsg_echo",
                              rpmsg_echo_thread, RT_NULL,
                              THREAD_STACK_SIZE,
                              THREAD_PRIORITY, THREAD_TIMESLICE);

    if (thread != RT_NULL)
        rt_thread_startup(thread); // 启动 rpmsg_echo 线程

    if (ret != RT_EOK)
    {
        return RT_ERROR;
    }

    rt_kprintf("rpmsg echo init end.\r\n");
    return RT_EOK;
}

• 创建 rpmsg 线程

rpmsg_echo.c

struct rt_rpmsg_ep_addr rpmsg_remote_echo = {
    "rpmsg_chrdev", 0x3000U, 0x1000
};

static void rpmsg_echo_thread(void *parameter)
{
    rt_uint32_t len = 0;
    rt_uint8_t buff[BUF_SIZE];
    // 读取 linux 侧发来的 rpmsg 消息
    while ((len = rt_device_read(rpmsg, rpmsg_remote_echo.src, buff, BUF_SIZE - 1)) >= 0)
    {
        buff[len] = 0;
        rt_kprintf("message:%s len:%d\r\n", buff, len);
        // 给 rtt 侧发送相同的消息
        rt_device_write(rpmsg, rpmsg_remote_echo.dst, buff, len);
    }
}

运行示例

操作步骤

1. RT-Thread 和 Linux 建立 rpmsg 通道

   上电启动后，RT-Thread 和 Linux 建立 rpmsg 通道，才能做后续的发送消息，在 RT-Thread 侧串口的终端输入 rpmsg_echo 命令，然后能在 Linux 侧串口输入dmesg | grep rpmsg看到如下打印， 代表已经建立好 rpmsg 通道

   RT-Thread 串口终端

   msh />rpmsg_echo
   [D/drv.rpmsg] rpmsg_chrdev is OK! src is 0x3000 dst is 0x1000
   rpmsg echo init end.
   msh />

   Linux 串口终端

   dmesg | grep rpmsg
           rtt_reserved (0x0000000003f00000--0x000000000bf00000) overlaps with rpmsg@7a00000 (0x0000000007a00000--0x0000000007b00000)
           amp-shmem@7b00000 (0x0000000007b00000--0x0000000007c00000) overlaps with rpmsg-dma@7b00000 (0x0000000007b00000--0x0000000007c00000)
   [    2.256773] OF: reserved mem: initialized node rpmsg-dma@7b00000, compatible id shared-dma-pool
   [    4.316256] rockchip-rpmsg 7a00000.rpmsg: rockchip rpmsg platform probe.
   [    4.316333] rockchip-rpmsg 7a00000.rpmsg: assigned reserved memory node rpmsg-dma@7b00000
   [    4.316341] rockchip-rpmsg 7a00000.rpmsg: rpdev vdev0: vring0 0x7a00000, vring1 0x7a08000
   [    4.316942] virtio_rpmsg_bus virtio0: rpmsg host is online
   [   35.335601] virtio_rpmsg_bus virtio0: creating channel rpmsg_chrdev addr 0x3000

2. Linux 和 RT-Thread 之间互发消息

   在 Linux 侧串口的终端输入rpmsg_echo命令，RT-Thread 侧看到的发送和接收消息日志

   Linux 串口终端

   root@ido:~# rpmsg_echo
   Sending message #0: hello there 0!, len: 14
   Receiving message #0: hello there 0!, len: 14
   Sending message #1: hello there 1!, len: 14
   Receiving message #1: hello there 1!, len: 14
   Sending message #2: hello there 2!, len: 14
   Receiving message #2: hello there 2!, len: 14
   Sending message #3: hello there 3!, len: 14
   Receiving message #3: hello there 3!, len: 14
   Sending message #4: hello there 4!, len: 14
   Receiving message #4: hello there 4!, len: 14
   Sending message #5: hello there 5!, len: 14
   Receiving message #5: hello there 5!, len: 14
   Sending message #6: hello there 6!, len: 14
   Receiving message #6: hello there 6!, len: 14
   Sending message #7: hello there 7!, len: 14
   Receiving message #7: hello there 7!, len: 14
   Sending message #8: hello there 8!, len: 14
   Receiving message #8: hello there 8!, len: 14
   Sending message #9: hello there 9!, len: 14
   Receiving message #9: hello there 9!, len: 14

   RT-Thread 串口终端

   message:hello there 0! len:14
   message:hello there 1! len:14
   message:hello there 2! len:14
   message:hello there 3! len:14
   message:hello there 4! len:14
   message:hello there 5! len:14
   message:hello there 6! len:14
   message:hello there 7! len:14
   message:hello there 8! len:14
   message:hello there 9! len:14