RK3399 DMA控制程序

RK3399是一款基于ARM架构的处理器，它提供了DMA控制器来优化数据传输速度。下面是一个简单的RK3399 DMA控制程序的示例代码：

#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>

#define DMA_TX_CHANNEL 0
#define DMA_RX_CHANNEL 1
#define BUFFER_SIZE 1024

// 定义DMA设备和通道
static struct dma_device *dma_dev;
static struct dma_chan *dma_tx_chan;
static struct dma_chan *dma_rx_chan;

// 定义DMA缓冲区
static dma_addr_t tx_dma_handle;
static dma_addr_t rx_dma_handle;
static char *tx_buffer;
static char *rx_buffer;

// 初始化DMA设备和通道
static int dma_init(void) {
    dma_dev = dmaengine_get_device("ffaa0000.dma");
    if (!dma_dev) {
        printk(KERN_ERR "Failed to get DMA device\n");
        return -ENODEV;
    }

    dma_tx_chan = dma_request_chan(dma_dev, "tx");
    if (!dma_tx_chan) {
        printk(KERN_ERR "Failed to get TX DMA channel\n");
        return -ENODEV;
    }

    dma_rx_chan = dma_request_chan(dma_dev, "rx");
    if (!dma_rx_chan) {
        printk(KERN_ERR "Failed to get RX DMA channel\n");
        return -ENODEV;
    }

    // 分配DMA缓冲区
    tx_buffer = dma_alloc_coherent(&dma_dev->dev, BUFFER_SIZE, &tx_dma_handle, GFP_KERNEL);
    if (!tx_buffer) {
        printk(KERN_ERR "Failed to allocate TX buffer\n");
        return -ENOMEM;
    }

    rx_buffer = dma_alloc_coherent(&dma_dev->dev, BUFFER_SIZE, &rx_dma_handle, GFP_KERNEL);
    if (!rx_buffer) {
        printk(KERN_ERR "Failed to allocate RX buffer\n");
        dma_free_coherent(&dma_dev->dev, BUFFER_SIZE, tx_buffer, tx_dma_handle);
        return -ENOMEM;
    }

    return 0;
}

// 发送数据
static int dma_send_data(char *data, size_t len) {
    struct dma_async_tx_descriptor *desc;
    struct dma_slave_config config = {
        .direction = DMA_MEM_TO_DEV,
        .src_addr = tx_dma_handle,
        .dst_addr = DMA_TX_CHANNEL,
        .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
        .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
        .src_maxburst = 1,
        .dst_maxburst = 1,
    };

    // 设置DMA配置
    dmaengine_slave_config(dma_tx_chan, &config);

    // 创建DMA事务
    desc = dmaengine_prep_slave_single(dma_tx_chan, data, len, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
    if (!desc) {
        printk(KERN_ERR "Failed to prepare TX DMA descriptor\n");
        return -EIO;
    }

    // 提交DMA事务
    dmaengine_submit(desc);
    dma_async_issue_pending(dma_tx_chan);

    return 0;
}

// 接收数据
static int dma_recv_data(char *data, size_t len) {
    struct dma_async_tx_descriptor *desc;
    struct dma_slave_config config = {
        .direction = DMA_DEV_TO_MEM,
        .src_addr = DMA_RX_CHANNEL,
        .dst_addr = rx_dma_handle,
        .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
        .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
        .src_maxburst = 1,
        .dst_maxburst = 1,
    };

    // 设置DMA配置
    dmaengine_slave_config(dma_rx_chan, &config);

    // 创建DMA事务
    desc = dmaengine_prep_slave_single(dma_rx_chan, data, len, DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT);
    if (!desc) {
        printk(KERN_ERR "Failed to prepare RX DMA descriptor\n");
        return -EIO;
    }

    // 提交DMA事务
    dmaengine_submit(desc);
    dma_async_issue_pending(dma_rx_chan);

    return 0;
}

// 释放DMA缓冲区和通道
static void dma_cleanup(void) {
    dmaengine_terminate_all(dma_tx_chan);
    dmaengine_terminate_all(dma_rx_chan);
    dma_release_channel(dma_tx_chan);
    dma_release_channel(dma_rx_chan);
    dma_free_coherent(&dma_dev->dev, BUFFER_SIZE, tx_buffer, tx_dma_handle);
    dma_free_coherent(&dma_dev->dev, BUFFER_SIZE, rx_buffer, rx_dma_handle);
}

// 模块加载函数
static int __init dma_test_init(void) {
    int ret;

    printk(KERN_INFO "RK3399 DMA test module loaded\n");

    // 初始化DMA设备和通道
    ret = dma_init();
    if (ret) {
        return ret;
    }

    // 发送和接收数据
    ret = dma_send_data("Hello, world!", 13);
    if (ret) {
        dma_cleanup();
        return ret;
    }

    ret = dma_recv_data(rx_buffer, BUFFER_SIZE);
    if (ret) {
        dma_cleanup();
        return ret;
    }

    printk(KERN_INFO "Received data: %s\n", rx_buffer);

    return 0;
}

// 模块卸载函数
static void __exit dma_test_exit(void) {
    printk(KERN_INFO "RK3399 DMA test module unloaded\n");

    // 释放DMA缓冲区和通道
    dma_cleanup();
}

module_init(dma_test_init);
module_exit(dma_test_exit);

MODULE_LICENSE("GPL");

这个程序使用了DMA发送和接收数据，通过DMA传输数据可以减少CPU的负担，提高系统性能。在程序中，我们首先通过`dmaengine_get_device`函数获取DMA设备，然后通过`dma_request_chan`函数获取DMA通道。接着，我们使用`dma_alloc_coherent`函数分配DMA缓冲区，这个函数会返回一个物理地址，我们需要将这个地址传给DMA控制器。在发送和接收数据时，我们需要设置DMA配置，并使用`dmaengine_prep_slave_single`函数创建DMA事务，最后通过`dmaengine_submit`和`dma_async_issue_pending`函数提交事务。在模块卸载时，我们需要使用`dma_release_channel`和`dma_free_coherent`函数释放DMA通道和缓冲区。