DMA330 内存到内存搬运代码

下面是一个简单的DMA330内存到内存搬运代码示例，假设源地址为src_addr，目标地址为dst_addr，搬运大小为size：

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

#define DMA_BUF_SIZE 4096

void dma_memcpy(void *dst_addr, void *src_addr, size_t size)
{
    struct dma_chan *chan;
    struct scatterlist sg_src, sg_dst;
    dma_addr_t src_dma_addr, dst_dma_addr;
    void *dma_buf;
    int ret;

    dma_buf = dma_alloc_coherent(NULL, DMA_BUF_SIZE, &src_dma_addr, GFP_KERNEL);
    if (!dma_buf) {
        pr_err("Failed to allocate DMA buffer\n");
        return;
    }

    chan = dma_request_chan(NULL, "dma0");
    if (IS_ERR(chan)) {
        pr_err("Failed to request DMA channel\n");
        dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
        return;
    }

    sg_init_table(&sg_src, 1);
    sg_set_buf(&sg_src, src_addr, size);
    sg_init_table(&sg_dst, 1);
    sg_set_buf(&sg_dst, dma_buf, size);

    ret = dma_map_sg(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
    if (ret != 1) {
        pr_err("Failed to map SG list for source\n");
        dma_release_channel(chan);
        dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
        return;
    }

    ret = dma_map_sg(chan->device->dev, &sg_dst, 1, DMA_FROM_DEVICE);
    if (ret != 1) {
        pr_err("Failed to map SG list for destination\n");
        dma_unmap_sg(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
        dma_release_channel(chan);
        dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
        return;
    }

    ret = dmaengine_prep_dma_memcpy(chan, dst_dma_addr, src_dma_addr, size, DMA_PREP_INTERRUPT);
    if (ret) {
        pr_err("Failed to prepare DMA transfer\n");
        dma_unmap_sg(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
        dma_unmap_sg(chan->device->dev, &sg_dst, 1, DMA_FROM_DEVICE);
        dma_release_channel(chan);
        dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
        return;
    }

    ret = dmaengine_submit(chan);
    if (ret) {
        pr_err("Failed to submit DMA transfer\n");
        dma_unmap_sg(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
        dma_unmap_sg(chan->device->dev, &sg_dst, 1, DMA_FROM_DEVICE);
        dma_release_channel(chan);
        dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
        return;
    }

    dma_async_issue_pending(chan);
    ret = dma_sync_sg_for_device(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
    if (ret != 1) {
        pr_err("Failed to sync SG list for source\n");
    }

    ret = dma_sync_sg_for_cpu(chan->device->dev, &sg_dst, 1, DMA_FROM_DEVICE);
    if (ret != 1) {
        pr_err("Failed to sync SG list for destination\n");
    }

    memcpy(dst_addr, dma_buf, size);

    dma_unmap_sg(chan->device->dev, &sg_src, 1, DMA_TO_DEVICE);
    dma_unmap_sg(chan->device->dev, &sg_dst, 1, DMA_FROM_DEVICE);
    dma_release_channel(chan);
    dma_free_coherent(NULL, DMA_BUF_SIZE, dma_buf, src_dma_addr);
}

该示例中，首先通过dma_alloc_coherent()函数分配DMA缓冲区，然后通过dma_request_chan()函数请求DMA通道，接着通过sg_init_table()和sg_set_buf()函数初始化源和目标scatterlist。然后通过dma_map_sg()函数将scatterlist映射到DMA地址空间中。接下来，通过dmaengine_prep_dma_memcpy()函数准备DMA传输，并通过dmaengine_submit()函数提交传输。最后，通过dma_async_issue_pending()函数发出异步传输请求，并通过dma_sync_sg_for_device()和dma_sync_sg_for_cpu()函数同步scatterlist。最终，通过memcpy()函数将DMA缓冲区中的数据复制到目标地址中，最后释放DMA资源。