Linux设备驱动程序允许FPGA直接DMA到CPU RAM

我正在编写一个 Linux设备驱动程序,允许FPGA(目前通过PCI Express连接到PC)将DMA数据直接写入CPU RAM.这需要在没有任何交互的情况下发生,并且用户空间需要访问数据.一些细节：
– 运行64位Fedora 14
– 系统有8GB的RAM
– FPGA(Cyclone IV)位于PCIe卡上

为了实现这一目标,我执行了以下操作：
– 使用memmap 6GB $2GB保留grub中的2GB内存(不启动是我添加内存= 2GB).我可以看到,在/ proc / meminfo中保留了2GB的RAM
– 映射BAR0以允许读取和写入FPGA寄存器(这非常有效)
– 在我的驱动程序中使用remap_pfn_range()实现了一个mmap函数
– 使用ioremap获取缓冲区的虚拟地址
– 添加了ioctl调用(用于测试)以将数据写入缓冲区
– 通过进行ioctl调用将数据写入缓冲区并验证数据是否来自用户空间的缓冲区来测试mmap

我面临的问题是当FPGA开始将DMA数据发送到我提供的缓冲区地址时.我不断得到PTE错误(来自DMAR :)或使用下面的代码我得到以下错误：
DMAR：[DMA写入]请求设备[01：00.0]故障添加器186dc5000
DMAR：[错误原因01]根条目中的当前位清除
DRHD：处理故障状态reg 3

第一行中的地址每次基于来自FPGA的DMA递增0x1000

这是我的init()代码：

#define IMG_BUF_OFFSET     0x180000000UL // Location in RAM (6GB)
#define IMG_BUF_SIZE       0x80000000UL  // Size of the Buffer (2GB)

#define pci_dma_h(addr) ((addr >> 16) >> 16)
#define pci_dma_l(addr) (addr & 0xffffffffUL)

if((pdev = pci_get_device(FPGA_VEN_ID,FPGA_DEV_ID,NULL)))
{
    printk("FPGA Found on the PCIe Busn");

    //  Enable the device 
    if(pci_enable_device(pdev))
    {
        printk("Failed to enable PCI devicen");
        return(-1);
    }
    //  Enable bus master
    pci_set_master(pdev);

    pci_read_config_word(pdev,PCI_VENDOR_ID,&id);
    printk("Vendor id: %xn",id);
    pci_read_config_word(pdev,PCI_DEVICE_ID,&id);
    printk("Device id: %xn",PCI_STATUS,&id);
    printk("Device Status: %xn",id);
    pci_read_config_dword(pdev,PCI_COMMAND,&temp);
    printk("Command Register : : %xn",temp);
    printk("Resources Allocated :n");
    pci_read_config_dword(pdev,PCI_BASE_ADDRESS_0,&temp);
    printk("BAR0 : %xn",temp);

  // Get the starting address of BAR0
  bar0_ptr = (unsigned int*)pcim_iomap(pdev,FPGA_CONFIG_SIZE);
  if(!bar0_ptr)
  {
     printk("Error mapping Bar0n");
     return -1;
  }
  printk("Remapped BAR0n");

  // Set DMA Masking
  if(!pci_set_dma_mask(pdev,DMA_BIT_MASK(64))) 
  {
     pci_set_consistent_dma_mask(pdev,DMA_BIT_MASK(64));
     printk("Device setup for 64bit DMAn");
  }
  else if(!pci_set_dma_mask(pdev,DMA_BIT_MASK(32)))
  {
     pci_set_consistent_dma_mask(pdev,DMA_BIT_MASK(32));
     printk("Device setup for 32bit DMAn");
  }
  else
  {
     printk(KERN_WARNING"No suitable DMA available.n");
     return -1;
  }

  // Get a pointer to reserved lower RAM in kernel address space (virtual address)
  virt_addr = ioremap(IMG_BUF_OFFSET,IMG_BUF_SIZE);
  kernel_image_buffer_ptr = (unsigned char*)virt_addr;
  memset(kernel_image_buffer_ptr,IMG_BUF_SIZE);
  printk("Remapped image buffer: 0x%pn",(void*)virt_addr);

}

这是我的mmap代码：

unsigned long image_buffer;
unsigned int  low;
unsigned int  high;

if(remap_pfn_range(vma,vma->vm_start,vma->vm_pgoff,vma->vm_end - vma->vm_start,vma->vm_page_prot))
{
   return(-EAGAIN);
}

image_buffer = (vma->vm_pgoff << PAGE_SHIFT);

if(0 > check_mem_region(IMG_BUF_OFFSET,IMG_BUF_SIZE))
{
   printk("Failed to check region...memory in usen");
   return -1;
}

request_mem_region(IMG_BUF_OFFSET,IMG_BUF_SIZE,DRV_NAME);

// Get the bus address from the virtual address above
//dma_page   = virt_to_page(addr);
//dma_offset = ((unsigned long)addr & ~PAGE_MASK);
//dma_addr   = pci_map_page(pdev,dma_page,dma_offset,PCI_DMA_FROMDEVICE);    
//dma_addr = pci_map_single(pdev,image_buffer,PCI_DMA_FROMDEVICE);   
//dma_addr = IMG_BUF_OFFSET;
//printk("DMA Address: 0x%pn",(void*)dma_addr);

// Write start or image buffer address to the FPGA
low  = pci_dma_l(image_buffer);
low &= 0xfffffffc;
high = pci_dma_h(image_buffer);
if(high != 0)
   low |= 0x00000001;

*(bar0_ptr + (17024/4)) = 0;

//printk("DMA Address LOW : 0x%xn",cpu_to_le32(low));
//printk("DMA Address HIGH: 0x%xn",cpu_to_le32(high));
*(bar0_ptr + (4096/4))  = cpu_to_le32(low); //2147483649; 
*(bar0_ptr + (4100/4))  = cpu_to_le32(high); 
*(bar0_ptr + (17052/4)) = cpu_to_le32(low & 0xfffffffe);//2147483648;

printk("Process Read Command: Addr:0x%x Ret:0x%xn",4096,*(bar0_ptr + (4096/4)));
printk("Process Read Command: Addr:0x%x Ret:0x%xn",4100,*(bar0_ptr + (4100/4)));
printk("Process Read Command: Addr:0x%x Ret:0x%xn",17052,*(bar0_ptr + (17052/4)));
return(0);

感谢您提供任何帮助.