pci_alloc_consistent 配合mmap

110730阅读　0评论2019-03-24　lelv123
分类：嵌入式

有这种需求的同行自然明白这2个为什么需要配合起来用。简单说说，我的需求是dma位于pci设备侧，pci主的cpu上应用程序直接mmap获取dma发来的数据。
猜测显卡的dma一般位于pci主，所以我在内核里没有找到pci_alloc_consistent 配合mmap的例子。
这个代码在loongson 3A这个极品芯片上都能通过，相信其他平台毫无障碍。
pci_alloc_consistent得到的是申请到的dma一致性缓冲区的内核态虚拟地址以及pci总线地址。
内核态虚拟地址转成物理地址后需要传递给应用做mmap的最后一个参数。

以下是简单驱动代码：

  1. #include <linux/module.h>
  2. #include <linux/kernel.h>
  3. #include <linux/pci.h>
  4. #include <linux/init.h>
  5. #include <linux/ioport.h>
  6. #include <linux/netdevice.h>
  7. #include <linux/etherdevice.h>
  8. #include <linux/delay.h>
  9. #include <linux/ethtool.h>
  10. #include <linux/mii.h>
  11. #include <linux/crc32.h>
  12. #include <linux/io.h>
  13. #include <linux/interrupt.h>
  14. #include <linux/module.h>
  15. #include <linux/kernel.h>
  16. #include <linux/types.h>
  17. #include <linux/miscdevice.h>
  18. #include <linux/ioport.h>
  19. #include <linux/fcntl.h>
  20. #include <linux/init.h>
  21. #include <linux/poll.h>
  22. #include <linux/proc_fs.h>
  23. #include <linux/seq_file.h>
  24. #include <linux/spinlock.h>
  25. #include <linux/sched.h>
  26. #include <linux/sysctl.h>
  27. #include <linux/wait.h>
  28. #include <linux/cdev.h>
  29. #include <linux/fs.h>
  30. #include <linux/delay.h>
  31. #include <linux/uaccess.h>
  32. #include <linux/device.h>
  33. #include <linux/err.h>
  34. #include <linux/fs.h>
  35. #include <asm/io.h>
  36. #include <asm/current.h>
  37. #include <asm/system.h>
  38. #include <linux/mm.h>
  39. #include <linux/mman.h>
  40. #include <linux/miscdevice.h>
  41. #include <linux/proc_fs.h>
  42. #include <linux/device.h>
  43. #include <linux/fs.h>
  44. #include <linux/slab.h>
  45. #include <linux/mm.h>
  46. #include <linux/slab.h>

  48. #define DEVICE_NAME "testc"
  49. #define MODNAME "pmc-test"
  50. #define MMAPBUF_LEN (16*1024*1024)

  52. struct my_testdev{
  53.     dev_t testc_dev_num;
  54.     struct class * testc_class;
  55.     unsigned long testc_kernel_virt_addr;

  57.     struct cdev test_cdev;
  58.     unsigned int current_pointer; /*char device offset ,目前同时只能一个程序读取 */
  59.     unsigned long mmap_phyaddr;
  60.     dma_addr_t mmap_pcibus_addr;
  61.     unsigned long mmap_kvirt_addr;
  62. };

  64. //不得已的一个全局变量
  65. struct my_testdev *priv;

  67. //仅仅是为了测试程序 手头只有这个卡
  68. static DEFINE_PCI_DEVICE_TABLE(netdrv_pci_tbl) = {
  69.     {0x8086, 0x10b9, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
  70.     {0,}
  71. };
  72. MODULE_DEVICE_TABLE(pci, netdrv_pci_tbl);


  75. static int testc_open(struct inode *inode, struct file *file)
  76. {
  77.     return 0;
  78. }

  80. static int testc_release(struct inode *inode, struct file *file)
  81. {

  83.     return 0;
  84. }


  87. static ssize_t testc_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  88. {

  90.     
  91.     return 0;
  92. }    

  94. static ssize_t testc_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  95. {

  97.     return 0;
  98. }

  100. static loff_t testc_llseek(struct file * file,loff_t offset,int orig)
  101. {
  102.     return 0;
  103. }


  106. static int testc_mmap(struct file *file, struct vm_area_struct *vma)
  107. {
  108.     
  109.     unsigned long size = vma->vm_end - vma->vm_start;
  110.     struct my_testdev *pri=priv;
  111.     printk("inmmap ,mmap_phyaddr %lx , mmap_kvirt_addr %lx \n",pri->mmap_phyaddr,pri->mmap_kvirt_addr);
  112.     printk("start %lx end %lx off %lx \n",vma->vm_start,vma->vm_end,vma->vm_pgoff);
  113. //pci_alloc_consistent申请到的内存已经是物理地址连续的 ，只要一个remap_pfn_range
  114.     remap_pfn_range(vma,vma->vm_start,(pri->mmap_phyaddr)>> PAGE_SHIFT,size,vma->vm_page_prot);

  116.     vma->vm_flags |= VM_RESERVED;    /* avoid to swap out this VMA */
  117.     return 0;

  119. }

  121. static const struct file_operations testc_fops = {
  122.     .read        = testc_read,
  123.     //.aio_read    = generic_file_aio_read,
  124.     .write        = testc_write,
  125.     //.aio_write    = blkdev_aio_write,
  126.     //.fsync        = blkdev_fsync,
  127.     .mmap        = testc_mmap,
  128.     .open        = testc_open,
  129.     .release    = testc_release,
  130.     //.unlocked_ioctl = raw_ioctl,
  131.     .llseek        = testc_llseek,
  132.     .owner        = THIS_MODULE,
  133. };


  136. static int __devinit pmc_probe(struct pci_dev *pdev,const struct pci_device_id *ent)
  137. {    
  138.     int ret;
  139.     int i;
  140.     struct device *x;
  141.     struct my_testdev *pri;
  142.     printk("--------%s %d\n",__FUNCTION__,__LINE__);
  143.     pri=kmalloc(sizeof(struct my_testdev),GFP_KERNEL);
  144.     memset(pri,0,sizeof(struct my_testdev));
  145.     priv=pri;
  146.     pci_set_drvdata(pdev, pri);
  147.     
  148.     

  150.     //char device
  151.     if(alloc_chrdev_region(&(pri->testc_dev_num), 0, 1,DEVICE_NAME))
  152.         {
  153.             printk("err----%s %d \n",__FILE__,__LINE__);
  154.             return -1;
  155.         }
  156.     pri->testc_class=class_create(THIS_MODULE,DEVICE_NAME);
  157.     cdev_init(&(pri->test_cdev),&testc_fops);
  158.     pri->test_cdev.owner=THIS_MODULE;

  160.     ret=cdev_add(&(pri->test_cdev),pri->testc_dev_num,1);
  161.     if(ret)
  162.         {
  163.             printk("err----%s %d \n",__FILE__,__LINE__);
  164.             return -1;
  165.         }
  166.     //设备节点自动生成
  167.     x=device_create(pri->testc_class,NULL,MKDEV(MAJOR(pri->testc_dev_num),0),pri,DEVICE_NAME);
  168.     if(x==NULL)
  169.         {
  170.             printk("err----%s %d \n",__FILE__,__LINE__);
  171.             return -1;
  172.         }
  173.     priv=pri;
  174.     priv->current_pointer=0;


  177. //mmap
  178.     pri->mmap_kvirt_addr=(unsigned long )pci_alloc_consistent(pdev,MMAPBUF_LEN,&(pri->mmap_pcibus_addr));
  179.     if((void *)pri->mmap_kvirt_addr==NULL)
  180.         {
  181.             return -1;
  182.         }
  183.     memset((void *)pri->mmap_kvirt_addr,0x0,MMAPBUF_LEN);
  184. //写入有意义的数据，方便在应用里验证确实映射了16MB
  185.     for(i=0;i<MMAPBUF_LEN/4;i++)
  186.         {
  187.             *(((u32 *)pri->mmap_kvirt_addr)+i)=i;
  188.         }

  190.     pri->mmap_phyaddr=virt_to_phys((void *)pri->mmap_kvirt_addr);
  191.     printk("mmap_phyaddr %lx , mmap_kvirt_addr %lx \n",pri->mmap_phyaddr,pri->mmap_kvirt_addr);
  192.     
  193.     return 0;
  194. }
  195. static void __devexit pmc_remove(struct pci_dev *pdev)
  196. {
  197.     struct my_testdev *pri = pci_get_drvdata(pdev);
  198.     pci_free_consistent(pdev, MMAPBUF_LEN,(void *)pri->mmap_kvirt_addr, pri->mmap_pcibus_addr);
  199.     
  200. }


  203. static struct pci_driver netdrv_pci_driver = {
  204.     .name        = MODNAME,
  205.     .id_table    = netdrv_pci_tbl,
  206.     .probe        = pmc_probe,
  207.     .remove        = __devexit_p(pmc_remove),

  209. };

  211. static int __init pmc_init_module(void)
  212. {
  213.     return pci_register_driver(&netdrv_pci_driver);
  214. }


  217. static void __exit pmc_cleanup_module(void)
  218. {
  219.     pci_unregister_driver(&netdrv_pci_driver);
  220. }

  222. module_init(pmc_init_module);
  223. module_exit(pmc_cleanup_module);


  226. MODULE_AUTHOR("deep_pro");
  227. MODULE_LICENSE("GPL");

简单的应用程序，注意mmap的最后一个参数是dma缓冲区的物理地址，演示程序里根据驱动的打印写的硬编码，最终还是要靠ioctl等机制实现自动从驱动取得。

点击(此处)折叠或打开

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <unistd.h>
  5. #include <errno.h>
  6. #include <limits.h>
  7. #include <linux/kernel.h>

  9. #include <byteswap.h>
  10. #include <unistd.h>
  11. #include <sys/types.h>
  12. #include <sys/mman.h>
  13. #include <sys/types.h>
  14. #include <sys/stat.h>
  15. #include <fcntl.h>

  17. #include <sys/ioctl.h>
  18. #define MMAP_LEN 16*1024*1024

  20. int main()
  21. {
  22.         int fd,i,ret;

  24.         char buf[0x20]={0};
  25.         unsigned int *mmap_data;

  27.         fd=open("/dev/testc",O_RDWR);
  28.         if(fd<0)
  29.         {
  30.                 perror("open:");
  31.                 return -1;
  32.         }
  33. //0xf7000000 这个是缓冲区的物理地址，要从驱动里得到
  34.         mmap_data=(unsigned int *)mmap(NULL,MMAP_LEN,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0xf7000000);
  35.         if(mmap_data==MAP_FAILED)
  36.         {
  37.                 perror("mmap");
  38.                 return -1;
  39.         }
  40. //测试mmap后的缓冲区读写 ，先写再读,这样执行第二遍应用就能验证写入成功
  41. for(i=14*1024*1024/4;i<(14*1024*1024+0x120)/4;i++)
  42.         {
  43.                 //mmap_buf[i]=0;
  44.                 printf("mmap_buf %02x :%x \n",i,*(mmap_data+i));
  45.                    *(mmap_data+i)+=1;
  46.         }

  48.         munmap(mmap_data,MMAP_LEN);

  50.         close(fd);
  51. }
执行2遍应用即能验证读写和确实映射了16MB




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