pci_alloc_consistent 配合mmap

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。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define DEVICE_NAME "testc"
#define MODNAME "pmc-test"
#define MMAPBUF_LEN (16*1024*1024)

struct my_testdev{
    dev_t testc_dev_num;
    struct class * testc_class;
    unsigned long testc_kernel_virt_addr;

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

//不得已的一个全局变量
struct my_testdev *priv;

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


static int testc_open(struct inode *inode, struct file *file)
{
    return 0;
}

static int testc_release(struct inode *inode, struct file *file)
{

    return 0;
}


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

    
    return 0;
}    

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

    return 0;
}

static loff_t testc_llseek(struct file * file,loff_t offset,int orig)
{
    return 0;
}


static int testc_mmap(struct file *file, struct vm_area_struct *vma)
{
    
    unsigned long size = vma->vm_end - vma->vm_start;
    struct my_testdev *pri=priv;
    printk("inmmap ,mmap_phyaddr %lx , mmap_kvirt_addr %lx \n",pri->mmap_phyaddr,pri->mmap_kvirt_addr);
    printk("start %lx end %lx off %lx \n",vma->vm_start,vma->vm_end,vma->vm_pgoff);
//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
    remap_pfn_range(vma,vma->vm_start,(pri->mmap_phyaddr)>> PAGE_SHIFT,size,vma->vm_page_prot);

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

}

static const struct file_operations testc_fops = {
    .read        = testc_read,
    //.aio_read    = generic_file_aio_read,
    .write        = testc_write,
    //.aio_write    = blkdev_aio_write,
    //.fsync        = blkdev_fsync,
    .mmap        = testc_mmap,
    .open        = testc_open,
    .release    = testc_release,
    //.unlocked_ioctl = raw_ioctl,
    .llseek        = testc_llseek,
    .owner        = THIS_MODULE,
};


static int __devinit pmc_probe(struct pci_dev *pdev,const struct pci_device_id *ent)
{    
    int ret;
    int i;
    struct device *x;
    struct my_testdev *pri;
    printk("--------%s %d\n",__FUNCTION__,__LINE__);
    pri=kmalloc(sizeof(struct my_testdev),GFP_KERNEL);
    memset(pri,0,sizeof(struct my_testdev));
    priv=pri;
    pci_set_drvdata(pdev, pri);
    
    

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

    ret=cdev_add(&(pri->test_cdev),pri->testc_dev_num,1);
    if(ret)
        {
            printk("err----%s %d \n",__FILE__,__LINE__);
            return -1;
        }
    //设备节点自动生成
    x=device_create(pri->testc_class,NULL,MKDEV(MAJOR(pri->testc_dev_num),0),pri,DEVICE_NAME);
    if(x==NULL)
        {
            printk("err----%s %d \n",__FILE__,__LINE__);
            return -1;
        }
    priv=pri;
    priv->current_pointer=0;


//mmap 
    pri->mmap_kvirt_addr=(unsigned long )pci_alloc_consistent(pdev,MMAPBUF_LEN,&(pri->mmap_pcibus_addr));
    if((void *)pri->mmap_kvirt_addr==NULL)
        {
            return -1;
        }
    memset((void *)pri->mmap_kvirt_addr,0x0,MMAPBUF_LEN);
//写入有意义的数据,方便在应用里验证确实映射了16MB
    for(i=0;immap_kvirt_addr)+i)=i;
        }

    pri->mmap_phyaddr=virt_to_phys((void *)pri->mmap_kvirt_addr);
    printk("mmap_phyaddr %lx , mmap_kvirt_addr %lx \n",pri->mmap_phyaddr,pri->mmap_kvirt_addr);
    
    return 0;
}
static void __devexit pmc_remove(struct pci_dev *pdev)
{
    struct my_testdev *pri = pci_get_drvdata(pdev);
    pci_free_consistent(pdev, MMAPBUF_LEN,(void *)pri->mmap_kvirt_addr, pri->mmap_pcibus_addr);
    
}


static struct pci_driver netdrv_pci_driver = {
    .name        = MODNAME,
    .id_table    = netdrv_pci_tbl,
    .probe        = pmc_probe,
    .remove        = __devexit_p(pmc_remove),

};

static int __init pmc_init_module(void)
{
    return pci_register_driver(&netdrv_pci_driver);
}


static void __exit pmc_cleanup_module(void)
{
    pci_unregister_driver(&netdrv_pci_driver);
}

module_init(pmc_init_module);
module_exit(pmc_cleanup_module);


MODULE_AUTHOR("deep_pro");
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。

#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#define MMAP_LEN 16*1024*1024

int main()
{
        int fd,i,ret;

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

        fd=open("/dev/testc",O_RDWR);
        if(fd<0)
        {
                perror("open:");
                return -1;
        }
//0xf7000000 这个是缓冲区的物理地址,要从驱动里得到
        mmap_data=(unsigned int *)mmap(NULL,MMAP_LEN,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0xf7000000);
        if(mmap_data==MAP_FAILED)
        {
                perror("mmap");
                return -1;
        }
//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
for(i=14*1024*1024/4;i<(14*1024*1024+0x120)/4;i++)
        {
                //mmap_buf[i]=0;
                printf("mmap_buf %02x :%x \n",i,*(mmap_data+i));
                   *(mmap_data+i)+=1;
        }

        munmap(mmap_data,MMAP_LEN);

        close(fd);
}


你可能感兴趣的:(linux)