linux駆動のDMA駆動

DMAは、CPUの参加を必要とせずに、周辺機器とシステムメモリとの双方向データ伝送を可能にするハードウェア機構である.これにより、システムCPUを実際のI/Oデータ伝送から解放し、システムのスループットを大幅に向上させ、伝送中に他のタスクを同時に実行することもできる.

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
static int major = 0;
#define MEM_CPY_NO_DMA 0
#define MEM_CPY_DMA 1
#define BUF_SIZE (512*1024)
static char *src;
static u32 src_phys;
static char *dst;
static u32 dst_phys;
static struct class *cls;
#define DMA0_BASE_ADDR 0x4B000000
#define DMA0_BASE_ADDR 0x4B000000
#define DMA0_BASE_ADDR 0x4B000000
#define DMA0_BASE_ADDR 0x4B000000

struct ex4412_dma_regs{
    unsigned long disrc;
    unsigned long disrcc;
    unsigned long didst;
    unsigned long didstc;
    unsigned long dcon;
    unsigned long dstat;
    unsigned long dcsrc;
    unsigned long dcdst;
    unsigned long dmasktrig;
};
static struct ex4412_dma_regs *dma_regs;
static DECLARE_WAIT_QUEUE_HEAD(dma_waitq);
static volatile int ev_dma = 0;
#define BUF_SIZE (512*1024)
static long ex_dma_ioctl(struct file *file, unsigned int node, unsigned long temp)
{
    int i;
    memset(src, 0xAA,BUF_SIZE);
    memset(dst,0x55,BUF_SIZE);
    switch(cmd)
    {
        case MEM_CPY_NO_DMA:
        {
            for(i=0;iif(memcmp(src,dst,BUF_SIZE)==0)
            {
                printk("MEM_CPY_NO_DMA OK
");
            }
            else
            {
                printk("MEM_CPY_DMA_ERROR")
            }
                break;
        }
        case MEM_CPY_DMA:
        {

            /* ， ， DMA*/
            dma_regs->dcsrc=src_phys;// 
            dma_regs->disrcc=(0<<1)|(0<<0);// AHB ， 
            dma_regs->didst=dst_phys;// 
            dma_regs->didstc=(0<<2)|(0<<1)|(0<<0);// AHB
            dma_regs->dcon=(1<<29)|(0<<28)|(0<<23)|(0<<20)|(BUF_SIZE<<0);// ， 

            // DMA
            dma_regs->dmasktrig=(1<<1)|(1<<0);
            wait_event_interruptible(dma_waitq,ev_dma);
            if(memcmp(src,dst,BUF_SIZE)==0)
            {
                printk("MEM_CPY_NO_DMA OK
");
            }
            else
            {
                printk("MEM_CPY_DMA_ERROR")
            }
            break;
        }

    }

}

static struct file_operations dma_fops={
    .owner=THIS_MODULE,
    ..unlocked_ioctl =ex_dma_ioctl,

}
static irqreturn_t ex4412_dma_irq(int irq, void *devid)
{
    ev_dma=1;
    wake_up_interruptible(&dma_waitq);
    return IRQ_HANDLED;

}
static int ex4412_dma_init()
{

    if(request_irq(IRQ_DMA0,ex4412_dma_irq,0,"ex4412_dma",1))
    {
        printk("can't request_irq for dma
");
        return -EBUSY;
    }
    src = dma_alloc_writecombine(NULL,BUF_SIZE,&src_phys,GFP_KERNEL);
    if(NULL==src)
    {
        free_irq(IRQ_DMA3, 1);
        printk("can't alloc buffer for src
");
        return -ENOMEM;

    }
    dst = dma_alloc_writecombine(NULL,BUF_SIZE,&dst_phys,GFP_KERNEL);
    if(NULL==dst)
    {
        free_irq(IRQ_DMA3, 1);
        dma_free_writecombine(NULL,BUF_SIZE,src,&src_phys);
        printk("can't alloc buffer dst
");
        return -ENOMEM;
    }
    major = register_chrdev(0,"ex4412_dma",&dma_fops);
    cls = class_create(THIS_MODULE,"s3c_dma");
    device_create(cls,NULL,MKDEV(major,0),NULL,"dma");//dev/dma
    dma_regs=ioremap(DMA0_BASE_ADDR, sizeof(struct ex4412_dma_regs));
    return 0;

}
static void ex4412_dma_exit()
{
    iounmap(dma_regs);
    device_destroy(cls,MKDEV(major,0));
    class_destroy(cls);
    unregister_chrdev(major,"ex4412_dma");
    dma_free_writecombine(NULL,BUF_SIZE,src,&src_phys);
    dma_free_writecombine(NULL,BUF_SIZE,dst,&dst_phys);
    free_irq(IRQ_DMA3, 1);

}
module_init(ex4412_dma_init);
module_exit(ex4412_dma_exit);

アプリケーション:

/*./dma_test nodma 100
    ./dma_test dma 100
*/


#include
#include
#include
#include
#include
void print_usage(char *name)
{
    printf("usage:
");
    printf("%s
",name);

}
int main(int argc,char **argv)
{
    int fd;
    if(argc!=3)
    {
        print_usage(argv[0]);
        return -1;
    }
    fd=open("/dev/dma",O_RDWR);
    if(fd<0)
    {
        printf("can't open /dev/dma
");
    }
    if(strcmp(argv[1],"nodma")==0)
    {
        while(1)
        {
            ioctl(fd,MEM_CPY_NO_DMA)
        }

    }
    else if(strcmp(argv[1],dma)==0)
    {
        while(1)
        {
            ioctl(fd,MEM_CPY_DMA)；
        }
    }
    else
    {
        print_usage(argv[0]);
        return -1;
    }
    return 0;


}

それぞれ実行./dma_test nodma 100 ././dma_test dma 100は異なる効果を見る