DMA操作驱动

#include "linux/module.h"

#include "linux/kernel.h"

#include "linux/fs.h"

#include "linux/init.h"

#include "linux/delay.h"

#include "linux/irq.h"

#include "asm/uaccess.h"

#include "asm/irq.h"

#include "asm/io.h"

#include "asm/arch/regs-gpio.h"

#include "asm/hardware.h"

#include "linux/poll.h"

#include "linux/dma-mapping.h"

#define MEM_CPY_NO_DMA 0

#define MEM_CPY_DMA 1

#define BUF_SIZE (512*1024)

#define DMA0_BASE_ADDR 0x4B000000

#define DMA1_BASE_ADDR 0x4B000040

#define DMA2_BASE_ADDR 0x4B000080

#define DMA3_BASE_ADDR 0x4B0000C0

struct s3c_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 int major = 0;

static char *src;

static u32 src_phys;

static char *dst;

static u32 dst_phys;

static struct class *cls;

static volatile struct s3c_dma_regs *dma_regs;

static DECLARE_WAIT_QUEUE_HEAD(dma_waitq);

// 中断事件标志, 中断服务程序将它置1，ioctl将它清0 //

static volatile int ev_dma = 0;

static int s3c_dma_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)

{

int i;

memset(src, 0xAA, BUF_SIZE);

memset(dst, 0x55, BUF_SIZE);

switch (cmd)

{

case MEM_CPY_NO_DMA :

{

for (i = 0; i < BUF_SIZE; i++)

dst[i] = src[i];

if (memcmp(src, dst, BUF_SIZE) == 0)

{

printk("MEM_CPY_NO_DMA OK\n");

}

else

{

printk("MEM_CPY_DMA ERROR\n");

}

break;

}

case MEM_CPY_DMA :

{

ev_dma = 0;

// 把源,目的,长度告诉DMA //

dma_regs->disrc = src_phys; // 源的物理地址 //

dma_regs->disrcc = (0<1) | (0<0); // 源位于AHB总线, 源地址递增 //

dma_regs->didst = dst_phys; // 目的的物理地址 //

dma_regs->didstc = (0<2) | (0<1) | (0<0); // 目的位于AHB总线, 目的地址递增 //

dma_regs->dcon = (1<30)|(1<29)|(0<28)|(1<27)|(0<23)|(0<20)|(BUF_SIZE<0); // 使能中断,单个传输,软件触发, //

// 启动DMA //

dma_regs->dmasktrig = (1<1) | (1<0);

// 如何知道DMA什么时候完成? //

// 休眠 //

wait_event_interruptible(dma_waitq, ev_dma);

if (memcmp(src, dst, BUF_SIZE) == 0)

{

printk("MEM_CPY_DMA OK\n");

}

else

{

printk("MEM_CPY_DMA ERROR\n");

}

break;

}

}

return 0;

}

static struct file_operations dma_fops = {

.owner = THIS_MODULE,

.ioctl = s3c_dma_ioctl,

};

static irqreturn_t s3c_dma_irq(int irq, void *devid)

{

// 唤醒 //

ev_dma = 1;

wake_up_interruptible(&dma_waitq); // 唤醒休眠的进程 //

return IRQ_HANDLED;

}

static int s3c_dma_init(void)

{

if (request_irq(IRQ_DMA3, s3c_dma_irq, 0, "s3c_dma", 1))

{

printk("cant request_irq for DMA\n");

return -EBUSY;

}

// 分配SRC, DST对应的缓冲区 //

src = dma_alloc_writecombine(NULL, BUF_SIZE, &src_phys, GFP_KERNEL);

if (NULL == src)

{

printk("cant alloc buffer for src\n");

free_irq(IRQ_DMA3, 1);

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("cant alloc buffer for dst\n");

return -ENOMEM;

}

major = register_chrdev(0, "s3c_dma", &dma_fops);

// 为了自动创建设备节点 //

cls = class_create(THIS_MODULE, "s3c_dma");

class_device_create(cls, NULL, MKDEV(major, 0), NULL, "dma");