DMA驱动程序_dma驱动怎么卸载

DMA驱动程序

在单CPU系统中，CPU同一时间只能做一件事，为了提高效率引入了DMA。

下面的代码用DMA方式实现两块内存之间的数据传输

大概步骤如下：

1. 把源,目的,长度告诉DMA

2.设置DMA参数

a. 地址（增，减，固定）

b. 启动方式（手工或外部）

3. 启动DMA

#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("can't 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("can't 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("can't 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"); /* /dev/dma */

dma_regs = ioremap(DMA3_BASE_ADDR, sizeof(struct s3c_dma_regs));

return 0;
}

static void s3c_dma_exit(void)
{
iounmap(dma_regs);
class_device_destroy(cls, MKDEV(major, 0));
class_destroy(cls);
unregister_chrdev(major, "s3c_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(s3c_dma_init);
module_exit(s3c_dma_exit);
MODULE_LICENSE("GPL");