转载： http://blog.ednchina.com/conan85420/431119/message.aspx
本程序首先输出目标地址空间的数据，然后连续发起两次DMA传输，最后再次输出DMA传输后目标地址空间的数据。
第二次发起可以在第一次DMA传输没有结束的情况下开始，不过要注意，两次的目标地址不能有重叠部分，否则发起会失败。
#include <stdio.h>
#include <stdlib.h>
#include "unistd.h"
#include "string.h"
#include "io.h"
#include "system.h"
#include "sys/alt_dma.h"
#include "sys/alt_cache.h"
#include "sys/alt_irq.h"
#include "alt_types.h"
#include "sys/alt_irq.h"
#include "altera_avalon_dma_regs.h"
#include "altera_avalon_uart_regs.h"
volatile char chr[20] = {1,2,3,4,6,5,7,8,9,10,
11,12,13,14,15,16,17,18,19,20} ;//数据源
volatile char chr2[20] = {1,2,3,4,6,5,7,8,9,10,
11,12,13,14,15,16,17,18,19,20} ;//数据源
static volatile int rx_done = 0;
static void done (void* handle, void* data)
{
rx_done++;
IOWR(LED_BASE,0, rx_done);//LED显示rx_done的变化
}
static void done2 (void* handle, void* data)
{
rx_done++;
IOWR(LED_BASE,0, rx_done);//LED显示rx_done的变化
}
int main (int argc, char* argv[], char* envp[])
{
alt_u8 i="0";
int rc;
alt_dma_txchan txchan;
alt_dma_rxchan rxchan;
void * tx_data = (void*) chr;
void * tx_data2 = (void*) chr2;
char *rx = (char *)ONCHIP_RAM_BASE;
char *rx2 = (char *)ONCHIP_RAM_BASE+20;
void* rx_buffer = (void*) ONCHIP_RAM_BASE;//0x00801000; /* pointer to rx buffer */
void* rx_buffer2 = (void*) ONCHIP_RAM_BASE+20;
IOWR(LED_BASE,0, 0);
for(i =0;i<20;i++) //串口输出目标地址空间的数据
{
printf ("%c",*(rx+i));
}
printf ("\n");
for(i =0;i<20;i++) //串口输出目标地址空间的数据
{
printf ("%c",*(rx2+i));
}
printf ("\n");
printf ("Let's begin!\n");
alt_dcache_flush_all();//清空数据缓存
if ((txchan = alt_dma_txchan_open("/dev/DMA0")) == NULL)
{
printf ("Failed to open transmit channel\n");
}
if ((rxchan = alt_dma_rxchan_open("/dev/DMA0")) == NULL)
{
printf ("Failed to open receive channel\n");
}
rc = alt_dma_rxchan_depth(rxchan);//获取最大可接受请求数量
printf ("rxchan_depth = %d\n",rc);
rc = alt_dma_txchan_space(txchan);//获取最大发送请求数目
printf ("txchan_depth = %d\n",rc);
/******************第一次DMA请求******************/
if ((rc = alt_dma_txchan_send (txchan,
tx_data,
20,
NULL,
NULL)) < 0)
{
printf ("Failed to post transmit request1, reason = %i\n", rc);
}
if ((rc = alt_dma_rxchan_prepare (rxchan,
rx_buffer,
20,
done,
NULL)) < 0)
{
printf ("Failed to post read request1, reason = %i\n", rc);
}
/******************第二次DMA请求******************/
if ((rc = alt_dma_txchan_send (txchan,
tx_data2,
20,
NULL,
NULL)) < 0)
{
printf ("Failed to post transmit request2, reason = %i\n", rc);
}
if ((rc = alt_dma_rxchan_prepare (rxchan,
rx_buffer2,
20,
done2,
NULL)) < 0)
{
printf ("Failed to post read request2, reason = %i\n", rc);
}
while (rx_done<2);//等待两次发送完毕
printf ("Transfer successful!\n");
for(i =0;i<20;i++)
{
printf ("%c",*(rx+i)); //再次输出dma传输后目标地址的数据
}
printf ("\n");
for(i =0;i<20;i++)
{
printf ("%c",*(rx2+i)); //再次输出dma传输后目标地址的数据
}
printf ("\n");
while(1);
return 0;
}