problem of DMA(Momery to memory)

Altera_Forum · ‎10-08-2009

#include"system.h"# include<stdio.h># include"altera_avalon_dma_regs.h"# include"altera_avalon_pio_regs.h"# include"alt_types.h"

alt_u8 tab[8]={'a','b','c','d','e','f','g','h'},des[8];

alt_u32 flag;

int main()

{

IOWR_ALTERA_AVALON_DMA_STATUS(DMA_BASE,0X00);

IOWR_ALTERA_AVALON_DMA_RADDRESS(DMA_BASE,tab);

IOWR_ALTERA_AVALON_DMA_WADDRESS(DMA_BASE,des);

IOWR_ALTERA_AVALON_DMA_LENGTH(DMA_BASE,8);

IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_BASE,0X289);

while(1)

{

if(0X01&IORD_ALTERA_AVALON_DMA_STATUS(DMA_BASE))

{

IOWR_ALTERA_AVALON_PIO_DATA(PIO_BASE,des[1]);

}

return 0;

}

the DMA seems to work,the LEN AND DONE of status register are set to 1,

but the des[8] did not receive anything from tab[8].

Altera_Forum · ‎10-09-2009

How do you check the contents of des? Does your CPU have a data cache? In that case you need to bypass the cache to read des.

Altera_Forum · ‎10-09-2009

yes,i have data cache.if i amend the code like this:

if(0X01&IORD_ALTERA_AVALON_DMA_STATUS(DMA_BASE))

{

IOWR_ALTERA_AVALON_PIO_DATA(PIO_BASE,tab[1]);

}

the IO is working.

thanks.

Altera_Forum · ‎10-09-2009

Oh sorry, I didn't see the des in your IOWR macro.

The problem if you read directly des[x] is that the data will be read from the data cache instead of main RAM, and the cache isn't updated by the DMA. One way to get around it is to use the remap function. This should work:

#include"system.h"
# include<stdio.h>
# include"altera_avalon_dma_regs.h"
# include"altera_avalon_pio_regs.h"
# include"alt_types.h"
#include "sys/alt_cache.h"
alt_u8 tab={'a','b','c','d','e','f','g','h'},des;
alt_u32 flag;
int main()
{
  alt_u8 *uncached_des = (alt_u8*) alt_remap_uncached(des,8);
  IOWR_ALTERA_AVALON_DMA_STATUS(DMA_BASE,0X00);
  IOWR_ALTERA_AVALON_DMA_RADDRESS(DMA_BASE,tab);
  IOWR_ALTERA_AVALON_DMA_WADDRESS(DMA_BASE,des);
  IOWR_ALTERA_AVALON_DMA_LENGTH(DMA_BASE,8);
  IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_BASE,0X289);
  while(1)
  {
    if(0X01&IORD_ALTERA_AVALON_DMA_STATUS(DMA_BASE))
    {
      IOWR_ALTERA_AVALON_PIO_DATA(PIO_BASE,uncached_des);
    }
  }
  return 0;
}

Altera_Forum · ‎10-09-2009

sorry,it still do not work.

Altera_Forum · ‎10-12-2009

After reading your control register, I saw that you enabled the WCON bit. You shouldn't enable it, the DMA musn't always write to the same address. Try this:

IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_BASE,0X89);

If it stills doesn't work, you should put a signaltap probe and see what the controller is doing.

Altera_Forum · ‎10-12-2009

i get it

thank you very much