Working with DMA

The DMA kernel driver is available under the kernel tree in the following location

      ...lsp/ti-davinci/arch/arm/mach-davinci/dma.c

that said, this driver is only accessible by other kernel drivers such as MMC driver and audio driver.  You could add proprietary ioctl request to the dma driver to allow user space access to DMA resources; however, this can be dangerous as you need to uderstand which DMA channels are dedicated to which peripherals and communication between ARM and MJCP.  What do you have in mind as far as DMA usage?

Thank you for your reply, Juan!

We tried use this for dm9000 driver. That is what we have done:

void dm9000_dmaHandler(int lch, unsigned short ch_status,void *data);

static void dm9000_outblk_8bit(void __iomem *reg, void *data, int count)
{
int res;

int i;

edmacc_paramentry_regs dmaParam;

//writesb(reg, data, count);

//заменить на write_DMA

printk("start %s, data = %p,count = %d, channel = %d,tcc = %d,reg = %p\n",

__FUNCTION__, data,count,lch,tcc,dmaTestData);

printk(KERN_INFO "requesting dma channel\n");

for (i = 12; i < 14; i++) {

res = davinci_request_dma(i,"dm9000_dma_tx",dm9000_dmaHandler,

dmaData,&lch,&tcc,0);

if (!res)

{

printk(KERN_INFO "allocated dma channel %d\n",lch);

break;

}

else

{

//printk(KERN_INFO "dma request error %d\n",res);

}

}

if (res)

printk(KERN_INFO "dma request error %d\n",res);

davinci_set_dma_transfer_params(lch, count, 1, 1,

0, ASYNC);

davinci_set_dma_dest_params(lch,reg, 0, 0);

davinci_set_dma_src_params(lch, data, 0, 0);

davinci_set_dma_src_index(lch, 0, 0);

davinci_set_dma_dest_index(lch, 0, 0);

res = davinci_start_dma(lch);

if (res)

{

printk("dm9000 dma start error\n");

}

printk("end %s\n",__FUNCTION__);

}

void dm9000_dmaHandler(int lch, unsigned short ch_status,void *data)

{

printk(KERN_INFO "%s, channel= %d,status = 0x%04X, data = %p\n",__FUNCTION__,lch,

ch_status,data);

davinci_stop_dma(lch);

davinci_free_dma(lch);

ch_status = ch_status;

data = data;

}

I cannot see anything obviously wrong in the code; can you try doing a DMA transfer from DDR2 to DDR2 first...this is probrably a easy way to verify if there is something wrong with the code or not...

Testing DMA transfer from DDR2 to DDR2.

Source:

static unsigned char dmaTestData[1536];
static unsigned char dmaTestSource[1536];

static void dm9000_outblk_8bit(void __iomem *reg, void *data, int count)
{
.........................................................................
 for (i = 0; i < 25; i++) {
dmaTestData[i] = 0;
dmaTestSource[i] = i + 1;
}
davinci_set_dma_transfer_params(lch, 25, 1, 1, 0, ASYNC);
davinci_set_dma_dest_params(lch,(unsigned long)virt_to_phys(dmaTestData), 0, 0);
davinci_set_dma_src_params(lch, (unsigned long)virt_to_phys(dmaTestSource), 0, 0);
davinci_set_dma_src_index(lch, 0, 0);
davinci_set_dma_dest_index(lch, 0, 0);
.........................................
}

void dm9000_dmaHandler(int lch, unsigned short ch_status,void *data)
{
int i;
......................................
 printk(KERN_INFO "dmaTestData:");
for (i = 0; i < 25; i++) {
printk(KERN_INFO "%02X ", dmaTestData[i]);
}
printk(KERN_INFO "\n");
...............................
}

Result:

start dm9000_outblk_8bit, data = c09c6202,count = 70, channel = 12,tcc = 12,reg = 0xC6864002
requesting dma channel
allocated dma channel 12
end dm9000_outblk_8bit
dm9000_dmaHandler, channel= 12,status = 0x0001, data = c0353c30
dmaTestData:<6>01 <6>02 <6>03 <6>04 <6>05 <6>06 <6>07 <6>08 <6>09 <6>0A <6>0B <6>0C <6>0D <6>0E <6>0F <6>10 <6>11 <6>12 <6>13 <6>14 <6>15 <6>16 <6>17 <6>18 <6>19 <6>

But with ping, as sample, this is don't work.