[LIP] DMA data transfer

Hi All,
I had gone through the Rubbini Book that to be
perticularly chap-13 for DMA Data Transfer.

Here is code for my driver for DMA transfer.

At open entry
dma_buff = __get_dma_pages(__GFP_DMA,
get_order(1024)); 
flags = claim_dma_lock ();
disable_dma (dma_ch);
clear_dma_ff (dma_ch);
//It Should be circular-Q that's the reason
DMA_AUTOINIT.
set_dma_mode (dma_ch, DMA_MODE_READ | DMA_AUTOINIT);
set_dma_addr (dma_ch, virt_to_bus (dma_buff));
set_dma_count (dma_ch,1024 );
enable_dma (dma_ch);
release_dma_lock (flags);
*******************************

At Read Entry
flags = claim_dma_lock ();
residue = get_dma_residue (dma_ch);
i = 1024 - residue;
// Copying the acquired data to tmp buff of 128 bytes
// mean time DMA can continue the data transfer 
for (i = 0; i < 128; i++)
	tbuff[i] = dma_buff[start + i];
__copy_to_user ((unsigned char *) buf, (unsigned char
*) tbuff, sizeof (tbuff));
*******************************
The user program will read these bytes and dump into a
file @ every one second.

The system is hanging without giving any message at
syslog/on console also.

I would like to know What would be the reason, I am
using the ReHat-8.0 with kernel-2.6.6
Any help or pointers/links is apreciated.

Thanks in advance
Regards
V. Kumar.




		
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