memory-to-memory sgdma problem

Hello,

I am testing the sgdma core by copy data from one on-chip-memory buffer to the other.

However, I met a confusing problem that the actual_transfered_bytes is always zero.

Can anybody help?

the sopc-builder system i used is as follows:

cpu

-----instruction_master

-----data_master

on-chip memory

-----s1

sgdma_0

-----csr

-----descriptor_read

-----descriptor_write

-----m_read

-----m_write

descriptor_read, descriptor_read, m_read and m_write are connected to s1 of on-chip memory. csr is connected to data_master of cpu.

the c code is as follows:

alt_u32 tx_buf[10], rx_buf[10];

alt_sgdma_descriptor desc, next;

int main()

{

alt_u32 i;

alt_sgdma_dev *sgdma_m2m;

alt_u8 status;

for(i=0;i<10;i++){

tx_buf = i+0x11111111;

rx_buf = 0;

}

sgdma_m2m = alt_avalon_sgdma_open ("/dev/sgdma_0");

/* This will create a descriptor that is capable of transmitting data from an Avalon-MM buffer

* to a packet enabled Avalon-ST FIFO component */

alt_avalon_sgdma_construct_mem_to_mem_desc(

&desc, // descriptor

&next, // next descriptor

tx_buf, // read buffer location

rx_buf, // write buffer location

(alt_u16) 10, // length of the buffer

0, // reads are not from a fixed location

0); // writes are not from a fixed location

/* Prime the SGDMA engines with the descriptor lists (first one, it's a linked list) */

status = alt_avalon_sgdma_do_sync_transfer(sgdma_m2m, &desc);

return 0;

}

After alt_avalon_sgdma_do_sync_transfer() is called,

status is 0x0C which is as supposed, but desc.actual_transfered_bytes is zero!

The values in rx_buf[] remains the original values, all zeros.

Any comments will be appreciated.