mSGDMA: Streaming to MM problem

Hi everyone,

Recently, I want to play with mSGDMA and learn about it so just make up my own project to test and see the behaviour and know how to control the mSGDMA. However, I got stuck and have tried everything I know but still cannot fix it.

HARDWARE:

-HPS with h2f_lw_bridge

-mSGDMA:

• Streaming to Memory Mapped
• Data width: 8
• Data Path FIFO depth: 32
• Descriptor FIFO depth: 32
• Maximum transfer length: 1KB
• Transfer type: Aligned Accesses
• Everything else is disabled

-My customized counter with streaming interface: I made this component just to test the mSGDMA. The counter increase the value every 1 second and output it in streaming interface. It has:

• Data width: 8 bits
• Data bits per symbol: 8 bits

-LED PIO: written by mSGDMA write master with the transfered data and it is supposed to increase every second.

SOFTWARE:

Here is C code:

typedef struct sgdma_descr
{
	uint32_t *read_addr;
	uint32_t *write_addr;
	uint32_t length;
	uint32_t control;
}sgdma_descr_t;
 
int main ()
{
	uint32_t status ;
	
	/*bridge configuration*/
	alt_bridge_init(ALT_BRIDGE_LWH2F,NULL,NULL);
	
	 alt_bridge_init(ALT_BRIDGE_H2F,NULL,NULL);
 
	sgdma_descr_t descr;
	sgdma_descr_t *descr_ptr = &descr;
 
        // configure the descriptor for ST to MM transferring
	descr->read_addr = NULL; 
	descr->write_addr = 0; // address of PIO seen by mSGDMA write master
	descr->length = 1;
	descr->control =(1<<31) ; // no setting, just go for one data transfer
 
       // feed the descriptor to the descriptor slave 
        alt_write_word(DESCR_RADDR,descr->read_addr);
	alt_write_word(DESCR_WADDR,descr->write_addr);
	alt_write_word(DESCR_LENGTH,descr->length);
	alt_write_word(DESCR_CONTROL,descr->control);
 
       uint32_t status;
	while(1)
	{
                // observe value inside the registers
		status = alt_read_word(CSR_STATUS);
		printf("Status: %u\n",status);
 
		status = alt_read_word(CSR_CONTROL);
		printf("CONTROL: %u\n",status);
 
		status = alt_read_word(CSR_LEVEL);
		printf("LEVEL: %u\n",status);
 
	}
	return 0;
}

It states that the mSGDMA is still busy transfering ( Busy bit is set ) and the descriptor buffer is empty ( Descriptor buffer empty bit is set and the value in Write fill level register is 0 ). However, I see nothing is transferred because the LEDs are not lighted up.

I had tried the same test with regular DMA Controller and it worked fine. But with mSGDMA it does not work with my test.

Hope someone can give me a hint how to fix this. Thanks in advance !

Cheers!