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Commands to modular SGDMA Read Master for a single and burst read ?

Honored Contributor II



I'm trying to use the modular SGDMA Read Master to allow my custom IP to read from On-Chip and SDRAM in my QSYS project. However, I'm having trouble figuring out how to interact with this Read Master in order to it have perform a read or burst read. All I have for documentation is the PDF (attached) from the modular SGDMA wiki but it's not complete. 


Below is my basic state machine for a single read and the simulation results are attached. I can read the correct data (0xFFFFFFFF) but I never see the done strobe while response_source_valid is asserted. 


Does anyone have any idea what I'm doing wrong ? Also, what would the steps be to perform a burst read ? 



always @ (posedge clk_in or negedge reset_n_in) begin 

if (~reset_n_in) master_read_FSM <= s0; 

else case (master_read_FSM) 

s0 : begin 

dma_read_master_0_command_sink_data_out <= 256'h0; 

dma_read_master_0_command_sink_valid_out <= 1'b0; 

dma_read_master_0_data_source_ready_out <= 1'b0; 

dma_read_master_0_response_source_ready_out <= 1'b0; 

master_read_FSM <= cmd_go_pulse ? s1 : s0; 


s1 : begin 

master_read_FSM <= dma_read_master_0_command_sink_ready_in ? s2 : s1 ; 


s2 : begin 

dma_read_master_0_command_sink_data_out[31:0] <= 32'h08000000; // address 31:0 

dma_read_master_0_command_sink_data_out[140:109] <= 32'h0; // address 63:32 

dma_read_master_0_command_sink_data_out[63:32] <= 32'h00000004; // length 

dma_read_master_0_command_sink_valid_out <= 1'b1; 

master_read_FSM <= s3 ; 


s3 : begin 

dma_read_master_0_command_sink_valid_out <= 1'b0; 

dma_read_master_0_data_source_ready_out <= 1'b1; 

dma_read_master_0_response_source_ready_out <= 1'b1; 

master_read_FSM <= dma_read_master_0_data_source_valid_in ? s4 : s3; 


s4 : begin 

slave_data_0_out <= dma_read_master_0_data_source_data_in; 

master_read_FSM <= (dma_read_master_0_response_source_valid_in && dma_read_master_0_response_source_data_in[2]) ? s0 : s4; 


default : master_read_FSM <= s0; 





Appreciate the help. 


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2 Replies
Honored Contributor II



In your test bench you may need to create structures for the DMA descriptors and then drive them to the DMA engine depending on the SRC valid and ready signals. take a look at the code snippet below.. It should give you an idea on how to write a TB for DMA 


reg read_addr_l; reg length; reg tx_channel; reg gen_sop; reg gen_eop; reg stop; reg reset; reg read_burst_count; reg read_stride; reg tx_error; reg early_done_enable; reg read_addr_h; reg reserved; reg dma_desc; //assign values to desc fields. assign reserved = 115'h0; assign gen_sop = 1'b1; assign gen_eop = 1'b1; assign stop = 1'b0; assign reset = 1'b0; assign read_addr_h = 32'h0; // assign your read address high bits here assign read_addr_l = 32'h0; // assign your read address low bits here assign length = 32'h0; // assign length of DMA transfer assign tx_channel = 8'h0; // assign tx channel here assign read_burst_count = 8'h0; // For burst transfers set value here assign early_done_enable = 1'b1; assign dma_desc = {reserved, read_address_h, early_done_enable, tx_error, read_stride, read_burst_count, reset, stop, gen_eop, gen_sop, tx_channel, length, read_address_l}; always@(posedge clkin or negedge reset_n_in) begin if(!reset_n_in) dma_desc <= 256'h0; snk_command_data <= 256'h0; else begin if(src_ready && src_valid) begin // check if source is ready and valid, then send desc data to DMA engine snk_command_data <= dma_desc; if( ) ... ...
Honored Contributor II

Thanks for the response eapenabrm. I don't fully understand what you mean. I'm trying to use the Read Master of the modular SGDMA by itself as an Avalon MM Read Master for my custom IP. My problem is that I don't know how to drive the Read Master module to perform a single read or burst read. The Read Master has a data source valid and ready as well as response source valid and ready. The valid signals are outputs from the Read Master while the ready signals are inputs which I need to drive. I'm not sure which SRC valid and ready signals you're referring to and how you can be monitoring both. Do you mind clarifying what you mean ? 


Just a side note, I also tried using the altera provided MM master template but couldn't get it to work in simulation. The waitrequest signal seemed to be stuck high forever.