Fork join for req-ack in loop

UVM
1

Below is my code for NUMLINES=4. If pkt_send_req comes on any of the requests, pkt_send_ack[i] must be asserted for once cycle within a delay of 1-32 cycles. I am not seeing the expected behavious. Total number of acks are not matching total number of reqs. Can you please correct this?

task foo_driver::drive_ack();
 int req_pos;
 int ack_pos;
 int pos;
 int delay_ack;
 int req_pos_q[$];
 int ack_q[$];
 semaphore mutex = new(1); // Create a semaphore with 1 token


 forever begin 
   @(posedge intf.clock);
   
	  fork
	   begin: requests
		  if(|intf.pkt_send_req ==1) begin
        val = intf.o_val;
        for (int i = 0; i < `NUM_LINES; i++) begin
            if (intf.pkt_send_req[i] == 1) begin
							mutex.get(); // Acquire the mutex
                req_pos_q.push_back(i);
							mutex.put(); // Release the mutex
            end
        end
			end	
		  else begin
				val = 0;
			end
		 end
		 begin: acks
        while (req_pos_q.size() != 0) begin
							mutex.get(); // Acquire the mutex
            		ack_pos = req_pos_q.pop_front();
						    ack_q.push_back(ack_pos);
							mutex.put(); // Release the mutex
            delay_ack = $urandom_range(32, 1);
            repeat (delay_ack) @(posedge intf.clock);
						pos=ack_q.pop_front();
            intf.pkt_send_ack[pos] <= 1'b1;
            @(posedge intf.clock);
            intf.pkt_send_ack[pos] <= 1'b0;
            @(posedge intf.clock);
        end
		 end
		join_none
   
end
endtask
2

Since you don’t have all the code shown, it’s hard to debug this. We can’t see the results you are getting. The while (req_pos_q.size() != 0) loop is in a race with the for loop in the request process. Also, it would be much simpler to use a mailbox#(int) req_pos_q instead of a queue wrapped around semaphores.

3

Can you please edit my above code to use mailbox instead?

4

The below code errors out randomly. It still does not generate equal number of acks for the reqs. Please help me fix this code.

task foo_driver::drive_ack();
 int req_pos;
 int ack_pos;
 int pos;
 int delay_ack;
mailbox req_mb = new();
mailbox ack_mb = new();



 forever begin 
   @(posedge intf.clock);
   
	  fork
	   begin: requests
		  if(|intf.pkt_send_req ==1) begin
                     val = intf.o_val;
                     for (int i = 0; i < `NUM_LINES; i++) begin
			automatic int k = i;
                         if (pkt_send_req[k] == 1) begin
            			  req_pos_mb.put(k);
				$display("req is here with k=%0d",k);
				$display("req size is %0d",req_pos_mb.num());
                        end
		   end	
		else begin
			val = 0;
		end
	  end
       begin:acks
          if(req_pos_mb.num()>0) begin
	        req_pos_mb.get(req_pos); // Get the request position from the mailbox
                ack_mb.put(req_pos); 
			
            delay_ack = $urandom_range(32, 1);
            repeat (delay_ack) @(posedge intf.clock);
		ack_mb.get(req_pos);
		 intf.pkt_send_ack[req_pos] <= 1'b1;
                @(posedge intf.clock);
                     intf.pkt_send_ack[req_pos] <= 1'b0;
                @(posedge intf.clock);
           end
       end
     join_none
   
end
endtask
5

Still very difficult to debug without more code shown. What outputs and errors are you getting?