Squashed B200 FPGA Source. Code from Josh Blum, Ian Buckley, and Matt Ettus.

Original-commit: 0df4b801a34697f2058b4a7b95e08d2a0576c9db

lib/control/axi_slave_mux.v

@@ -0,0 +1,122 @@
+//
+// Copyright 2012 Ettus Research LLC
+//
+
+
+   
+
+`define LOG2(N) (\
+                 N < 2 ? 0 : \
+                 N < 4 ? 1 : \
+                 N < 8 ? 2 : \
+                 N < 16 ? 3 : \
+                 N < 32 ? 4 : \
+                 N < 64 ? 5 : \
+		 N < 128 ? 6 : \
+		 N < 256 ? 7 : \
+		 N < 512 ? 8 : \
+		 N < 1024 ? 9 : \
+                 10)
+
+
+module axi_slave_mux
+  #(
+    parameter FIFO_WIDTH = 64, // AXI4-STREAM data bus width
+    parameter DST_WIDTH = 16,  // Width of DST field we are routing on.
+    parameter NUM_INPUTS = 2   // number of input AXI buses
+    )
+    (
+     input 				 clk,
+     input 				 reset,
+     input 				 clear,
+     // Inputs
+     input [(FIFO_WIDTH*NUM_INPUTS)-1:0] i_tdata,
+     input [NUM_INPUTS-1:0] 		 i_tvalid,
+     input [NUM_INPUTS-1:0] 		 i_tlast,
+     output [NUM_INPUTS-1:0] 		 i_tready,
+     // Forwarding Flags
+     input [NUM_INPUTS-1:0] 		 forward_valid,
+     output reg [NUM_INPUTS-1:0] 	 forward_ack,
+     // Output
+     output [FIFO_WIDTH-1:0] 		 o_tdata,
+     output 				 o_tvalid,
+     output 				 o_tlast,
+     input 				 o_tready
+     );
+
+   wire [FIFO_WIDTH-1:0] i_tdata_array [0:NUM_INPUTS-1];
+   
+   reg [`LOG2(NUM_INPUTS):0] select;
+   reg 			     enable;
+
+
+   reg 			     state;
+
+   localparam CHECK_THIS_INPUT = 0;
+   localparam WAIT_LAST = 1;
+   
+
+   always @(posedge clk)
+     if (reset | clear) begin
+	state <= CHECK_THIS_INPUT;
+	select <= 0;
+	enable <= 0;
+	forward_ack <= 0;	
+     end else begin
+	case(state)
+	  // Is the currently selected input addressing this slave with a ready packet?
+	  CHECK_THIS_INPUT:  begin
+	     if (forward_valid[select]) begin
+		enable <= 1;
+		forward_ack[select] <= 1;
+		state <= WAIT_LAST;
+	     end else if (select == NUM_INPUTS - 1 ) begin
+		select <= 0;
+	     end else begin
+		select <= select + 1;
+	     end
+	  end
+	  // Assert ACK immediately to forwarding logic and then wait for end of packet.
+	  WAIT_LAST: begin
+	    
+	     if (i_tlast[select] && i_tvalid[select] && o_tready) begin
+		if (select == NUM_INPUTS - 1 ) begin
+		   select <= 0;
+		end else begin
+		   select <= select + 1;
+		end
+		state <= CHECK_THIS_INPUT;
+		forward_ack <= 0;
+		enable <= 0;
+	     end else begin
+		forward_ack[select] <= 1;
+		enable <= 1;
+	     end
+	  end
+	endcase // case(state)
+     end
+	
+   //
+   // Combinatorial mux
+   //
+   genvar m;
+     
+   generate
+      for (m = 0; m < NUM_INPUTS; m = m + 1) begin: form_buses
+	 assign i_tdata_array[m] = i_tdata[(m*FIFO_WIDTH)+FIFO_WIDTH-1:m*FIFO_WIDTH];
+      end
+   endgenerate
+
+   assign 	o_tdata = i_tdata_array[select];
+   assign 	o_tvalid = enable && i_tvalid[select];
+   assign 	o_tlast = enable && i_tlast[select];
+ //  assign 	i_tready = {NUM_INPUTS{o_tready}} & (enable << select);
+
+   generate
+      for (m = 0; m < NUM_INPUTS; m = m + 1) begin: form_ready
+	 assign i_tready[m] = o_tready && enable && (select == m);
+      end
+   endgenerate
+
+    
+endmodule // axi_slave_mux