u2/u2p: short fifos put on both sides of ll8_to_fifo19

1 files changed, 44 insertions, 27 deletions

diff --git a/usrp2/fifo/ll8_to_fifo19.v b/usrp2/fifo/ll8_to_fifo19.v
index af3b91afb..3c95c2374 100644
--- a/usrp2/fifo/ll8_to_fifo19.v
+++ b/usrp2/fifo/ll8_to_fifo19.v
@@ -10,33 +10,42 @@ module ll8_to_fifo19
    output [18:0] f19_data,
    output f19_src_rdy_o,
    input f19_dst_rdy_i );
+
+   // Short FIFO on input to guarantee no deadlock
+   wire [7:0] ll_data_int;
+   wire       ll_sof_int, ll_eof_int, ll_src_rdy_int, ll_dst_rdy_int;
+   wire       ll_dst_rdy;
+   
+   ll8_shortfifo head_fifo
+     (.clk(clk), .reset(reset), .clear(clear),
+      .datain(ll_data), .sof_i(~ll_sof_n), .eof_i(~ll_eof_n),
+      .error_i(0), .src_rdy_i(~ll_src_rdy_n), .dst_rdy_o(ll_dst_rdy),
+      .dataout(ll_data_int), .sof_o(ll_sof_int), .eof_o(ll_eof_int),
+      .error_o(), .src_rdy_o(ll_src_rdy_int), .dst_rdy_i(ll_dst_rdy_int));
+
+   assign ll_dst_rdy_n = ~ll_dst_rdy;
    
+   // Actual ll8_to_fifo19 which could deadlock if not connected to a shortfifo
    localparam XFER_EMPTY       = 0;
    localparam XFER_HALF        = 1;
    localparam XFER_HALF_WRITE  = 3;
    
-   // Why anybody would use active low in an FPGA is beyond me...
-   wire  ll_sof      = ~ll_sof_n;
-   wire  ll_eof      = ~ll_eof_n;
-   wire  ll_src_rdy  = ~ll_src_rdy_n;
-   wire  ll_dst_rdy;
-   assign    ll_dst_rdy_n  = ~ll_dst_rdy;
-   
-   wire  xfer_out 	   = f19_src_rdy_o & f19_dst_rdy_i;
-   wire  xfer_in 	   = ll_src_rdy & ll_dst_rdy; 
-   
-   reg 	 hold_sof;
-   wire  f19_sof, f19_eof, f19_occ;
+   wire [18:0] f19_data_int;
+   wire        f19_sof_int, f19_eof_int, f19_occ_int, f19_src_rdy_int, f19_dst_rdy_int;
+
+   wire        xfer_out    = f19_src_rdy_int & f19_dst_rdy_int;
+   wire        xfer_in 	   = ll_src_rdy_int & ll_dst_rdy_int; 
+   reg 	       hold_sof;
    
-   reg [1:0] state;
-   reg [7:0] hold_reg;
+   reg [1:0]   state;
+   reg [7:0]   hold_reg;
    
    always @(posedge clk)
-     if(ll_src_rdy & (state==XFER_EMPTY))
-       hold_reg 	      <= ll_data;
+     if(ll_src_rdy_int & (state==XFER_EMPTY))
+       hold_reg 	      <= ll_data_int;
    
    always @(posedge clk)
-     if(ll_sof & (state==XFER_EMPTY))
+     if(ll_sof_int & (state==XFER_EMPTY))
        hold_sof 	      <= 1;
      else if(xfer_out)
        hold_sof 	      <= 0;
@@ -47,27 +56,35 @@ module ll8_to_fifo19
      else
        case(state)
 	 XFER_EMPTY :
-	   if(ll_src_rdy)
-	     if(ll_eof)
+	   if(ll_src_rdy_int)
+	     if(ll_eof_int)
 	       state 	      <= XFER_HALF_WRITE;
 	     else
 	       state 	      <= XFER_HALF;
 	 XFER_HALF :
-	   if(ll_src_rdy & f19_dst_rdy_i)
+	   if(ll_src_rdy_int & f19_dst_rdy_int)
 	       state 	      <= XFER_EMPTY;
          XFER_HALF_WRITE :
-	   if(f19_dst_rdy_i)
+	   if(f19_dst_rdy_int)
 	     state 	<= XFER_EMPTY;
        endcase // case (state)
       
-   assign ll_dst_rdy 	 = (state==XFER_EMPTY) | ((state==XFER_HALF)&f19_dst_rdy_i);
-   assign f19_src_rdy_o  = (state==XFER_HALF_WRITE) | ((state==XFER_HALF)&ll_src_rdy);
+   assign ll_dst_rdy_int = (state==XFER_EMPTY) | ((state==XFER_HALF)&f19_dst_rdy_int);
+   assign f19_src_rdy_int= (state==XFER_HALF_WRITE) | ((state==XFER_HALF)&ll_src_rdy_int);
    
-   assign f19_sof 	 = hold_sof | (ll_sof & (state==XFER_HALF));
-   assign f19_eof 	 = (state == XFER_HALF_WRITE) | ll_eof;
-   assign f19_occ 	 = (state == XFER_HALF_WRITE);
+   assign f19_sof_int 	 = hold_sof | (ll_sof_int & (state==XFER_HALF));
+   assign f19_eof_int 	 = (state == XFER_HALF_WRITE) | ll_eof_int;
+   assign f19_occ_int 	 = (state == XFER_HALF_WRITE);
    
-   assign f19_data 	 = {f19_occ,f19_eof,f19_sof,hold_reg,ll_data};
+   assign f19_data_int 	 = {f19_occ_int,f19_eof_int,f19_sof_int,hold_reg,ll_data_int};
+
+   // Shortfifo on output to guarantee no deadlock
+   fifo_short #(.WIDTH(19)) tail_fifo
+     (.clk(clk),.reset(reset),.clear(clear),
+      .datain(f19_data_int), .src_rdy_i(f19_src_rdy_int), .dst_rdy_o(f19_dst_rdy_int),
+      .dataout(f19_data), .src_rdy_o(f19_src_rdy_o), .dst_rdy_i(f19_dst_rdy_i),
+      .space(),.occupied() );
       
+   
 endmodule // ll8_to_fifo19