First cut at passing data buffers around on GPMC bus

2 files changed, 122 insertions, 11 deletions

diff --git a/usrp2/gpmc/dbsm.v b/usrp2/gpmc/dbsm.v
new file mode 100644
index 000000000..0f27be46a
--- /dev/null
+++ b/usrp2/gpmc/dbsm.v
@@ -0,0 +1,88 @@
+
+module bsm
+  (input clk, input reset, input clear,
+   input write_done,
+   input read_done,
+   output readable,
+   output writeable);
+
+   reg 	  state;
+   localparam ST_WRITEABLE = 0;
+   localparam ST_READABLE = 1;
+   
+   always @(posedge clk)
+     if(reset | clear)
+       state <= ST_WRITEABLE;
+     else
+       case(state)
+	 ST_WRITEABLE :
+	   if(write_done)
+	     state <= ST_READABLE;
+	 ST_READABLE :
+	   if(read_done)
+	     state <= ST_WRITEABLE;
+       endcase // case (state)
+
+   assign readable = (state == ST_READABLE);
+   assign writeable = (state == ST_WRITEABLE);
+   
+endmodule // bsm
+
+module dbsm
+  (input clk, input reset, input clear,
+   output reg read_sel, output read_ready, input read_done,
+   output reg write_sel, output write_ready, input write_done);
+
+   localparam NUM_BUFS = 2;
+
+   wire       [NUM_BUFS-1:0] readable, writeable, read_done_buf, write_done_buf;
+   
+   // Two of these buffer state machines
+   genvar     i;
+   for(i=0;i<NUM_BUFS;i=i+1)
+     generate
+	bsm bsm(.clk(clk), .reset(reset), .clear(clear), 
+		.write_done((write_sel == i) & write_done), 
+		.read_done((read_sel == i) & read_done), 
+		.readable(readable[i]), .writeable(writeable[i]));
+     endgenerate
+   
+   reg 	 full;
+   
+   always @(posedge clk)
+     if(reset | clear)
+       begin
+	  write_sel <= 0;
+	  full <= 0;
+       end
+     else
+       if(write_done)
+	 if(writeable[write_sel]==(NUM_BUFS-1))
+	   begin
+	      write_sel <= 0;
+	      if(read_sel == 0)
+		full <= 1;
+	   end
+	 else
+	   begin
+	      write_sel <= write_sel + 1;
+	      if(read_sel == write_sel + 1)
+		full <= 1;
+	   end // else: !if(writeable[write_sel]==(NUM_BUFS-1))
+       else if(read_done)
+	 full <= 0;
+
+   always @(posedge clk)
+     if(reset | clear)
+       read_sel <= 0;
+     else
+       if(read_done)
+	 if(readable[read_sel]==(NUM_BUFS-1))
+	   read_sel <= 0;
+	 else
+	   read_sel <= read_sel + 1;
+          
+   assign write_ready = writeable[write_sel];
+   assign read_ready = readable[read_sel];
+
+endmodule // dbsm
diff --git a/usrp2/gpmc/gpmc.v b/usrp2/gpmc/gpmc.v
index 88f6809f8..91d02bfec 100644
--- a/usrp2/gpmc/gpmc.v
+++ b/usrp2/gpmc/gpmc.v
@@ -1,4 +1,3 @@
-`timescale 1ns / 1ps
 //////////////////////////////////////////////////////////////////////////////////
 
 module gpmc
@@ -6,6 +5,9 @@ module gpmc
    input EM_CLK, inout [15:0] EM_D, input [10:1] EM_A, input [1:0] EM_NBE,
    input EM_WAIT0, input EM_NCS4, input EM_NCS6, input EM_NWE, input EM_NOE,
 
+   // GPIOs for FIFO signalling
+   output rx_have_data, output tx_have_space,
+   
    // Wishbone signals
    input wb_clk, input wb_rst,
    output reg [10:0] wb_adr_o, output reg [15:0] wb_dat_mosi, input [15:0] wb_dat_miso,
@@ -13,8 +15,8 @@ module gpmc
 
    // RAM Interface signals
    input ram_clk, 
-   input read_en, input read_sel, input [8:0] read_addr, output [31:0] read_data, output read_rdy,
-   input write_en, input write_sel, input [8:0] write_addr, input [31:0] write_data, output write_rdy
+   input read_en, input [8:0] read_addr, output [31:0] read_data, output read_ready, input read_done,
+   input write_en, input [8:0] write_addr, input [31:0] write_data, output write_ready, input write_done
    );
 
    wire 	EM_output_enable = (~EM_NOE & (~EM_NCS4 | ~EM_NCS6));
@@ -25,14 +27,35 @@ module gpmc
 
    // CS4 is RAM_2PORT for high-speed data
    // Writes go into one RAM, reads come from the other
+
+
+   // ////////////////////////////////////////////
+   // Write path
+   wire 	read_sel_in, write_sel_in, clear_in;
+   wire 	write_done_in = ~EM_NCS4 & ~EM_NWE & (EM_A == 10'h3FF);
+   
+   ram_2port_mixed_width buffer_in
+     (.clk16(wb_clk), .en16(~EM_NCS4), .we16(~EM_NWE), .addr16({write_sel_in,EM_A}), .di16(EM_D), .do16(),
+      .clk32(ram_clk), .en32(read_en), .we32(0), .addr32({read_sel_in,read_addr}), .di32(0), .do32(read_data));
+
+   dbsm dbsm_in(.clk(wb_clk), .reset(wb_rst), .clear(clear_in),
+		.read_sel(read_sel_in), .read_ready(read_ready), .read_done(read_done),
+		.write_sel(write_sel_in), .write_ready(tx_have_space), .write_done(write_done_in));
+
+   
+   
+   // ////////////////////////////////////////////
+   // Read path
+   wire 	read_sel_out, write_sel_out, clear_out;
+   wire 	read_done_out = ~EM_NCS4 & ~EM_NOE & (EM_A == 10'h3FF);
    
-   ram_2port_mixed_width buffer_from_host
-     (.clk16(wb_clk), .en16(~EM_NCS4), .we16(~EM_NWE), .addr16({store_pg,EM_A}), .di16(EM_D), .do16(),
-      .clk32(ram_clk), .en32(read_en), .we32(0), .addr32({read_sel,read_addr}), .di32(0), .do32(read_data));
+   ram_2port_mixed_width buffer_out
+     (.clk16(wb_clk), .en16(~EM_NCS4), .we16(0), .addr16({read_sel_out,EM_A}), .di16(0), .do16(EM_D_ram),
+      .clk32(ram_clk), .en32(write_en), .we32(write_en), .addr32({write_sel_out,write_addr}), .di32(write_data), .do32());
 
-   ram_2port_mixed_width buffer_to_host
-     (.clk16(wb_clk), .en16(~EM_NCS4), .we16(0), .addr16({retr_page,EM_A}), .di16(0), .do16(EM_D_ram),
-      .clk32(ram_clk), .en32(write_en), .we32(write_en), .addr32({write_sel,write_addr}), .di32(write_data), .do32());
+   dbsm dbsm_out(.clk(wb_clk), .reset(wb_rst), .clear(clear_out),
+		 .read_sel(read_sel_out), .read_ready(rx_have_data), .read_done(read_done_out),
+		 .write_sel(write_sel_out), .write_ready(write_ready), .write_done(write_done));
 
    // CS6 is Control, Wishbone bus bridge (wb master)
    // Sync version
@@ -67,13 +90,13 @@ module gpmc
    assign wb_cyc_o = wb_stb_o;
 
    always @(posedge wb_clk)
-     if( ~cs_del[0] & (we_del == 2'b10) )
+     if(~cs_del[0] & (we_del == 2'b10) )
        wb_we_o <= 1;
      else if(wb_ack_i)  // Turn off we when done.  Could also use we_del[0], others...
        wb_we_o <= 0;
 
    always @(posedge wb_clk)
-     if( ~cs_del[0] & ((we_del == 2'b10) | (oe_del == 2'b10)))
+     if(~cs_del[0] & ((we_del == 2'b10) | (oe_del == 2'b10)))
        wb_stb_o <= 1;
      else if(wb_ack_i)
        wb_stb_o <= 0;