More extensive overhaul of the PTP period output module to improve resource consumption and parallelize computation

Signed-off-by: Alex Forencich <alex@alexforencich.com>

Author: alexforencich

rtl/ptp_perout.v

@@ -1,6 +1,6 @@
 /*
 
-Copyright (c) 2019 Alex Forencich
+Copyright (c) 2019-2024 Alex Forencich
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -77,15 +77,12 @@ module ptp_perout #
     output wire         output_pulse
 );
 
-localparam [2:0]
+localparam [1:0]
     STATE_IDLE = 3'd0,
-    STATE_UPDATE_RISE_1 = 3'd1,
-    STATE_UPDATE_RISE_2 = 3'd2,
-    STATE_UPDATE_FALL_1 = 3'd3,
-    STATE_UPDATE_FALL_2 = 3'd4,
-    STATE_WAIT_EDGE = 3'd5;
+    STATE_UPDATE_RISE = 3'd1,
+    STATE_UPDATE_FALL = 3'd2;
 
-reg [2:0] state_reg = STATE_IDLE, state_next;
+reg [1:0] state_reg = STATE_IDLE, state_next;
 
 reg [47:0] time_s_reg = 0;
 reg [30:0] time_ns_reg = 0;
@@ -95,9 +92,9 @@ reg [47:0] next_rise_s_reg = 0, next_rise_s_next;
 reg [30:0] next_rise_ns_reg = 0, next_rise_ns_next;
 reg [15:0] next_rise_fns_reg = 0, next_rise_fns_next;
 
-reg [47:0] next_fall_s_reg = 0, next_fall_s_next;
-reg [30:0] next_fall_ns_reg = 0, next_fall_ns_next;
-reg [15:0] next_fall_fns_reg = 0, next_fall_fns_next;
+reg [47:0] next_edge_s_reg = 0, next_edge_s_next;
+reg [30:0] next_edge_ns_reg = 0, next_edge_ns_next;
+reg [15:0] next_edge_fns_reg = 0, next_edge_fns_next;
 
 reg [47:0] start_s_reg = OUT_START_S;
 reg [30:0] start_ns_reg = OUT_START_NS;
@@ -116,6 +113,7 @@ reg [15:0] ts_96_fns_inc_reg = 0, ts_96_fns_inc_next;
 reg [30:0] ts_96_ns_ovf_reg = 0, ts_96_ns_ovf_next;
 reg [15:0] ts_96_fns_ovf_reg = 0, ts_96_fns_ovf_next;
 
+reg restart_reg = 1'b1;
 reg locked_reg = 1'b0, locked_next;
 reg error_reg = 1'b0, error_next;
 reg ffwd_reg = 1'b0, ffwd_next;
@@ -133,9 +131,9 @@ always @* begin
     next_rise_ns_next = next_rise_ns_reg;
     next_rise_fns_next = next_rise_fns_reg;
 
-    next_fall_s_next = next_fall_s_reg;
-    next_fall_ns_next = next_fall_ns_reg;
-    next_fall_fns_next = next_fall_fns_reg;
+    next_edge_s_next = next_edge_s_reg;
+    next_edge_ns_next = next_edge_ns_reg;
+    next_edge_fns_next = next_edge_fns_reg;
 
     ts_96_ns_inc_next = ts_96_ns_inc_reg;
     ts_96_fns_inc_next = ts_96_fns_inc_reg;
@@ -149,97 +147,97 @@ always @* begin
     level_next = level_reg;
     output_next = output_reg;
 
-    if (input_start_valid || input_period_valid || input_ts_step) begin
-        locked_next = 1'b0;
-        level_next = 1'b0;
-        output_next = 1'b0;
-        error_next = input_ts_step;
-        state_next = STATE_IDLE;
-    end else begin
-        case (state_reg)
-            STATE_IDLE: begin
-                // set next rise to start time
-                next_rise_s_next = start_s_reg;
-                next_rise_ns_next = start_ns_reg;
-                if (FNS_ENABLE) begin
-                    next_rise_fns_next = start_fns_reg;
-                end
-                locked_next = 1'b0;
-                ffwd_next = 1'b1;
-                output_next = 1'b0;
-                level_next = 1'b0;
-                state_next = STATE_WAIT_EDGE;
-            end
-            STATE_UPDATE_RISE_1: begin
-                // set next rise time to next rise time plus period
+    case (state_reg)
+        STATE_IDLE: begin
+            if (ffwd_reg || level_reg) begin
+                // fast forward or falling edge, set up for next rising edge
+                // set next rise time to previous rise time plus period
                 {ts_96_ns_inc_next, ts_96_fns_inc_next} = {next_rise_ns_reg, next_rise_fns_reg} + {period_ns_reg, period_fns_reg};
                 {ts_96_ns_ovf_next, ts_96_fns_ovf_next} = {next_rise_ns_reg, next_rise_fns_reg} + {period_ns_reg, period_fns_reg} - {31'd1_000_000_000, 16'd0};
-                state_next = STATE_UPDATE_RISE_2;
-            end
-            STATE_UPDATE_RISE_2: begin
-                if (!ts_96_ns_ovf_reg[30]) begin
-                    // if the overflow lookahead did not borrow, one second has elapsed
-                    next_rise_s_next = next_rise_s_reg + period_s_reg + 1;
-                    next_rise_ns_next = ts_96_ns_ovf_reg;
-                    next_rise_fns_next = ts_96_fns_ovf_reg;
-                end else begin
-                    // no increment seconds field
-                    next_rise_s_next = next_rise_s_reg + period_s_reg;
-                    next_rise_ns_next = ts_96_ns_inc_reg;
-                    next_rise_fns_next = ts_96_fns_inc_reg;
-                end
-                state_next = STATE_WAIT_EDGE;
-            end
-            STATE_UPDATE_FALL_1: begin
-                // set next fall time to next rise time plus width
+            end else begin
+                // rising edge; set up for next falling edge
+                // set next fall time to previous rise time plus width
                 {ts_96_ns_inc_next, ts_96_fns_inc_next} = {next_rise_ns_reg, next_rise_fns_reg} + {width_ns_reg, width_fns_reg};
                 {ts_96_ns_ovf_next, ts_96_fns_ovf_next} = {next_rise_ns_reg, next_rise_fns_reg} + {width_ns_reg, width_fns_reg} - {31'd1_000_000_000, 16'd0};
-                state_next = STATE_UPDATE_FALL_2;
             end
-            STATE_UPDATE_FALL_2: begin
-                if (!ts_96_ns_ovf_reg[30]) begin
-                    // if the overflow lookahead did not borrow, one second has elapsed
-                    next_fall_s_next = next_rise_s_reg + width_s_reg + 1;
-                    next_fall_ns_next = ts_96_ns_ovf_reg;
-                    next_fall_fns_next = ts_96_fns_ovf_reg;
-                end else begin
-                    // no increment seconds field
-                    next_fall_s_next = next_rise_s_reg + width_s_reg;
-                    next_fall_ns_next = ts_96_ns_inc_reg;
-                    next_fall_fns_next = ts_96_fns_inc_reg;
-                end
-                state_next = STATE_WAIT_EDGE;
-            end
-            STATE_WAIT_EDGE: begin
-                if ((!level_reg || ffwd_reg) && ((time_s_reg > next_rise_s_reg) || (time_s_reg == next_rise_s_reg && {time_ns_reg, time_fns_reg} > {next_rise_ns_reg, next_rise_fns_reg}))) begin
-                    // rising edge
-                    if (ffwd_reg) begin
-                        output_next = 1'b0;
-                        level_next = 1'b0;
-                        state_next = STATE_UPDATE_RISE_1;
-                    end else begin
-                        locked_next = 1'b1;
-                        error_next = 1'b0;
-                        output_next = enable;
-                        level_next = 1'b1;
-                        state_next = STATE_UPDATE_FALL_1;
-                    end
-                end else if (level_reg && ((time_s_reg > next_fall_s_reg) || (time_s_reg == next_fall_s_reg && {time_ns_reg, time_fns_reg} > {next_fall_ns_reg, next_fall_fns_reg}))) begin
-                    // falling edge
+
+            // wait for edge
+            if ((time_s_reg > next_edge_s_reg) || (time_s_reg == next_edge_s_reg && {time_ns_reg, time_fns_reg} > {next_edge_ns_reg, next_edge_fns_reg})) begin
+                if (ffwd_reg || level_reg) begin
+                    // fast forward or falling edge, set up for next rising edge
                     output_next = 1'b0;
                     level_next = 1'b0;
-                    state_next = STATE_UPDATE_RISE_1;
+                    state_next = STATE_UPDATE_RISE;
                 end else begin
-                    ffwd_next = 1'b0;
-                    state_next = STATE_WAIT_EDGE;
+                    // rising edge; set up for next falling edge
+                    locked_next = 1'b1;
+                    error_next = 1'b0;
+                    output_next = enable;
+                    level_next = 1'b1;
+                    state_next = STATE_UPDATE_FALL;
                 end
+            end else begin
+                ffwd_next = 1'b0;
+                state_next = STATE_IDLE;
             end
-        endcase
+        end
+        STATE_UPDATE_RISE: begin
+            if (!ts_96_ns_ovf_reg[30]) begin
+                // if the overflow lookahead did not borrow, one second has elapsed
+                next_edge_s_next = next_rise_s_reg + period_s_reg + 1;
+                next_edge_ns_next = ts_96_ns_ovf_reg;
+                next_edge_fns_next = ts_96_fns_ovf_reg;
+            end else begin
+                // no increment seconds field
+                next_edge_s_next = next_rise_s_reg + period_s_reg;
+                next_edge_ns_next = ts_96_ns_inc_reg;
+                next_edge_fns_next = ts_96_fns_inc_reg;
+            end
+            next_rise_s_next = next_edge_s_next;
+            next_rise_ns_next = next_edge_ns_next;
+            next_rise_fns_next = next_edge_fns_next;
+            state_next = STATE_IDLE;
+        end
+        STATE_UPDATE_FALL: begin
+            if (!ts_96_ns_ovf_reg[30]) begin
+                // if the overflow lookahead did not borrow, one second has elapsed
+                next_edge_s_next = next_rise_s_reg + width_s_reg + 1;
+                next_edge_ns_next = ts_96_ns_ovf_reg;
+                next_edge_fns_next = ts_96_fns_ovf_reg;
+            end else begin
+                // no increment seconds field
+                next_edge_s_next = next_rise_s_reg + width_s_reg;
+                next_edge_ns_next = ts_96_ns_inc_reg;
+                next_edge_fns_next = ts_96_fns_inc_reg;
+            end
+            state_next = STATE_IDLE;
+        end
+    endcase
+
+    if (restart_reg || input_ts_step) begin
+        // set next rise and next edge to start time
+        next_rise_s_next = start_s_reg;
+        next_rise_ns_next = start_ns_reg;
+        if (FNS_ENABLE) begin
+            next_rise_fns_next = start_fns_reg;
+        end
+        next_edge_s_next = start_s_reg;
+        next_edge_ns_next = start_ns_reg;
+        if (FNS_ENABLE) begin
+            next_edge_fns_next = start_fns_reg;
+        end
+        locked_next = 1'b0;
+        ffwd_next = 1'b1;
+        output_next = 1'b0;
+        level_next = 1'b0;
+        error_next = input_ts_step;
+        state_next = STATE_IDLE;
     end
 end
 
 always @(posedge clk) begin
     state_reg <= state_next;
+    restart_reg <= 1'b0;
 
     time_s_reg <= input_ts_96[95:48];
     time_ns_reg <= input_ts_96[45:16];
@@ -253,6 +251,7 @@ always @(posedge clk) begin
         if (FNS_ENABLE) begin
             start_fns_reg <= input_start[15:0];
         end
+        restart_reg <= 1'b1;
     end
 
     if (input_period_valid) begin
@@ -261,6 +260,7 @@ always @(posedge clk) begin
         if (FNS_ENABLE) begin
             period_fns_reg <= input_period[15:0];
         end
+        restart_reg <= 1'b1;
     end
 
     if (input_width_valid) begin
@@ -277,10 +277,10 @@ always @(posedge clk) begin
         next_rise_fns_reg <= next_rise_fns_next;
     end
 
-    next_fall_s_reg <= next_fall_s_next;
-    next_fall_ns_reg <= next_fall_ns_next;
+    next_edge_s_reg <= next_edge_s_next;
+    next_edge_ns_reg <= next_edge_ns_next;
     if (FNS_ENABLE) begin
-        next_fall_fns_reg <= next_fall_fns_next;
+        next_edge_fns_reg <= next_edge_fns_next;
     end
 
     ts_96_ns_inc_reg <= ts_96_ns_inc_next;
@@ -314,6 +314,7 @@ always @(posedge clk) begin
         width_ns_reg <= OUT_WIDTH_NS;
         width_fns_reg <= OUT_WIDTH_FNS;
 
+        restart_reg <= 1'b1;
         locked_reg <= 1'b0;
         error_reg <= 1'b0;
         output_reg <= 1'b0;