From ee143d80d65708c578c069d222cdddfb68c04110 Mon Sep 17 00:00:00 2001
From: Laszlo Nagy <laszlo.nagy@analog.com>
Date: Thu, 3 Sep 2020 15:21:47 +0100
Subject: [PATCH] jesd204_rx/jesd204_rx_ctrl: Fix de-glitch mechanism

The previous implementation of the de-glitch only delayed the assertion
of the SYNC phase by 64 clock cycles with the DEGLITCH state but if meanwhile
one of the lanes got into a bad state cgs_ready de-asserted the state machine
continued to go SYNCHRONIZED (DATA) state.
This change extends the required number of consecutive cycles while all lanes
must stay in data phase before moving the link to SYNCHRONIZED state from 8 to 256;
This increases the reliability of link bring-up without needing extra
link restarts from software side.
---
 library/jesd204/jesd204_rx/jesd204_rx_ctrl.v | 59 +++++++-------------
 1 file changed, 20 insertions(+), 39 deletions(-)

diff --git a/library/jesd204/jesd204_rx/jesd204_rx_ctrl.v b/library/jesd204/jesd204_rx/jesd204_rx_ctrl.v
index de233112f..9ad73ea50 100644
--- a/library/jesd204/jesd204_rx/jesd204_rx_ctrl.v
+++ b/library/jesd204/jesd204_rx/jesd204_rx_ctrl.v
@@ -68,19 +68,13 @@ module jesd204_rx_ctrl #(
   output [NUM_LINKS-1:0] sync,
   output reg latency_monitor_reset,
 
-  output reg [1:0] status_state
+  output [1:0] status_state
 );
 
-localparam STATUS_STATE_RESET = 2'h1;
-localparam STATUS_STATE_WAIT_FOR_PHY = 2'h1;
-localparam STATUS_STATE_CGS = 2'h2;
-localparam STATUS_STATE_SYNCHRONIZED = 2'h3;
-
 localparam STATE_RESET = 0;
 localparam STATE_WAIT_FOR_PHY = 1;
 localparam STATE_CGS = 2;
-localparam STATE_DEGLITCH = 3;
-localparam STATE_SYNCHRONIZED = 4;
+localparam STATE_SYNCHRONIZED = 3;
 
 reg [2:0] state = STATE_RESET;
 reg [2:0] next_state = STATE_RESET;
@@ -91,24 +85,17 @@ reg [NUM_LINKS-1:0] sync_n = {NUM_LINKS{1'b1}};
 reg en_align = 1'b0;
 reg state_good = 1'b0;
 
-reg [2:0] good_counter = 'h00;
-reg [9:0] deglitch_counter = 'h3ff;
+reg [7:0] good_counter = 'h00;
+
+wire [7:0] good_cnt_limit_s;
+wire       good_cnt_limit_reached_s;
 
 assign cgs_reset = cgs_rst;
 assign ifs_reset = ifs_rst;
 assign sync = sync_n;
 assign phy_en_char_align = en_align;
 
-always @(posedge clk) begin
-  case (state)
-  STATE_RESET: status_state <= STATUS_STATE_RESET;
-  STATE_WAIT_FOR_PHY: status_state <= STATUS_STATE_WAIT_FOR_PHY;
-  STATE_CGS: status_state <= STATUS_STATE_CGS;
-  STATE_DEGLITCH: status_state <= STATUS_STATE_CGS;
-  STATE_SYNCHRONIZED: status_state <= STATUS_STATE_SYNCHRONIZED;
-  default: status_state <= STATUS_STATE_RESET;
-  endcase
-end
+assign status_state = state;
 
 always @(posedge clk) begin
   case (state)
@@ -132,33 +119,28 @@ always @(posedge clk) begin
   endcase
 end
 
-always @(posedge clk) begin
-  case (state)
-  STATE_DEGLITCH: begin
-    if (deglitch_counter != 'h00) begin
-      deglitch_counter <= deglitch_counter - 1'b1;
-    end
-  end
-  default: begin
-    deglitch_counter <= 'h3f;
-  end
-  endcase
-end
-
 always @(*) begin
   case (state)
   STATE_RESET: state_good <= 1'b1;
   STATE_WAIT_FOR_PHY: state_good <= phy_ready;
   STATE_CGS: state_good <= &(cgs_ready | cfg_lanes_disable);
-  STATE_DEGLITCH: state_good <= deglitch_counter == 'h00;
   STATE_SYNCHRONIZED: state_good <= 1'b1;
   default: state_good <= 1'b0;
   endcase
 end
 
+assign good_cnt_limit_s = (state == STATE_CGS) ? 'hff : 'h7;
+assign good_cnt_limit_reached_s = good_counter == good_cnt_limit_s;
+
 always @(posedge clk) begin
-  if (state_good == 1'b1) begin
-    good_counter <= good_counter + 1'b1;
+  if (reset) begin
+    good_counter <= 'h00;
+  end else if (state_good == 1'b1) begin
+    if (good_cnt_limit_reached_s) begin
+      good_counter <= 'h00;
+    end else begin
+      good_counter <= good_counter + 1'b1;
+    end
   end else begin
     good_counter <= 'h00;
   end
@@ -175,8 +157,7 @@ always @(*) begin
   case (state)
   STATE_RESET: next_state <= STATE_WAIT_FOR_PHY;
   STATE_WAIT_FOR_PHY: next_state <= STATE_CGS;
-  STATE_CGS: next_state <= STATE_DEGLITCH;
-  STATE_DEGLITCH: next_state <= STATE_SYNCHRONIZED;
+  STATE_CGS: next_state <= STATE_SYNCHRONIZED;
   default: next_state <= state_good ? state : STATE_RESET;
   endcase
 end
@@ -185,7 +166,7 @@ always @(posedge clk) begin
   if (reset == 1'b1) begin
     state <= STATE_RESET;
   end else begin
-    if (good_counter == 'h7) begin
+    if (good_cnt_limit_reached_s) begin
       state <= next_state;
     end
   end