From cabff0295de36f105a929ba66e7445da041a9a40 Mon Sep 17 00:00:00 2001
From: Daniel Jobson <jobson@tillitis.se>
Date: Fri, 22 Nov 2024 13:40:43 +0100
Subject: [PATCH] tb: make timer core testbench selftesting

- Compare against an expected result and count errors
- Exit with the right error code
- Clean up the output
---
 .../core/timer/tb/tb_timer_core.v             | 75 ++++++++++++++++---
 1 file changed, 63 insertions(+), 12 deletions(-)

diff --git a/hw/application_fpga/core/timer/tb/tb_timer_core.v b/hw/application_fpga/core/timer/tb/tb_timer_core.v
index cdb65c80..44d05cea 100644
--- a/hw/application_fpga/core/timer/tb/tb_timer_core.v
+++ b/hw/application_fpga/core/timer/tb/tb_timer_core.v
@@ -122,14 +122,18 @@ module tb_timer_core ();
   //----------------------------------------------------------------
   task reset_dut;
     begin
+      if (tb_monitor) begin
       $display("--- DUT before reset:");
-      dump_dut_state();
+        dump_dut_state();
+      end
       $display("--- Toggling reset.");
       tb_reset_n = 0;
       #(2 * CLK_PERIOD);
       tb_reset_n = 1;
+      if (tb_monitor) begin 
       $display("--- DUT after reset:");
-      dump_dut_state();
+        dump_dut_state();
+      end
     end
   endtask  // reset_dut
 
@@ -182,28 +186,71 @@ module tb_timer_core ();
 
   //----------------------------------------------------------------
   // test1()
+  //
+  // Set prescaler and timer and count until the timer returns expired.
+  // Check so the clock cycles passed adds up to timer * prescaler + 1.
   //----------------------------------------------------------------
   task test1;
-    begin
+    begin : test1
+      reg [31 : 0] test1_cycle_ctr_start;
+      reg [31 : 0] test1_counted_num_cycles;
+      reg [31 : 0] test1_expected_num_cycles;
+
       tc_ctr = tc_ctr + 1;
-      tb_monitor = 1;
 
-      $display("--- test1 started.");
-      dump_dut_state();
+      $display("");
+      $display("--- test1: Run timer to set value started.");
+      $display("--- test1: prescaler: 6, timer: 9. Should take 6*9 + 1 = 55 cycles..");
+
       tb_prescaler_init = 32'h6;
       tb_timer_init     = 32'h9;
+      test1_expected_num_cycles = tb_prescaler_init * tb_timer_init + 1;
+
       #(CLK_PERIOD);
       tb_start = 1'h1;
+      test1_cycle_ctr_start = cycle_ctr;
       #(CLK_PERIOD);
       tb_start = 1'h0;
-      wait_done();
       #(CLK_PERIOD);
-      tb_monitor = 0;
-      $display("--- test1 completed.");
+
+      while (tb_running) begin
+        #(CLK_PERIOD);
+      end
+      test1_counted_num_cycles = cycle_ctr - test1_cycle_ctr_start;
+
+
+      if (test1_counted_num_cycles == test1_expected_num_cycles) begin
+        $display("--- test1: Correct number of cycles counted: %0d", test1_counted_num_cycles);
+      end
+      else begin
+        $display("--- test1: Error, expected %0d cycles, counted cycles: %0d",
+                 test1_expected_num_cycles, test1_counted_num_cycles);
+        error_ctr = error_ctr + 1;
+      end
+
+
+
+      $display("--- test1: Completed.");
       $display("");
     end
   endtask  // test1
 
+  //----------------------------------------------------------------
+  // exit_with_error_code()
+  //
+  // Exit with the right error code
+  //----------------------------------------------------------------
+  task exit_with_error_code;
+    begin
+      if (error_ctr == 0) begin
+        $finish(0);
+      end
+      else begin
+        $fatal(1);
+      end
+    end
+  endtask  // exit_with_error_code
+
 
   //----------------------------------------------------------------
   // timer_core_test
@@ -211,7 +258,9 @@ module tb_timer_core ();
   // Test vectors from:
   //----------------------------------------------------------------
   initial begin : timer_core_test
-    $display("--- Simulation of timer core started.");
+    $display("");
+    $display("   -= Simulation of timer core started =-");
+    $display("     ===============================");
     $display("");
 
     init_sim();
@@ -220,8 +269,10 @@ module tb_timer_core ();
     test1();
 
     $display("");
-    $display("--- Simulation of timer core completed.");
-    $finish;
+    $display("   -= Simulation of timer core completed =-");
+    $display("     ===============================");
+    $display("");
+    exit_with_error_code();
   end  // timer_core_test
 endmodule  // tb_timer_core