From 41b99a093408b9ed2742d7debbdae4a144d4f975 Mon Sep 17 00:00:00 2001
From: Slawomir Siluk <slaweksiluk@gazeta.pl>
Date: Mon, 23 Nov 2020 09:43:46 +0100
Subject: [PATCH] push avalon master read req msg one cycle earlier (fix #695)
 (#696)
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Co-authored-by: Sławomir Siluk <slawomir.siluk@enamorint.com>
---
 .../src/avalon_master.vhd                     |  4 +-
 .../test/avalon_tb.vhd                        | 75 +++++++++++++++++++
 2 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 vunit/vhdl/verification_components/test/avalon_tb.vhd

diff --git a/vunit/vhdl/verification_components/src/avalon_master.vhd b/vunit/vhdl/verification_components/src/avalon_master.vhd
index f15d6be12..2e29efbb1 100644
--- a/vunit/vhdl/verification_components/src/avalon_master.vhd
+++ b/vunit/vhdl/verification_components/src/avalon_master.vhd
@@ -78,9 +78,9 @@ begin
           address <= pop_std_ulogic_vector(request_msg);
           byteenable(byteenable'range) <= (others => '1');
           read <= '1';
+          push(acknowledge_queue, request_msg);
           wait until rising_edge(clk) and waitrequest = '0';
           read <= '0';
-          push(acknowledge_queue, request_msg);
 
         elsif msg_type = bus_burst_read_msg then
           while rnd.Uniform(0.0, 1.0) > read_high_probability loop
@@ -92,9 +92,9 @@ begin
           burstcount <= std_logic_vector(to_unsigned(burst, burstcount'length));
           byteenable(byteenable'range) <= (others => '1');
           read <= '1';
+          push(burst_acknowledge_queue, request_msg);
           wait until rising_edge(clk) and waitrequest = '0';
           read <= '0';
-          push(burst_acknowledge_queue, request_msg);
           push(burstlen_queue, burst);
 
         elsif msg_type = bus_write_msg then
diff --git a/vunit/vhdl/verification_components/test/avalon_tb.vhd b/vunit/vhdl/verification_components/test/avalon_tb.vhd
new file mode 100644
index 000000000..fa7142e03
--- /dev/null
+++ b/vunit/vhdl/verification_components/test/avalon_tb.vhd
@@ -0,0 +1,75 @@
+-- This Source Code Form is subject to the terms of the Mozilla Public
+-- License, v. 2.0. If a copy of the MPL was not distributed with this file,
+-- You can obtain one at http://mozilla.org/MPL/2.0/.
+--
+-- Copyright (c) 2014-2020, Lars Asplund lars.anders.asplund@gmail.com
+
+-- This test bench is to reproduce issue with pop form empty queue in modelsim.
+library ieee;
+use ieee.std_logic_1164.all;
+
+library vunit_lib;
+context vunit_lib.vunit_context;
+context vunit_lib.vc_context;
+
+entity avalon_tb is
+    generic (runner_cfg : string);
+end avalon_tb;
+
+architecture testbench of avalon_tb is
+
+    -- Avalon-MM Slave --
+    signal av_address : std_logic_vector(31 downto 0);
+    signal av_write : std_logic := '0';
+    signal av_writedata : std_logic_vector(31 downto 0) := (others=> '0');
+    signal av_read : std_logic := '0';
+    signal av_readdata : std_logic_vector(31 downto 0) := (others=> '0');
+    signal av_byteenable : std_logic_vector(3 downto 0);
+    signal av_burstcount : std_logic_vector(3 downto 0);
+
+    constant avalon_bus : bus_master_t := new_bus(data_length => 32, address_length => av_address'length);
+
+    signal clk : std_logic := '0';
+
+    constant CLK_period : time := 20 ns;
+
+begin
+    avalon_master : entity vunit_lib.avalon_master
+    generic map (
+        bus_handle => avalon_bus,
+        use_readdatavalid => false,
+        fixed_read_latency => 0
+    )
+    port map (
+      clk => clk,
+      address => av_address,
+      byteenable => av_byteenable,
+      burstcount => av_burstcount,
+      write => av_write,
+      writedata => av_writedata,
+      read => av_read,
+      readdata => av_readdata,
+      readdatavalid => '0',
+      waitrequest => '0'
+    );
+
+    -- Clock process definitions
+    CLK_process: process
+    begin
+        clk <= '0';
+        wait for CLK_period/2;
+        clk <= '1';
+        wait for CLK_period/2;
+    end process;
+
+    tests: process
+    begin
+        test_runner_setup(runner, runner_cfg);
+
+        wait for CLK_period*2;
+
+        check_bus(net, avalon_bus, 0, (0 to 31 => '0'));
+
+        test_runner_cleanup(runner);
+    end process;
+end;