hdl: [bugfix] fix message queue area selection during wb read cycles

This is a partial revert of fdc2c469, where the strobe signal was also used to avoid double writes/reads (because the cycle signal lasts two cycles). In practice this introduced a bug when doing a read cycle, where the data is lost because it becomes available after the strobe is deasserted. The solution is to stop looking at the strobe for area selection, but keep it for defining the read/write cycle.

hdl: [bugfix] fix message queue area selection during wb read cycles
This is a partial revert of fdc2c469, where the strobe signal was also used to avoid double writes/reads (because the cycle signal lasts two cycles). In practice this introduced a bug when doing a read cycle, where the data is lost because it becomes available after the strobe is deasserted. The solution is to stop looking at the strobe for area selection, but keep it for defining the read/write cycle.
4f4b361d · Dimitris Lampridis · 1c12b54e · 4f4b361d
Commit 4f4b361d authored Jan 06, 2023 by Dimitris Lampridis
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mt_mqueue_wishbone_slave.vhd hdl/rtl/mqueue/mt_mqueue_wishbone_slave.vhd +4 -6

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--- a/hdl/rtl/mqueue/mt_mqueue_wishbone_slave.vhd
+++ b/hdl/rtl/mqueue/mt_mqueue_wishbone_slave.vhd
@@ -64,17 +64,15 @@ architecture arch of mt_mqueue_wishbone_slave is

  signal wb_write : std_logic;
  signal wb_read  : std_logic;
-  signal wb_en    : std_logic;

 begin  -- arch

-  wb_en        <= slave_i.cyc and slave_i.stb;
  slot_num     <= slave_i.adr(18 downto 16);
-  in_area_sel  <= wb_en when slave_i.adr(15) = '0' else '0';
-  out_area_sel <= wb_en when slave_i.adr(15) = '1' else '0';
+  in_area_sel  <= slave_i.cyc when slave_i.adr(15) = '0' else '0';
+  out_area_sel <= slave_i.cyc when slave_i.adr(15) = '1' else '0';

-  wb_write <= wb_en and slave_i.we;
-  wb_read  <= wb_en and not slave_i.we;
+  wb_write <= slave_i.cyc and slave_i.stb and slave_i.we;
+  wb_read  <= slave_i.cyc and slave_i.stb and not slave_i.we;

  gen_slots : for i in 0 to g_CONFIG.slot_count-1 generate
    incoming_o(i) <=