From 8953fe2731eb24845a4bebd10695f92a98b383b5 Mon Sep 17 00:00:00 2001
From: Peter Lawrence <majbthrd@gmail.com>
Date: Sun, 13 Dec 2020 15:46:00 -0600
Subject: [PATCH 1/2] remedy endless feedback loop

---
 src/dm_mem.sv | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/src/dm_mem.sv b/src/dm_mem.sv
index 178259f..5e2a796 100755
--- a/src/dm_mem.sv
+++ b/src/dm_mem.sv
@@ -132,18 +132,41 @@ module dm_mem #(
   typedef enum logic [1:0] { Idle, Go, Resume, CmdExecuting } state_e;
   state_e state_d, state_q;
 
+  // hart state decode
+  always_comb begin : p_state_decode
+    go               = 1'b0;
+    resume           = 1'b0;
+    cmdbusy_o        = 1'b1;
+
+    unique case (state_q)
+      Idle: begin
+        cmdbusy_o = 1'b0;
+        end
+      Go: begin
+        // we are already busy here since we scheduled the execution of a program
+        cmdbusy_o = 1'b1;
+        go        = 1'b1;
+      end
+      Resume: begin
+        cmdbusy_o = 1'b1;
+        resume = 1'b1;
+      end
+      CmdExecuting: begin
+        cmdbusy_o = 1'b1;
+        go        = 1'b0;
+      end
+      default: ;
+    endcase
+  end
+  
   // hart ctrl queue
   always_comb begin : p_hart_ctrl_queue
     cmderror_valid_o = 1'b0;
     cmderror_o       = dm::CmdErrNone;
     state_d          = state_q;
-    go               = 1'b0;
-    resume           = 1'b0;
-    cmdbusy_o        = 1'b1;
 
     unique case (state_q)
       Idle: begin
-        cmdbusy_o = 1'b0;
         if (cmd_valid_i && halted_q_aligned[hartsel] && !unsupported_command) begin
           // give the go signal
           state_d = Go;
@@ -161,9 +184,6 @@ module dm_mem #(
       end
 
       Go: begin
-        // we are already busy here since we scheduled the execution of a program
-        cmdbusy_o = 1'b1;
-        go        = 1'b1;
         // the thread is now executing the command, track its state
         if (going) begin
             state_d = CmdExecuting;
@@ -171,16 +191,12 @@ module dm_mem #(
       end
 
       Resume: begin
-        cmdbusy_o = 1'b1;
-        resume = 1'b1;
         if (resuming_q_aligned[hartsel]) begin
           state_d = Idle;
         end
       end
 
       CmdExecuting: begin
-        cmdbusy_o = 1'b1;
-        go        = 1'b0;
         // wait until the hart has halted again
         if (halted_aligned[hartsel]) begin
           state_d = Idle;

From 4a3b7862056dbdeeabaedfae29de1c478ab199ab Mon Sep 17 00:00:00 2001
From: Peter Lawrence <majbthrd@gmail.com>
Date: Sun, 28 Feb 2021 16:38:03 -0600
Subject: [PATCH 2/2] alternate remedy for endless feedback loop

---
 src/dm_mem.sv | 46 ++++++++++++++++++----------------------------
 1 file changed, 18 insertions(+), 28 deletions(-)
 mode change 100755 => 100644 src/dm_mem.sv

diff --git a/src/dm_mem.sv b/src/dm_mem.sv
old mode 100755
new mode 100644
index 5e2a796..b83de45
--- a/src/dm_mem.sv
+++ b/src/dm_mem.sv
@@ -132,33 +132,6 @@ module dm_mem #(
   typedef enum logic [1:0] { Idle, Go, Resume, CmdExecuting } state_e;
   state_e state_d, state_q;
 
-  // hart state decode
-  always_comb begin : p_state_decode
-    go               = 1'b0;
-    resume           = 1'b0;
-    cmdbusy_o        = 1'b1;
-
-    unique case (state_q)
-      Idle: begin
-        cmdbusy_o = 1'b0;
-        end
-      Go: begin
-        // we are already busy here since we scheduled the execution of a program
-        cmdbusy_o = 1'b1;
-        go        = 1'b1;
-      end
-      Resume: begin
-        cmdbusy_o = 1'b1;
-        resume = 1'b1;
-      end
-      CmdExecuting: begin
-        cmdbusy_o = 1'b1;
-        go        = 1'b0;
-      end
-      default: ;
-    endcase
-  end
-  
   // hart ctrl queue
   always_comb begin : p_hart_ctrl_queue
     cmderror_valid_o = 1'b0;
@@ -167,6 +140,9 @@ module dm_mem #(
 
     unique case (state_q)
       Idle: begin
+        cmdbusy_o = 1'b0;
+        go        = 1'b0;
+        resume    = 1'b0;
         if (cmd_valid_i && halted_q_aligned[hartsel] && !unsupported_command) begin
           // give the go signal
           state_d = Go;
@@ -184,6 +160,10 @@ module dm_mem #(
       end
 
       Go: begin
+        // we are already busy here since we scheduled the execution of a program
+        cmdbusy_o = 1'b1;
+        go        = 1'b1;
+        resume    = 1'b0;
         // the thread is now executing the command, track its state
         if (going) begin
             state_d = CmdExecuting;
@@ -191,19 +171,29 @@ module dm_mem #(
       end
 
       Resume: begin
+        cmdbusy_o = 1'b1;
+        go        = 1'b0;
+        resume    = 1'b1;
         if (resuming_q_aligned[hartsel]) begin
           state_d = Idle;
         end
       end
 
       CmdExecuting: begin
+        cmdbusy_o = 1'b1;
+        go        = 1'b0;
+        resume    = 1'b0;
         // wait until the hart has halted again
         if (halted_aligned[hartsel]) begin
           state_d = Idle;
         end
       end
 
-      default: ;
+      default: begin
+        cmdbusy_o = 1'b1;
+        go        = 1'b0;
+        resume    = 1'b0;
+      end
     endcase
 
     // only signal once that cmd is unsupported so that we can clear cmderr