Fix PPC/NPC tracking of debug unit

controller.sv

@@ -299,7 +299,7 @@ module riscv_controller
 
           // take care of debug
           // branch conditional will be handled in next state
-          if(trap_hit_i && jump_in_dec_i != `BRANCH_COND)
+          if (trap_hit_i)
           begin
             // halt pipeline immediately
             halt_if_o = 1'b1;

debug_unit.sv

@@ -59,15 +59,18 @@ module riscv_debug_unit
   input  logic [31:0] regfile_rdata_i,
 
   // Signals for PPC & NPC register
-  input logic  [31:0] curr_pc_if_i,
-  input logic  [31:0] curr_pc_id_i,
-  input logic  [31:0] branch_pc_i,
+  input  logic [31:0] curr_pc_if_i,
+  input  logic [31:0] curr_pc_id_i,
+  input  logic [31:0] branch_pc_i,
+
+  input  logic  [1:0] jump_in_ex_i,
+  input  logic        branch_taken_i,
 
   output logic [31:0] npc_o,
   output logic        set_npc_o
-
 );
 
+
   // registers for debug control
   logic [1:0] DSR_DP,  DSR_DN;  // Debug Stop Register: IIE, INTE
   logic [1:0] DMR1_DP, DMR1_DN; // only single step trace and branch trace bits
@@ -75,9 +78,14 @@ module riscv_debug_unit
   // BP control FSM
   enum logic [2:0] {Idle, Trap, DebugStall, StallCore} BP_State_SN, BP_State_SP;
 
+  // ppc/npc tracking
+  enum logic [1:0] {IFID, IFEX, IDEX} pc_tracking_fsm_cs, pc_tracking_fsm_ns;
+  logic [31:0] ppc_int, npc_int;
+
   // ack to debug interface
   assign dbginf_ack_o = dbginf_strobe_i && ((BP_State_SP == StallCore) || (dbginf_addr_i[15:11] == 5'b00110));
 
+
   always_comb
   begin
     BP_State_SN  = BP_State_SP;
@@ -155,11 +163,11 @@ module riscv_debug_unit
           11'd0: begin // NPC
             set_npc_o = dbginf_we_i;
 
-            dbginf_data_o = curr_pc_if_i;
+            dbginf_data_o = npc_int;
           end
 
           11'd1: begin // PPC
-            dbginf_data_o = curr_pc_id_i;
+            dbginf_data_o = ppc_int;
           end
 
           11'd16: begin // SP_DMR1
@@ -207,17 +215,66 @@ module riscv_debug_unit
     end
   end
 
+
+  always_comb
+  begin
+    pc_tracking_fsm_ns = pc_tracking_fsm_cs;
+
+    ppc_int = curr_pc_id_i;
+    npc_int = curr_pc_if_i;
+
+    // PPC/NPC mux
+    unique case (pc_tracking_fsm_cs)
+      IFID: begin
+        ppc_int = curr_pc_id_i;
+        npc_int = curr_pc_if_i;
+      end
+
+      IFEX: begin
+        ppc_int = branch_pc_i;
+        npc_int = curr_pc_if_i;
+      end
+
+      IDEX: begin
+        ppc_int = branch_pc_i;
+        npc_int = curr_pc_id_i;
+
+        if (set_npc_o)
+          pc_tracking_fsm_ns = IFEX;
+      end
+
+      default: begin
+        pc_tracking_fsm_ns = IFID;
+      end
+    endcase
+
+    // set state if trap is encountered
+    if (stall_core_o && (BP_State_SP != StallCore)) begin
+      pc_tracking_fsm_ns = IFID;
+
+      if (jump_in_ex_i == `BRANCH_COND) begin
+        if (branch_taken_i)
+          pc_tracking_fsm_ns = IFEX;
+        else
+          pc_tracking_fsm_ns = IDEX;
+      end
+    end
+  end
+
+
   always_ff@(posedge clk, negedge rst_n)
   begin
-    if (~rst_n) begin
-      DMR1_DP     <= 2'b0;
-      DSR_DP      <= 'b0;
-      BP_State_SP <= Idle;
+    if (rst_n == 1'b0) begin
+      DMR1_DP            <= 2'b0;
+      DSR_DP             <= 'b0;
+      BP_State_SP        <= Idle;
+      pc_tracking_fsm_cs <= IFID;
     end
     else begin
-      DMR1_DP     <= DMR1_DN;
-      DSR_DP      <= DSR_DN;
-      BP_State_SP <= BP_State_SN;
+      DMR1_DP            <= DMR1_DN;
+      DSR_DP             <= DSR_DN;
+      BP_State_SP        <= BP_State_SN;
+      pc_tracking_fsm_cs <= pc_tracking_fsm_ns;
     end
   end
 

riscv_core.sv

@@ -646,6 +646,10 @@ module riscv_core
     .curr_pc_if_i    ( current_pc_if   ), // from IF stage
     .curr_pc_id_i    ( current_pc_id   ), // from IF stage
     .branch_pc_i     ( branch_pc_ex    ), // PC of last executed branch (in EX stage)
+
+    .jump_in_ex_i    ( jump_in_ex      ),
+    .branch_taken_i  ( branch_decision ),
+
     .npc_o           ( dbg_npc         ), // PC from debug unit
     .set_npc_o       ( dbg_set_npc     )  // set PC to new value
   );