Fix DPC write and DCSR Cause

config/shared/debug.vh

@@ -143,6 +143,14 @@
 `define AAR64  3
 `define AAR128 4
 
+// debug mode cause
+`define CAUSE_EBREAK       3'h1
+`define CAUSE_TRIGGER      3'h2
+`define CAUSE_HALTREQ      3'h3
+`define CAUSE_STEP         3'h4
+`define CAUSE_RESETHALTREQ 3'h5
+`define CAUSE_GROUP        3'h6
+
 // Register Numbers (regno)
 // (Table 3.3)
 // 0x0000 – 0x0fff | CSRs. The “PC” can be accessed here through dpc.

src/debug/dmc.sv

@@ -31,23 +31,26 @@
 // In a multihart system, this module should be instantiated under wallypipelinedcore
 
 module dmc (
-  input  logic clk, reset,
+  input  logic       clk, reset,
-  input  logic Step,
+  input  logic       Step,
-  input  logic HaltReq,      // Initiates core halt
+  input  logic       HaltReq,      // Initiates core halt
-  input  logic ResumeReq,    // Initiates core resume
+  input  logic       ResumeReq,    // Initiates core resume
-  input  logic HaltOnReset,  // Halts core immediately on hart reset
+  input  logic       HaltOnReset,  // Halts core immediately on hart reset
-  input  logic AckHaveReset, // Clears HaveReset status
+  input  logic       AckHaveReset, // Clears HaveReset status
 
-  output logic DebugMode,
+  output logic       DebugMode,
-  output logic ResumeAck,      // Signals Hart has been resumed
+  output logic [2:0] DebugCause,     // Reason Hart entered debug mode
-  output logic HaveReset,      // Signals Hart has been reset
+  output logic       ResumeAck,      // Signals Hart has been resumed
-  output logic DebugStall,     // Stall signal goes to hazard unit
+  output logic       HaveReset,      // Signals Hart has been reset
+  output logic       DebugStall,     // Stall signal goes to hazard unit
 
-  output logic CapturePCNextF, // Store PCNextF in DPC when entering Debug Mode
+  output logic       EnterDebugMode, // Store PCNextF in DPC when entering Debug Mode
-  output logic ForceDPCNextF,  // Updates PCNextF with the current value of DPC
+  output logic       ExitDebugMode,  // Updates PCNextF with the current value of DPC
-  output logic ForceNOP        // Fills the pipeline with NOP
+  output logic       ForceNOP        // Fills the pipeline with NOP
 );
-  enum logic [1:0] {RUNNING, FLUSH, HALTED, RESUME} State;
+  `include "debug.vh"
+
+enum logic [1:0] {RUNNING, FLUSH, HALTED, RESUME} State;
 
   localparam NOP_CYCLE_DURATION = 0;
   logic [$clog2(NOP_CYCLE_DURATION+1)-1:0] Counter;
@@ -62,20 +65,24 @@ module dmc (
   assign DebugMode = (State != RUNNING);
   assign DebugStall = (State == HALTED);
 
-  assign CapturePCNextF = (State == FLUSH) & (Counter == 0);
+  assign EnterDebugMode = (State == FLUSH) & (Counter == 0);
-  assign ForceDPCNextF = (State == HALTED) & ResumeReq;
+  assign ExitDebugMode = (State == HALTED) & ResumeReq;
   assign ForceNOP = (State == FLUSH);
 
   always_ff @(posedge clk) begin
     if (reset) begin
       State <= HaltOnReset ? HALTED : RUNNING;
+      DebugCause <= HaltOnReset ? `CAUSE_RESETHALTREQ : 0;
     end else begin
       case (State)
         RUNNING : begin
           if (HaltReq) begin
             Counter <= 0;
             State <= FLUSH;
+            DebugCause <= `CAUSE_HALTREQ;
           end 
+          //else if (eBreak) TODO: halt on ebreak if DCSR bit is set
+          // DebugCause <= `CAUSE_EBREAK;
         end
 
         // fill the pipe with NOP before halting
@@ -95,6 +102,7 @@ module dmc (
           if (Step) begin
             Counter <= 0;
             State <= FLUSH;
+            DebugCause <= `CAUSE_STEP;
           end else begin
             State <= RUNNING;
             ResumeAck <= 1;

src/ifu/ifu.sv

@@ -98,10 +98,10 @@ module ifu import cvw::*;  #(parameter cvw_t P) (
   output logic                 ICacheAccess,                             // Report I$ read to performance counters
   output logic                 ICacheMiss,                               // Report I$ miss to performance counters
   // Debug Mode logic
-  (* mark_debug = "true" *)input  logic                 ForceDPCNextF,
+  input  logic                 ExitDebugMode,
-  (* mark_debug = "true" *)input  logic [P.XLEN-1:0]    DPC,
+  input  logic [P.XLEN-1:0]    DPC,
-  (* mark_debug = "true" *)output logic [P.XLEN-1:0]    PCNextF,                                  // Next PCF, selected from Branch predictor, Privilege, or PC+2/4
+  output logic [P.XLEN-1:0]    PCNextF,                                  // Next PCF, selected from Branch predictor, Privilege, or PC+2/4
-  (* mark_debug = "true" *)input  logic                 ForceNOP,
+  input  logic                 ForceNOP,
   // Debug scan chain
   input  logic                 DebugScanEn,
   input  logic                 DebugScanIn,
@@ -327,8 +327,8 @@ module ifu import cvw::*;  #(parameter cvw_t P) (
   mux3 #(P.XLEN) pcmux3(PC2NextF, EPCM, TrapVectorM, {TrapM, RetM}, UnalignedPCNextF);
   if (P.DEBUG_SUPPORTED) begin
     mux2 #(P.XLEN) pcresetmux({UnalignedPCNextF[P.XLEN-1:1], 1'b0}, P.RESET_VECTOR[P.XLEN-1:0], reset, PCNextFM);
-    assign PCNextF = ForceDPCNextF ? DPC : PCNextFM;
+    assign PCNextF = ExitDebugMode ? DPC : PCNextFM;
-    flopen #(P.XLEN) pcreg(clk, ~StallF | reset | ForceDPCNextF, PCNextF, PCF);
+    flopen #(P.XLEN) pcreg(clk, ~StallF | reset | ExitDebugMode, PCNextF, PCF);
   end else begin
     mux2 #(P.XLEN) pcresetmux({UnalignedPCNextF[P.XLEN-1:1], 1'b0}, P.RESET_VECTOR[P.XLEN-1:0], reset, PCNextF);
     flopen #(P.XLEN) pcreg(clk, ~StallF | reset, PCNextF, PCF);

src/privileged/csr.sv

@@ -94,10 +94,11 @@ module csr import cvw::*;  #(parameter cvw_t P) (
   output logic                     IllegalCSRAccessM,         // Illegal CSR access: CSR doesn't exist or is inaccessible at this privilege level
   output logic                     BigEndianM,                // memory access is big-endian based on privilege mode and STATUS register endian fields
   // Debug Mode output
+  input  logic [2:0]               DebugCause,
   output logic                     Step,
   output logic [P.XLEN-1:0]        DPC,
   input  logic [P.XLEN-1:0]        PCNextF,
-  input  logic                     CapturePCNextF,
+  input  logic                     EnterDebugMode,
   // Debug scan chain
   input  logic                     DebugSel,
   input  logic [11:0]              DebugRegAddr,
@@ -304,7 +305,7 @@ module csr import cvw::*;  #(parameter cvw_t P) (
   if (P.DEBUG_SUPPORTED) begin:csrd
     csrd #(P) csrd(.clk, .reset,
     .CSRWriteDM, .CSRAdrM(CSRAdrDM), .CSRWriteValM(CSRWriteValDM), .CSRDReadValM, .IllegalCSRDAccessM,
-    .Step, .DPC, .PCNextF, .CapturePCNextF);
+    .DebugCause, .Step, .DPC, .PCNextF, .EnterDebugMode);
   end else begin
     assign CSRDReadValM = '0;
     assign IllegalCSRDAccessM = 1'b1; // Debug isn't supported

src/privileged/csrd.sv

@@ -34,10 +34,11 @@ module csrd import cvw::*;  #(parameter cvw_t P) (
   output logic [P.XLEN-1:0] CSRDReadValM,
   output logic              IllegalCSRDAccessM,
 
+  input  logic [2:0]        DebugCause,
   output logic              Step,
   output logic [P.XLEN-1:0] DPC,
   input  logic [P.XLEN-1:0] PCNextF,
-  input  logic              CapturePCNextF
+  input  logic              EnterDebugMode
 );
   `include "debug.vh"
 
@@ -45,8 +46,8 @@ module csrd import cvw::*;  #(parameter cvw_t P) (
   localparam DPC_ADDR  = 12'h7B1;  // Debug PC 
 
   // TODO: these registers are only accessible from Debug Mode.
-  logic [31:0] DCSR_REGW;
+  logic [31:0] DCSR;
-  logic [P.XLEN-1:0] DPC_REGW, DPCWriteVal;
+  logic [P.XLEN-1:0] DPCWriteVal;
   logic WriteDCSRM;
   logic WriteDPCM;
 
@@ -60,7 +61,7 @@ module csrd import cvw::*;  #(parameter cvw_t P) (
   const logic       StepIE = 0;
   const logic       StopCount = 0;
   const logic       StopTime = 0;
-  logic [2:0]       Cause;     // TODO: give reason for entering debug mode
+  logic [2:0]       Cause;
   const logic       V = 0;
   const logic       MPrvEn = 0;
   logic             NMIP;      // pending non-maskable interrupt
@@ -68,34 +69,37 @@ module csrd import cvw::*;  #(parameter cvw_t P) (
 
 
 
+  always_ff @(posedge clk) begin
+    if (reset) begin
+      Prv <= 3;
+      Cause <= 0;
+    end else if (EnterDebugMode) begin
+    //  Prv <= // hart priv mode
+      Cause <= DebugCause;
+    end else if (WriteDCSRM) begin
+      Prv <= CSRWriteValM[`PRV]; // TODO: overwrite hart privilege mode
+    end
+  end
+
   assign WriteDCSRM = CSRWriteDM & (CSRAdrM == DCSR_ADDR);
   assign WriteDPCM  = CSRWriteDM & (CSRAdrM == DPC_ADDR);
 
-  always_ff @(posedge clk) begin
-    if (reset)
-      Prv <= 3;
-    //else if (Halt) // TODO: trigger when hart enters debug mode
-    //  Prv <= // hart priv mode
-    else if (WriteDCSRM)
-      Prv <= CSRWriteValM[`PRV]; // TODO: overwrite hart privilege mode
-  end
-
   flopenr #(4) DCSRreg (clk, reset, WriteDCSRM, 
     {CSRWriteValM[`EBREAKM], CSRWriteValM[`EBREAKS], CSRWriteValM[`EBREAKU], CSRWriteValM[`STEP]}, 
     {ebreakM, ebreakS, ebreakU, Step});
 
-  assign DCSR_REGW = {4'b0100, 10'b0, ebreakVS, ebreakVU, ebreakM, 1'b0, ebreakS, ebreakU, StepIE,
+  assign DCSR = {4'b0100, 10'b0, ebreakVS, ebreakVU, ebreakM, 1'b0, ebreakS, ebreakU, StepIE,
                       StopCount, StopTime, Cause, V, MPrvEn, NMIP, Step, Prv};
 
-  assign DPCWriteVal = CapturePCNextF ? PCNextF : CSRWriteValM;
+  assign DPCWriteVal = EnterDebugMode ? PCNextF : CSRWriteValM;
-  flopenr #(P.XLEN) DPCreg (clk, reset, WriteDPCM | CapturePCNextF, DPCWriteVal, DPC_REGW);
+  flopenr #(P.XLEN) DPCreg (clk, reset, WriteDPCM | EnterDebugMode, DPCWriteVal, DPC);
 
   always_comb begin
     CSRDReadValM = 0;
     IllegalCSRDAccessM = 0;
     case (CSRAdrM)
-      DCSR_ADDR : CSRDReadValM = DCSR_REGW;
+      DCSR_ADDR : CSRDReadValM = DCSR;
-      DPC_ADDR  : CSRDReadValM = DPC_REGW;
+      DPC_ADDR  : CSRDReadValM = DPC;
       default: IllegalCSRDAccessM = 1'b1;
     endcase
   end

src/privileged/privileged.sv

@@ -98,10 +98,11 @@ module privileged import cvw::*;  #(parameter cvw_t P) (
   // Fault outputs                                                         
   output logic              wfiM, IntPendingM,                              // Stall in Memory stage for WFI until interrupt pending or timeout
   // Debuge Mode
+  input  logic [2:0]        DebugCause,
   output logic              Step,
   output logic [P.XLEN-1:0] DPC,
   input  logic [P.XLEN-1:0] PCNextF,
-  input  logic              CapturePCNextF,
+  input  logic              EnterDebugMode,
   // Debug scan chain
   input  logic              DebugSel,
   input  logic [11:0]       DebugRegAddr,
@@ -161,7 +162,7 @@ module privileged import cvw::*;  #(parameter cvw_t P) (
     .SetFflagsM, .FRM_REGW, .ENVCFG_CBE, .ENVCFG_PBMTE, .ENVCFG_ADUE,
     .EPCM, .TrapVectorM,
     .CSRReadValW, .IllegalCSRAccessM, .BigEndianM,
-    .Step, .DPC, .PCNextF, .CapturePCNextF,
+    .DebugCause, .Step, .DPC, .PCNextF, .EnterDebugMode,
     .DebugSel, .DebugRegAddr, .DebugCapture, .DebugRegUpdate, .DebugScanEn, .DebugScanIn, .DebugScanOut);
 
   // pipeline early-arriving trap sources

src/wally/wallypipelinedcore.sv

@@ -193,9 +193,10 @@ module wallypipelinedcore import cvw::*; #(parameter cvw_t P) (
 
   // Debug mode logic
   logic [P.XLEN-1:0]             DPC, PCNextF;
-  logic                          ForceDPCNextF;
+  logic                          ExitDebugMode;
-  logic                          CapturePCNextF;
+  logic                          EnterDebugMode;
   logic                          ForceNOP;
+  logic [2:0]                    DebugCause;
   // Debug register scan chain interconnects
   logic [2:0]                    DebugScanReg;
 
@@ -221,7 +222,7 @@ module wallypipelinedcore import cvw::*; #(parameter cvw_t P) (
     .STATUS_MPP, .ENVCFG_PBMTE, .ENVCFG_ADUE, .ITLBWriteF, .sfencevmaM, .ITLBMissF,
     // pmp/pma (inside mmu) signals. 
     .PMPCFG_ARRAY_REGW,  .PMPADDR_ARRAY_REGW, .InstrAccessFaultF, .InstrUpdateDAF,
-    .ForceDPCNextF, .DPC, .PCNextF, .ForceNOP,
+    .ExitDebugMode, .DPC, .PCNextF, .ForceNOP,
     .DebugScanEn(DebugScanEn & MiscSel), .DebugScanIn(DebugScanReg[0]), .DebugScanOut(DebugScanReg[1]));
     
   // integer execution unit: integer register file, datapath and controller
@@ -320,8 +321,8 @@ module wallypipelinedcore import cvw::*; #(parameter cvw_t P) (
     dmc debugcontrol(
       .clk, .reset,
       .Step, .HaltReq, .ResumeReq, .HaltOnReset, .AckHaveReset,
-      .ResumeAck, .HaveReset, .DebugMode, .DebugStall,
+      .ResumeAck, .HaveReset, .DebugMode, .DebugCause, .DebugStall,
-      .CapturePCNextF, .ForceDPCNextF, .ForceNOP);
+      .EnterDebugMode, .ExitDebugMode, .ForceNOP);
   end else begin
     assign DebugStall = 1'b0;
   end
@@ -349,7 +350,7 @@ module wallypipelinedcore import cvw::*; #(parameter cvw_t P) (
       .STATUS_MXR, .STATUS_SUM, .STATUS_MPRV, .STATUS_MPP, .STATUS_FS, 
       .PMPCFG_ARRAY_REGW, .PMPADDR_ARRAY_REGW, 
       .FRM_REGW, .ENVCFG_CBE, .ENVCFG_PBMTE, .ENVCFG_ADUE, .wfiM, .IntPendingM, .BigEndianM,
-      .Step, .DPC, .PCNextF, .CapturePCNextF,
+      .DebugCause, .Step, .DPC, .PCNextF, .EnterDebugMode,
       .DebugSel(CSRSel), .DebugRegAddr, .DebugCapture, .DebugRegUpdate, .DebugScanEn(DebugScanEn & CSRSel), .DebugScanIn, .DebugScanOut(CSRScanOut));
     if (P.DEBUG_SUPPORTED) begin
       flopenrs #(1) scantrapm (.clk, .reset, .en(DebugCapture), .d(TrapM), .q(), .scan(DebugScanEn), .scanin(DebugScanIn), .scanout(DebugScanReg[0]));