First implementation of WFI timeout wait

pipelined/config/buildroot/wally-config.vh

@@ -78,6 +78,9 @@
 // Address space
 `define RESET_VECTOR 64'h0000000000001000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/fpga/wally-config.vh

@@ -79,6 +79,9 @@
 // Address space
 `define RESET_VECTOR 64'h0000000000001000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv32e/wally-config.vh

@@ -80,6 +80,9 @@
 // Address space
 `define RESET_VECTOR 32'h80000000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv32gc/wally-config.vh

@@ -78,6 +78,9 @@
 // Address space
 `define RESET_VECTOR 32'h80000000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv32ia/wally-config.vh

@@ -80,6 +80,9 @@
 // Address space
 `define RESET_VECTOR 32'h80000000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv32ic/wally-config.vh

@@ -78,6 +78,9 @@
 // Address space
 `define RESET_VECTOR 32'h80000000
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv64BP/wally-config.vh

@@ -82,6 +82,9 @@
 // Bus Interface width
 `define AHBW 64
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv64fp/wally-config.vh

@@ -84,6 +84,9 @@
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // *** each of these is `PA_BITS wide. is this paramaterizable INSIDE the config file?
 `define BOOTROM_SUPPORTED 1'b1
 `define BOOTROM_BASE   56'h00001000 // spec had been 0x1000 to 0x2FFF, but dh truncated to 0x1000 to 0x1FFF because upper half seems to be all zeros and this is easier for decoder

pipelined/config/rv64gc/wally-config.vh

@@ -82,6 +82,9 @@
 // Bus Interface width
 `define AHBW 64
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Physiccal Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv64ia/wally-config.vh

@@ -82,6 +82,9 @@
 // Bus Interface width
 `define AHBW 64
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Physiccal Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/config/rv64ic/wally-config.vh

@@ -82,6 +82,9 @@
 // Bus Interface width
 `define AHBW 64
 
+// WFI Timeout Wait
+`define WFI_TIMEOUT_BIT 20
+
 // Peripheral Physiccal Addresses
 // Peripheral memory space extends from BASE to BASE+RANGE
 // Range should be a thermometer code with 0's in the upper bits and 1s in the lower bits

pipelined/src/privileged/privdec.sv

@@ -33,7 +33,8 @@
 
 module privdec (
   input  logic [31:20] InstrM,
-  input  logic         PrivilegedM, IllegalIEUInstrFaultM, IllegalCSRAccessM, IllegalFPUInstrM, TrappedSRETM,
+  input  logic         PrivilegedM, IllegalIEUInstrFaultM, IllegalCSRAccessM, IllegalFPUInstrM, 
+  input  logic         TrappedSRETM, WFITimeoutM,
   input  logic [1:0]   PrivilegeModeW, 
   input  logic         STATUS_TSR,
   output logic         IllegalInstrFaultM,
@@ -51,7 +52,6 @@ module privdec (
   assign wfiM =       PrivilegedM & (InstrM[31:20] == 12'b000100000101);
   assign sfencevmaM = PrivilegedM & (InstrM[31:25] ==  7'b0001001); // *** & (PrivilegedModeW == `M_MODE | ~STATUS_TVM); // *** does this work in U mode?
   assign IllegalPrivilegedInstrM = PrivilegedM & ~(sretM|mretM|ecallM|ebreakM|wfiM|sfencevmaM);
-  assign IllegalInstrFaultM = (IllegalIEUInstrFaultM & IllegalFPUInstrM) | IllegalPrivilegedInstrM | IllegalCSRAccessM | TrappedSRETM; // *** generalize this for other instructions
+  assign IllegalInstrFaultM = (IllegalIEUInstrFaultM & IllegalFPUInstrM) | IllegalPrivilegedInstrM | IllegalCSRAccessM | 
-
+                               TrappedSRETM | WFITimeoutM; // *** generalize this for other instructions
-  // *** initially, wfi is nop
 endmodule

pipelined/src/privileged/privileged.sv

@@ -104,6 +104,7 @@ module privileged (
   logic [11:0] MIP_REGW, MIE_REGW, SIP_REGW, SIE_REGW;
   logic md;
   logic       StallMQ;
+  logic WFITimeoutM; 
 
 
   ///////////////////////////////////////////
@@ -114,24 +115,6 @@ module privileged (
   assign md = CauseM[`XLEN-1] ? MIDELEG_REGW[CauseM[3:0]] : MEDELEG_REGW[CauseM[`LOG_XLEN-1:0]];
   
   // PrivilegeMode FSM
-/* -----\/----- EXCLUDED -----\/-----
-  always_comb begin
-    TrappedSRETM = 0;
-    if (mretM)      NextPrivilegeModeM = STATUS_MPP;
-    else if (sretM) 
-      if (STATUS_TSR & PrivilegeModeW == `S_MODE) begin
-        TrappedSRETM = 1;
-                    NextPrivilegeModeM = PrivilegeModeW;
-      end else      NextPrivilegeModeM = {1'b0, STATUS_SPP};
-    else if (TrapM) begin // Change privilege based on DELEG registers (see 3.1.8)
-      if (`S_SUPPORTED & md & (PrivilegeModeW == `U_MODE | PrivilegeModeW == `S_MODE))
-                    NextPrivilegeModeM = `S_MODE;
-      else          NextPrivilegeModeM = `M_MODE;
-    end else        NextPrivilegeModeM = PrivilegeModeW;
-  end
-
- -----/\----- EXCLUDED -----/\----- */
-  
   always_comb begin
     if (TrapM) begin // Change privilege based on DELEG registers (see 3.1.8)
       if (`S_SUPPORTED & md & (PrivilegeModeW == `U_MODE | PrivilegeModeW == `S_MODE))
@@ -149,14 +132,21 @@ module privileged (
 
   flopenl #(2) privmodereg(clk, reset, ~StallW, NextPrivilegeModeM, `M_MODE, PrivilegeModeW);
 
-  // *** WFI could be implemented here and depends on TW
+  ///////////////////////////////////////////
+  // WFI timeout Privileged Spec 3.1.6.5
+  ///////////////////////////////////////////
+  if (`U_SUPPORTED) begin
+    logic [`WFI_TIMEOUT_BIT:0] WFICount;
+    floprc #(`WFI_TIMEOUT_BIT+1) wficountreg(clk, reset, ~wfiM, WFICount+1, WFICount);  // count while in WFI
+    assign WFITimeoutM = STATUS_TW & PrivilegeModeW != `M_MODE & WFICount[`WFI_TIMEOUT_BIT]; 
+  end else assign WFITimeoutM = 0;
 
   ///////////////////////////////////////////
   // decode privileged instructions
   ///////////////////////////////////////////
 
    privdec pmd(.InstrM(InstrM[31:20]), 
-              .PrivilegedM, .IllegalIEUInstrFaultM, .IllegalCSRAccessM, .IllegalFPUInstrM, .TrappedSRETM,
+              .PrivilegedM, .IllegalIEUInstrFaultM, .IllegalCSRAccessM, .IllegalFPUInstrM, .TrappedSRETM, .WFITimeoutM,
               .PrivilegeModeW, .STATUS_TSR, .IllegalInstrFaultM, 
               .sretM, .mretM, .ecallM, .ebreakM, .wfiM, .sfencevmaM);