Replaced muxing of upper address bits with disregarding their match. Moved WriteEnables gate into tlblru to eliminate WriteLines

wally-pipelined/src/mmu/tlb.sv

@@ -91,10 +91,10 @@ module tlb #(parameter TLB_ENTRIES = 8,
   logic Translate;
 
   // Store current virtual memory mode (SV32, SV39, SV48, ect...)
-  logic [`SVMODE_BITS-1:0] SvMode;
+  //logic [`SVMODE_BITS-1:0] SvMode;
   logic  [1:0]       EffectivePrivilegeMode; // privilege mode, possibly modified by MPRV
 
-  logic [TLB_ENTRIES-1:0] ReadLines, WriteLines, WriteEnables, PTE_G; // used as the one-hot encoding of WriteIndex
+  logic [TLB_ENTRIES-1:0] ReadLines, WriteEnables, PTE_G; // used as the one-hot encoding of WriteIndex
 
   // Sections of the virtual and physical addresses
   logic [`VPN_BITS-1:0] VirtualPageNumber;
@@ -106,29 +106,17 @@ module tlb #(parameter TLB_ENTRIES = 8,
   logic [7:0]           PTEAccessBits;
   logic [11:0]          PageOffset;
 
-  logic PTE_D, PTE_A, PTE_U, PTE_X, PTE_W, PTE_R; // Useful PTE Control Bits
+  logic                  PTE_D, PTE_A, PTE_U, PTE_X, PTE_W, PTE_R; // Useful PTE Control Bits
   logic [1:0]            HitPageType;
   logic                  CAMHit;
+  logic                  SV39Mode;
   logic [`ASID_BITS-1:0] ASID;
 
   // Grab the sv mode from SATP and determine whether translation should occur
   assign ASID = SATP_REGW[`ASID_BASE+`ASID_BITS-1:`ASID_BASE];
 
   // Determine whether to write TLB
-  assign WriteEnables = WriteLines & {(TLB_ENTRIES){TLBWrite}};
-
-  // The bus width is always the largest it could be for that XLEN. For example, vpn will be 36 bits wide in rv64
-  // this, even though it could be 27 bits (SV39) or 36 bits (SV48) wide. When the value of VPN is narrower,
-  // is shorter, the extra bits are used as padded zeros on the left of the full value.
-  generate
-    if (`XLEN == 32) begin
-      assign VirtualPageNumber = VirtualAddress[`VPN_BITS+11:12];
-    end else begin
-      assign VirtualPageNumber = (SvMode == `SV48) ?
-                                 VirtualAddress[`VPN_BITS+11:12] :
-                                 {{`VPN_SEGMENT_BITS{1'b0}}, VirtualAddress[3*`VPN_SEGMENT_BITS+11:12]};
-    end
-  endgenerate
+  assign VirtualPageNumber = VirtualAddress[`VPN_BITS+11:12];
 
   tlbcontrol tlbcontrol(.*);
 

wally-pipelined/src/mmu/tlbcam.sv

@@ -34,6 +34,7 @@ module tlbcam #(parameter TLB_ENTRIES = 8,
   input logic                     clk, reset,
   input logic [`VPN_BITS-1:0]     VirtualPageNumber,
   input logic [1:0]               PageTypeWriteVal,
+  input  logic                    SV39Mode,
   input logic                     TLBFlush,
   input logic [TLB_ENTRIES-1:0]   WriteEnables,
   input logic [TLB_ENTRIES-1:0]   PTE_G,

wally-pipelined/src/mmu/tlbcamline.sv

@@ -33,6 +33,7 @@ module tlbcamline #(parameter KEY_BITS = 20,
   input  logic                  clk, reset,
   input  logic [`VPN_BITS-1:0]  VirtualPageNumber, // The requested page number to compare against the key
   input  logic [`ASID_BITS-1:0] ASID,
+  input  logic                  SV39Mode,
   input  logic                  WriteEnable,  // Write a new entry to this line
   input  logic                  PTE_G,
   input  logic [1:0]            PageTypeWriteVal,
@@ -86,7 +87,7 @@ module tlbcamline #(parameter KEY_BITS = 20,
       assign Match0 = (Query0 == Key0) || (PageType > 2'd0); // least signifcant section
       assign Match1 = (Query1 == Key1) || (PageType > 2'd1);
       assign Match2 = (Query2 == Key2) || (PageType > 2'd2);
-      assign Match3 = (Query3 == Key3); // this should always match in sv39 since both vPN3 and key3 are zeroed by the pagetable walker before getting to the cam
+      assign Match3 = (Query3 == Key3) || SV39Mode; // this should always match in sv39 because they aren't used
       
       assign Match = Match0 & Match1 & Match2 & Match3 & Valid;
     end

wally-pipelined/src/mmu/tlbcontrol.sv

@@ -49,21 +49,26 @@ module tlbcontrol #(parameter TLB_ENTRIES = 8,
   output logic             TLBHit,
   output logic             TLBPageFault,
   output logic [1:0]       EffectivePrivilegeMode,
-  output logic [`SVMODE_BITS-1:0] SvMode,
+  output logic             SV39Mode,
   output logic             Translate
 );
 
   // Sections of the page table entry
   logic [11:0]          PageOffset;
+  logic [`SVMODE_BITS-1:0] SVMode;
 
   logic PTE_D, PTE_A, PTE_U, PTE_X, PTE_W, PTE_R; // Useful PTE Control Bits
   logic                  DAFault;
   logic                  TLBAccess;
 
   // Grab the sv mode from SATP and determine whether translation should occur
-  assign SvMode = SATP_REGW[`XLEN-1:`XLEN-`SVMODE_BITS];
+  assign SVMode = SATP_REGW[`XLEN-1:`XLEN-`SVMODE_BITS];
   assign EffectivePrivilegeMode = (ITLB == 1) ? PrivilegeModeW : (STATUS_MPRV ? STATUS_MPP : PrivilegeModeW); // DTLB uses MPP mode when MPRV is 1
-  assign Translate = (SvMode != `NO_TRANSLATE) & (EffectivePrivilegeMode != `M_MODE) & ~ DisableTranslation; 
+  assign Translate = (SVMode != `NO_TRANSLATE) & (EffectivePrivilegeMode != `M_MODE) & ~ DisableTranslation; 
+  generate
+      if (`XLEN==64) assign SV39Mode = (SVMode == `SV39);
+      else           assign SV39Mode = 0;
+  endgenerate
 
   // Determine whether TLB is being used
   assign TLBAccess = ReadAccess || WriteAccess;

wally-pipelined/src/mmu/tlblru.sv

@@ -30,10 +30,11 @@ module tlblru #(parameter TLB_ENTRIES = 8) (
   input  logic                TLBFlush,
   input  logic [TLB_ENTRIES-1:0] ReadLines,
   input  logic                CAMHit,
-  output logic [TLB_ENTRIES-1:0] WriteLines
+  output logic [TLB_ENTRIES-1:0] WriteEnables
 );
 
   logic [TLB_ENTRIES-1:0] RUBits, RUBitsNext, RUBitsAccessed;
+  logic [TLB_ENTRIES-1:0] WriteLines;
   logic [TLB_ENTRIES-1:0] AccessLines; // One-hot encodings of which line is being accessed
   logic                AllUsed;  // High if the next access causes all RU bits to be 1
 
@@ -41,6 +42,7 @@ module tlblru #(parameter TLB_ENTRIES = 8) (
   tlbpriority #(TLB_ENTRIES) nru(~RUBits, WriteLines);
 
   // Track recently used lines, updating on a CAM Hit or TLB write
+  assign WriteEnables = WriteLines & {(TLB_ENTRIES){TLBWrite}};
   assign AccessLines = TLBWrite ? WriteLines : ReadLines;
   assign RUBitsAccessed = AccessLines | RUBits;
   assign AllUsed = &RUBitsAccessed; // if all recently used, then clear to none