TLB cleanup

wally-pipelined/src/mmu/priorityencoder.sv

@@ -31,7 +31,7 @@
 
 `include "wally-config.vh"
 
-module priorityencoder #(parameter BINARY_BITS = 3) (
+module tlbpriority #(parameter BINARY_BITS = 3) (
   input  logic  [2**BINARY_BITS - 1:0] onehot,
   output logic  [BINARY_BITS - 1:0] binary
 );

wally-pipelined/src/mmu/tlb.sv

@@ -148,7 +148,6 @@ module tlb #(parameter ENTRY_BITS = 3,
   assign WriteAccess = TLBAccessType[0];
   assign TLBAccess = ReadAccess || WriteAccess;
 
-  assign PageOffset = VirtualAddress[11:0];
 
   // TLB entries are evicted according to the LRU algorithm
   tlblru #(ENTRY_BITS) lru(.*);
@@ -157,11 +156,15 @@ module tlb #(parameter ENTRY_BITS = 3,
   tlbram #(ENTRY_BITS) tlbram(.*);
   tlbcam #(ENTRY_BITS, `VPN_BITS, `VPN_SEGMENT_BITS) tlbcam(.*);
 
+  // Replace segments of the virtual page number with segments of the physical
+  // page number. For 4 KB pages, the entire virtual page number is replaced.
+  // For superpages, some segments are considered offsets into a larger page.
+  tlbphysicalpagemask PageMask(VirtualPageNumber, PhysicalPageNumber, HitPageType, PhysicalPageNumberMixed);
+
   // unswizzle useful PTE bits
   assign {PTE_U, PTE_X, PTE_W, PTE_R} = PTEAccessBits[4:1];
  
   // Check whether the access is allowed, page faulting if not.
-  // *** We might not have S mode.
   generate
     if (ITLB == 1) begin
       logic ImproperPrivilege;
@@ -189,28 +192,12 @@ module tlb #(parameter ENTRY_BITS = 3,
     end
   endgenerate
 
-  // Replace segments of the virtual page number with segments of the physical
-  // page number. For 4 KB pages, the entire virtual page number is replaced.
-  // For superpages, some segments are considered offsets into a larger page.
-  tlbphysicalpagemask PageMask(VirtualPageNumber, PhysicalPageNumber, HitPageType, PhysicalPageNumberMixed);
-
-  // Provide physical address only on TLBHits to cause catastrophic errors if
-  // garbage address is used.
-  assign PhysicalAddressFull = TLBHit ? {PhysicalPageNumberMixed, PageOffset} : '0;
 
   // Output the hit physical address if translation is currently on.
-/*  generate
-    if (`XLEN == 32) begin
-      VirtualAddressPALen = {2'b0, VirtualAddress};
-
-       mux2 #(`PA_BITS) addressmux({2'b0, VirtualAddress}, PhysicalAddressFull, Translate, PhysicalAddress);
-    end else begin
-      VirtualAddressPALen = VirtualAddress[`PA_BITS-1:0];
-      mux2 #(`PA_BITS) addressmux(VirtualAddress[`PA_BITS-1:0], PhysicalAddressFull, Translate, PhysicalAddress);
-    end
-  endgenerate*/
-
+  // Provide physical address of zero if not TLBHits, to cause segmentation error if miss somehow percolated through signal
   assign VAExt = {2'b00, VirtualAddress}; // extend length of virtual address if necessary for RV32
+  assign PageOffset = VirtualAddress[11:0];
+  assign PhysicalAddressFull = TLBHit ? {PhysicalPageNumberMixed, PageOffset} : '0;
   mux2 #(`PA_BITS) addressmux(VAExt[`PA_BITS-1:0], PhysicalAddressFull, Translate, PhysicalAddress);
 
   assign TLBHit = CAMHit & TLBAccess;

wally-pipelined/src/mmu/tlbcam.sv

@@ -34,8 +34,6 @@ module tlbcam #(parameter ENTRY_BITS = 3,
   input logic                     clk, reset,
   input logic [KEY_BITS-1:0]      VirtualPageNumber,
   input logic [1:0]               PageTypeWriteVal,
-//  input logic [`SVMODE_BITS-1:0]  SvMode, // *** may not need to be used.
-//  input logic                     TLBWrite,
   input logic                     TLBFlush,
   input logic [2**ENTRY_BITS-1:0] WriteEnables,
 
@@ -56,23 +54,11 @@ module tlbcam #(parameter ENTRY_BITS = 3,
   // of page type. However, matches are determined based on a subset of the
   // page number segments.
 
-  camline #(KEY_BITS, SEGMENT_BITS) camlines[NENTRIES-1:0](
+  tlbcamline #(KEY_BITS, SEGMENT_BITS) camlines[NENTRIES-1:0](
     .CAMLineWrite(WriteEnables),
-        .PageType(PageTypeList),
-        .Match(Matches),
-        .*);
-/*
-  generate
-    genvar i;
-    for (i = 0; i < NENTRIES; i++) begin
-      camline #(KEY_BITS, SEGMENT_BITS) camline(
-        .CAMLineWrite(WriteEnables[i]),
-        .PageType(PageTypeList[i]),
-        .Match(Matches[i]),
-        .*);
-    end
-  endgenerate
-  */
+    .PageType(PageTypeList),
+    .Match(Matches),
+    .*);
 
   // In case there are multiple matches in the CAM, select only one
   // *** it might be guaranteed that the CAM will never have multiple matches.

wally-pipelined/src/mmu/tlbcamline.sv

@@ -1,5 +1,5 @@
 ///////////////////////////////////////////
-// camline.sv
+// tlbcamline.sv
 //
 // Written: tfleming@hmc.edu & jtorrey@hmc.edu 6 April 2021
 // Modified: kmacsaigoren@hmc.edu 1 June 2021
@@ -28,7 +28,7 @@
 
 `include "wally-config.vh"
 
-module camline #(parameter KEY_BITS = 20,
+module tlbcamline #(parameter KEY_BITS = 20,
                   parameter SEGMENT_BITS = 10) (
   input logic                 clk, reset,
 
@@ -85,12 +85,12 @@ module camline #(parameter KEY_BITS = 20,
       assign {Key3, Key2, Key1, Key0} = Key;
 
       // Calculate the actual match value based on the input vpn and the page type.
-      // For example, a gigapage in SV only cares about VPN[2], so VPN[0] and VPN[1]
+      // For example, a gigapage in SV39 only cares about VPN[2], so VPN[0] and VPN[1]
       // should automatically match.
       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); // this should always match in sv39 since both vPN3 and key3 are zeroed by the pagetable walker before getting to the cam
       
       assign Match = Match0 & Match1 & Match2 & Match3 & Valid;
     end

wally-pipelined/src/mmu/tlbphysicalpagemask.sv

@@ -28,7 +28,7 @@
 
 `include "wally-config.vh"
 
-module physicalpagemask (
+module tlbphysicalpagemask (
     input logic [`VPN_BITS-1:0]    VPN,
     input logic [`PPN_BITS-1:0]    PPN,
     input logic [1:0]              PageType,

wally-pipelined/src/mmu/tlbram.sv

@@ -46,16 +46,7 @@ module tlbram #(parameter ENTRY_BITS = 3) (
 
   // Generate a flop for every entry in the RAM
   flopenr #(`XLEN) pteflops[NENTRIES-1:0](clk, reset, WriteEnables, PTEWriteVal, ram);
-/*
-  generate
-    genvar i;
-    for (i = 0; i < NENTRIES; i++) begin:  tlb_ram_flops
-      flopenr #(`XLEN) pteflop(clk, reset, WriteEnables[i],
-        PTEWriteVal, ram[i]);
-    end
-  endgenerate
-*/
-
+  
   assign PageTableEntry = ram[VPNIndex];
   assign PTEAccessBits = PageTableEntry[7:0];
   assign PhysicalPageNumber = PageTableEntry[`PPN_BITS+9:10];