TLB cleanup

wally-pipelined/src/mmu/tlb.sv

@@ -121,6 +121,7 @@ module tlb #(parameter ENTRY_BITS = 3,
 
   // Grab the sv mode from SATP and determine whether translation should occur
   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; 
 
   // Decode the integer encoded WriteIndex into the one-hot encoded WriteLines
@@ -152,6 +153,7 @@ module tlb #(parameter ENTRY_BITS = 3,
   // TLB entries are evicted according to the LRU algorithm
   tlblru #(ENTRY_BITS) lru(.*);
 
+  // TLB memory
   tlbram #(ENTRY_BITS) tlbram(.*);
   tlbcam #(ENTRY_BITS, `VPN_BITS, `VPN_SEGMENT_BITS) tlbcam(.*);
 
@@ -164,8 +166,6 @@ module tlb #(parameter ENTRY_BITS = 3,
     if (ITLB == 1) begin
       logic ImproperPrivilege;
 
-      assign EffectivePrivilegeMode = PrivilegeModeW; // ITLB ignores MPRV
-
       // User mode may only execute user mode pages, and supervisor mode may
       // only execute non-user mode pages.
       assign ImproperPrivilege = ((EffectivePrivilegeMode == `U_MODE) && ~PTE_U) ||
@@ -174,8 +174,6 @@ module tlb #(parameter ENTRY_BITS = 3,
     end else begin
       logic ImproperPrivilege, InvalidRead, InvalidWrite;
 
-      assign EffectivePrivilegeMode = STATUS_MPRV ? STATUS_MPP : PrivilegeModeW; // DTLB uses MPP mode when MPRV is 1
-
       // User mode may only load/store from user mode pages, and supervisor mode
       // may only access user mode pages when STATUS_SUM is low.
       assign ImproperPrivilege = ((EffectivePrivilegeMode == `U_MODE) && ~PTE_U) ||
@@ -194,11 +192,11 @@ module tlb #(parameter ENTRY_BITS = 3,
   // 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.
-  physicalpagemask PageNumberMixer(VirtualPageNumber, PhysicalPageNumber, HitPageType, PhysicalPageNumberMixed);
+  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;
+  assign PhysicalAddressFull = TLBHit ? {PhysicalPageNumberMixed, PageOffset} : '0;
 
   // Output the hit physical address if translation is currently on.
 /*  generate

wally-pipelined/src/mmu/tlbphysicalpagemask.sv

@@ -1,5 +1,5 @@
 ///////////////////////////////////////////
-// physicalpagemask.sv
+// tlbphysicalpagemask.sv
 //
 // Written: David Harris and kmacsaigoren@hmc.edu 7 June 2021
 // Modified:
@@ -40,13 +40,11 @@ module physicalpagemask (
   logic [`PPN_BITS-1:0] ZeroExtendedVPN;
   logic [`PPN_BITS-1:0] PageNumberMask;
 
-  assign ZeroExtendedVPN = {{EXTRA_BITS{1'b0}}, VPN}; // forces the VPN to be the same width as PPN.
-
   generate
     if (`XLEN == 32) begin
       always_comb 
         case (PageType[0])
-          // *** the widths of these constansts are hardocded here to match `PPN_BITS in the wally-constants file.
+          // the widths of these constansts are hardocded here to match `PPN_BITS in the wally-constants file.
           0: PageNumberMask = 22'h3FFFFF; // kilopage: 22 bits of PPN, 0 bits of VPN
           1: PageNumberMask = 22'h3FFC00; // megapage: 12 bits of PPN, 10 bits of VPN
         endcase
@@ -57,7 +55,7 @@ module physicalpagemask (
           1: PageNumberMask = 44'hFFFFFFFFE00; // megapage: 35 bits of PPN, 9 bits of VPN
           2: PageNumberMask = 44'hFFFFFFC0000; // gigapage: 26 bits of PPN, 18 bits of VPN
           3: PageNumberMask = 44'hFFFF8000000; // terapage: 17 bits of PPN, 27 bits of VPN
-          // *** make sure that this doesnt break when using sv39. In that case, all of these
+          //     Bus widths accomodate SV48. In SV39, all of these
           //     busses are the widths for sv48, but extra bits should be zeroed out by the mux
           //     in the tlb when it generates VPN from the full virtualadress.
         endcase
@@ -65,6 +63,7 @@ module physicalpagemask (
   endgenerate
 
   // merge low segments of VPN with high segments of PPN decided by the pagetype.
+  assign ZeroExtendedVPN = {{EXTRA_BITS{1'b0}}, VPN}; // forces the VPN to be the same width as PPN.
   assign MixedPageNumber = (ZeroExtendedVPN & ~PageNumberMask) | (PPN & PageNumberMask);
 
 endmodule