-# this file has been generated by sv2nmigen
-
-from nmigen import Signal, Module, Const, Cat, Elaboratable
-
-
-
-class tlb(Elaboratable):
-
- def __init__(self):
- self.clk_i = Signal() # input
- self.rst_ni = Signal() # input
- self.flush_i = Signal() # input
- self.lu_access_i = Signal() # input
- self.lu_asid_i = Signal(ASID_WIDTH) # input
- self.lu_vaddr_i = Signal(64) # input
- self.lu_is_2M_o = Signal() # output
- self.lu_is_1G_o = Signal() # output
- self.lu_hit_o = Signal() # output
- def elaborate(self, platform=None):
- m = Module()
- return m
-
-#// Copyright 2018 ETH Zurich and University of Bologna.
-#// Copyright and related rights are licensed under the Solderpad Hardware
-#// License, Version 0.51 (the "License"); you may not use this file except in
-#// compliance with the License. You may obtain a copy of the License at
-#// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
-#// or agreed to in writing, software, hardware and materials distributed under
-#// this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
-#// CONDITIONS OF ANY KIND, either express or implied. See the License for the
-#// specific language governing permissions and limitations under the License.
-#//
-#// Author: David Schaffenrath, TU Graz
-#// Author: Florian Zaruba, ETH Zurich
-#// Date: 21.4.2017
-#// Description: Translation Lookaside Buffer, SV39
-#// fully set-associative
-#
-#//import ariane_pkg::*;
-#
-#module tlb #(
-# parameter int TLB_ENTRIES = 4,
-# parameter int ASID_WIDTH = 1
-# )(
-# input logic clk_i, // Clock
-# input logic rst_ni, // Asynchronous reset active low
-# input logic flush_i, // Flush signal
-# // Update TLB
-# //input tlb_update_t update_i,
-# // Lookup signals
-# input logic lu_access_i,
-# input logic [ASID_WIDTH-1:0] lu_asid_i,
-# input logic [63:0] lu_vaddr_i,
-# //output riscv::pte_t lu_content_o,
-# output logic lu_is_2M_o,
-# output logic lu_is_1G_o,
-# output logic lu_hit_o
-#);
-#
-""" #docstring_begin
- // SV39 defines three levels of page tables
- struct packed {
- logic [ASID_WIDTH-1:0] asid;
- logic [8:0] vpn2;
- logic [8:0] vpn1;
- logic [8:0] vpn0;
- logic is_2M;
- logic is_1G;
- logic valid;
- } [TLB_ENTRIES-1:0] tags_q, tags_n;
-
- riscv::pte_t [TLB_ENTRIES-1:0] content_q, content_n;
- logic [8:0] vpn0, vpn1, vpn2;
- logic [TLB_ENTRIES-1:0] lu_hit; // to replacement logic
- logic [TLB_ENTRIES-1:0] replace_en; // replace the following entry, set by replacement strategy
- //-------------
- // Translation
- //-------------
- always_comb begin : translation
- vpn0 = lu_vaddr_i[20:12];
- vpn1 = lu_vaddr_i[29:21];
- vpn2 = lu_vaddr_i[38:30];
-
- // default assignment
- lu_hit = '{default: 0};
- lu_hit_o = 1'b0;
- lu_content_o = '{default: 0};
- lu_is_1G_o = 1'b0;
- lu_is_2M_o = 1'b0;
-
- for (int unsigned i = 0; i < TLB_ENTRIES; i++) begin
- // first level match, this may be a giga page, check the ASID flags as well
- if (tags_q[i].valid && lu_asid_i == tags_q[i].asid && vpn2 == tags_q[i].vpn2) begin
- // second level
- if (tags_q[i].is_1G) begin
- lu_is_1G_o = 1'b1;
- lu_content_o = content_q[i];
- lu_hit_o = 1'b1;
- lu_hit[i] = 1'b1;
- // not a giga page hit so check further
- end else if (vpn1 == tags_q[i].vpn1) begin
- // this could be a 2 mega page hit or a 4 kB hit
- // output accordingly
- if (tags_q[i].is_2M || vpn0 == tags_q[i].vpn0) begin
- lu_is_2M_o = tags_q[i].is_2M;
- lu_content_o = content_q[i];
- lu_hit_o = 1'b1;
- lu_hit[i] = 1'b1;
- end
- end
- end
- end
- end
-
- // ------------------
- // Update and Flush
- // ------------------
- always_comb begin : update_flush
- tags_n = tags_q;
- content_n = content_q;
-
- for (int unsigned i = 0; i < TLB_ENTRIES; i++) begin
- if (flush_i) begin
- // invalidate logic
- if (lu_asid_i == 1'b0) // flush everything if ASID is 0
- tags_n[i].valid = 1'b0;
- else if (lu_asid_i == tags_q[i].asid) // just flush entries from this ASID
- tags_n[i].valid = 1'b0;
-
- // normal replacement
- end else if (update_i.valid & replace_en[i]) begin
- // update tag array
- tags_n[i] = '{
- asid: update_i.asid,
- vpn2: update_i.vpn [26:18],
- vpn1: update_i.vpn [17:9],
- vpn0: update_i.vpn [8:0],
- is_1G: update_i.is_1G,
- is_2M: update_i.is_2M,
- valid: 1'b1
- };
- // and content as well
- content_n[i] = update_i.content;
- end
- end
- end
-
- // -----------------------------------------------
- // PLRU - Pseudo Least Recently Used Replacement
- // -----------------------------------------------
- logic[2*(TLB_ENTRIES-1)-1:0] plru_tree_q, plru_tree_n;
- always_comb begin : plru_replacement
- plru_tree_n = plru_tree_q;
- // The PLRU-tree indexing:
- // lvl0 0
- // / \
- // / \
- // lvl1 1 2
- // / \ / \
- // lvl2 3 4 5 6
- // / \ /\/\ /\
- // ... ... ... ...
- // Just predefine which nodes will be set/cleared
- // E.g. for a TLB with 8 entries, the for-loop is semantically
- // equivalent to the following pseudo-code:
- // unique case (1'b1)
- // lu_hit[7]: plru_tree_n[0, 2, 6] = {1, 1, 1};
- // lu_hit[6]: plru_tree_n[0, 2, 6] = {1, 1, 0};
- // lu_hit[5]: plru_tree_n[0, 2, 5] = {1, 0, 1};
- // lu_hit[4]: plru_tree_n[0, 2, 5] = {1, 0, 0};
- // lu_hit[3]: plru_tree_n[0, 1, 4] = {0, 1, 1};
- // lu_hit[2]: plru_tree_n[0, 1, 4] = {0, 1, 0};
- // lu_hit[1]: plru_tree_n[0, 1, 3] = {0, 0, 1};
- // lu_hit[0]: plru_tree_n[0, 1, 3] = {0, 0, 0};
- // default: begin /* No hit */ end
- // endcase
- for (int unsigned i = 0; i < TLB_ENTRIES; i++) begin
- automatic int unsigned idx_base, shift, new_index;
- // we got a hit so update the pointer as it was least recently used
- if (lu_hit[i] & lu_access_i) begin
- // Set the nodes to the values we would expect
- for (int unsigned lvl = 0; lvl < $clog2(TLB_ENTRIES); lvl++) begin
- idx_base = $unsigned((2**lvl)-1);
- // lvl0 <=> MSB, lvl1 <=> MSB-1, ...
- shift = $clog2(TLB_ENTRIES) - lvl;
- // to circumvent the 32 bit integer arithmetic assignment
- new_index = ~((i >> (shift-1)) & 32'b1);
- plru_tree_n[idx_base + (i >> shift)] = new_index[0];
- end
- end
- end
- // Decode tree to write enable signals
- // Next for-loop basically creates the following logic for e.g. an 8 entry
- // TLB (note: pseudo-code obviously):
- // replace_en[7] = &plru_tree_q[ 6, 2, 0]; //plru_tree_q[0,2,6]=={1,1,1}
- // replace_en[6] = &plru_tree_q[~6, 2, 0]; //plru_tree_q[0,2,6]=={1,1,0}
- // replace_en[5] = &plru_tree_q[ 5,~2, 0]; //plru_tree_q[0,2,5]=={1,0,1}
- // replace_en[4] = &plru_tree_q[~5,~2, 0]; //plru_tree_q[0,2,5]=={1,0,0}
- // replace_en[3] = &plru_tree_q[ 4, 1,~0]; //plru_tree_q[0,1,4]=={0,1,1}
- // replace_en[2] = &plru_tree_q[~4, 1,~0]; //plru_tree_q[0,1,4]=={0,1,0}
- // replace_en[1] = &plru_tree_q[ 3,~1,~0]; //plru_tree_q[0,1,3]=={0,0,1}
- // replace_en[0] = &plru_tree_q[~3,~1,~0]; //plru_tree_q[0,1,3]=={0,0,0}
- // For each entry traverse the tree. If every tree-node matches,
- // the corresponding bit of the entry's index, this is
- // the next entry to replace.
- for (int unsigned i = 0; i < TLB_ENTRIES; i += 1) begin
- automatic logic en;
- automatic int unsigned idx_base, shift, new_index;
- en = 1'b1;
- for (int unsigned lvl = 0; lvl < $clog2(TLB_ENTRIES); lvl++) begin
- idx_base = $unsigned((2**lvl)-1);
- // lvl0 <=> MSB, lvl1 <=> MSB-1, ...
- shift = $clog2(TLB_ENTRIES) - lvl;
-
- // en &= plru_tree_q[idx_base + (i>>shift)] == ((i >> (shift-1)) & 1'b1);
- new_index = (i >> (shift-1)) & 32'b1;
- if (new_index[0]) begin
- en &= plru_tree_q[idx_base + (i>>shift)];
- end else begin
- en &= ~plru_tree_q[idx_base + (i>>shift)];
- end
- end
- replace_en[i] = en;
- end
- end
-
- // sequential process
- always_ff @(posedge clk_i or negedge rst_ni) begin
- if(~rst_ni) begin
- tags_q <= '{default: 0};
- content_q <= '{default: 0};
- plru_tree_q <= '{default: 0};
- end else begin
- tags_q <= tags_n;
- content_q <= content_n;
- plru_tree_q <= plru_tree_n;
- end
- end
- //--------------
- // Sanity checks
- //--------------
-
- //pragma translate_off
- `ifndef VERILATOR
-
- initial begin : p_assertions
- assert ((TLB_ENTRIES % 2 == 0) && (TLB_ENTRIES > 1))
- else begin $error("TLB size must be a multiple of 2 and greater than 1"); $stop(); end
- assert (ASID_WIDTH >= 1)
- else begin $error("ASID width must be at least 1"); $stop(); end
- end
-
- // Just for checking
- function int countSetBits(logic[TLB_ENTRIES-1:0] vector);
- automatic int count = 0;
- foreach (vector[idx]) begin
- count += vector[idx];
- end
- return count;
- endfunction
-
- assert property (@(posedge clk_i)(countSetBits(lu_hit) <= 1))
- else begin $error("More then one hit in TLB!"); $stop(); end
- assert property (@(posedge clk_i)(countSetBits(replace_en) <= 1))
- else begin $error("More then one TLB entry selected for next replace!"); $stop(); end
-
- `endif
- //pragma translate_on
-"""
-#endmodule
-#
-#
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