+// 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: Florian Zaruba, ETH Zurich
+// Date: 19.04.2017
+// Description: Load Store Unit, handles address calculation and memory interface signals
+
+//import ariane_pkg::*;
+
+module load_store_unit #(
+ parameter int ASID_WIDTH = 1
+ // parameter ariane_pkg::ariane_cfg_t ArianeCfg = ariane_pkg::ArianeDefaultConfig
+)(
+ input logic clk_i,
+ input logic rst_ni,
+ input logic flush_i,
+ output logic no_st_pending_o,
+ input logic amo_valid_commit_i,
+
+
+ //input fu_data_t fu_data_i,
+ output logic lsu_ready_o, // FU is ready e.g. not busy
+ input logic lsu_valid_i, // Input is valid
+
+ output logic [TRANS_ID_BITS-1:0] load_trans_id_o, // ID of scoreboard entry at which to write back
+ output logic [63:0] load_result_o,
+ output logic load_valid_o,
+ //output exception_t load_exception_o, // to WB, signal exception status LD exception
+
+ output logic [TRANS_ID_BITS-1:0] store_trans_id_o, // ID of scoreboard entry at which to write back
+ output logic [63:0] store_result_o,
+ output logic store_valid_o,
+ //output exception_t store_exception_o, // to WB, signal exception status ST exception
+
+ input logic commit_i, // commit the pending store
+ output logic commit_ready_o, // commit queue is ready to accept another commit request
+
+ input logic enable_translation_i, // enable virtual memory translation
+ input logic en_ld_st_translation_i, // enable virtual memory translation for load/stores
+
+ // icache translation requests
+ //input icache_areq_o_t icache_areq_i,
+ //output icache_areq_i_t icache_areq_o,
+
+ //input riscv::priv_lvl_t priv_lvl_i, // From CSR register file
+ //input riscv::priv_lvl_t ld_st_priv_lvl_i, // From CSR register file
+ input logic sum_i, // From CSR register file
+ input logic mxr_i, // From CSR register file
+ input logic [43:0] satp_ppn_i, // From CSR register file
+ input logic [ASID_WIDTH-1:0] asid_i, // From CSR register file
+ input logic flush_tlb_i,
+ // Performance counters
+ output logic itlb_miss_o,
+ output logic dtlb_miss_o
+
+ // interface to dcache
+ //input dcache_req_o_t [2:0] dcache_req_ports_i,
+ //output dcache_req_i_t [2:0] dcache_req_ports_o,
+ // AMO interface
+ //output amo_req_t amo_req_o,
+ //input amo_resp_t amo_resp_i
+);
+ #docstring_begin
+ // data is misaligned
+ logic data_misaligned;
+ // --------------------------------------
+ // 1st register stage - (stall registers)
+ // --------------------------------------
+ // those are the signals which are always correct
+ // e.g.: they keep the value in the stall case
+ lsu_ctrl_t lsu_ctrl;
+
+ logic pop_st;
+ logic pop_ld;
+
+ // ------------------------------
+ // Address Generation Unit (AGU)
+ // ------------------------------
+ // virtual address as calculated by the AGU in the first cycle
+ logic [63:0] vaddr_i;
+ logic [7:0] be_i;
+
+ assign vaddr_i = $unsigned($signed(fu_data_i.imm) + $signed(fu_data_i.operand_a));
+
+ logic st_valid_i;
+ logic ld_valid_i;
+ logic ld_translation_req;
+ logic st_translation_req;
+ logic [63:0] ld_vaddr;
+ logic [63:0] st_vaddr;
+ logic translation_req;
+ logic translation_valid;
+ logic [63:0] mmu_vaddr;
+ logic [63:0] mmu_paddr;
+ exception_t mmu_exception;
+ logic dtlb_hit;
+
+ logic ld_valid;
+ logic [TRANS_ID_BITS-1:0] ld_trans_id;
+ logic [63:0] ld_result;
+ logic st_valid;
+ logic [TRANS_ID_BITS-1:0] st_trans_id;
+ logic [63:0] st_result;
+
+ logic [11:0] page_offset;
+ logic page_offset_matches;
+
+ exception_t misaligned_exception;
+ exception_t ld_ex;
+ exception_t st_ex;
+
+ // -------------------
+ // MMU e.g.: TLBs/PTW
+ // -------------------
+ mmu #(
+ .INSTR_TLB_ENTRIES ( 16 ),
+ .DATA_TLB_ENTRIES ( 16 ),
+ .ASID_WIDTH ( ASID_WIDTH ),
+ .ArianeCfg ( ArianeCfg )
+ ) i_mmu (
+ // misaligned bypass
+ .misaligned_ex_i ( misaligned_exception ),
+ .lsu_is_store_i ( st_translation_req ),
+ .lsu_req_i ( translation_req ),
+ .lsu_vaddr_i ( mmu_vaddr ),
+ .lsu_valid_o ( translation_valid ),
+ .lsu_paddr_o ( mmu_paddr ),
+ .lsu_exception_o ( mmu_exception ),
+ .lsu_dtlb_hit_o ( dtlb_hit ), // send in the same cycle as the request
+ // connecting PTW to D$ IF
+ .req_port_i ( dcache_req_ports_i [0] ),
+ .req_port_o ( dcache_req_ports_o [0] ),
+ // icache address translation requests
+ .icache_areq_i ( icache_areq_i ),
+ .icache_areq_o ( icache_areq_o ),
+ .*
+ );
+ // ------------------
+ // Store Unit
+ // ------------------
+ store_unit i_store_unit (
+ .clk_i,
+ .rst_ni,
+ .flush_i,
+ .no_st_pending_o,
+
+ .valid_i ( st_valid_i ),
+ .lsu_ctrl_i ( lsu_ctrl ),
+ .pop_st_o ( pop_st ),
+ .commit_i,
+ .commit_ready_o,
+ .amo_valid_commit_i,
+
+ .valid_o ( st_valid ),
+ .trans_id_o ( st_trans_id ),
+ .result_o ( st_result ),
+ .ex_o ( st_ex ),
+ // MMU port
+ .translation_req_o ( st_translation_req ),
+ .vaddr_o ( st_vaddr ),
+ .paddr_i ( mmu_paddr ),
+ .ex_i ( mmu_exception ),
+ .dtlb_hit_i ( dtlb_hit ),
+ // Load Unit
+ .page_offset_i ( page_offset ),
+ .page_offset_matches_o ( page_offset_matches ),
+ // AMOs
+ .amo_req_o,
+ .amo_resp_i,
+ // to memory arbiter
+ .req_port_i ( dcache_req_ports_i [2] ),
+ .req_port_o ( dcache_req_ports_o [2] )
+ );
+
+ // ------------------
+ // Load Unit
+ // ------------------
+ load_unit i_load_unit (
+ .valid_i ( ld_valid_i ),
+ .lsu_ctrl_i ( lsu_ctrl ),
+ .pop_ld_o ( pop_ld ),
+
+ .valid_o ( ld_valid ),
+ .trans_id_o ( ld_trans_id ),
+ .result_o ( ld_result ),
+ .ex_o ( ld_ex ),
+ // MMU port
+ .translation_req_o ( ld_translation_req ),
+ .vaddr_o ( ld_vaddr ),
+ .paddr_i ( mmu_paddr ),
+ .ex_i ( mmu_exception ),
+ .dtlb_hit_i ( dtlb_hit ),
+ // to store unit
+ .page_offset_o ( page_offset ),
+ .page_offset_matches_i ( page_offset_matches ),
+ // to memory arbiter
+ .req_port_i ( dcache_req_ports_i [1] ),
+ .req_port_o ( dcache_req_ports_o [1] ),
+ .*
+ );
+
+ // ----------------------------
+ // Output Pipeline Register
+ // ----------------------------
+ shift_reg #(
+ .dtype ( logic[$bits(ld_valid) + $bits(ld_trans_id) + $bits(ld_result) + $bits(ld_ex) - 1: 0]),
+ .Depth ( NR_LOAD_PIPE_REGS )
+ ) i_pipe_reg_load (
+ .clk_i,
+ .rst_ni,
+ .d_i ( {ld_valid, ld_trans_id, ld_result, ld_ex} ),
+ .d_o ( {load_valid_o, load_trans_id_o, load_result_o, load_exception_o} )
+ );
+
+ shift_reg #(
+ .dtype ( logic[$bits(st_valid) + $bits(st_trans_id) + $bits(st_result) + $bits(st_ex) - 1: 0]),
+ .Depth ( NR_STORE_PIPE_REGS )
+ ) i_pipe_reg_store (
+ .clk_i,
+ .rst_ni,
+ .d_i ( {st_valid, st_trans_id, st_result, st_ex} ),
+ .d_o ( {store_valid_o, store_trans_id_o, store_result_o, store_exception_o} )
+ );
+
+ // determine whether this is a load or store
+ always_comb begin : which_op
+
+ ld_valid_i = 1'b0;
+ st_valid_i = 1'b0;
+
+ translation_req = 1'b0;
+ mmu_vaddr = 64'b0;
+
+ // check the operator to activate the right functional unit accordingly
+ unique case (lsu_ctrl.fu)
+ // all loads go here
+ LOAD: begin
+ ld_valid_i = lsu_ctrl.valid;
+ translation_req = ld_translation_req;
+ mmu_vaddr = ld_vaddr;
+ end
+ // all stores go here
+ STORE: begin
+ st_valid_i = lsu_ctrl.valid;
+ translation_req = st_translation_req;
+ mmu_vaddr = st_vaddr;
+ end
+ // not relevant for the LSU
+ default: ;
+ endcase
+ end
+
+
+ // ---------------
+ // Byte Enable
+ // ---------------
+ // we can generate the byte enable from the virtual address since the last
+ // 12 bit are the same anyway
+ // and we can always generate the byte enable from the address at hand
+ assign be_i = be_gen(vaddr_i[2:0], extract_transfer_size(fu_data_i.operator));
+
+ // ------------------------
+ // Misaligned Exception
+ // ------------------------
+ // we can detect a misaligned exception immediately
+ // the misaligned exception is passed to the functional unit via the MMU, which in case
+ // can augment the exception if other memory related exceptions like a page fault or access errors
+ always_comb begin : data_misaligned_detection
+
+ misaligned_exception = {
+ 64'b0,
+ 64'b0,
+ 1'b0
+ };
+
+ data_misaligned = 1'b0;
+
+ if (lsu_ctrl.valid) begin
+ case (lsu_ctrl.operator)
+ // double word
+ LD, SD, FLD, FSD,
+ AMO_LRD, AMO_SCD,
+ AMO_SWAPD, AMO_ADDD, AMO_ANDD, AMO_ORD,
+ AMO_XORD, AMO_MAXD, AMO_MAXDU, AMO_MIND,
+ AMO_MINDU: begin
+ if (lsu_ctrl.vaddr[2:0] != 3'b000) begin
+ data_misaligned = 1'b1;
+ end
+ end
+ // word
+ LW, LWU, SW, FLW, FSW,
+ AMO_LRW, AMO_SCW,
+ AMO_SWAPW, AMO_ADDW, AMO_ANDW, AMO_ORW,
+ AMO_XORW, AMO_MAXW, AMO_MAXWU, AMO_MINW,
+ AMO_MINWU: begin
+ if (lsu_ctrl.vaddr[1:0] != 2'b00) begin
+ data_misaligned = 1'b1;
+ end
+ end
+ // half word
+ LH, LHU, SH, FLH, FSH: begin
+ if (lsu_ctrl.vaddr[0] != 1'b0) begin
+ data_misaligned = 1'b1;
+ end
+ end
+ // byte -> is always aligned
+ default:;
+ endcase
+ end
+
+ if (data_misaligned) begin
+
+ if (lsu_ctrl.fu == LOAD) begin
+ misaligned_exception = {
+ riscv::LD_ADDR_MISALIGNED,
+ lsu_ctrl.vaddr,
+ 1'b1
+ };
+
+ end else if (lsu_ctrl.fu == STORE) begin
+ misaligned_exception = {
+ riscv::ST_ADDR_MISALIGNED,
+ lsu_ctrl.vaddr,
+ 1'b1
+ };
+ end
+ end
+
+ // we work with SV39, so if VM is enabled, check that all bits [63:38] are equal
+ if (en_ld_st_translation_i && !((&lsu_ctrl.vaddr[63:38]) == 1'b1 || (|lsu_ctrl.vaddr[63:38]) == 1'b0)) begin
+
+ if (lsu_ctrl.fu == LOAD) begin
+ misaligned_exception = {
+ riscv::LD_ACCESS_FAULT,
+ lsu_ctrl.vaddr,
+ 1'b1
+ };
+
+ end else if (lsu_ctrl.fu == STORE) begin
+ misaligned_exception = {
+ riscv::ST_ACCESS_FAULT,
+ lsu_ctrl.vaddr,
+ 1'b1
+ };
+ end
+ end
+ end
+
+ // ------------------
+ // LSU Control
+ // ------------------
+ // new data arrives here
+ lsu_ctrl_t lsu_req_i;
+
+ assign lsu_req_i = {lsu_valid_i, vaddr_i, fu_data_i.operand_b, be_i, fu_data_i.fu, fu_data_i.operator, fu_data_i.trans_id};
+
+ lsu_bypass lsu_bypass_i (
+ .lsu_req_i ( lsu_req_i ),
+ .lus_req_valid_i ( lsu_valid_i ),
+ .pop_ld_i ( pop_ld ),
+ .pop_st_i ( pop_st ),
+
+ .lsu_ctrl_o ( lsu_ctrl ),
+ .ready_o ( lsu_ready_o ),
+ .*
+ );
+#docstring_end
+endmodule
+
+#docstring_begin
+// ------------------
+// LSU Control
+// ------------------
+// The LSU consists of two independent block which share a common address translation block.
+// The one block is the load unit, the other one is the store unit. They will signal their readiness
+// with separate signals. If they are not ready the LSU control should keep the last applied signals stable.
+// Furthermore it can be the case that another request for one of the two store units arrives in which case
+// the LSU control should sample it and store it for later application to the units. It does so, by storing it in a
+// two element FIFO. This is necessary as we only know very late in the cycle whether the load/store will succeed (address check,
+// TLB hit mainly). So we better unconditionally allow another request to arrive and store this request in case we need to.
+module lsu_bypass (
+ input logic clk_i,
+ input logic rst_ni,
+ input logic flush_i,
+
+ input lsu_ctrl_t lsu_req_i,
+ input logic lus_req_valid_i,
+ input logic pop_ld_i,
+ input logic pop_st_i,
+
+ output lsu_ctrl_t lsu_ctrl_o,
+ output logic ready_o
+ );
+
+ lsu_ctrl_t [1:0] mem_n, mem_q;
+ logic read_pointer_n, read_pointer_q;
+ logic write_pointer_n, write_pointer_q;
+ logic [1:0] status_cnt_n, status_cnt_q;
+
+ logic empty;
+ assign empty = (status_cnt_q == 0);
+ assign ready_o = empty;
+
+ always_comb begin
+ automatic logic [1:0] status_cnt;
+ automatic logic write_pointer;
+ automatic logic read_pointer;
+
+ status_cnt = status_cnt_q;
+ write_pointer = write_pointer_q;
+ read_pointer = read_pointer_q;
+
+ mem_n = mem_q;
+ // we've got a valid LSU request
+ if (lus_req_valid_i) begin
+ mem_n[write_pointer_q] = lsu_req_i;
+ write_pointer++;
+ status_cnt++;
+ end
+
+ if (pop_ld_i) begin
+ // invalidate the result
+ mem_n[read_pointer_q].valid = 1'b0;
+ read_pointer++;
+ status_cnt--;
+ end
+
+ if (pop_st_i) begin
+ // invalidate the result
+ mem_n[read_pointer_q].valid = 1'b0;
+ read_pointer++;
+ status_cnt--;
+ end
+
+ if (pop_st_i && pop_ld_i)
+ mem_n = '0;
+
+ if (flush_i) begin
+ status_cnt = '0;
+ write_pointer = '0;
+ read_pointer = '0;
+ mem_n = '0;
+ end
+ // default assignments
+ read_pointer_n = read_pointer;
+ write_pointer_n = write_pointer;
+ status_cnt_n = status_cnt;
+ end
+
+ // output assignment
+ always_comb begin : output_assignments
+ if (empty) begin
+ lsu_ctrl_o = lsu_req_i;
+ end else begin
+ lsu_ctrl_o = mem_q[read_pointer_q];
+ end
+ end
+
+ // registers
+ always_ff @(posedge clk_i or negedge rst_ni) begin
+ if (~rst_ni) begin
+ mem_q <= '0;
+ status_cnt_q <= '0;
+ write_pointer_q <= '0;
+ read_pointer_q <= '0;
+ end else begin
+ mem_q <= mem_n;
+ status_cnt_q <= status_cnt_n;
+ write_pointer_q <= write_pointer_n;
+ read_pointer_q <= read_pointer_n;
+ end
+ end
+endmodule
+#docstring_end
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