rtl:core: ifu support for boot from flash

Signed-off-by: liangkangnan <liangkangnan@163.com>
pull/4/head
liangkangnan 2021-11-25 09:00:09 +08:00
parent d67f1abab3
commit 3120110be3
2 changed files with 105 additions and 0 deletions

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@ -14,7 +14,14 @@
limitations under the License. limitations under the License.
*/ */
// 从Flash启动时打开下面这个宏
//`define FLASH_BOOT
`ifdef FLASH_BOOT
`define CPU_RESET_ADDR 32'h01000000 // CPU复位地址
`else
`define CPU_RESET_ADDR 32'h00000000 // CPU复位地址 `define CPU_RESET_ADDR 32'h00000000 // CPU复位地址
`endif
`define CPU_CLOCK_HZ 25000000 // CPU时钟(25MHZ) `define CPU_CLOCK_HZ 25000000 // CPU时钟(25MHZ)
`define JTAG_RESET_FF_LEVELS 5 `define JTAG_RESET_FF_LEVELS 5

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@ -44,6 +44,102 @@ module ifu #(
); );
// 从(Nor)Flash启动(非易失)
`ifdef FLASH_BOOT
localparam S_RESET = 3'b001;
localparam S_FETCH = 3'b010;
localparam S_VALID = 3'b100;
reg[2:0] state_d, state_q;
wire inst_valid;
wire[31:0] fetch_addr_n;
reg[31:0] fetch_addr_q;
wire prdt_taken;
wire[31:0] prdt_addr;
always @ (*) begin
state_d = state_q;
case (state_q)
// 复位
S_RESET: begin
// 复位撤销后转到取指状态
if (rst_n) begin
state_d = S_FETCH;
end
end
// 取指
S_FETCH: begin
// 取指有效
if (instr_gnt_i & (~stall_i[`STALL_IF]) & (~flush_i)) begin
state_d = S_VALID;
end
end
// 指令有效
S_VALID: begin
// 回到取指状态
if (stall_i[`STALL_IF] || instr_rvalid_i || flush_i) begin
state_d = S_FETCH;
end
end
default: ;
endcase
end
// 指令有效
assign inst_valid = (state_q == S_VALID) & instr_rvalid_i & id_ready_i;
assign inst_valid_o = inst_valid;
// 指令无效时有nop指令代替
assign inst_o = inst_valid ? instr_rdata_i: `INST_NOP;
assign pc_o = fetch_addr_q;
// 更新取指地址
assign fetch_addr_n = flush_i ? flush_addr_i:
prdt_taken ? prdt_addr:
inst_valid ? fetch_addr_q + 4'h4:
fetch_addr_q;
// 取指请求
assign instr_req_o = (~stall_i[`STALL_IF]) & (state_q == S_FETCH) & (~flush_i);
// 取指地址(4字节对齐)
assign instr_addr_o = {fetch_addr_q[31:2], 2'b00};
always @ (posedge clk or negedge rst_n) begin
if (!rst_n) begin
state_q <= S_RESET;
fetch_addr_q <= `CPU_RESET_ADDR;
end else begin
state_q <= state_d;
fetch_addr_q <= fetch_addr_n;
end
end
// 分支预测
if (BranchPredictor) begin: g_branch_predictor
bpu u_bpu(
.clk(clk),
.rst_n(rst_n),
.inst_i(instr_rdata_i),
.inst_valid_i(inst_valid),
.pc_i(fetch_addr_q),
.prdt_taken_o(prdt_taken),
.prdt_addr_o(prdt_addr)
);
end else begin: g_no_branch_predictor
assign prdt_taken = 1'b0;
assign prdt_addr = 32'h0;
end
// 从Rom启动(易失)
`else
localparam S_RESET = 3'b001; localparam S_RESET = 3'b001;
localparam S_FETCH = 3'b010; localparam S_FETCH = 3'b010;
localparam S_VALID = 3'b100; localparam S_VALID = 3'b100;
@ -142,4 +238,6 @@ module ifu #(
assign prdt_addr = 32'h0; assign prdt_addr = 32'h0;
end end
`endif
endmodule endmodule