`default_nettype none
/*
 *  Copyright (C) 2017  Clifford Wolf <clifford@clifford.at>
 *  Copyright (C) 2018  Tim Edwards <tim@efabless.com>
 *  Copyright (C) 2020  Anton Blanchard <anton@linux.ibm.com>
 *
 *  Permission to use, copy, modify, and/or distribute this software for any
 *  purpose with or without fee is hereby granted, provided that the above
 *  copyright notice and this permission notice appear in all copies.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

`timescale 1 ns / 1 ps

module tbuart_expect_seven # (
	parameter baud_rate = 115200
) (
	input ser_rx
);
	reg [3:0] recv_state;
	reg [2:0] recv_divcnt;
	reg [7:0] recv_pattern;

	reg clk;

	initial begin
		clk <= 1'b0;
		recv_state <= 0;
		recv_divcnt <= 0;
		recv_pattern <= 0;
	end

	// Our simulation is in nanosecond steps and we want 5 clocks per bit,
	// ie 10 clock transitions
	always #(1000000000/baud_rate/10) clk <= (clk === 1'b0);

	always @(posedge clk) begin
		recv_divcnt <= recv_divcnt + 1;
		case (recv_state)
			0: begin
				if (!ser_rx)
					recv_state <= 1;
				recv_divcnt <= 0;
			end
			1: begin
				if (2*recv_divcnt > 3'd3) begin
					recv_state <= 2;
					recv_divcnt <= 0;
				end
			end
			10: begin
				if (recv_divcnt > 3'd3) begin
					recv_state <= 0;
					$display("Got %c from Microwatt", recv_pattern);
					// Expecting 7 back
					if (recv_pattern == 55) begin
						$finish;
					end else begin
						$fatal;
					end
				end
			end
			default: begin
				if (recv_divcnt > 3'd3) begin
					recv_pattern <= {ser_rx, recv_pattern[7:1]};
					recv_state <= recv_state + 1;
					recv_divcnt <= 0;
				end
			end
		endcase
	end
endmodule

module uart_tb;
	reg clock;
	reg RSTB;
	reg microwatt_reset;
	reg power1, power2;
	reg power3, power4;
	reg uart_rx;

	wire gpio;
	wire [37:0] mprj_io;
	wire [15:0] checkbits;
	wire user_flash_csb;
	wire user_flash_clk;
	inout user_flash_io0;
	inout user_flash_io1;
	wire uart_tx;

	assign mprj_io[7] = microwatt_reset;

	assign mprj_io[35] = 1'b1; // Boot from flash

	assign user_flash_csb = mprj_io[8];
	assign user_flash_clk = mprj_io[9];
	assign user_flash_io0 = mprj_io[10];
	assign mprj_io[11] = user_flash_io1;

	assign checkbits = mprj_io[31:16];

	assign uart_tx = mprj_io[6];
	assign mprj_io[5] = uart_rx;

	assign mprj_io[3] = 1'b1;  // Force CSB high.

	// 100 MHz clock
	always #5 clock <= (clock === 1'b0);

	initial begin
		clock = 0;
	end

	initial begin
		//$dumpfile("uart.vcd");
		//$dumpvars(0, uart_tb);

		$display("Microwatt UART rx -> tx test");

		repeat (1500000) @(posedge clock);
		$finish;
	end

	initial begin
		RSTB <= 1'b0;
		microwatt_reset <= 1'b1;
		#1000;
		microwatt_reset <= 1'b0;
		// Note: keep management engine in reset
		//RSTB <= 1'b1;
	end

	initial begin		// Power-up sequence
		power1 <= 1'b0;
		power2 <= 1'b0;
		power3 <= 1'b0;
		power4 <= 1'b0;
		#100;
		power1 <= 1'b1;
		#100;
		power2 <= 1'b1;
		#100;
		power3 <= 1'b1;
		#100;
		power4 <= 1'b1;
	end

	initial begin
		uart_rx <= 1'b1;

		wait(checkbits == 16'h0ffe)
		$display("Microwatt alive!");

		// 115200 = 8680 ns per bit
		$display("Writing 7 to Microwatt uart");
		uart_rx <= 1'b0;
		#8680
		uart_rx <= 1'b1;
		#8680
		uart_rx <= 1'b1;
		#8680
		uart_rx <= 1'b1;
		#8680
		uart_rx <= 1'b0;
		#8680
		uart_rx <= 1'b1;
		#8680
		uart_rx <= 1'b1;
		#8680
		uart_rx <= 1'b0;
		#8680
		uart_rx <= 1'b0;
		#8680
		$display("Done. Waiting for Microwatt to send 7 back");
		uart_rx <= 1'b1;
	end

	wire VDD3V3 = power1;
	wire VDD1V8 = power2;
	wire USER_VDD3V3 = power3;
	wire USER_VDD1V8 = power4;
	wire VSS = 1'b0;

	caravel uut (
		.vddio	  (VDD3V3),
		.vssio	  (VSS),
		.vdda	  (VDD3V3),
		.vssa	  (VSS),
		.vccd	  (VDD1V8),
		.vssd	  (VSS),
		.vdda1    (USER_VDD3V3),
		.vdda2    (USER_VDD3V3),
		.vssa1	  (VSS),
		.vssa2	  (VSS),
		.vccd1	  (USER_VDD1V8),
		.vccd2	  (USER_VDD1V8),
		.vssd1	  (VSS),
		.vssd2	  (VSS),
		.clock	  (clock),
		.gpio     (gpio),
		.mprj_io  (mprj_io),
		.resetb	  (RSTB)
	);

	spiflash_microwatt #(
		.FILENAME("microwatt.hex")
	) spiflash_microwatt (
		.csb(user_flash_csb),
		.clk(user_flash_clk),
		.io0(user_flash_io0),
		.io1(user_flash_io1)
	);

	tbuart_expect_seven #(
		.baud_rate(115200)
	) tbuart (
		.ser_rx(uart_tx)
	);

endmodule
`default_nettype wire