From ff7855900d4f4b8d3ccd840e54f5d9c940c4f7e4 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Mon, 7 Aug 2017 16:27:57 +0200
Subject: [PATCH] Refactor picosoc flash_io interfaces

---
 picosoc/picosoc.v     | 43 ++++++++++-----------
 picosoc/spiflash.v    | 33 +++++++++-------
 picosoc/spiflash_tb.v | 87 ++++++++++++++++++++++---------------------
 picosoc/spimemio.v    | 56 ++++++++++++++++++++--------
 picosoc/testbench.v   |  5 +--
 5 files changed, 129 insertions(+), 95 deletions(-)

diff --git a/picosoc/picosoc.v b/picosoc/picosoc.v
index 6521152..23260c9 100644
--- a/picosoc/picosoc.v
+++ b/picosoc/picosoc.v
@@ -88,31 +88,32 @@ module picosoc (
 	);
 
 	spimemio spimemio (
-		.clk(clk),
-		.resetn(resetn),
-		.valid (mem_valid && mem_addr[31:24] == 8'h 01),
-		.ready (spimem_ready),
-		.addr  (mem_addr[23:0]),
-		.rdata (spimem_rdata),
+		.clk    (clk),
+		.resetn (resetn),
+		.valid  (mem_valid && mem_addr[31:24] == 8'h 01),
+		.ready  (spimem_ready),
+		.addr   (mem_addr[23:0]),
+		.rdata  (spimem_rdata),
 
-		.flash_csb (flash_csb),
-		.flash_clk (flash_clk),
+		.flash_csb    (flash_csb   ),
+		.flash_clk    (flash_clk   ),
 
-		.flash_io0 (flash_io0_do),
-		.flash_io1 (flash_io1_di),
-		.flash_io2 (flash_io2_di),
-		.flash_io3 (flash_io3_di)
+		.flash_io0_oe (flash_io0_oe),
+		.flash_io1_oe (flash_io1_oe),
+		.flash_io2_oe (flash_io2_oe),
+		.flash_io3_oe (flash_io3_oe),
+
+		.flash_io0_do (flash_io0_do),
+		.flash_io1_do (flash_io1_do),
+		.flash_io2_do (flash_io2_do),
+		.flash_io3_do (flash_io3_do),
+
+		.flash_io0_di (flash_io0_di),
+		.flash_io1_di (flash_io1_di),
+		.flash_io2_di (flash_io2_di),
+		.flash_io3_di (flash_io3_di)
 	);
 
-	assign flash_io0_oe = 1;
-	assign flash_io1_oe = 0;
-	assign flash_io2_oe = 0;
-	assign flash_io3_oe = 0;
-
-	assign flash_io1_do = 0;
-	assign flash_io2_do = 0;
-	assign flash_io3_do = 0;
-
 	reg [31:0] memory [0:MEM_WORDS-1];
 
 	always @(posedge clk) begin
diff --git a/picosoc/spiflash.v b/picosoc/spiflash.v
index c1e9615..6e6137f 100644
--- a/picosoc/spiflash.v
+++ b/picosoc/spiflash.v
@@ -15,15 +15,23 @@
  *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *
- *
- *  Supported commands:
- *     AB, B9, FF, 03, EB, ED
- *
- *  Well written SPI flash data sheets:
- *     Cypress S25FL064L http://www.cypress.com/file/316661/download
- *
  */
 
+`timescale 1 ns / 1 ps
+
+//
+// Simple SPI flash simulation model
+//
+// This model samples io input signals 1ns before the SPI clock edge and
+// updates output signals 1ns after the SPI clock edge.
+//
+// Supported commands:
+//    AB, B9, FF, 03, EB, ED
+//
+// Well written SPI flash data sheets:
+//    Cypress S25FL064L http://www.cypress.com/file/316661/download
+//
+
 module spiflash (
 	input csb,
 	input clk,
@@ -47,7 +55,6 @@ module spiflash (
 	reg [7:0] spi_out;
 	reg spi_io_vld;
 
-	reg qspi_active = 0;
 	reg powered_up = 0;
 
 	localparam [3:0] mode_spi         = 1;
@@ -69,10 +76,10 @@ module spiflash (
 	reg io2_dout = 0;
 	reg io3_dout = 0;
 
-	assign io0 = io0_oe ? io0_dout : 1'bz;
-	assign io1 = io1_oe ? io1_dout : 1'bz;
-	assign io2 = io2_oe ? io2_dout : 1'bz;
-	assign io3 = io3_oe ? io3_dout : 1'bz;
+	assign #1 io0 = io0_oe ? io0_dout : 1'bz;
+	assign #1 io1 = io1_oe ? io1_dout : 1'bz;
+	assign #1 io2 = io2_oe ? io2_dout : 1'bz;
+	assign #1 io3 = io3_oe ? io3_dout : 1'bz;
 
 	wire io0_delayed;
 	wire io1_delayed;
@@ -105,7 +112,7 @@ module spiflash (
 					powered_up = 0;
 
 				if (spi_cmd == 8'h ff)
-					qspi_active = 0;
+					xip_cmd = 0;
 			end
 
 			if (powered_up && spi_cmd == 'h 03) begin
diff --git a/picosoc/spiflash_tb.v b/picosoc/spiflash_tb.v
index 769a3a0..ce2e949 100644
--- a/picosoc/spiflash_tb.v
+++ b/picosoc/spiflash_tb.v
@@ -17,6 +17,8 @@
  *
  */
 
+`timescale 1 ns / 1 ps
+
 module testbench;
 	reg flash_csb = 1;
 	reg flash_clk = 0;
@@ -69,10 +71,10 @@ module testbench;
 
 	task xfer_begin;
 		begin
-			#50;
+			#5;
 			flash_csb = 0;
 			$display("-- BEGIN");
-			#50;
+			#5;
 		end
 	endtask
 
@@ -83,17 +85,17 @@ module testbench;
 			flash_io2_oe = 0;
 			flash_io3_oe = 0;
 
-			#50;
+			#5;
 			flash_clk = 1;
-			#50;
+			#5;
 			flash_clk = 0;
-			#50;
+			#5;
 		end
 	endtask
 
 	task xfer_end;
 		begin
-			#50;
+			#5;
 			flash_csb = 1;
 			flash_io0_oe = 0;
 			flash_io1_oe = 0;
@@ -101,7 +103,7 @@ module testbench;
 			flash_io3_oe = 0;
 			$display("-- END");
 			$display("");
-			#50;
+			#5;
 		end
 	endtask
 
@@ -116,15 +118,15 @@ module testbench;
 
 			for (i = 0; i < 8; i=i+1) begin
 				flash_io0_dout = data[7-i];
-				#50;
+				#5;
+				flash_clk = 1;
 				rdata[7-i] = flash_io1;
-				flash_clk <= 1;
-				#50;
+				#5;
 				flash_clk = 0;
 			end
 
 			$display("--  SPI SDR  %02x %02x", data, rdata);
-			#50;
+			#5;
 		end
 	endtask
 
@@ -142,23 +144,23 @@ module testbench;
 			flash_io2_dout = data[6];
 			flash_io3_dout = data[7];
 
-			#50;
+			#5;
 			flash_clk = 1;
-			#50;
-			flash_clk = 0;
 
+			#5;
+			flash_clk = 0;
 			flash_io0_dout = data[0];
 			flash_io1_dout = data[1];
 			flash_io2_dout = data[2];
 			flash_io3_dout = data[3];
 
-			#50;
+			#5;
 			flash_clk = 1;
-			#50;
+			#5;
 			flash_clk = 0;
 
 			$display("-- QSPI SDR  %02x --", data);
-			#50;
+			#5;
 		end
 	endtask
 
@@ -170,26 +172,28 @@ module testbench;
 			flash_io2_oe = 0;
 			flash_io3_oe = 0;
 
-			#50;
+			#5;
+			flash_clk = 1;
 			rdata[4] = flash_io0;
 			rdata[5] = flash_io1;
 			rdata[6] = flash_io2;
 			rdata[7] = flash_io3;
-			flash_clk <= 1;
-			#50;
+
+			#5;
 			flash_clk = 0;
 
-			#50;
+			#5;
+			flash_clk = 1;
 			rdata[0] = flash_io0;
 			rdata[1] = flash_io1;
 			rdata[2] = flash_io2;
 			rdata[3] = flash_io3;
-			flash_clk <= 1;
-			#50;
+
+			#5;
 			flash_clk = 0;
 
 			$display("-- QSPI SDR  -- %02x", rdata);
-			#50;
+			#5;
 		end
 	endtask
 
@@ -202,24 +206,23 @@ module testbench;
 			flash_io2_oe = 1;
 			flash_io3_oe = 1;
 
-			flash_io0_dout <= data[4];
-			flash_io1_dout <= data[5];
-			flash_io2_dout <= data[6];
-			flash_io3_dout <= data[7];
+			flash_io0_dout = data[4];
+			flash_io1_dout = data[5];
+			flash_io2_dout = data[6];
+			flash_io3_dout = data[7];
 
-			#50;
+			#5;
 			flash_clk = 1;
+			flash_io0_dout = data[0];
+			flash_io1_dout = data[1];
+			flash_io2_dout = data[2];
+			flash_io3_dout = data[3];
 
-			flash_io0_dout <= data[0];
-			flash_io1_dout <= data[1];
-			flash_io2_dout <= data[2];
-			flash_io3_dout <= data[3];
-
-			#50;
+			#5;
 			flash_clk = 0;
 
 			$display("-- QSPI DDR  %02x --", data);
-			#50;
+			#5;
 		end
 	endtask
 
@@ -231,22 +234,22 @@ module testbench;
 			flash_io2_oe = 0;
 			flash_io3_oe = 0;
 
-			#50;
+			#5;
+			flash_clk = 1;
 			rdata[4] = flash_io0;
 			rdata[5] = flash_io1;
 			rdata[6] = flash_io2;
 			rdata[7] = flash_io3;
-			flash_clk <= 1;
 
-			#50;
+			#5;
+			flash_clk = 0;
 			rdata[0] = flash_io0;
 			rdata[1] = flash_io1;
 			rdata[2] = flash_io2;
 			rdata[3] = flash_io3;
-			flash_clk <= 0;
 
 			$display("-- QSPI DDR  -- %02x", rdata);
-			#50;
+			#5;
 		end
 	endtask
 
@@ -351,7 +354,7 @@ module testbench;
 		xfer_qspi_ddr_rd; expect(word1[31:24]);
 		xfer_end;
 
-		#500;
+		#5;
 
 		if (errcount) begin
 			$display("FAIL");
diff --git a/picosoc/spimemio.v b/picosoc/spimemio.v
index 6bb4ea6..57347cc 100644
--- a/picosoc/spimemio.v
+++ b/picosoc/spimemio.v
@@ -27,10 +27,21 @@ module spimemio (
 
 	output reg flash_csb,
 	output reg flash_clk,
-	output     flash_io0,
-	input      flash_io1,
-	input      flash_io2,
-	input      flash_io3
+
+	output reg flash_io0_oe,
+	output reg flash_io1_oe,
+	output reg flash_io2_oe,
+	output reg flash_io3_oe,
+
+	output reg flash_io0_do,
+	output reg flash_io1_do,
+	output reg flash_io2_do,
+	output reg flash_io3_do,
+
+	input      flash_io0_di,
+	input      flash_io1_di,
+	input      flash_io2_di,
+	input      flash_io3_di
 );
 	parameter ENABLE_PREFETCH = 1;
 
@@ -39,36 +50,49 @@ module spimemio (
 
 	reg [31:0] buffer;
 	reg [6:0] xfer_cnt;
+	reg pulse_csb_8;
 	reg xfer_wait;
 	reg prefetch;
 
-	reg spi_mosi;
-	wire spi_miso;
-
-	assign flash_io0 = spi_mosi;
-	assign spi_miso = flash_io1;
-
 	always @(posedge clk) begin
 		ready <= 0;
 		if (!resetn) begin
-			flash_csb <= 1;
-			flash_clk <= 1;
-			xfer_cnt <= 8;
-			buffer <= 8'hAB << 24;
 			addr_q_vld <= 0;
 			xfer_wait <= 0;
 			prefetch <= 0;
+
+			xfer_cnt <= 16;
+			pulse_csb_8 <= 1;
+			buffer <= {8'h FF, 8'h AB, 16'h 0000};
+
+			flash_csb <= 1;
+			flash_clk <= 1;
+
+			flash_io0_oe <= 0;
+			flash_io1_oe <= 0;
+			flash_io2_oe <= 0;
+			flash_io3_oe <= 0;
+
+			flash_io0_do <= 0;
+			flash_io1_do <= 0;
+			flash_io2_do <= 0;
+			flash_io3_do <= 0;
 		end else
 		if (xfer_cnt) begin
+			if (xfer_cnt == 8 && pulse_csb_8) begin
+				pulse_csb_8 <= 0;
+				flash_csb <= 1;
+			end else
 			if (flash_csb) begin
 				flash_csb <= 0;
 			end else
 			if (flash_clk) begin
 				flash_clk <= 0;
-				spi_mosi <= buffer[31];
+				flash_io0_oe <= 1;
+				flash_io0_do <= buffer[31];
 			end else begin
 				flash_clk <= 1;
-				buffer <= {buffer, spi_miso};
+				buffer <= {buffer, flash_io1_di};
 				xfer_cnt <= xfer_cnt - 1;
 			end
 		end else
diff --git a/picosoc/testbench.v b/picosoc/testbench.v
index 8d968e0..6b1cae2 100644
--- a/picosoc/testbench.v
+++ b/picosoc/testbench.v
@@ -17,6 +17,8 @@
  *
  */
 
+`timescale 1 ns / 1 ps
+
 module testbench;
 	reg clk;
 	always #5 clk = (clk === 1'b0);
@@ -37,9 +39,6 @@ module testbench;
 		$stop;
 	end
 
-	wire [31:0] gpio_i = 0;
-	wire [31:0] gpio_o;
-
 	wire flash_csb;
 	wire flash_clk;