mii_io: Add isolation support

The specification requires that the MII be isolated before the STA
clears the BMCR.ISOLATE bit. Add support for this to the MII I/O
modules.

Signed-off-by: Sean Anderson <seanga2@gmail.com>

rtl/mii_io_rx.v

@@ -7,8 +7,10 @@
 `include "io.vh"
 
 module mii_io_rx (
-	/* On-chip */
 	input clk,
+	input isolate,
+
+	/* On-chip */
 	input ce,
 	input valid,
 	input err,
@@ -56,28 +58,31 @@ module mii_io_rx (
 
 `ifdef SYNTHESIS
 	SB_IO #(
-		.PIN_TYPE(`PIN_OUTPUT_ALWAYS | `PIN_OUTPUT_DDR)
+		.PIN_TYPE(`PIN_OUTPUT_ENABLE | `PIN_OUTPUT_DDR)
 	) rx_clk_pin (
 		.PACKAGE_PIN(rx_clk),
 		.OUTPUT_CLK(clk),
+		.OUTPUT_ENABLE(!isolate),
 		.D_OUT_0(rx_clk_p_next),
 		.D_OUT_1(rx_clk_n)
 	);
 
 	SB_IO #(
-		.PIN_TYPE(`PIN_OUTPUT_ALWAYS | `PIN_OUTPUT_REGISTERED)
+		.PIN_TYPE(`PIN_OUTPUT_ENABLE | `PIN_OUTPUT_REGISTERED)
 	) rx_dv_pin (
 		.PACKAGE_PIN(rx_dv),
 		.CLOCK_ENABLE(ce),
+		.OUTPUT_ENABLE(!isolate),
 		.OUTPUT_CLK(clk),
 		.D_OUT_0(valid)
 	);
 
 	SB_IO #(
-		.PIN_TYPE(`PIN_OUTPUT_ALWAYS | `PIN_OUTPUT_REGISTERED)
+		.PIN_TYPE(`PIN_OUTPUT_ENABLE | `PIN_OUTPUT_REGISTERED)
 	) rx_er_pin (
 		.PACKAGE_PIN(rx_er),
 		.CLOCK_ENABLE(ce),
+		.OUTPUT_ENABLE(!isolate),
 		.OUTPUT_CLK(clk),
 		.D_OUT_0(err)
 	);
@@ -85,10 +90,11 @@ module mii_io_rx (
 	genvar i;
 	generate for (i = 0; i < 4; i = i + 1) begin
 		SB_IO #(
-			.PIN_TYPE(`PIN_OUTPUT_ALWAYS | `PIN_OUTPUT_REGISTERED)
+			.PIN_TYPE(`PIN_OUTPUT_ENABLE | `PIN_OUTPUT_REGISTERED)
 		) rxd_pin (
 			.PACKAGE_PIN(rxd[i]),
 			.CLOCK_ENABLE(ce),
+			.OUTPUT_ENABLE(!isolate),
 			.OUTPUT_CLK(clk),
 			.D_OUT_0(data[i])
 		);
@@ -96,16 +102,23 @@ module mii_io_rx (
 	endgenerate
 `else
 	always @(posedge clk) begin
-		rx_clk <= rx_clk_p_next;
+		if (isolate) begin
-		if (ce) begin
+			rx_dv <= 1'bz;
+			rx_er <= 1'bz;
+			rxd <= 4'bz;
+		end else if (ce) begin
 			rx_dv <= valid;
 			rx_er <= err;
 			rxd <= data;
 		end
 	end
 
-	always @(negedge clk)
+	always @(posedge clk, negedge clk) begin
-		rx_clk <= rx_clk_n;
+		if (isolate)
+			rx_clk <= 1'bz;
+		else
+			rx_clk <= clk ? rx_clk_p_next : rx_clk_n;
+	end
 `endif
 
 	`DUMP(0)

rtl/mii_io_tx.v

@@ -7,8 +7,10 @@
 `include "io.vh"
 
 module mii_io_tx (
-	/* On-chip */
 	input clk,
+	input isolate,
+
+	/* On-chip */
 	output reg ce,
 	output reg enable,
 	output reg err,
@@ -21,7 +23,7 @@ module mii_io_tx (
 	input [3:0] txd
 );
 
-	reg ce_next;
+	reg ce_next, raw_enable;
 	reg tx_clk_p_next, tx_clk_n, tx_clk_n_next;
 	reg [2:0] counter, counter_next;
 	/* I have no idea why we need to use initial... */
@@ -44,6 +46,8 @@ module mii_io_tx (
 			counter_next = 4;
 		end
 		endcase
+
+		enable = raw_enable && !isolate;
 	end
 
 	always @(posedge clk) begin
@@ -54,10 +58,11 @@ module mii_io_tx (
 
 `ifdef SYNTHESIS
 	SB_IO #(
-		.PIN_TYPE(`PIN_OUTPUT_ALWAYS | `PIN_OUTPUT_DDR)
+		.PIN_TYPE(`PIN_OUTPUT_ENABLE | `PIN_OUTPUT_DDR)
 	) tx_clk_pin (
 		.PACKAGE_PIN(tx_clk),
 		.OUTPUT_CLK(clk),
+		.OUTPUT_ENABLE(!isolate),
 		.D_OUT_0(tx_clk_p_next),
 		.D_OUT_1(tx_clk_n)
 	);
@@ -68,7 +73,7 @@ module mii_io_tx (
 		.PACKAGE_PIN(tx_en),
 		.CLOCK_ENABLE(ce_next),
 		.INPUT_CLK(clk),
-		.D_IN_0(enable)
+		.D_IN_0(raw_enable)
 	);
 
 	SB_IO #(
@@ -94,16 +99,19 @@ module mii_io_tx (
 	endgenerate
 `else
 	always @(posedge clk) begin
-		tx_clk <= tx_clk_p_next;
 		if (ce_next) begin
-			enable <= tx_en;
+			raw_enable <= tx_en;
 			err <= tx_er;
 			data <= txd;
 		end
 	end
 
-	always @(negedge clk)
+	always @(posedge clk, negedge clk) begin
-		tx_clk <= tx_clk_n;
+		if (isolate)
+			tx_clk <= 1'bz;
+		else
+			tx_clk <= clk ? tx_clk_p_next : tx_clk_n;
+	end
 `endif
 
 	`DUMP(0)

tb/mii_io_rx.py

@@ -12,10 +12,11 @@ from .util import ClockEnable
 
 @cocotb.test(timeout_time=500, timeout_unit='ns')
 async def test_io(io):
+    io.isolate.value = 0
+    io.ce.value = 0
     io.valid.value = LogicArray('X')
     io.err.value = LogicArray('X')
     io.data.value = LogicArray('X' * 4)
-    io.ce.value = 0
     await Timer(1)
     await cocotb.start(Clock(io.clk, 8, units='ns').start())
     await ClockCycles(io.clk, 1)
@@ -78,3 +79,10 @@ async def test_io(io):
     await recv_datum(0, 1, 8)
     await recv_datum(1, 0, 9)
     await recv_datum(0, 1, 10)
+
+    io.isolate.value = 1
+    await FallingEdge(io.clk)
+    assert io.rx_clk.value.binstr == 'z'
+    assert io.rx_dv.value.binstr == 'z'
+    assert io.rx_er.value.binstr == 'z'
+    assert io.rxd.value.binstr == 'zzzz'

tb/mii_io_tx.py

@@ -12,6 +12,7 @@ from .util import ClockEnable
 
 @cocotb.test(timeout_time=500, timeout_unit='ns')
 async def test_io(io):
+    io.isolate.value = 0
     io.tx_en.value = LogicArray('X')
     io.tx_er.value = LogicArray('X')
     io.txd.value = LogicArray('X' * 4)
@@ -49,3 +50,10 @@ async def test_io(io):
     await recv_datum(0, 1, 3)
     await recv_datum(1, 0, 4)
     await recv_datum(0, 1, 5)
+
+    io.isolate.value = 1
+    io.tx_en.value = 1
+    await RisingEdge(io.clk)
+    assert io.tx_clk.value.binstr == 'z'
+    await RisingEdge(io.ce)
+    assert not io.enable.value