gateware/icE1usb: Replace custom I2C core with SB_I2C wrapper

The hard IP kind of sucks ... but we don't need i2c much (or at
all really) and using the hard IP is nearly free (LC-wise).

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

gateware/cores/no2ice40

@@ -1 +1 @@
-Subproject commit aef7d3a8ed1db329fe4815453d52518b9a08e633
+Subproject commit e2a0c694e0565ca8e065d27ac82f6746c3cb28a0

gateware/icE1usb/doc/mem-map.md

@@ -18,7 +18,8 @@ Overview
 |`0x87000000` |                  | E1 core         | [`no2e1`](../../cores/no2e1/doc/mem-map.md). See notes below.
 |`0x88000000` |                  | Misc            | See below
 |`0x89000000` |                  | GPS UART        | [`no2misc/uart_wb`](../../cores/no2misc/doc/uart_wb.md)
-|`0x8a000000` |                  | I2C             | See below
+|`0x8a000000` |                  | I2C (\*)        | See below
+|`0x8a000000` |                  | I2C (\*)        | [`no2ice40/ice40_i2c_wb`](../../cores/no2ice40/doc/ice40_i2c_wb.md)
 
 
 Memory
@@ -293,6 +294,9 @@ Channels :
 
 Very simple I2C core.
 
+Note: This is only one of the possible build option. Alternatively the bitstream can be built
+using a `SB_I2C` wrapper for I2C support. In which case, refer to the lattice documentation.
+
 #### Command (Write Only, addr `0x00`)
 
 ```text

gateware/icE1usb/rtl/top.v

@@ -11,6 +11,9 @@
 
 `default_nettype none
 
+`define WITH_SB_I2C
+// `define WITH_CUSTOM_I2C
+
 module top (
 	// E1 PHY
 	input  wire e1A_rx_hi_p,
@@ -281,6 +284,27 @@ module top (
 	// I2C [2]
 	// ---
 
+`ifdef WITH_SB_I2C
+
+	// Hard-IP
+	ice40_i2c_wb #(
+		.WITH_IOB(1),
+		.UNIT(0)
+	) i2c_I (
+		.i2c_scl  (i2c_scl),
+		.i2c_sda  (i2c_sda),
+		.wb_addr  (wb_addr[3:0]),
+		.wb_rdata (wb_rdata[2]),
+		.wb_wdata (wb_wdata),
+		.wb_we    (wb_we),
+		.wb_cyc   (wb_cyc[2]),
+		.wb_ack   (wb_ack[2]),
+		.clk      (clk_sys),
+		.rst      (rst_sys)
+	);
+
+`elsif WITH_CUSTOM_I2C
+
 	// Controller
 	i2c_master_wb #(
 		.DW(3),
@@ -324,6 +348,14 @@ module top (
 		.D_IN_0       (i2c_sda_i)
 	);
 
+`else
+
+	// Dummy
+	assign wb_ack[2] = wb_cyc[2];
+	assign wb_rdata[2] = 32'h00000000;
+
+`endif
+
 
 	// E1 LEDs & Button
 	// ----------------