lss: Add I2C slave APB master module and testbench

Signed-off-by: Alex Forencich <alex@alexforencich.com>

src/lss/tb/taxi_i2c_slave_apb_master/Makefile

@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: CERN-OHL-S-2.0
+#
+# Copyright (c) 2020-2026 FPGA Ninja, LLC
+#
+# Authors:
+# - Alex Forencich
+
+TOPLEVEL_LANG = verilog
+
+SIM ?= verilator
+WAVES ?= 0
+
+COCOTB_HDL_TIMEUNIT = 1ns
+COCOTB_HDL_TIMEPRECISION = 1ns
+
+RTL_DIR = ../../rtl
+LIB_DIR = ../../lib
+TAXI_SRC_DIR = $(LIB_DIR)/taxi/src
+
+DUT      = taxi_i2c_slave_apb_master
+COCOTB_TEST_MODULES = test_$(DUT)
+COCOTB_TOPLEVEL     = test_$(DUT)
+MODULE   = $(COCOTB_TEST_MODULES)
+TOPLEVEL = $(COCOTB_TOPLEVEL)
+VERILOG_SOURCES += $(COCOTB_TOPLEVEL).sv
+VERILOG_SOURCES += $(RTL_DIR)/$(DUT).f
+
+# handle file list files
+process_f_file = $(call process_f_files,$(addprefix $(dir $1),$(shell cat $1)))
+process_f_files = $(foreach f,$1,$(if $(filter %.f,$f),$(call process_f_file,$f),$f))
+uniq_base = $(if $1,$(call uniq_base,$(foreach f,$1,$(if $(filter-out $(notdir $(lastword $1)),$(notdir $f)),$f,))) $(lastword $1))
+VERILOG_SOURCES := $(call uniq_base,$(call process_f_files,$(VERILOG_SOURCES)))
+
+# module parameters
+export PARAM_FILTER_LEN := 4
+export PARAM_APB_DATA_W := 32
+export PARAM_APB_ADDR_W := 16
+
+ifeq ($(SIM), icarus)
+	PLUSARGS += -fst
+
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-P $(COCOTB_TOPLEVEL).$(subst PARAM_,,$(v))=$($(v)))
+else ifeq ($(SIM), verilator)
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-G$(subst PARAM_,,$(v))=$($(v)))
+
+	ifeq ($(WAVES), 1)
+		COMPILE_ARGS += --trace-fst
+		VERILATOR_TRACE = 1
+	endif
+endif
+
+include $(shell cocotb-config --makefiles)/Makefile.sim

src/lss/tb/taxi_i2c_slave_apb_master/test_taxi_i2c_slave_apb_master.py

@@ -0,0 +1,186 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: CERN-OHL-S-2.0
+"""
+
+Copyright (c) 2020-2026 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+"""
+
+import itertools
+import logging
+import os
+import struct
+
+import cocotb_test.simulator
+
+import cocotb
+from cocotb.clock import Clock
+from cocotb.triggers import RisingEdge
+from cocotb.regression import TestFactory
+
+from cocotbext.i2c import I2cMaster
+from cocotbext.axi import ApbBus, ApbRam
+
+
+class TB:
+    def __init__(self, dut):
+        self.dut = dut
+
+        self.log = logging.getLogger("cocotb.tb")
+        self.log.setLevel(logging.DEBUG)
+
+        cocotb.start_soon(Clock(dut.clk, 8, units="ns").start())
+
+        self.i2c_master = I2cMaster(sda=dut.i2c_sda_o, sda_o=dut.i2c_sda_i,
+            scl=dut.i2c_scl_o, scl_o=dut.i2c_scl_i, speed=4000e3)
+
+        self.apb_ram = ApbRam(ApbBus.from_entity(dut.m_apb), dut.clk, dut.rst, size=2**16)
+
+        dut.enable.setimmediatevalue(1)
+        dut.device_address.setimmediatevalue(0x50)
+
+    def set_backpressure_generator(self, generator=None):
+        if generator:
+            self.apb_ram.set_pause_generator(generator())
+
+    async def cycle_reset(self):
+        self.dut.rst.setimmediatevalue(0)
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+        self.dut.rst.value = 1
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+        self.dut.rst.value = 0
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+
+
+async def run_test_write(dut, data_in=None, backpressure_inserter=None):
+
+    tb = TB(dut)
+
+    byte_lanes = tb.apb_ram.byte_lanes
+
+    await tb.cycle_reset()
+
+    tb.set_backpressure_generator(backpressure_inserter)
+
+    for length in range(1, byte_lanes*2):
+        for offset in range(byte_lanes):
+            tb.log.info("length %d, offset %d", length, offset)
+            addr = offset+0x1000
+            test_data = bytearray([x % 256 for x in range(length)])
+
+            tb.apb_ram.write(addr-128, b'\xaa'*(length+256))
+
+            await tb.i2c_master.write(0x50, struct.pack('>H', addr)+test_data)
+            await tb.i2c_master.send_stop()
+
+            tb.log.debug("%s", tb.apb_ram.hexdump_str((addr & ~0xf)-16, (((addr & 0xf)+length-1) & ~0xf)+48))
+
+            assert tb.apb_ram.read(addr, length) == test_data
+            assert tb.apb_ram.read(addr-1, 1) == b'\xaa'
+            assert tb.apb_ram.read(addr+length, 1) == b'\xaa'
+
+    await RisingEdge(dut.clk)
+    await RisingEdge(dut.clk)
+
+
+async def run_test_read(dut, data_in=None, backpressure_inserter=None):
+
+    tb = TB(dut)
+
+    byte_lanes = tb.apb_ram.byte_lanes
+
+    await tb.cycle_reset()
+
+    tb.set_backpressure_generator(backpressure_inserter)
+
+    for length in range(1, byte_lanes*2):
+        for offset in range(byte_lanes):
+            tb.log.info("length %d, offset %d", length, offset)
+            addr = offset+0x1000
+            test_data = bytearray([x % 256 for x in range(length)])
+
+            tb.apb_ram.write(addr, test_data)
+
+            await tb.i2c_master.write(0x50, struct.pack('>H', addr))
+            data = await tb.i2c_master.read(0x50, length)
+            await tb.i2c_master.send_stop()
+
+            assert data == test_data
+
+    await RisingEdge(dut.clk)
+    await RisingEdge(dut.clk)
+
+
+def cycle_pause():
+    return itertools.cycle([1, 1, 1, 0])
+
+
+if getattr(cocotb, 'top', None) is not None:
+
+    for test in [run_test_write, run_test_read]:
+
+        factory = TestFactory(test)
+        factory.add_option("backpressure_inserter", [None, cycle_pause])
+        factory.generate_tests()
+
+
+# cocotb-test
+
+tests_dir = os.path.abspath(os.path.dirname(__file__))
+rtl_dir = os.path.abspath(os.path.join(tests_dir, '..', '..', 'rtl'))
+lib_dir = os.path.abspath(os.path.join(tests_dir, '..', '..', 'lib'))
+taxi_src_dir = os.path.abspath(os.path.join(lib_dir, 'taxi', 'src'))
+
+
+def process_f_files(files):
+    lst = {}
+    for f in files:
+        if f[-2:].lower() == '.f':
+            with open(f, 'r') as fp:
+                l = fp.read().split()
+            for f in process_f_files([os.path.join(os.path.dirname(f), x) for x in l]):
+                lst[os.path.basename(f)] = f
+        else:
+            lst[os.path.basename(f)] = f
+    return list(lst.values())
+
+
+def test_taxi_i2c_slave_apb_master(request):
+    dut = "taxi_i2c_slave_apb_master"
+    module = os.path.splitext(os.path.basename(__file__))[0]
+    toplevel = module
+
+    verilog_sources = [
+        os.path.join(tests_dir, f"{toplevel}.sv"),
+        os.path.join(rtl_dir, f"{dut}.f"),
+    ]
+
+    verilog_sources = process_f_files(verilog_sources)
+
+    parameters = {}
+
+    parameters['FILTER_LEN'] = 4
+    parameters['APB_DATA_W'] = 32
+    parameters['APB_ADDR_W'] = 16
+
+    extra_env = {f'PARAM_{k}': str(v) for k, v in parameters.items()}
+
+    sim_build = os.path.join(tests_dir, "sim_build",
+        request.node.name.replace('[', '-').replace(']', ''))
+
+    cocotb_test.simulator.run(
+        simulator="verilator",
+        python_search=[tests_dir],
+        verilog_sources=verilog_sources,
+        toplevel=toplevel,
+        module=module,
+        parameters=parameters,
+        sim_build=sim_build,
+        extra_env=extra_env,
+    )

src/lss/tb/taxi_i2c_slave_apb_master/test_taxi_i2c_slave_apb_master.sv

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: CERN-OHL-S-2.0
+/*
+
+Copyright (c) 2025-2026 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+*/
+
+`resetall
+`timescale 1ns / 1ps
+`default_nettype none
+
+/*
+ * I2C slave APB master testbench
+ */
+module test_taxi_i2c_slave_apb_master #
+(
+    /* verilator lint_off WIDTHTRUNC */
+    parameter FILTER_LEN = 4,
+    parameter APB_DATA_W = 32,
+    parameter APB_ADDR_W = 16
+    /* verilator lint_on WIDTHTRUNC */
+)
+();
+
+logic clk;
+logic rst;
+
+logic i2c_scl_i;
+logic i2c_scl_o;
+logic i2c_sda_i;
+logic i2c_sda_o;
+
+taxi_apb_if #(
+    .DATA_W(APB_DATA_W),
+    .ADDR_W(APB_ADDR_W),
+    .PAUSER_EN(0),
+    .PWUSER_EN(0),
+    .PRUSER_EN(0),
+    .PBUSER_EN(0)
+) m_apb();
+
+logic busy;
+logic [6:0] bus_address;
+logic bus_addressed;
+logic bus_active;
+
+logic [15:0] prescale;
+logic stop_on_idle;
+
+logic enable;
+logic [6:0] device_address;
+
+taxi_i2c_slave_apb_master #(
+    .FILTER_LEN(FILTER_LEN)
+)
+uut (
+    .clk(clk),
+    .rst(rst),
+
+    /*
+     * I2C interface
+     */
+    .i2c_scl_i(i2c_scl_i),
+    .i2c_scl_o(i2c_scl_o),
+    .i2c_sda_i(i2c_sda_i),
+    .i2c_sda_o(i2c_sda_o),
+
+    /*
+     * APB master interface
+     */
+    .m_apb(m_apb),
+
+    /*
+     * Status
+     */
+    .busy(busy),
+    .bus_address(bus_address),
+    .bus_addressed(bus_addressed),
+    .bus_active(bus_active),
+
+    /*
+     * Configuration
+     */
+    .enable(enable),
+    .device_address(device_address)
+);
+
+endmodule
+
+`resetall