taxi/tb/lfsr/taxi_lfsr_descramble/test_taxi_lfsr_descramble.py

#!/usr/bin/env python
# SPDX-License-Identifier: CERN-OHL-S-2.0
"""

Copyright (c) 2023-2025 FPGA Ninja, LLC

Authors:
- Alex Forencich

"""

import itertools
import logging
import os

import pytest
import cocotb_test.simulator

import cocotb
from cocotb.clock import Clock
from cocotb.triggers import RisingEdge
from cocotb.regression import TestFactory


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, 10, units="ns").start())

        dut.data_in.setimmediatevalue(0)
        dut.data_in_valid.setimmediatevalue(0)

    async def 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)


def chunks(lst, n, padvalue=None):
    return itertools.zip_longest(*[iter(lst)]*n, fillvalue=padvalue)


def scramble_64b66b(data, state=0x3ffffffffffffff):
    data_out = bytearray()
    for d in data:
        b = 0
        for i in range(8):
            if bool(state & (1 << 38)) ^ bool(state & (1 << 57)) ^ bool(d & (1 << i)):
                state = ((state & 0x1ffffffffffffff) << 1) | 1
                b = b | (1 << i)
            else:
                state = (state & 0x1ffffffffffffff) << 1
        data_out.append(b)
    return data_out


def descramble_64b66b(data, state=0x3ffffffffffffff):
    data_out = bytearray()
    for d in data:
        b = 0
        for i in range(8):
            if bool(state & (1 << 38)) ^ bool(state & (1 << 57)) ^ bool(d & (1 << i)):
                b = b | (1 << i)
            state = (state & 0x1ffffffffffffff) << 1 | bool(d & (1 << i))
        data_out += bytearray([b])
    return data_out


async def run_test_descramble(dut, ref_scramble):

    data_width = len(dut.data_in)
    byte_lanes = data_width // 8

    tb = TB(dut)

    await tb.reset()

    block = bytearray(itertools.islice(itertools.cycle(range(256)), 1024))

    scr = scramble_64b66b(block)

    dscr = descramble_64b66b(scr)

    assert dscr == block

    ref_iter = iter(chunks(block, byte_lanes))

    first = True
    for b in chunks(scr, byte_lanes):
        dut.data_in.value = int.from_bytes(b, 'little')
        dut.data_in_valid.value = 1
        await RisingEdge(dut.clk)

        val = dut.data_out.value.integer

        if not first:
            ref = int.from_bytes(bytes(next(ref_iter)), 'little')

            tb.log.info("Descrambled: 0x%x (ref: 0x%x)", val, ref)

            assert ref == val

        first = False

    dut.data_in_valid.value = 0

    await RisingEdge(dut.clk)


if cocotb.SIM_NAME:

    # if cocotb.top.LFSR_POLY.value == 0x8000000001:
    if int(cocotb.top.LFSR_W.value) == 58:
        factory = TestFactory(run_test_descramble)
        factory.add_option("ref_scramble", [scramble_64b66b])
        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'))


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())


@pytest.mark.parametrize(("lfsr_w", "lfsr_poly", "lfsr_init", "lfsr_galois", "reverse", "data_w"), [
            (58,  "58'h8000000001", "'1", 0, 1, 8),
            (58,  "58'h8000000001", "'1", 0, 1, 64),
        ])
def test_taxi_lfsr_descramble(request, lfsr_w, lfsr_poly, lfsr_init, lfsr_galois, reverse, data_w):
    dut = "taxi_lfsr_descramble"
    module = os.path.splitext(os.path.basename(__file__))[0]
    toplevel = dut

    verilog_sources = [
        os.path.join(rtl_dir, "lfsr", f"{dut}.sv"),
        os.path.join(rtl_dir, "lfsr", "taxi_lfsr.sv"),
    ]

    verilog_sources = process_f_files(verilog_sources)

    parameters = {}

    parameters['LFSR_W'] = lfsr_w
    parameters['LFSR_POLY'] = lfsr_poly
    parameters['LFSR_INIT'] = lfsr_init
    parameters['LFSR_GALOIS'] = f"1'b{lfsr_galois}"
    parameters['REVERSE'] = f"1'b{reverse}"
    parameters['DATA_W'] = data_w

    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,
    )