digilent_cmod_a7.py

#!/usr/bin/env python3

#
# This file is part of LiteX-Boards.
#
# Copyright (c) 2021 Michael T. Mayers <michael@tweakoz.com>
# SPDX-License-Identifier: BSD-2-Clause

import os
import sys
import argparse

from migen import *

from litex.build.io import CRG
from litex.build.xilinx.vivado import vivado_build_args, vivado_build_argdict

from litex_boards.platforms import digilent_cmod_a7

from litex.soc.cores.clock import *
from litex.soc.integration.soc_core import *
from litex.soc.integration.soc import SoCRegion
from litex.soc.integration.builder import *
from litex.soc.cores.led import LedChaser
from litex.soc.interconnect import wishbone

from litex.soc.integration.soc import colorer

kB = 1024
mB = 1024*kB

class _CRG(Module):
    def __init__(self, platform, sys_clk_freq):
        self.rst = Signal()
        self.cpu_reset = Signal()

        self.clock_domains.cd_sys       = ClockDomain()
        self.clock_domains.cd_sys4x     = ClockDomain(reset_less=True)
        self.clock_domains.cd_sys4x_dqs = ClockDomain(reset_less=True)

        # # #

        plls_clk12 = platform.request("clk12")
        rst_n  = platform.request("cpu_reset")
        self.comb += self.cpu_reset.eq(rst_n)

        self.submodules.pll = pll = S7MMCM(speedgrade=-1)
        self.comb += pll.reset.eq(self.cpu_reset | self.rst)

        pll.register_clkin(plls_clk12, 12e6)
        pll.create_clkout(self.cd_sys,       sys_clk_freq)
        pll.create_clkout(self.cd_sys4x,     4*sys_clk_freq)
        pll.create_clkout(self.cd_sys4x_dqs, 4*sys_clk_freq, phase=90)

        platform.add_false_path_constraints(self.cd_sys.clk, pll.clkin) # Ignore sys_clk to pll.clkin path created by SoC's rst.

# AsyncSRAM ------------------------------------------------------------------------------------------

class AsyncSRAM(Module):
    def __init__(self, platform, size):
        addr_width = size//8
        data_width = 8
        self.bus = wishbone.Interface(data_width=data_width,adr_width=addr_width)
        issiram = platform.request("issiram")
        addr = issiram.addr
        data = issiram.data
        wen = issiram.wen
        cen = issiram.cen
        ########################
        tristate_data = TSTriple(data_width)
        self.specials += tristate_data.get_tristate(data)
        ########################
        chip_ena = self.bus.cyc & self.bus.stb & self.bus.sel[0]
        write_ena = (chip_ena & self.bus.we)
        ########################
        # external write enable, 
        # external chip enable, 
        # internal tristate write enable
        ########################
        self.comb += [
            cen.eq(~chip_ena),
            wen.eq(~write_ena),
            tristate_data.oe.eq(write_ena)
        ]
        ########################
        # address and data
        ########################
        self.comb += [
            addr.eq(self.bus.adr[:addr_width]),
            self.bus.dat_r.eq(tristate_data.i[:data_width]),
            tristate_data.o.eq(self.bus.dat_w[:data_width])
        ]
        ########################
        # generate ack
        ########################
        self.sync += [
            self.bus.ack.eq(self.bus.cyc & self.bus.stb & ~self.bus.ack),
        ]
        ########################

def addAsyncSram(soc, platform, name, origin, size):
    ram_bus = wishbone.Interface(data_width=soc.bus.data_width)
    ram     = AsyncSRAM(platform,size)
    soc.bus.add_slave(name, ram.bus, SoCRegion(origin=origin, size=size, mode="rw"))
    soc.check_if_exists(name)
    soc.logger.info("ISSIRAM {} {} {}.".format(
        colorer(name),
        colorer("added", color="green"),
        soc.bus.regions[name]))
    setattr(soc.submodules, name, ram)

# BaseSoC ------------------------------------------------------------------------------------------

class BaseSoC(SoCCore):
    def __init__(self,  variant="a7-35",
                 toolchain="vivado",
                 sys_clk_freq=int(100e6),
                 with_led_chaser=True,
                 ident_version=True, 
                 with_jtagbone=True, 
                 with_mapped_flash=False, 
                 **kwargs):

        platform = digilent_cmod_a7.Platform()

        # SoCCore ----------------------------------------------------------------------------------
        SoCCore.__init__(self, platform, sys_clk_freq,
            ident          = "LiteX SoC on Digilent CmodA7",
            ident_version  = True,
            **kwargs)

        # CRG --------------------------------------------------------------------------------------

        self.submodules.crg = _CRG(platform, sys_clk_freq)

        addAsyncSram(self,platform,"main_ram",0x40000000,512*1024)        

        # Leds -------------------------------------------------------------------------------------
        if with_led_chaser:
            self.submodules.leds = LedChaser(
                pads         = platform.request_all("user_led"),
                sys_clk_freq = sys_clk_freq)

# Build --------------------------------------------------------------------------------------------

def main():
    parser = argparse.ArgumentParser(description="LiteX SoC on Arty A7")
    parser.add_argument("--toolchain",           default="vivado",                 help="Toolchain use to build (default: vivado)")
    parser.add_argument("--build",               action="store_true",              help="Build bitstream")
    parser.add_argument("--load",                action="store_true",              help="Load bitstream")
    parser.add_argument("--variant",             default="a7-35",                  help="Board variant: a7-35 (default) or a7-100")
    parser.add_argument("--sys-clk-freq",        default=48e6,                    help="System clock frequency (default: 48MHz)")

    builder_args(parser)
    soc_core_args(parser)
    vivado_build_args(parser)
    args = parser.parse_args()

    soc = BaseSoC(
        variant           = args.variant,
        toolchain         = args.toolchain,
        sys_clk_freq      = int(float(args.sys_clk_freq)),
        **soc_core_argdict(args)
    )

    builder_argd = builder_argdict(args)

    builder = Builder(soc, **builder_argd)
    builder_kwargs = vivado_build_argdict(args) if args.toolchain == "vivado" else {}
    builder.build(**builder_kwargs, run=args.build)

if __name__ == "__main__":
    main()