litex/liteeth/phy/mii.py

from migen.fhdl.std import *
from migen.genlib.fsm import FSM, NextState
from migen.flow.actor import Sink, Source
from migen.bank.description import *
from migen.genlib.resetsync import AsyncResetSynchronizer

from liteethernet.common import *

class MIIPHYTX(Module):
	def __init__(self, pads):
		self.sink = sink = Sink(eth_description(8))
		###
		tx_en_r = Signal()
		tx_data_r = Signal(4)
		self.sync += [
			pads.tx_er.eq(0),
			pads.tx_en.eq(tx_en_r),
			pads.tx_data.eq(tx_data_r),
		]

		fsm = FSM(reset_state="IDLE")
		self.submodules += fsm
		fsm.act("IDLE",
			sink.ack.eq(1),
			If(sink.stb & sink.sop,
				sink.ack.eq(0),
				NextState("SEND_LO")
			)
		)
		fsm.act("SEND_LO",
			tx_data_r.eq(sink.d[0:4]),
			tx_en_r.eq(1),
			NextState("SEND_HI")
		)
		fsm.act("SEND_HI",
			tx_data_r.eq(sink.d[4:8]),
			tx_en_r.eq(1),
			sink.ack.eq(1),
			If(sink.stb & sink.eop,
				NextState("IDLE")
			).Else(
				NextState("SEND_LO")
			)
		)

class MIIPHYRX(Module):
	def __init__(self, pads):
		self.source = source = Source(eth_description(8))
		###
		sop = source.sop
		set_sop = Signal()
		clr_sop = Signal()
		self.sync += \
			If(clr_sop,
				sop.eq(0)
			).Elif(set_sop,
				sop.eq(1)
			)

		lo = Signal(4)
		hi = Signal(4)
		load_nibble = Signal(2)
		self.sync  += \
			If(load_nibble[0],
				lo.eq(pads.rx_data)
			).Elif(load_nibble[1],
				hi.eq(pads.rx_data)
			)
		self.comb += [
			source.d.eq(Cat(lo, hi))
		]

		fsm = FSM(reset_state="IDLE")
		self.submodules += fsm
		fsm.act("IDLE",
			set_sop.eq(1),
			If(pads.dv,
				load_nibble.eq(0b01),
				NextState("LOAD_HI")
			)
		)
		fsm.act("LOAD_LO",
			source.stb.eq(1),
			If(pads.dv,
				clr_sop.eq(1),
				load_nibble.eq(0b01),
				NextState("LOAD_HI")
			).Else(
				source.eop.eq(1),
				NextState("IDLE")
			)
		)
		fsm.act("LOAD_HI",
			load_nibble.eq(0b10),
			NextState("LOAD_LO")
		)

class MIIPHYCRG(Module, AutoCSR):
	def __init__(self, clock_pads, pads):
		self._reset = CSRStorage()
		###
		self.sync.base50 += clock_pads.phy.eq(~clock_pads.phy)

		self.clock_domains.cd_eth_rx = ClockDomain()
		self.clock_domains.cd_eth_tx = ClockDomain()
		self.comb += self.cd_eth_rx.clk.eq(clock_pads.rx)
		self.comb += self.cd_eth_tx.clk.eq(clock_pads.tx)

		reset = self._reset.storage
		self.comb += pads.rst_n.eq(~reset)
		self.specials += [
			AsyncResetSynchronizer(self.cd_eth_tx, reset),
			AsyncResetSynchronizer(self.cd_eth_rx, reset),
		]

class MIIPHY(Module, AutoCSR):
	def __init__(self, clock_pads, pads):
		self.dw = 8
		self.submodules.crg = MIIPHYCRG(clock_pads, pads)
		self.submodules.tx = RenameClockDomains(MIIPHYTX(pads), "eth_tx")
		self.submodules.rx = RenameClockDomains(MIIPHYRX(pads), "eth_rx")
		self.sink, self.source = self.tx.sink, self.rx.source