litex/lib/sata/link/cont.py

from migen.fhdl.std import *
from migen.genlib.misc import optree

from lib.sata.common import *
from lib.sata.link.scrambler import Scrambler

class SATACONTInserter(Module):
	def __init__(self, description):
		self.sink = sink = Sink(description)
		self.source = source = Source(description)

		###

		# Detect consecutive primitives
		# tn insert CONT
		counter = Counter(max=4)
		self.submodules += counter

		is_primitive = Signal()
		last_was_primitive = Signal()
		last_primitive = Signal(32)
		change = Signal()

		cont_insert = Signal()
		scrambler_insert = Signal()
		last_primitive_insert = Signal()
		last_primitive_insert_d = Signal()

		self.comb += [
			is_primitive.eq(sink.charisk != 0),
			change.eq((sink.data != last_primitive) | ~is_primitive),
			cont_insert.eq(~change & (counter.value == 1)),
			scrambler_insert.eq(~change & (counter.value == 2)),
			last_primitive_insert.eq((counter.value == 2) & (
				(~is_primitive & last_was_primitive) |
				(is_primitive & (last_primitive == primitives["HOLD"]) & (last_primitive != sink.data))))
		]

		self.sync += \
			If(sink.stb & source.ack,
				last_primitive_insert_d.eq(last_primitive_insert),
				If(is_primitive,
					last_primitive.eq(sink.data),
					last_was_primitive.eq(1)
				).Else(
					last_was_primitive.eq(0)
				)
			)
		self.comb += \
			If(sink.stb & source.ack,
				If(change | last_primitive_insert_d,
					counter.reset.eq(1)
				).Else(
					counter.ce.eq(~scrambler_insert)
				)
			)

		# scrambler (between CONT and next primitive)
		scrambler = InsertReset(Scrambler())
		self.submodules += scrambler
		self.comb += [
			scrambler.reset.eq(ResetSignal()), #XXX: should be reseted on COMINIT / COMRESET
			scrambler.ce.eq(scrambler_insert & source.stb & source.ack)
		]

		# Datapath
		self.comb += [
			Record.connect(sink, source),
			If(sink.stb,
				If(cont_insert,
					source.charisk.eq(0b0001),
					source.data.eq(primitives["CONT"])
				).Elif(scrambler_insert,
					source.charisk.eq(0b0000),
					source.data.eq(scrambler.value)
				).Elif(last_primitive_insert,
					source.stb.eq(1),
					sink.ack.eq(0),
					source.charisk.eq(0b0001),
					source.data.eq(last_primitive)
				)
			)
		]

class SATACONTRemover(Module):
	def __init__(self, description):
		self.sink = sink = Sink(description)
		self.source = source = Source(description)

		###

		# Detect CONT
		is_primitive = Signal()
		is_cont = Signal()
		in_cont = Signal()
		cont_ongoing = Signal()

		self.comb += [
			is_primitive.eq(sink.charisk != 0),
			is_cont.eq(is_primitive & (sink.data == primitives["CONT"]))
		]
		self.sync += \
			If(is_cont,
				in_cont.eq(1)
			).Elif(is_primitive,
				in_cont.eq(0)
			)
		self.comb += cont_ongoing.eq(is_cont | (in_cont & ~is_primitive))

		# Datapath
		last_primitive = Signal()
		self.sync += [
			If(is_primitive & ~is_cont,
				last_primitive.eq(sink.data)
			)
		]
		self.comb += [
			Record.connect(sink, source),
			If(cont_ongoing,
				source.charisk.eq(0b0001),
				source.data.eq(last_primitive)
			)
		]