litex/migen/flow/plumbing.py

from migen.fhdl.std import *
from migen.flow.actor import *
from migen.genlib.record import *
from migen.genlib.misc import optree

class Buffer(PipelinedActor):
	def __init__(self, layout):
		self.d = Sink(layout)
		self.q = Source(layout)
		PipelinedActor.__init__(self, 1)
		self.sync += If(self.pipe_ce, self.q.payload.eq(self.d.payload))

class Combinator(Module):
	def __init__(self, layout, subrecords):
		self.source = Source(layout)
		sinks = []
		for n, r in enumerate(subrecords):
			s = Sink(layout_partial(layout, *r))
			setattr(self, "sink"+str(n), s)
			sinks.append(s)
		self.busy = Signal()

		###
	
		self.comb += [
			self.busy.eq(0),
			self.source.stb.eq(optree("&", [sink.stb for sink in sinks]))
		]
		self.comb += [sink.ack.eq(self.source.ack & self.source.stb) for sink in sinks]
		self.comb += [self.source.payload.eq(sink.payload) for sink in sinks]

class Splitter(Module):
	def __init__(self, layout, subrecords):
		self.sink = Sink(layout)
		sources = []
		for n, r in enumerate(subrecords):
			s = Source(layout_partial(layout, *r))
			setattr(self, "source"+str(n), s)
			sources.append(s)
		self.busy = Signal()
		
		###

		self.comb += [source.payload.eq(self.sink.payload) for source in sources]
		already_acked = Signal(len(sources))
		self.sync += If(self.sink.stb,
				already_acked.eq(already_acked | Cat(*[s.ack for s in sources])),
				If(self.sink.ack, already_acked.eq(0))
			)
		self.comb += self.sink.ack.eq(optree("&",
				[s.ack | already_acked[n] for n, s in enumerate(sources)]))
		for n, s in enumerate(sources):
			self.comb += s.stb.eq(self.sink.stb & ~already_acked[n])

# Actors whose layout should be inferred from what their single sink is connected to.
layout_sink = {Buffer, Splitter}
# Actors whose layout should be inferred from what their single source is connected to.
layout_source = {Buffer, Combinator}
# All actors.
actors = layout_sink | layout_source