bus/asmi: port sharing support

migen/bus/asmibus.py

@@ -1,6 +1,7 @@
 from migen.fhdl.structure import *
 from migen.fhdl.module import Module, FinalizeError
 from migen.genlib.misc import optree
+from migen.genlib import roundrobin
 from migen.bus.transactions import *
 from migen.sim.generic import Proxy
 
@@ -300,3 +301,83 @@ class Target(Module):
 		else:
 			s.wr(self.hub.call, 0)
 			self._calling_tag = -1
+
+# Port sharing
+
+class SharedPort:
+	def __init__(self, base_port):
+		if not base_port.finalized:
+			raise FinalizeError
+		self.finalized = True
+
+		nslots = len(base_port.slots)
+
+		self.hub = base_port.hub
+		self.base = base_port.base
+		# 1 if that slot is assigned to us
+		self.slots = [Signal() for i in range(nslots)]
+		
+		# request issuance
+		self.adr = Signal(self.hub.aw)
+		self.we = Signal()
+		self.stb = Signal()
+		if nslots > 1:
+			self.tag_issue = Signal(max=nslots)
+		self.ack = Signal()
+		
+		# request completion
+		self.call = Signal()
+		self.tag_call = Signal(self.hub.tagbits)
+		self.dat_r = Signal(self.hub.dw)
+		self.dat_w = Signal(self.hub.dw)
+		self.dat_wm = Signal(self.hub.dw//8)
+
+	def get_call_expression(self, slotn=0):
+		if not self.finalized:
+			raise FinalizeError
+		return self.call \
+			& (self.tag_call == (self.base + slotn))
+
+class PortSharer(Module):
+	def __init__(self, base_port, nshares):
+		self.shared_ports = [SharedPort(base_port) for i in range(nshares)]
+
+		###
+
+		# request issuance
+		self.submodules.rr = roundrobin.RoundRobin(nshares, roundrobin.SP_CE)
+		self.comb += [
+			self.rr.request.eq(Cat(*[sp.stb for sp in self.shared_ports])),
+			self.rr.ce.eq(base_port.ack)
+		]
+		self.comb += [
+			base_port.adr.eq(Array(sp.adr for sp in self.shared_ports)[self.rr.grant]),
+			base_port.we.eq(Array(sp.we for sp in self.shared_ports)[self.rr.grant]),
+			base_port.stb.eq(Array(sp.stb for sp in self.shared_ports)[self.rr.grant]),
+		]
+		if hasattr(base_port, "tag_issue"):
+			self.comb += [sp.tag_issue.eq(base_port.tag_issue) for sp in self.shared_ports]
+		self.comb += [sp.ack.eq(base_port.ack & (self.rr.grant == n)) for n, sp in enumerate(self.shared_ports)]
+
+		# request completion
+		self.comb += [sp.call.eq(base_port.call & Array(sp.slots)[base_port.tag_call-base_port.base])
+			for sp in self.shared_ports]
+		self.comb += [sp.tag_call.eq(base_port.tag_call) for sp in self.shared_ports]
+		self.comb += [sp.dat_r.eq(base_port.dat_r) for sp in self.shared_ports]
+		self.comb += [
+			base_port.dat_w.eq(optree("|", [sp.dat_w for sp in self.shared_ports])),
+			base_port.dat_wm.eq(optree("|", [sp.dat_wm for sp in self.shared_ports])),
+		]
+		
+		# request ownership tracking
+		if hasattr(base_port, "tag_issue"):
+			for sp in self.shared_ports:
+				self.sync += If(sp.stb & sp.ack, Array(sp.slots)[sp.tag_issue].eq(1))
+				for n, slot in enumerate(sp.slots):
+					self.sync += If(base_port.call & (base_port.tag_call == (base_port.base + n)), slot.eq(0))
+		else:
+			for sp in self.shared_ports:
+				self.sync += [
+					If(sp.stb & sp.ack, sp.slots[0].eq(1)),
+					If(base_port.call & (base_port.tag_call == base_port.base), sp.slots[0].eq(0))
+				]