From 945d655d451f513095a1ea3cb603b7ebe97b3b89 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Fri, 10 Feb 2012 15:21:04 +0100
Subject: [PATCH] bus: ASMI hub (untested)

---
 migen/bus/asmibus.py | 140 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 migen/bus/asmibus.py

diff --git a/migen/bus/asmibus.py b/migen/bus/asmibus.py
new file mode 100644
index 000000000..e52a9a20b
--- /dev/null
+++ b/migen/bus/asmibus.py
@@ -0,0 +1,140 @@
+from migen.fhdl.structure import *
+
+class FinalizeError(Exception):
+	pass
+
+(SLOT_EMPTY, SLOT_PENDING, SLOT_PROCESSING) = range(3)
+
+class Slot:
+	def __init__(self, aw, time):
+		self.state = Signal(BV(2))
+		self.we = Signal()
+		self.adr = Signal(BV(aw))
+		self.time = time
+		if self.time:
+			self._counter = Signal(BV(bits_for(time)))
+			self.mature = Signal()
+		
+		self.allocate = Signal()
+		self.allocate_we = Signal()
+		self.allocate_adr = Signal(BV(aw))
+		self.process = Signal()
+		self.call = Signal()
+	
+	def get_fragment(self):
+		comb = []
+		sync = [
+			If(self.allocate,
+				self.state.eq(SLOT_PENDING)
+				self.we.eq(self.allocate_we),
+				self.adr.eq(self.allocate_adr)
+			),
+			If(self.process, self.state.eq(SLOT_PROCESSING)),
+			If(self.call, self.state.eq(SLOT_EMPTY))
+		]
+		if self.time:
+			comb += [
+				self.mature.eq(self._counter == 0)
+			]
+			sync += [
+				If(self.allocate,
+					self._counter.eq(self.time)
+				).Elif(self._counter.eq != 0,
+					self._counter.eq(self._counter - 1)
+				)
+			]
+		return Fragment(comb, sync)
+
+class Port:
+	def __init__(self, hub, nslots):
+		self.hub = hub
+		self.slots = [Slot(self.hub.aw, self.hub.time) for i in range(nslots)]
+		self.finalized = False
+		
+		# request issuance
+		self.adr = Signal(BV(self.hub.aw))
+		self.we = Signal()
+		self.stb = Signal()
+		# tag_issue is created by finalize()
+		self.ack = Signal()
+		
+		# request completion
+		self.call = Signal()
+		# tag_call is created by finalize()
+		self.dat_r = Signal(BV(self.hub.dw))
+		self.dat_w = Signal(BV(self.hub.dw))
+		self.dat_wm = Signal(BV(self.hub.dw//8))
+	
+	def finalize(self, tagbits, base):
+		if self.finalized:
+			raise FinalizeError
+		self.tagbits = tagbits
+		self.base = base
+		nslots = len(self.slots)
+		if nslots > 1:
+			self.tag_issue = Signal(BV(bits_for(nslots-1)))
+		self.tag_call = Signal(BV(tagbits))
+	
+	def get_call_expression(self, slotn=0):
+		if not self.finalized:
+			raise FinalizeError
+		return self.call \
+			&& (self.tag_call == Constant(self.base + slotn, BV(self.tagbits)))
+		
+	def get_fragment(self):
+		if not self.finalized:
+			raise FinalizeError
+		
+		slots_fragment = sum([s.get_fragment() for s in self.slots], Fragment())
+		
+		comb = []
+		sync = []
+		
+		# allocate
+		for s in self.slots:
+			comb += [
+				s.allocate_we.eq(self.we),
+				s.allocate_adr.eq(self.adr)
+			]
+		choose_slot = None
+		for s in reversed(self.slots):
+			choose_slot = If(s.state == SLOT_EMPTY,
+				self.ack.eq(1),
+				s.allocate.eq(self.stb)
+			).Else(choose_slot)
+		comb.append(choose_slot)
+		
+		# call
+		comb += [s.call.eq(self.get_call_expression(n))
+			for n, s in enumerate(self.slots)]
+		
+		return slots_fragment + Fragment(comb, sync)
+
+class Hub:
+	def __init__(self, aw, dw, time=0):
+		self.aw = aw
+		self.dw = dw
+		self.time = time
+		self.ports = []
+		self.finalized = False
+	
+	def get_port(self, nslots=1):
+		if self.finalized:
+			raise FinalizeError
+		self.ports.append(Port(self, nslots))
+	
+	def finalize(self):
+		if self.finalized:
+			raise FinalizeError
+		self.finalized = True
+		nslots = sum([len(port.slots) for port in self.ports])
+		tagbits = bits_for(nslots-1)
+		base = 0
+		for port in self.ports:
+			port.finalize(tagbits, base)
+			base += len(port.slots)
+	
+	def get_fragment(self):
+		if not self.finalized:
+			raise FinalizeError
+		return sum([port.get_fragment() for port in self.ports])