wishbone: arbiter

migen/bus/wishbone.py

@@ -1,5 +1,7 @@
 from migen.fhdl import structure as f
-from .simple import Simple
+from migen.corelogic import roundrobin, multimux
+from .simple import Simple, GetSigName
+from functools import partial
 
 _desc = [
 	(True,	"adr",	32),
@@ -22,3 +24,33 @@ class Master(Simple):
 class Slave(Simple):
 	def __init__(self, name=""):
 		Simple.__init__(self, _desc, True, name)
+
+class Arbiter:
+	def __init__(self, masters, target):
+		self.masters = masters
+		self.target = target
+		self.rr = roundrobin.Inst(len(self.masters))
+
+	def GetFragment(self):
+		comb = []
+		
+		# mux master->slave signals
+		m2s_names = [GetSigName(x, False) for x in _desc if x[0]]
+		m2s_masters = [[getattr(m, name) for name in m2s_names] for m in self.masters]
+		m2s_target = [getattr(self.target, name) for name in m2s_names]
+		comb += multimux.MultiMux(self.rr.grant, m2s_masters, m2s_target)
+		
+		# connect slave->master signals
+		s2m_names = [GetSigName(x, False) for x in _desc if not x[0]]
+		for name in s2m_names:
+			source = getattr(self.target, name)
+			for m in self.masters:
+				dest = getattr(m, name)
+				comb.append(f.Assign(dest, source))
+		
+		# connect bus requests to round-robin selector
+		reqs = [m.cyc_o for m in self.masters]
+		comb.append(f.Assign(self.rr.request, f.Cat(*reqs)))
+		
+		return f.Fragment(comb) + self.rr.GetFragment()
+