bus: add DFI

doc/migen.txt

@@ -367,6 +367,8 @@ slave interfaces of the following buses:
     software.
   - ASMIbus, a split-transaction bus optimized for use with a
     high-performance, out-of-order SDRAM controller.
+  - DFI [12] (partial), a standard interface protocol between memory
+    controller logic and PHY interfaces.
 
 It also provides interconnect components for these buses, such as
 arbiters and address decoders. The strength of the Migen procedurally
@@ -476,3 +478,4 @@ References:
 [ 9] http://orc-apps.sourceforge.net/
 [10] http://opendf.sourceforge.net/
 [11] http://networkx.lanl.gov/
+[12] http://www.ddr-phy.org/

migen/bus/dfi.py

@@ -0,0 +1,54 @@
+from migen.fhdl.structure import *
+from migen.bus.simple import *
+
+def phase_description(a, ba, d):
+	return Description(
+		(M_TO_S,	"address",	a),
+		(M_TO_S,	"bank",		ba),
+		(M_TO_S,	"cas_n",	1),
+		(M_TO_S,	"cke",		1),
+		(M_TO_S,	"cs_n",		1),
+		(M_TO_S,	"ras_n",	1),
+		(M_TO_S,	"we_n",		1),
+
+		(M_TO_S,	"wrdata",	d),
+		(M_TO_S,	"wrdata_en",	1),
+		(M_TO_S,	"wrdata_mask",	d//8),
+
+		(M_TO_S,	"rddata_en",	1),
+		(S_TO_M,	"rddata",	d),
+		(S_TO_M,	"rddata_valid",	1)
+	)
+
+class Interface:
+	def __init__(self, a, ba, d, nphases=1):
+		self.pdesc = phase_description(a, ba, d)
+		self.phases = [SimpleInterface(self.pdesc) for i in range(nphases)]
+
+	# Returns pairs (DFI-mandated signal name, Migen signal object)
+	def get_standard_names(self):
+		r = []
+		add_suffix = len(self.phases) > 1
+		for n, phase in enumerate(self.phases):
+			for signal in self.pdesc.desc:
+				if add_suffix:
+					if signal[0] == M_TO_S:
+						suffix = "_p" + int(n)
+					else:
+						suffix = "_w" + int(n)
+				else:
+					suffix = ""
+			r.append(("dfi_" + signal[1] + suffix, getattr(self, signal[1])))
+		return r
+
+class Interconnect:
+	def __init__(self, master, slave):
+		self.master = master
+		self.slave = slave
+
+	def get_fragment(self):
+		f = Fragment()
+		for pm, ps in zip(self.master.phases, self.slave.phases):
+			ic = SimpleInterconnect(pm, [ps])
+			f += ic.get_fragment()
+		return f