From 35f9f2e9d7c7dd374a0decea8a5ee28cfaa87f4c Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Sat, 8 Jun 2013 15:49:50 +0200
Subject: [PATCH] bus/lasmi: interface definition and crossbar (untested)

---
 migen/bus/lasmibus.py | 147 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 migen/bus/lasmibus.py

diff --git a/migen/bus/lasmibus.py b/migen/bus/lasmibus.py
new file mode 100644
index 000000000..728aa27df
--- /dev/null
+++ b/migen/bus/lasmibus.py
@@ -0,0 +1,147 @@
+from migen.fhdl.std import *
+from migen.genlib import roundrobin
+from migen.genlib.record import *
+from migen.genlib.misc import optree
+
+class Interface(Record):
+	def __init__(self, aw, dw, nbanks, read_latency, write_latency):
+		self.aw = aw
+		self.dw = dw
+		self.nbanks = nbanks
+		self.read_latency = read_latency
+		self.write_latency = write_latency
+
+		bank_layout = [
+			("adr",		aw,		DIR_M_TO_S),
+			("we",		1,		DIR_M_TO_S),
+			("stb",		1,		DIR_M_TO_S),
+			("ack",		1,		DIR_S_TO_M)
+		]
+		if nbanks > 1:
+			layout = [("bank"+str(i), bank_layout) for i in range(nbanks)]
+		else:
+			layout = bank_layout
+		layout += [
+			("dat_w",	dw, 	DIR_M_TO_S),
+			("dat_we",	dw//8, 	DIR_M_TO_S),
+			("dat_r",	dw, 	DIR_S_TO_M)
+		]
+		Record.__init__(self, layout)
+
+def _getattr_all(l, attr):
+	it = iter(l)
+	r = getattr(next(it), attr)
+	for e in it:
+		if getattr(e, attr) != r:
+			raise ValueError
+	return r
+
+class Crossbar(Module):
+	def __init__(self, controllers, nmasters, cba_shift):
+		ncontrollers = len(controllers)
+		rca_bits = _getattr_all(controllers, "aw")
+		dw = _getattr_all(controllers, "dw")
+		nbanks = _getattr_all(controllers, "nbanks")
+		read_latency = _getattr_all(controllers, "read_latency")
+		write_latency = _getattr_all(controllers, "write_latency")
+
+		bank_bits = log2_int(nbanks, False)
+		controller_bits = log2_int(ncontrollers, False)
+		self.masters = [Interface(rca_bits + bank_bits + controller_bits, dw, 1, read_latency, write_latency)
+			for i in range(nmasters)]
+		masters_a = Array(self.masters)
+
+		###
+
+		m_ca, m_ba, m_rca = self._split_master_addresses(controller_bits, bank_bits, rca_bits, cba_shift)
+		
+		for nc, controller in enumerate(controllers):
+			if controller_bits:
+				controller_selected = [ca == nc for ca in m_ca]
+			else:
+				controller_selected = [1]*nmasters
+			for nb in range(nbanks):
+				bank = getattr(controller, "bank"+str(nb))
+
+				# arbitrate
+				rr = roundrobin.RoundRobin(nmasters, roundrobin.SP_CE)
+				self.submodules += rr
+				bank_selected = [cs & (ba == nb) for cs, ba in zip(controller_selected, m_ba)]
+				bank_requested = [bs & master.stb for bs, master in zip(bank_selected, self.masters)]
+				self.comb += [
+					rr.request.eq(Cat(*bank_requested)),
+					rr.ce.eq(~bank.stb | bank.ack)
+				]
+
+				# route requests
+				self.comb += [
+					bank.adr.eq(Array(m_rca)[rr.grant]),
+					bank.we.eq(masters_a[rr.grant].we),
+					bank.stb.eq(masters_a[rr.grant].stb),
+					masters_a[rr.grant].ack.eq(bank.ack)
+				]
+
+			# route data writes
+			controller_selected_wl = controller_selected
+			for i in range(write_latency):
+				n_controller_selected_wl = [Signal() for i in range(nmasters)]
+				self.sync += [n.eq(o) for n, o in zip(n_controller_selected_wl, controller_selected_wl)]
+				controller_selected_wl = n_controller_selected_wl
+			dat_w_maskselect = []
+			dat_we_maskselect = []
+			for master, selected in zip(self.masters, controller_selected_wl):
+				o_dat_w = Signal(dw)
+				o_dat_we = Signal(dw//8)
+				self.comb += If(selected,
+						o_dat_w.eq(master.dat_w),
+						o_dat_we.eq(master.dat_we)
+					)
+				dat_w_maskselect.append(o_dat_w)
+				dat_we_maskselect.append(o_dat_we)
+			self.comb += [
+				controller.dat_w.eq(optree("|", dat_w_maskselect)),
+				controller.dat_we.eq(optree("|", dat_we_maskselect))
+			]
+
+		# route data reads
+		if controller_bits:
+			for master in self.masters:
+				controller_sel = Signal(controller_bits)
+				for nc, controller in enumerate(controllers):
+					for nb in range(nbanks):
+						bank = getattr(controller, "bank"+str(nb))
+						self.comb += If(bank.stb & bank.ack, controller_sel.eq(nc))
+				for i in range(read_latency):
+					n_controller_sel = Signal(controller_bits)
+					self.sync += n_controller_sel.eq(controller_sel)
+					controller_sel = n_controller_sel
+				self.comb += master.dat_r.eq(Array(controllers)[controller_sel].dat_r)
+		else:
+			self.comb += [master.dat_r.eq(controllers[0].dat_r) for master in self.masters]
+
+	def _split_master_addresses(self, controller_bits, bank_bits, rca_bits, cba_shift):
+		m_ca = []	# controller address
+		m_ba = []	# bank address
+		m_rca = []	# row and column address
+		for master in self.masters:
+			cba = Signal(controller_bits + bank_bits)
+			rca = Signal(rca_bits)
+			cba_upper = cba_shift + controller_bits + bank_bits
+			self.comb += cba.eq(master.adr[cba_shift:cba_upper])
+			if cba_shift < rca_bits:
+				self.comb += rca.eq(Cat(master.adr[:cba_shift], master.adr[cba_upper:]))
+			else:
+				self.comb += rca.eq(master.adr[:cba_shift])
+
+			if controller_bits:
+				ca = Signal(controller_bits)
+				ba = Signal(bank_bits)
+				self.comb += Cat(ba, ca).eq(cba)
+			else:
+				ca = None
+				ba = cba
+
+			m_ca.append(ca)
+			m_ba.append(ba)
+			m_rca.append(rca)
+		return m_ca, m_ba, m_rca