From cdda1beea80d4c66d97b980c1184a5fb9c1aa613 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Mon, 21 Jul 2014 13:17:21 -0600
Subject: [PATCH] soc/rtio: refactor, share counter and underflow detector

---
 soc/artiqlib/rtio/__init__.py | 90 +++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 40 deletions(-)

diff --git a/soc/artiqlib/rtio/__init__.py b/soc/artiqlib/rtio/__init__.py
index 89e6b2166..5a73a6e20 100644
--- a/soc/artiqlib/rtio/__init__.py
+++ b/soc/artiqlib/rtio/__init__.py
@@ -3,41 +3,59 @@ from migen.bank.description import *
 from migen.genlib.fifo import SyncFIFOBuffered
 from migen.genlib.cdc import MultiReg
 
-class RTIOChannelO(Module):
-	def __init__(self, signal, counter_width, fifo_depth):
-		self.submodules.fifo = SyncFIFOBuffered([
-			("timestamp", counter_width), ("value", 1)],
-			fifo_depth)
-
-		self.event = self.fifo.din
-		self.writable = self.fifo.writable
-		self.we = self.fifo.we
+class RTIOBankO(Module):
+	def __init__(self, channels, counter_width, fifo_depth):
+		self.sel = Signal(max=len(channels))
+		self.timestamp = Signal(counter_width)
+		self.value = Signal()
+		self.writable = Signal()
+		self.we = Signal()
 		self.underflow = Signal()
-		self.level = self.fifo.level
+		self.level = Signal(bits_for(fifo_depth))
 
 		###
 
 		counter = Signal(counter_width)
-		self.sync += counter.eq(counter + 1)
-
-		self.sync += If(self.we & self.writable,
-			If(self.event.timestamp < counter + 2,
-				self.underflow.eq(1)
+		self.sync += [
+			counter.eq(counter + 1),
+			If(self.we & self.writable,
+				If(self.timestamp < counter + 2, self.underflow.eq(1))
 			)
-		)
-
-		time_hit = Signal()
-		self.comb += [
-			time_hit.eq(self.fifo.readable &
-				(self.fifo.dout.timestamp == counter)),
-			self.fifo.re.eq(time_hit)
 		]
-		self.sync += If(time_hit, signal.eq(self.fifo.dout.value))
+
+		fifos = []
+		for n, channel in enumerate(channels):
+			fifo = SyncFIFOBuffered([
+				("timestamp", counter_width), ("value", 1)],
+				fifo_depth)
+			self.submodules += fifo
+			fifos.append(fifo)
+
+			# FIFO write
+			self.comb += [
+				fifo.din.timestamp.eq(self.timestamp),
+				fifo.din.value.eq(self.value),
+				fifo.we.eq(self.we & (self.sel == n))
+			]
+
+			# FIFO read
+			time_hit = Signal()
+			self.comb += [
+				time_hit.eq(fifo.readable &
+					(fifo.dout.timestamp == counter)),
+				fifo.re.eq(time_hit)
+			]
+			self.sync += If(time_hit, channel.eq(fifo.dout.value))
+
+		selfifo = Array(fifos)[self.sel]
+		self.comb += self.writable.eq(selfifo.writable), self.level.eq(selfifo.level)
 
 class RTIO(Module, AutoCSR):
 	def __init__(self, channels, counter_width=32, ofifo_depth=8, ififo_depth=8):
+		self.submodules.bank_o = InsertReset(RTIOBankO(channels, counter_width, ofifo_depth))
+
 		self._r_reset = CSRStorage(reset=1)
-		self._r_chan_sel = CSRStorage(bits_for(len(channels)-1))
+		self._r_chan_sel = CSRStorage(flen(self.bank_o.sel))
 		self._r_o_timestamp = CSRStorage(counter_width)
 		self._r_o_value = CSRStorage()
 		self._r_o_writable = CSRStatus()
@@ -45,21 +63,13 @@ class RTIO(Module, AutoCSR):
 		self._r_o_underflow = CSRStatus()
 		self._r_o_level = CSRStatus(bits_for(ofifo_depth))
 
-		channel_os = []
-		for n, channel in enumerate(channels):
-			channel_o = InsertReset(RTIOChannelO(channel, counter_width, ofifo_depth))
-			self.submodules += channel_o
-			channel_os.append(channel_o)
-			self.comb += [
-				channel_o.reset.eq(self._r_reset.storage),
-				channel_o.event.timestamp.eq(self._r_o_timestamp.storage),
-				channel_o.event.value.eq(self._r_o_value.storage),
-				channel_o.we.eq(self._r_o_we.re & (self._r_chan_sel.storage == n))
-			]
-
-		channel_o = Array(channel_os)[self._r_chan_sel.storage]
 		self.comb += [
-			self._r_o_writable.status.eq(channel_o.writable),
-			self._r_o_underflow.status.eq(channel_o.underflow),
-			self._r_o_level.status.eq(channel_o.level)
+			self.bank_o.reset.eq(self._r_reset.storage),
+			self.bank_o.sel.eq(self._r_chan_sel.storage),
+			self.bank_o.timestamp.eq(self._r_o_timestamp.storage),
+			self.bank_o.value.eq(self._r_o_value.storage),
+			self._r_o_writable.status.eq(self.bank_o.writable),
+			self.bank_o.we.eq(self._r_o_we.re),
+			self._r_o_underflow.status.eq(self.bank_o.underflow),
+			self._r_o_level.status.eq(self.bank_o.level)
 		]