From 5e5f436aa67eef84f2b2085c73f421d28ade6ae8 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Wed, 24 Sep 2014 21:30:25 +0200
Subject: [PATCH] uart: split it and use dataflow

This make the code easier to understand and allow the reuse of UARTRX & UARTTX
on designs without CPU (e.g miscope).
---
 misoclib/uart/__init__.py | 140 +++++++++++++++++++++++---------------
 1 file changed, 85 insertions(+), 55 deletions(-)

diff --git a/misoclib/uart/__init__.py b/misoclib/uart/__init__.py
index 1e080655..126be9d1 100644
--- a/misoclib/uart/__init__.py
+++ b/misoclib/uart/__init__.py
@@ -3,64 +3,25 @@ from migen.genlib.cdc import MultiReg
 from migen.bank.description import *
 from migen.bank.eventmanager import *
 from migen.genlib.record import Record
-from migen.sim.generic import Simulator, TopLevel
-from migen.sim import icarus
+from migen.flow.actor import Sink, Source
 
-class UART(Module, AutoCSR):
-	def __init__(self, pads, clk_freq, baud=115200):
-		self._r_rxtx = CSR(8)
-
-		self.submodules.ev = EventManager()
-		self.ev.tx = EventSourceProcess()
-		self.ev.rx = EventSourcePulse()
-		self.ev.finalize()
-
-		# Tuning word value
-		tuning_word=int((baud/clk_freq)*2**32)
-		self._r_tuning_word = CSRStorage(32, reset=tuning_word)
+class UARTRX(Module):
+	def __init__(self, pads, tuning_word):
+		self.source = Source([("d", 8)])
 
 		###
 
 		uart_clk_rxen = Signal()
-		uart_clk_txen = Signal()
 		phase_accumulator_rx = Signal(32)
-		phase_accumulator_tx = Signal(32)
 
-		pads.tx.reset = 1
-
-		# TX
-		tx_reg = Signal(8)
-		tx_bitcount = Signal(4)
-		tx_busy = self.ev.tx.trigger
-		self.sync += [
-			If(self._r_rxtx.re,
-				tx_reg.eq(self._r_rxtx.r),
-				tx_bitcount.eq(0),
-				tx_busy.eq(1),
-				pads.tx.eq(0)
-			).Elif(uart_clk_txen & tx_busy,
-				tx_bitcount.eq(tx_bitcount + 1),
-				If(tx_bitcount == 8,
-					pads.tx.eq(1)
-				).Elif(tx_bitcount == 9,
-					pads.tx.eq(1),
-					tx_busy.eq(0)
-				).Else(
-					pads.tx.eq(tx_reg[0]),
-					tx_reg.eq(Cat(tx_reg[1:], 0))
-				)
-			)
-		]
-		
-		# RX
 		rx = Signal()
 		self.specials += MultiReg(pads.rx, rx)
 		rx_r = Signal()
 		rx_reg = Signal(8)
 		rx_bitcount = Signal(4)
 		rx_busy = Signal()
-		rx_done = self.ev.rx.trigger
-		rx_data = self._r_rxtx.w
+		rx_done = self.source.stb
+		rx_data = self.source.payload.d
 		self.sync += [
 			rx_done.eq(0),
 			rx_r.eq(rx),
@@ -88,21 +49,89 @@ class UART(Module, AutoCSR):
 				)
 			)
 		]
-
-
-		self.sync += [
+		self.sync += \
 				If(rx_busy,
-					Cat(phase_accumulator_rx, uart_clk_rxen).eq(phase_accumulator_rx + self._r_tuning_word.storage)
+					Cat(phase_accumulator_rx, uart_clk_rxen).eq(phase_accumulator_rx + tuning_word)
 				).Else(
 					Cat(phase_accumulator_rx, uart_clk_rxen).eq(2**31)
-				),
+				)
+
+class UARTTX(Module):
+	def __init__(self, pads, tuning_word):
+		self.sink = Sink([("d", 8)])
+
+		###
+
+		uart_clk_txen = Signal()
+		phase_accumulator_tx = Signal(32)
+
+		pads.tx.reset = 1
 
+		tx_reg = Signal(8)
+		tx_bitcount = Signal(4)
+		tx_busy = Signal()
+		self.sync += [
+			self.sink.ack.eq(0),
+			If(self.sink.stb & ~tx_busy & ~self.sink.ack,
+				tx_reg.eq(self.sink.payload.d),
+				tx_bitcount.eq(0),
+				tx_busy.eq(1),
+				pads.tx.eq(0)
+			).Elif(uart_clk_txen & tx_busy,
+				tx_bitcount.eq(tx_bitcount + 1),
+				If(tx_bitcount == 8,
+					pads.tx.eq(1)
+				).Elif(tx_bitcount == 9,
+					pads.tx.eq(1),
+					tx_busy.eq(0),
+					self.sink.ack.eq(1),
+				).Else(
+					pads.tx.eq(tx_reg[0]),
+					tx_reg.eq(Cat(tx_reg[1:], 0))
+				)
+			)
+		]
+		self.sync += [
 				If(tx_busy,
-					Cat(phase_accumulator_tx, uart_clk_txen).eq(phase_accumulator_tx + self._r_tuning_word.storage)
+					Cat(phase_accumulator_tx, uart_clk_txen).eq(phase_accumulator_tx + tuning_word)
 				).Else(
 					Cat(phase_accumulator_tx, uart_clk_txen).eq(0)
 				)
-			     ]
+		]
+
+class UART(Module, AutoCSR):
+	def __init__(self, pads, clk_freq, baud=115200):
+		self._r_rxtx = CSR(8)
+
+		self.submodules.ev = EventManager()
+		self.ev.tx = EventSourcePulse()
+		self.ev.rx = EventSourcePulse()
+		self.ev.finalize()
+
+		# Tuning word value
+		self._tuning_word = CSRStorage(32, reset=int((baud/clk_freq)*2**32))
+		tuning_word = self._tuning_word.storage
+
+		###
+
+		self.submodules.rx = UARTRX(pads, tuning_word)
+		self.submodules.tx = UARTTX(pads, tuning_word)
+
+		self.sync += [
+			If(self._r_rxtx.re,
+				self.tx.sink.stb.eq(1),
+				self.tx.sink.payload.d.eq(self._r_rxtx.r),
+			).Elif(self.tx.sink.ack,
+				self.tx.sink.stb.eq(0)
+			),
+			If(self.rx.source.stb,
+				self._r_rxtx.w.eq(self.rx.source.d)
+			)
+		]
+		self.comb += [
+			self.ev.tx.trigger.eq(self.tx.sink.stb & self.tx.sink.ack),
+			self.ev.rx.trigger.eq(self.rx.source.stb) #self.rx.source.ack supposed to be always 1
+		]
 
 class UARTTB(Module):
 	def __init__(self):
@@ -134,8 +163,6 @@ class UARTTB(Module):
 		tx_string = "01234"
 		print("Sending string: " + tx_string)
 		for c in tx_string:
-			while selfp.slave.ev.tx.trigger == 1:
-				yield
 			selfp.slave._r_rxtx.r = ord(c)
 			selfp.slave._r_rxtx.re = 1
 			yield
@@ -162,6 +189,8 @@ class UARTTB(Module):
 				print("FAILURE: sent decimal value "+str(val)+" (char "+chr(val)+") instead of "+c)
 			else:
 				print("SUCCESS: sent "+c)
+			while selfp.slave.ev.tx.trigger != 1:
+				yield
 
 		# Then receive a character
 
@@ -195,7 +224,8 @@ class UARTTB(Module):
 		while True:
 			yield
 
-
 if __name__ == "__main__":
+	from migen.sim.generic import Simulator, TopLevel
+	from migen.sim import icarus
 	with Simulator(UARTTB(), TopLevel("top.vcd", clk_period=int(1/0.08333333)), icarus.Runner(keep_files=False)) as s:
 		s.run(20000)
-- 
2.30.2