From fcf2f7517c2508f29f0110b3bb176d6f1e6e61c7 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Fri, 31 Oct 2014 12:56:03 +0100
Subject: [PATCH] crc: generate error asynchronously to avoid stalling the flow
 and simplify

---
 migen/actorlib/crc.py | 76 +++++++++++++++++++++----------------------
 migen/genlib/crc.py   |  2 +-
 2 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/migen/actorlib/crc.py b/migen/actorlib/crc.py
index 74139c94..ab5ebf7a 100644
--- a/migen/actorlib/crc.py
+++ b/migen/actorlib/crc.py
@@ -23,30 +23,30 @@ class CRCInserter(Module):
 		Packets output with CRC.
 	"""
 	def __init__(self, crc_class, layout):
-		self.sink = Sink(layout, True)
-		self.source = Source(layout, True)
+		self.sink = sink = Sink(layout, True)
+		self.source = source = Source(layout, True)
 		self.busy = Signal()
 
 		###
 
-		dw = flen(self.sink.d)
+		dw = flen(sink.d)
 		self.submodules.crc = crc_class(dw)
 		self.submodules.fsm = fsm = FSM(reset_state="IDLE")
 
 		fsm.act("IDLE",
 			self.crc.reset.eq(1),
-			self.sink.ack.eq(1),
-			If(self.sink.stb & self.sink.sop,
-				self.sink.ack.eq(0),
+			sink.ack.eq(1),
+			If(sink.stb & sink.sop,
+				sink.ack.eq(0),
 				NextState("COPY"),
 			)
 		)
 		fsm.act("COPY",
-			self.crc.ce.eq(self.sink.stb & self.source.ack),
-			self.crc.d.eq(self.sink.d),
-			Record.connect(self.sink, self.source),
-			self.source.eop.eq(0),
-			If(self.sink.stb & self.sink.eop & self.source.ack,
+			self.crc.ce.eq(sink.stb & source.ack),
+			self.crc.d.eq(sink.d),
+			Record.connect(sink, source),
+			source.eop.eq(0),
+			If(sink.stb & sink.eop & source.ack,
 				NextState("INSERT"),
 			)
 		)
@@ -54,11 +54,11 @@ class CRCInserter(Module):
 		cnt = Signal(max=ratio, reset=ratio-1)
 		cnt_done = Signal()
 		fsm.act("INSERT",
-			self.source.stb.eq(1),
-			chooser(self.crc.value, cnt, self.source.d, reverse=True),
+			source.stb.eq(1),
+			chooser(self.crc.value, cnt, source.d, reverse=True),
 			If(cnt_done,
-				self.source.eop.eq(1),
-				If(self.source.ack, NextState("IDLE"))
+				source.eop.eq(1),
+				If(source.ack, NextState("IDLE"))
 			)
 		)
 		self.comb += cnt_done.eq(cnt == 0)
@@ -66,7 +66,7 @@ class CRCInserter(Module):
 			If(fsm.ongoing("IDLE"),
 				cnt.eq(cnt.reset)
 			).Elif(fsm.ongoing("INSERT") & ~cnt_done,
-				cnt.eq(cnt - self.source.ack)
+				cnt.eq(cnt - source.ack)
 			)
 		self.comb += self.busy.eq(~fsm.ongoing("IDLE"))
 
@@ -89,45 +89,45 @@ class CRCChecker(Module):
 	sink : in
 		Packets input with CRC.
 	source : out
-		Packets output with CRC and "discarded" set to 0
-		on eop if CRC OK / set to 1 is CRC KO.
+		Packets output with CRC and "error" set to 0
+		on eop when CRC OK / set to 1 when CRC KO.
 	"""
 	def __init__(self, crc_class, layout):
-		self.sink = Sink(layout, True)
-		self.source = Source(layout, True)
+		self.sink = sink = Sink(layout, True)
+		self.source = source = Source(layout, True)
 		self.busy = Signal()
 
 		###
 
-		dw = flen(self.sink.d)
+		dw = flen(sink.d)
 		self.submodules.crc = crc_class(dw)
 
-		fsm = FSM(reset_state="IDLE")
+		fsm = FSM(reset_state="RESET_CRC")
 		self.submodules += fsm
 
-		fsm.act("IDLE",
+		fsm.act("RESET_CRC",
+			sink.ack.eq(0),
 			self.crc.reset.eq(1),
-			self.sink.ack.eq(self.sink.stb),
-			If(self.sink.stb & self.sink.sop,
-				self.sink.ack.eq(0),
+			NextState("IDLE")
+		)
+		fsm.act("IDLE",
+			sink.ack.eq(sink.stb),
+			If(sink.stb & sink.sop,
+				Record.connect(sink, source),
+				self.crc.ce.eq(sink.ack),
+				self.crc.d.eq(sink.d),
 				NextState("COPY")
 			)
 		)
 		fsm.act("COPY",
-			Record.connect(self.sink, self.source),
-			self.crc.ce.eq(self.sink.stb & (self.sink.ack | self.sink.eop)),
-			self.crc.d.eq(self.sink.d),
-			If(self.sink.stb & self.sink.eop,
-				self.sink.ack.eq(0),
-				self.source.stb.eq(0),
-				NextState("CHECK")
+			Record.connect(sink, source),
+			self.crc.ce.eq(sink.stb & sink.ack),
+			self.crc.d.eq(sink.d),
+			source.error.eq(sink.eop & self.crc.error),
+			If(sink.stb & sink.ack & sink.eop,
+				NextState("RESET_CRC")
 			)
 		)
-		fsm.act("CHECK",
-			Record.connect(self.sink, self.source),
-			self.source.discarded.eq(self.crc.error),
-			If(self.source.stb & self.source.ack, NextState("IDLE"))
-		)
 		self.comb += self.busy.eq(~fsm.ongoing("IDLE"))
 
 class CRC32Checker(CRCChecker):
diff --git a/migen/genlib/crc.py b/migen/genlib/crc.py
index afd40fd5..e0a6672c 100644
--- a/migen/genlib/crc.py
+++ b/migen/genlib/crc.py
@@ -108,5 +108,5 @@ class CRC32(Module):
 			self.engine.last.eq(reg),
 
 			self.value.eq(~reg[::-1]),
-			self.error.eq(reg != self.check)
+			self.error.eq(self.engine.next != self.check)
 		]
-- 
2.30.2