From 80622986686cdd5b4508f5de576402fc643e4b6e Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Mon, 3 Nov 2014 18:54:41 +0100
Subject: [PATCH] link: add CRC and testbench

---
 lib/sata/link/crc.py         | 106 +++++++++++++++++++++++++++++++++++
 lib/sata/link/test/Makefile  |   3 +-
 lib/sata/link/test/crc_tb.py |  52 +++++++++++++++++
 lib/sata/std.py              |   8 +++
 4 files changed, 168 insertions(+), 1 deletion(-)
 create mode 100644 lib/sata/link/crc.py
 create mode 100644 lib/sata/link/test/crc_tb.py
 create mode 100644 lib/sata/std.py

diff --git a/lib/sata/link/crc.py b/lib/sata/link/crc.py
new file mode 100644
index 00000000..8f483005
--- /dev/null
+++ b/lib/sata/link/crc.py
@@ -0,0 +1,106 @@
+from migen.fhdl.std import *
+from migen.genlib.misc import optree
+
+class CRCEngine(Module):
+	"""Cyclic Redundancy Check Engine
+
+	Compute next CRC value from last CRC value and data input using
+	an optimized asynchronous LFSR.
+
+	Parameters
+	----------
+	width : int
+		Width of the data bus and CRC.
+	polynom : int
+		Polynom of the CRC (ex: 0x04C11DB7 for IEEE 802.3 CRC)
+
+	Attributes
+	----------
+	d : in
+		Data input.
+	last : in
+		last CRC value.
+	next :
+		next CRC value.
+	"""
+	def __init__(self, width, polynom):
+		self.d = Signal(width)
+		self.last = Signal(width)
+		self.next = Signal(width)
+
+		###
+
+
+		def _optimize_eq(l):
+			"""
+			Replace even numbers of XORs in the equation
+			with an equivalent XOR
+			"""
+			d = {}
+			for e in l:
+				if e in d:
+					d[e] += 1
+				else:
+					d[e] = 1
+			r = []
+			for key, value in d.items():
+				if value%2 != 0:
+					r.append(key)
+			return r
+
+		new = Signal(32)
+		self.comb += new.eq(self.last ^ self.d)
+
+		# compute and optimize CRC's LFSR
+		curval = [[("new", i)] for i in range(width)]
+		for i in range(width):
+			feedback = curval.pop()
+			curval.insert(0, feedback)
+			for j in range(1, width-1):
+				if (polynom&(1<<j)):
+					curval[j] += feedback
+				curval[j] = _optimize_eq(curval[j])
+
+		# implement logic
+		for i in range(width):
+			xors = []
+			for t, n in curval[i]:
+				if t == "new":
+					xors += [new[n]]
+			self.comb += self.next[i].eq(optree("^", xors))
+
+@DecorateModule(InsertReset)
+@DecorateModule(InsertCE)
+class SATACRC(Module):
+	"""SATA CRC
+
+	Implement a SATA CRC generator/checker
+
+	Attributes
+	----------
+	value : out
+		CRC value (used for generator).
+	error : out
+		CRC error (used for checker).
+	"""
+	width = 32
+	polynom = 0x04C11DB7
+	init = 0x52325032
+	check = 0xC704DD7B
+	def __init__(self):
+		self.d = Signal(self.width)
+		self.value = Signal(self.width)
+		self.error = Signal()
+
+		###
+
+		self.submodules.engine = CRCEngine(self.width, self.polynom)
+		reg_i = Signal(self.width, reset=self.init)
+		self.sync += reg_i.eq(self.engine.next)
+		self.comb += [
+			self.engine.d.eq(self.d),
+			self.engine.last.eq(reg_i),
+
+			self.value.eq(reg_i),
+			self.error.eq(self.engine.next != self.check)
+		]
diff --git a/lib/sata/link/test/Makefile b/lib/sata/link/test/Makefile
index e75c5fa3..92c9db9c 100644
--- a/lib/sata/link/test/Makefile
+++ b/lib/sata/link/test/Makefile
@@ -1,4 +1,4 @@
-MSCDIR = ../../../
+MSCDIR = ../../../../
 PYTHON = python3
 
 CMD = PYTHONPATH=$(MSCDIR) $(PYTHON)
@@ -9,6 +9,7 @@ CFLAGS =-Wall -O0
 crc_tb:
 	$(CC) $(CFLAGS) $(INC) -o crc crc.c
 	./crc /> crc_ref
+	$(CMD) crc_tb.py
 
 scrambler_tb:
 	$(CC) $(CFLAGS) $(INC) -o scrambler scrambler.c
diff --git a/lib/sata/link/test/crc_tb.py b/lib/sata/link/test/crc_tb.py
new file mode 100644
index 00000000..459e4e17
--- /dev/null
+++ b/lib/sata/link/test/crc_tb.py
@@ -0,0 +1,52 @@
+from subprocess import check_output
+
+from migen.fhdl.std import *
+
+from lib.sata.std import *
+from lib.sata.link.crc import *
+
+def check(ref, res):
+	shift = 0
+	while((ref[0] != res[0]) and (len(res)>1)):
+		res.pop(0)
+		shift += 1
+	length = min(len(ref), len(res))
+	errors = 0
+	for i in range(length):
+		if ref.pop(0) != res.pop(0):
+			errors += 1
+	return shift, length, errors
+
+class TB(Module):
+	def __init__(self):
+		self.submodules.crc = SATACRC()
+
+	def gen_simulation(self, selfp):
+		
+	# init CRC
+		selfp.crc.d = 0x12345678
+		selfp.crc.ce = 1
+		selfp.crc.reset = 1
+		yield
+		selfp.crc.reset = 0
+
+	# get C code results
+		ref = []
+		f = open("crc_ref", "r")
+		for l in f:
+			ref.append(int(l, 16))
+		f.close()
+
+	# log results
+		res = []
+		for i in range(256):
+			res.append(selfp.crc.value)
+			yield
+
+	# check results
+		s, l, e = check(ref, res)
+		print("shift "+ str(s) + " / length " + str(l) + " / errors " + str(e))
+
+if __name__ == "__main__":
+	from migen.sim.generic import run_simulation
+	run_simulation(TB(), ncycles=1000, vcd_name="my.vcd", keep_files=True)
diff --git a/lib/sata/std.py b/lib/sata/std.py
new file mode 100644
index 00000000..3f3ea2f4
--- /dev/null
+++ b/lib/sata/std.py
@@ -0,0 +1,8 @@
+from migen.fhdl.std import *
+
+def phy_layout(dw):
+	layout = [
+		("p_packetized", True),
+		("d", dw)
+	]
+	return layout
-- 
2.30.2