From 86f852a5f1568952c5d342f837e7deda7a7db162 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Fri, 18 Apr 2014 13:49:58 +0200
Subject: [PATCH] wishbone2lasmi: support lasmim data_width < wishbone
 data_width

---
 migen/bus/wishbone2lasmi.py | 71 +++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 19 deletions(-)

diff --git a/migen/bus/wishbone2lasmi.py b/migen/bus/wishbone2lasmi.py
index 39a9daeb..cda742e6 100644
--- a/migen/bus/wishbone2lasmi.py
+++ b/migen/bus/wishbone2lasmi.py
@@ -6,29 +6,29 @@ from migen.genlib.record import Record, layout_len
 
 # cachesize (in 32-bit words) is the size of the data store, must be a power of 2
 class WB2LASMI(Module):
-	def __init__(self, cachesize, lasmim, wbm=None):
-		if wbm is None:
-			wbm = wishbone.Interface()
-		self.wishbone = wbm
+	def __init__(self, cachesize, lasmim):
+		self.wishbone = wishbone.Interface()
 
 		###
 
 		data_width = flen(self.wishbone.dat_r)
-		if lasmim.dw < data_width:
-			raise ValueError("LASMI data width must be >= {dw}".format(dw=data_width))
-		if (lasmim.dw % data_width) != 0:
+		if lasmim.dw > data_width and (lasmim.dw % data_width) != 0:
 			raise ValueError("LASMI data width must be a multiple of {dw}".format(dw=data_width))
+		if lasmim.dw < data_width and (data_width % lasmim.dw) != 0:
+			raise ValueError("WISHBONE data width must be a multiple of {dw}".format(dw=lasmim.dw))
 
 		# Split address:
 		# TAG | LINE NUMBER | LINE OFFSET
-		offsetbits = log2_int(lasmim.dw//data_width)
+		offsetbits = log2_int(max(lasmim.dw//data_width, 1))
 		addressbits = lasmim.aw + offsetbits
 		linebits = log2_int(cachesize) - offsetbits
 		tagbits = addressbits - linebits
+		wordbits = data_width//lasmim.dw
 		adr_offset, adr_line, adr_tag = split(self.wishbone.adr, offsetbits, linebits, tagbits)
+		word = Signal(wordbits) if wordbits else None
 		
 		# Data memory
-		data_mem = Memory(lasmim.dw, 2**linebits)
+		data_mem = Memory(lasmim.dw*2**wordbits, 2**linebits)
 		data_port = data_mem.get_port(write_capable=True, we_granularity=8)
 		self.specials += data_mem, data_port
 		
@@ -43,16 +43,16 @@ class WB2LASMI(Module):
 		self.comb += [
 			data_port.adr.eq(adr_line),
 			If(write_from_lasmi,
-				data_port.dat_w.eq(lasmim.dat_r),
-				data_port.we.eq(Replicate(1, lasmim.dw//8))
+				displacer(lasmim.dat_r, word, data_port.dat_w),
+				displacer(Replicate(1, lasmim.dw//8), word, data_port.we)
 			).Else(
-				data_port.dat_w.eq(Replicate(self.wishbone.dat_w, lasmim.dw//data_width)),
+				data_port.dat_w.eq(Replicate(self.wishbone.dat_w, max(lasmim.dw//data_width, 1))),
 				If(self.wishbone.cyc & self.wishbone.stb & self.wishbone.we & self.wishbone.ack,
 					displacer(self.wishbone.sel, adr_offset, data_port.we, 2**offsetbits, reverse=True)
 				)
 			),
 			If(write_to_lasmi, 
-				lasmim.dat_w.eq(data_port.dat_r),
+				chooser(data_port.dat_r, word, lasmim.dat_w),
 				lasmim.dat_we.eq(2**(lasmim.dw//8)-1)
 			),
 			chooser(data_port.dat_r, adr_offset_r, self.wishbone.dat_r, reverse=True)
@@ -73,13 +73,34 @@ class WB2LASMI(Module):
 			
 		self.comb += [
 			tag_port.adr.eq(adr_line),
-			tag_di.tag.eq(adr_tag),
-			lasmim.adr.eq(Cat(adr_line, tag_do.tag))
+			tag_di.tag.eq(adr_tag)
 		]
-		
+		if word is not None:
+			self.comb += lasmim.adr.eq(Cat(word, adr_line, tag_do.tag))
+		else:
+			self.comb += lasmim.adr.eq(Cat(adr_line, tag_do.tag))		
+			
+		# Lasmim word computation, word_clr and word_inc will be simplified
+		# at synthesis when wordbits=0
+		word_clr = Signal()
+		word_inc = Signal()
+		if word is not None:
+			self.sync += \
+				If(word_clr,
+					word.eq(0),
+				).Elif(word_inc,
+					word.eq(word+1)
+				)
+
+		def word_is_last(word):
+			if word is not None:
+				return word == 2**wordbits-1
+			else:
+				return 1
+
 		# Control FSM
 		assert(lasmim.write_latency >= 1 and lasmim.read_latency >= 1)
-		fsm = FSM()
+		fsm = FSM(reset_state="IDLE")
 		self.submodules += fsm
 		
 		fsm.delayed_enter("EVICT_DATAD", "EVICT_DATA", lasmim.write_latency-1)
@@ -89,6 +110,7 @@ class WB2LASMI(Module):
 			If(self.wishbone.cyc & self.wishbone.stb, NextState("TEST_HIT"))
 		)
 		fsm.act("TEST_HIT",
+			word_clr.eq(1),
 			If(tag_do.tag == adr_tag,
 				self.wishbone.ack.eq(1),
 				If(self.wishbone.we,
@@ -115,12 +137,18 @@ class WB2LASMI(Module):
 		)
 		fsm.act("EVICT_DATA",
 			write_to_lasmi.eq(1),
-			NextState("REFILL_WRTAG")
+			word_inc.eq(1),
+			If(word_is_last(word),
+				NextState("REFILL_WRTAG"),
+			).Else(
+				NextState("EVICT_REQUEST")
+			)
 		)
 		
 		fsm.act("REFILL_WRTAG",
 			# Write the tag first to set the LASMI address
 			tag_port.we.eq(1),
+			word_clr.eq(1),
 			NextState("REFILL_REQUEST")
 		)
 		fsm.act("REFILL_REQUEST",
@@ -132,5 +160,10 @@ class WB2LASMI(Module):
 		)
 		fsm.act("REFILL_DATA",
 			write_from_lasmi.eq(1),
-			NextState("TEST_HIT")
+			word_inc.eq(1),
+			If(word_is_last(word),
+				NextState("TEST_HIT"),
+			).Else(
+				NextState("REFILL_REQUEST")
+			)
 		)
-- 
2.30.2