From cb324ea47c1f19e06ad2d6c054584c6cc6b3cb6c Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Mon, 23 May 2016 14:17:22 +0200
Subject: [PATCH] frontend/bist: LiteDRAMBISTGenerator can now be asynchronous

---
 litedram/frontend/bist.py | 79 +++++++++++++++++++++++++++++----------
 test/bist_tb.py           | 12 ++++--
 2 files changed, 68 insertions(+), 23 deletions(-)

diff --git a/litedram/frontend/bist.py b/litedram/frontend/bist.py
index f0c7f77..d7ede79 100644
--- a/litedram/frontend/bist.py
+++ b/litedram/frontend/bist.py
@@ -2,6 +2,7 @@ from functools import reduce
 from operator import xor
 
 from litex.gen import *
+from litex.gen.genlib.cdc import PulseSynchronizer, BusSynchronizer
 
 from litex.soc.interconnect.csr import *
 
@@ -30,8 +31,44 @@ class LFSR(Module):
         ]
 
 
-class LiteDRAMBISTGenerator(Module, AutoCSR):
+class _LiteDRAMBISTGenerator(Module):
     def __init__(self, dram_port):
+        self.reset = Signal()
+        self.shoot = Signal()
+        self.done = Signal()
+        self.base = Signal(dram_port.aw)
+        self.length = Signal(dram_port.aw)
+
+        # # #
+
+        self.submodules.dma = dma = LiteDRAMDMAWriter(dram_port)
+
+        self.submodules.lfsr = lfsr = LFSR(dram_port.dw)
+        self.comb += lfsr.reset.eq(self.reset)
+
+        enable = Signal()
+        counter = Signal(dram_port.aw)
+        self.comb += enable.eq(counter != 0)
+        self.sync += [
+            If(self.shoot,
+                counter.eq(self.length)
+            ).Elif(lfsr.ce,
+                counter.eq(counter - 1)
+            )
+        ]
+
+        self.comb += [
+            dma.sink.valid.eq(enable),
+            dma.sink.address.eq(self.base + counter),
+            dma.sink.data.eq(lfsr.o),
+            lfsr.ce.eq(enable & dma.sink.ready),
+
+            self.done.eq(~enable)
+        ]
+
+
+class LiteDRAMBISTGenerator(Module, AutoCSR):
+    def __init__(self, dram_port, cd="sys"):
         self.reset = CSR()
         self.shoot = CSR()
         self.done = CSRStatus()
@@ -40,29 +77,33 @@ class LiteDRAMBISTGenerator(Module, AutoCSR):
 
         # # #
 
-        self.submodules.dma = dma = LiteDRAMDMAWriter(dram_port)
+        generator = _LiteDRAMBISTGenerator(dram_port)
+        self.submodules += ClockDomainsRenamer(cd)(generator)
 
-        self.submodules.lfsr = lfsr = LFSR(dram_port.dw)
-        self.comb += lfsr.reset.eq(self.reset.re)
+        reset_sync = PulseSynchronizer("sys", cd)
+        shoot_sync = PulseSynchronizer("sys", cd)
+        done_sync = BusSynchronizer(1, cd, "sys")
+        self.submodules += reset_sync, shoot_sync, done_sync
 
-        enable = Signal()
-        counter = Signal(dram_port.aw)
-        self.comb += enable.eq(counter != 0)
-        self.sync += [
-            If(self.shoot.re,
-                counter.eq(self.length.storage)
-            ).Elif(lfsr.ce,
-                counter.eq(counter - 1)
-            )
-        ]
+        base_sync = BusSynchronizer(dram_port.aw, "sys", cd, 8)
+        length_sync = BusSynchronizer(dram_port.aw, "sys", cd, 8)
+        self.submodules += base_sync, length_sync
 
         self.comb += [
-            dma.sink.valid.eq(enable),
-            dma.sink.address.eq(self.base.storage + counter),
-            dma.sink.data.eq(lfsr.o),
-            lfsr.ce.eq(enable & dma.sink.ready),
+            reset_sync.i.eq(self.reset.re),
+            generator.reset.eq(reset_sync.o),
 
-            self.done.status.eq(~enable)
+            shoot_sync.i.eq(self.shoot.re),
+            generator.shoot.eq(shoot_sync.o),
+
+            done_sync.i.eq(generator.done),
+            self.done.status.eq(done_sync.o),
+
+            base_sync.i.eq(self.base.storage),
+            generator.base.eq(base_sync.o),
+
+            length_sync.i.eq(self.length.storage),
+            generator.length.eq(length_sync.o)
         ]
 
 
diff --git a/test/bist_tb.py b/test/bist_tb.py
index d081e4c..160d378 100644
--- a/test/bist_tb.py
+++ b/test/bist_tb.py
@@ -21,21 +21,25 @@ def main_generator(dut):
     # write
     yield dut.generator.base.storage.eq(16)
     yield dut.generator.length.storage.eq(64)
-    yield
+    for i in range(8):
+        yield
     yield dut.generator.shoot.re.eq(1)
     yield
     yield dut.generator.shoot.re.eq(0)
-    yield
+    for i in range(8):
+        yield
     while((yield dut.generator.done.status) == 0):
         yield
     # read
     yield dut.checker.base.storage.eq(16)
     yield dut.checker.length.storage.eq(64)
-    yield
+    for i in range(8):
+        yield
     yield dut.checker.shoot.re.eq(1)
     yield
     yield dut.checker.shoot.re.eq(0)
-    yield
+    for i in range(8):
+        yield
     while((yield dut.checker.done.status) == 0):
         yield
     # check