From d42c8912fa9d68cdc21cf1262e867b2e1eda02dd Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Fri, 5 Apr 2019 19:56:48 +0100
Subject: [PATCH] tracking down sync failure when stage not dynamically ready

---
 src/add/singlepipe.py    |  2 +-
 src/add/test_buf_pipe.py | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/add/singlepipe.py b/src/add/singlepipe.py
index 5c19fd66..e32a0c67 100644
--- a/src/add/singlepipe.py
+++ b/src/add/singlepipe.py
@@ -602,7 +602,7 @@ class BufferedPipeline(ControlBase):
             self.m.d.sync += eq(r_data, result) # update buffer
 
         with self.m.If(self.n.i_ready): # next stage is ready
-            with self.m.If(self.p.o_ready): # not stalled
+            with self.m.If(self.p._o_ready): # not stalled
                 # nothing in buffer: send (processed) input direct to output
                 self.m.d.sync += [self.n._o_valid.eq(p_i_valid),
                                   eq(self.n.o_data, result), # update output
diff --git a/src/add/test_buf_pipe.py b/src/add/test_buf_pipe.py
index 31555635..7cdb7ebd 100644
--- a/src/add/test_buf_pipe.py
+++ b/src/add/test_buf_pipe.py
@@ -205,6 +205,7 @@ class Test5:
                     send = True
                 else:
                     send = randint(0, send_range) != 0
+                send = True
                 o_p_ready = yield self.dut.p.o_ready
                 if not o_p_ready:
                     yield
@@ -597,6 +598,7 @@ class ExampleStageDelayCls(StageCls):
     @property
     def p_o_ready(self):
         return Const(1)
+        return self.count == 0
 
     @property
     def n_o_valid(self):
@@ -607,6 +609,11 @@ class ExampleStageDelayCls(StageCls):
         """
         return i + 1
 
+    def elaborate(self, platform):
+        m = Module()
+        m.d.sync += self.count.eq(~self.count)
+        return m
+
 
 class ExampleBufDelayedPipe(BufferedPipeline):
     """ an example of how to use the buffered pipeline.
@@ -616,6 +623,11 @@ class ExampleBufDelayedPipe(BufferedPipeline):
         stage = ExampleStageDelayCls()
         BufferedPipeline.__init__(self, stage, stage_ctl=True)
 
+    def elaborate(self, platform):
+        m = BufferedPipeline.elaborate(self, platform)
+        m.submodules.stage = self.stage
+        return m
+
 
 class ExampleBufPipe3(ControlBase):
     """ Example of how to do delayed pipeline, where the stage signals
-- 
2.30.2