tb: Break out the core of pcs_send_codes into its own function

The PMA also has to deal with "recoverd bitstreams" (that is, inputs which
can have 0, 1, or 2 valid bits). Export the core of pcs_send_codes into its
own function, as it is useful for generating these signals.

Signed-off-by: Sean Anderson <seanga2@gmail.com>

tb/pcs.py

@@ -2,7 +2,6 @@
 # Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
 
 import enum
-import random
 import itertools
 
 import cocotb
@@ -11,7 +10,7 @@ from cocotb.regression import TestFactory
 from cocotb.triggers import ClockCycles, Edge, RisingEdge, FallingEdge, Timer
 from cocotb.types import LogicArray
 
-from .util import alist, classproperty, ReverseList, timeout
+from .util import *
 
 class Code(enum.Enum):
     _0 = (0b11110, '0')
@@ -195,49 +194,9 @@ async def pcs_recv_packet(pcs):
         yield code.data
     raise PrematureEndError()
 
-def one_valid():
-    return 1
-
-def two_valid():
-    return 2
-
-def rand_valid():
-    return random.randrange(3)
-
-class saw_valid:
-    def __init__(self):
-        self.last = 0
-        # Lie for TestFactory
-        self.__qualname__ = self.__class__.__qualname__
-
-    def __call__(self):
-        self.last += 1
-        if self.last > 2:
-            self.last = 0
-        return self.last
-
 async def pcs_send_codes(pcs, codes, valids):
-    await FallingEdge(pcs.rx_clk)
+    await send_recovered_bits(pcs.rx_clk, pcs.pma_data_rx, pcs.pma_data_rx_valid,
-    bits = itertools.chain(*codes)
+                              itertools.chain(*codes), valids)
-    try:
-        while True:
-            valid = valids()
-            pcs.pma_data_rx_valid.value = valid
-            if valid == 0:
-                data = 'XX'
-            elif valid == 1:
-                data = (next(bits), 'X')
-            else:
-                first = next(bits)
-                try:
-                    second = next(bits)
-                except StopIteration:
-                    second = 'X'
-                data = (first, second)
-            pcs.pma_data_rx.value = LogicArray(data)
-            await FallingEdge(pcs.rx_clk)
-    except StopIteration:
-        pass
 
 @cocotb.test(timeout_time=10, timeout_unit='us')
 async def test_tx(pcs):

tb/util.py

@@ -2,10 +2,12 @@
 # Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
 
 import functools
+import random
 
 import cocotb
-from cocotb.triggers import with_timeout
 from cocotb.result import SimTimeoutError
+from cocotb.triggers import with_timeout, FallingEdge
+from cocotb.types import LogicArray
 
 async def alist(xs):
     return [x async for x in xs]
@@ -65,3 +67,46 @@ class ReverseList(list):
 
     def __iter__(self):
         return super().__reversed__()
+
+def one_valid():
+    return 1
+
+def two_valid():
+    return 2
+
+def rand_valid():
+    return random.randrange(3)
+
+class saw_valid:
+    def __init__(self):
+        self.last = 0
+        # Lie for TestFactory
+        self.__qualname__ = self.__class__.__qualname__
+
+    def __call__(self):
+        self.last += 1
+        if self.last > 2:
+            self.last = 0
+        return self.last
+
+async def send_recovered_bits(clk, data, valid, bits, valids):
+    await FallingEdge(clk)
+    try:
+        while True:
+            v = valids()
+            valid.value = v
+            if v == 0:
+                d = 'XX'
+            elif v == 1:
+                d = (next(bits), 'X')
+            else:
+                first = next(bits)
+                try:
+                    second = next(bits)
+                except StopIteration:
+                    second = 'X'
+                d = (first, second)
+            data.value = LogicArray(d)
+            await FallingEdge(clk)
+    except StopIteration:
+        pass