Put sources and sinks to sleep based on clock enables

Signed-off-by: Alex Forencich <alex@alexforencich.com>

cocotbext/eth/gmii.py

@@ -266,6 +266,10 @@ class GmiiSource(Reset):
 
         clock_edge_event = RisingEdge(self.clock)
 
+        enable_event = None
+        if self.enable is not None:
+            enable_event = RisingEdge(self.enable)
+
         while True:
             await clock_edge_event
 
@@ -330,6 +334,9 @@ class GmiiSource(Reset):
                     self.active = False
                     self.idle_event.set()
 
+            elif self.enable is not None and not self.enable.value:
+                await enable_event
+
 
 class GmiiSink(Reset):
 
@@ -432,6 +439,10 @@ class GmiiSink(Reset):
 
         clock_edge_event = RisingEdge(self.clock)
 
+        enable_event = None
+        if self.enable is not None:
+            enable_event = RisingEdge(self.enable)
+
         while True:
             await clock_edge_event
 
@@ -492,6 +503,9 @@ class GmiiSink(Reset):
                     frame.data.append(d_val)
                     frame.error.append(er_val)
 
+            elif self.enable is not None and not self.enable.value:
+                await enable_event
+
 
 class GmiiPhy:
     def __init__(self, txd, tx_er, tx_en, tx_clk, gtx_clk, rxd, rx_er, rx_dv, rx_clk,