[low-power] fix csl channel (#5501)

If CSL Channel is never specified, the actual CSL channel should
always be the phy channel that the device is using. If CSL Channel
hasn't been specified and radio channel changes, the actual CSL
channel should also change. In current implementation, CSL Channel is
by default a valid value (not specified by upper layer) and wouldn't
change when radio channel changes even if it's never specified.

This commit fixes this issue. On CSL receiver, a bit is extracted from
mCslChannel to be used as a flag mIsCslChannelSpecified. If it is
false, mCslChannel would keep synchronized to the value of
mRadioChannel in Mac and Csl Channel TLV wouldn't be appended in Child
Update Request to its parent. On CSL transmitter, CSL channel info in
child is allowed to be 0. If it's 0, the channel info in frame would
be set using Mac::GetPanChannel.

tests/scripts/thread-cert/config.py

@@ -229,6 +229,7 @@ def create_default_mle_tlvs_factories():
         mle.TlvType.PANID: mle.PanIdFactory(),
         mle.TlvType.ACTIVE_TIMESTAMP: mle.ActiveTimestampFactory(),
         mle.TlvType.PENDING_TIMESTAMP: mle.PendingTimestampFactory(),
+        mle.TlvType.CSL_CHANNEL: mle.CslChannelFactory(),
         mle.TlvType.CSL_SYNCHRONIZED_TIMEOUT: mle.CslSynchronizedTimeoutFactory(),
         mle.TlvType.ACTIVE_OPERATIONAL_DATASET: mle.ActiveOperationalDatasetFactory(),
         mle.TlvType.PENDING_OPERATIONAL_DATASET: mle.PendingOperationalDatasetFactory(),

tests/scripts/thread-cert/mle.py

@@ -87,6 +87,7 @@ class TlvType(IntEnum):
     ACTIVE_OPERATIONAL_DATASET = 24
     PENDING_OPERATIONAL_DATASET = 25
     THREAD_DISCOVERY = 26
+    CSL_CHANNEL = 80
     CSL_SYNCHRONIZED_TIMEOUT = 85
     TIME_REQUEST = 252
     TIME_PARAMETER = 253
@@ -1048,6 +1049,20 @@ class ThreadDiscoveryFactory:
         return ThreadDiscovery(tlvs)
 
 
+class CslChannel:
+    # TODO: Not implemented yet
+
+    def __init__(self):
+        print("CslChannel is not implemented yet.")
+
+
+class CslChannelFactory:
+    # TODO: Not implemented yet
+
+    def parse(self, data, message_info):
+        return CslChannel()
+
+
 class CslSynchronizedTimeout:
     # TODO: Not implemented yet
 

tests/scripts/thread-cert/v1_2_test_csl_transmission.py

@@ -29,6 +29,7 @@
 
 import unittest
 
+import mle
 import thread_cert
 
 LEADER = 1
@@ -55,7 +56,6 @@ class SSED_CslTransmission(thread_cert.TestCase):
 
         self.nodes[SSED_1].set_csl_period(CSL_PERIOD)
         self.nodes[SSED_1].set_csl_timeout(CSL_TIMEOUT)
-        self.nodes[SSED_1].set_csl_channel(CSL_CHANNEL)
 
         self.nodes[SSED_1].get_csl_info()
 
@@ -71,6 +71,27 @@ class SSED_CslTransmission(thread_cert.TestCase):
         self.assertTrue(self.nodes[LEADER].ping(self.nodes[SSED_1].get_rloc()))
         self.simulator.go(5)
 
+        ssed_messages = self.simulator.get_messages_sent_by(SSED_1)
+        msg = ssed_messages.next_mle_message(mle.CommandType.CHILD_UPDATE_REQUEST)
+        msg.assertMleMessageDoesNotContainTlv(mle.CslChannel)
+
+        self.nodes[SSED_1].set_csl_channel(CSL_CHANNEL)
+        self.simulator.go(1)
+        ssed_messages = self.simulator.get_messages_sent_by(SSED_1)
+        msg = ssed_messages.next_mle_message(mle.CommandType.CHILD_UPDATE_REQUEST)
+        msg.assertMleMessageContainsTlv(mle.CslChannel)
+        self.assertTrue(self.nodes[LEADER].ping(self.nodes[SSED_1].get_rloc()))
+        self.simulator.go(5)
+
+        self.nodes[SSED_1].set_csl_channel(0)
+        self.simulator.go(1)
+        self.assertTrue(self.nodes[LEADER].ping(self.nodes[SSED_1].get_rloc()))
+        self.simulator.go(5)
+
+        ssed_messages = self.simulator.get_messages_sent_by(SSED_1)
+        msg = ssed_messages.next_mle_message(mle.CommandType.CHILD_UPDATE_REQUEST)
+        msg.assertMleMessageDoesNotContainTlv(mle.CslChannel)
+
         self.nodes[SSED_1].set_csl_period(0)
         self.assertFalse(self.nodes[LEADER].ping(self.nodes[SSED_1].get_rloc()))
         self.simulator.go(2)