VOL-3840: Fix invalid Get Response payload size configuration at openonu-go adapter

- also some pm notes md file updates included in this patch.

Change-Id: I793fa6004baedcad560d7f6caede214ff8cdc073
diff --git a/PM_Notes.md b/PM_Notes.md
index e0a6ba5..a3d6e64 100644
--- a/PM_Notes.md
+++ b/PM_Notes.md
@@ -48,7 +48,7 @@
 
 ## Basic KPI Format (**KpiEvent2**)
 
-The KPI information is published on the kafka bus under the _voltha.kpi_ topic. For
+The KPI information is published on the kafka bus under the _voltha.events_ topic. For
 VOLTHA PM information, the kafka key is empty and the value is a JSON message composed
 of the following key-value pairs.
 
@@ -87,7 +87,7 @@
 as simple as possible.
 
 Here is an JSON _example_ of a current KPI published on the kafka bus under the
-_voltha.kpi_ topic.
+_voltha.events_ topic.
 
 ```json
    "kpiEvent2":{
@@ -140,7 +140,7 @@
 ### Set default sampling rate
 
 ```
- voltctl device pmconfig frequency set <sampling-rate> <onu-device-id>
+ voltctl device pmconfig frequency set <onu-device-id> <sampling-rate>
 ```
 Note1: Sampling rate unit is in seconds
 
@@ -163,10 +163,12 @@
 ### Set group frequency
 
 ```
-voltctl device pmconfig group set <frequency> <onu-device-id> <group-name>
+voltctl device pmconfig group set <onu-device-id> <group-name> <frequency>
 ```
 Note1 : The `frequency` has to be greater than 0 and a multiple of _FrequencyGranularity_ which is currently set to 5.
 
+Note2 : The `frequency` of L2 PM counters is fixed at 15m and cannot be changed.
+
 ### Listen for KPI events on kafka
 
 ```
@@ -177,8 +179,6 @@
 ## Remaining work
 The following Metrics could be supported in the future.
 
-- Ethernet_Bridge_Port_History
-- Ethernet_UNI_History
 - FEC_History
 - GEM_Port_History
 - xgPON_TC_History
diff --git a/VERSION b/VERSION
index 94fcfcb..1abf7ca 100755
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.2.4-dev164
+1.2.4-dev165
diff --git a/internal/pkg/onuadaptercore/onu_metrics_manager.go b/internal/pkg/onuadaptercore/onu_metrics_manager.go
index 3110501..ff33f5b 100644
--- a/internal/pkg/onuadaptercore/onu_metrics_manager.go
+++ b/internal/pkg/onuadaptercore/onu_metrics_manager.go
@@ -146,7 +146,10 @@
 	SyncTimeRetryInterval  = 15      // Unit seconds
 	L2PmCreateAttempts     = 3
 	L2PmCollectAttempts    = 3
-	MaxL2PMGetPayLoadSize  = 29
+	// Per Table 11.2.9-1 – OMCI baseline message limitations in G.988 spec, the max GET Response
+	// payload size is 25. We define 24 (one less) to allow for dynamic insertion of IntervalEndTime
+	// attribute (1 byte) in L2 PM GET Requests.
+	MaxL2PMGetPayLoadSize = 24
 )
 
 // EthernetUniHistoryName specific constants