[nrf528xx] ensure there is no radio pending events after diag is disabled (#4343)

examples/platforms/nrf528xx/src/diag.c

@@ -415,6 +415,9 @@ void otPlatDiagModeSet(bool aMode)
     {
         otPlatRadioReceive(NULL, sChannel);
         otPlatRadioSleep(NULL);
+
+        // Clear all remaining events before switching to MAC callbacks.
+        nrf5RadioClearPendingEvents();
     }
     else
     {

examples/platforms/nrf528xx/src/platform-nrf5.h

@@ -166,6 +166,12 @@ void nrf5RadioDeinit(void);
  */
 void nrf5RadioProcess(otInstance *aInstance);
 
+/**
+ * Function for clearing Radio driver pending events.
+ *
+ */
+void nrf5RadioClearPendingEvents(void);
+
 /**
  * Initialization of hardware crypto engine.
  *

examples/platforms/nrf528xx/src/radio.c

@@ -254,6 +254,21 @@ void nrf5RadioDeinit(void)
     sPendingEvents = 0;
 }
 
+void nrf5RadioClearPendingEvents(void)
+{
+    sPendingEvents = 0;
+
+    for (uint32_t i = 0; i < NRF_802154_RX_BUFFERS; i++)
+    {
+        if (sReceivedFrames[i].mPsdu != NULL)
+        {
+            uint8_t *bufferAddress   = &sReceivedFrames[i].mPsdu[-1];
+            sReceivedFrames[i].mPsdu = NULL;
+            nrf_802154_buffer_free_raw(bufferAddress);
+        }
+    }
+}
+
 otRadioState otPlatRadioGetState(otInstance *aInstance)
 {
     OT_UNUSED_VARIABLE(aInstance);