transceiver: Avoid sending clock indications when trx is not powered on

Stop calling writeClockInterface() when receiving commands in Transceiver::driveControl,
otherwise it fools osmo-bts-trx clock skew check because it is always sending a clock
indication with the same fn when it issues any commands during the time in between
CMD POWEROFF and RSP POWERON, because fn is not increased during that period.

Also use mForceClockInterface flag to delay delivery of first IND CLOCK until we start
serving frames, otherwise the first one is sent and only after a long period of time
the next clock indications are sent, when the radio starts to process bursts. That makes
osmo-bts-trx unhappy because it expects to receive an IND CLOCK aprox at least every
400 frames. This way also we send the first IND CLOCK after the RSP POWERON 0 response.

Change-Id: I91b81a4d7627cec39c1814a39ed4be306681b874
diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp
index d5b75d7..bf2dd6e 100644
--- a/Transceiver52M/Transceiver.cpp
+++ b/Transceiver52M/Transceiver.cpp
@@ -121,7 +121,7 @@
     mClockSocket(wBasePort, wTRXAddress, mBasePort + 100),
     mTransmitLatency(wTransmitLatency), mRadioInterface(wRadioInterface),
     rssiOffset(wRssiOffset),
-    mSPSTx(tx_sps), mSPSRx(rx_sps), mChans(chans), mEdge(false), mOn(false),
+    mSPSTx(tx_sps), mSPSRx(rx_sps), mChans(chans), mEdge(false), mOn(false), mForceClockInterface(false),
     mTxFreq(0.0), mRxFreq(0.0), mTSC(0), mMaxExpectedDelayAB(0), mMaxExpectedDelayNB(0),
     mWriteBurstToDiskMask(0)
 {
@@ -273,7 +273,7 @@
                             TxUpperLoopAdapter, (void*) chan);
   }
 
-  writeClockInterface();
+  mForceClockInterface = true;
   mOn = true;
   return true;
 }
@@ -677,9 +677,6 @@
 
   sscanf(buffer,"%3s %s",cmdcheck,command);
 
-  if (!chan)
-    writeClockInterface();
-
   if (strcmp(cmdcheck,"CMD")!=0) {
     LOG(WARNING) << "bogus message on control interface";
     return;
@@ -873,9 +870,9 @@
 {
   if (!mRadioInterface->driveReceiveRadio()) {
     usleep(100000);
-  } else {
-    if (mTransmitDeadlineClock > mLastClockUpdateTime + GSM::Time(216,0))
-      writeClockInterface();
+  } else if (mForceClockInterface || mTransmitDeadlineClock > mLastClockUpdateTime + GSM::Time(216,0)) {
+    mForceClockInterface = false;
+    writeClockInterface();
   }
 }
 
diff --git a/Transceiver52M/Transceiver.h b/Transceiver52M/Transceiver.h
index 26d6c3c..1eb1d1d 100644
--- a/Transceiver52M/Transceiver.h
+++ b/Transceiver52M/Transceiver.h
@@ -208,6 +208,7 @@
 
   bool mEdge;
   bool mOn;	                           ///< flag to indicate that transceiver is powered on
+  bool mForceClockInterface;           ///< flag to indicate whether IND CLOCK shall be sent unconditionally after transceiver is started
   bool mHandover[8][8];                ///< expect handover to the timeslot/subslot
   double mTxFreq;                      ///< the transmit frequency
   double mRxFreq;                      ///< the receive frequency