Don't reset kernel frequency on start without drift file

reference.c

@@ -141,6 +141,7 @@ REF_Initialise(void)
           our_frequency_ppm = file_freq_ppm;
           our_skew = 1.0e-6 * file_skew_ppm;
           LOG(LOGS_INFO, LOGF_Reference, "Frequency %.3f +- %.3f ppm read from %s", file_freq_ppm, file_skew_ppm, drift_file);
+          LCL_SetAbsoluteFrequency(our_frequency_ppm);
         } else {
           LOG(LOGS_WARN, LOGF_Reference, "Could not parse valid frequency and skew from driftfile %s",
               drift_file);
@@ -155,7 +156,12 @@ REF_Initialise(void)
     drift_file_age = 0.0;
   }
     
-  LCL_SetAbsoluteFrequency(our_frequency_ppm);
+  if (our_frequency_ppm == 0.0) {
+    our_frequency_ppm = LCL_ReadAbsoluteFrequency();
+    if (our_frequency_ppm != 0.0) {
+      LOG(LOGS_INFO, LOGF_Reference, "Initial frequency %.3f ppm", our_frequency_ppm);
+    }
+  }
 
   logfileid = CNF_GetLogTracking() ? LOG_FileOpen("tracking",
       "   Date (UTC) Time     IP Address   St   Freq ppm   Skew ppm     Offset")

sys_linux.c

@@ -720,15 +720,17 @@ read_frequency(void)
   double tick_term;
   double unscaled_freq;
   double freq_term;
+  long tick;
 
-  if (TMX_GetFrequency(&unscaled_freq) < 0) {
+  if (TMX_GetFrequency(&unscaled_freq, &tick) < 0) {
     LOG_FATAL(LOGF_SysLinux, "adjtimex() failed");
   }
 
-  /* Use current_tick here rather than txc.tick, otherwise we're
-     thrown off course when doing a fast slew (in which case, txc.tick
-     is nowhere near the nominal value) */
-  tick_term = dhz * (double)(nominal_tick - current_tick);
+  if (fast_slewing) {
+      tick -= slewing_tick - current_tick;
+  }
+
+  tick_term = dhz * (double)(nominal_tick - tick);
   freq_term = unscaled_freq / freq_scale;
   
 #if 0
@@ -1043,19 +1045,13 @@ void
 SYS_Linux_Initialise(void)
 {
   long offset;
+  double freq;
 
   offset_register = 0.0;
   fast_slewing = 0;
 
   get_version_specific_details();
 
-  current_tick = nominal_tick;
-  current_total_tick = 1.0 / dhz;
-
-  lcl_RegisterSystemDrivers(read_frequency, set_frequency,
-                            accrue_offset, apply_step_offset,
-                            get_offset_correction, set_leap);
-
   offset = 0;
   if (TMX_ApplyOffset(&offset) < 0) {
     LOG_FATAL(LOGF_SysLinux, "adjtimex() failed");
@@ -1072,6 +1068,14 @@ SYS_Linux_Initialise(void)
   }
 
   TMX_SetSync(CNF_GetRTCSync());
+
+  /* Read current kernel frequency */
+  TMX_GetFrequency(&freq, &current_tick);
+  current_total_tick = (current_tick + freq / freq_scale / dhz) / 1.0e6;
+
+  lcl_RegisterSystemDrivers(read_frequency, set_frequency,
+                            accrue_offset, apply_step_offset,
+                            get_offset_correction, set_leap);
 }
 
 /* ================================================== */

wrap_adjtimex.c

@@ -86,13 +86,14 @@ TMX_SetFrequency(double *freq, long tick)
 }
 
 int
-TMX_GetFrequency(double *freq)
+TMX_GetFrequency(double *freq, long *tick)
 {
   struct timex txc;
   int result;
   txc.modes = 0; /* pure read */
   result = adjtimex(&txc);
   *freq = txc.freq / (double)(1 << SHIFT_USEC);
+  *tick = txc.tick;
   return result;
 }
 

wrap_adjtimex.h

@@ -67,7 +67,7 @@ struct tmx_params {
 int TMX_SetTick(long tick);
 int TMX_ApplyOffset(long *offset);
 int TMX_SetFrequency(double *freq, long tick);
-int TMX_GetFrequency(double *freq);
+int TMX_GetFrequency(double *freq, long *tick);
 int TMX_GetOffsetLeft(long *offset);
 int TMX_ReadCurrentParams(struct tmx_params *params);
 int TMX_SetLeap(int leap);