hwclock: add support for tracking hardware clocks

Add a general support for tracking independent hardware clocks like PTP
hardware clocks (PHC) or real-time clocks (RTC).

diff --git a/hwclock.c b/hwclock.c
new file mode 100644 (file)
index 0000000..e987daa
--- /dev/null
+++ b/hwclock.c
@@ -0,0 +1,202 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2016
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Tracking of hardware clocks (e.g. RTC, PHC)
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "array.h"
+#include "hwclock.h"
+#include "local.h"
+#include "logging.h"
+#include "memory.h"
+#include "regress.h"
+#include "util.h"
+
+/* Maximum number of samples per clock */
+#define MAX_SAMPLES 16
+
+/* Minimum interval between samples (in seconds) */
+#define MIN_SAMPLE_SEPARATION 1.0
+
+struct HCL_Instance_Record {
+  /* HW and local reference timestamp */
+  struct timespec hw_ref;
+  struct timespec local_ref;
+
+  /* Samples stored as intervals (uncorrected for frequency error)
+     relative to local_ref and hw_ref */
+  double x_data[MAX_SAMPLES];
+  double y_data[MAX_SAMPLES];
+
+  /* Number of samples */
+  int n_samples;
+
+  /* Flag indicating the offset and frequency values are valid */
+  int valid_coefs;
+
+  /* Estimated offset and frequency of HW clock relative to local clock */
+  double offset;
+  double frequency;
+};
+
+/* ================================================== */
+
+static void
+handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
+            double doffset, LCL_ChangeType change_type, void *anything)
+{
+  HCL_Instance clock;
+  double delta;
+
+  clock = anything;
+
+  if (clock->n_samples)
+    UTI_AdjustTimespec(&clock->local_ref, cooked, &clock->local_ref, &delta, dfreq, doffset);
+  if (clock->valid_coefs)
+    clock->frequency /= 1.0 - dfreq;
+}
+
+/* ================================================== */
+
+HCL_Instance
+HCL_CreateInstance(void)
+{
+  HCL_Instance clock;
+
+  clock = MallocNew(struct HCL_Instance_Record);
+  clock->x_data[0] = 0.0;
+  clock->y_data[0] = 0.0;
+  clock->n_samples = 0;
+  clock->valid_coefs = 0;
+
+  LCL_AddParameterChangeHandler(handle_slew, clock);
+
+  return clock;
+}
+
+/* ================================================== */
+
+void HCL_DestroyInstance(HCL_Instance clock)
+{
+  LCL_RemoveParameterChangeHandler(handle_slew, clock);
+  Free(clock);
+}
+
+/* ================================================== */
+
+int
+HCL_NeedsNewSample(HCL_Instance clock, struct timespec *now)
+{
+  if (!clock->n_samples ||
+      fabs(UTI_DiffTimespecsToDouble(now, &clock->local_ref) >= MIN_SAMPLE_SEPARATION))
+    return 1;
+
+  return 0;
+}
+
+/* ================================================== */
+
+void
+HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
+                     struct timespec *local_ts, double err)
+{
+  double hw_delta, local_delta, local_freq, raw_freq;
+  int i, n_runs, best_start;
+
+  local_freq = 1.0 - LCL_ReadAbsoluteFrequency() / 1.0e6;
+
+  /* Shift old samples */
+  if (clock->n_samples) {
+    if (clock->n_samples >= MAX_SAMPLES)
+      clock->n_samples--;
+
+    hw_delta = UTI_DiffTimespecsToDouble(hw_ts, &clock->hw_ref);
+    local_delta = UTI_DiffTimespecsToDouble(local_ts, &clock->local_ref) / local_freq;
+
+    if (hw_delta <= 0.0 || local_delta < MIN_SAMPLE_SEPARATION / 2.0) {
+      clock->n_samples = 0;
+      DEBUG_LOG(LOGF_HwClocks, "HW clock reset interval=%f", local_delta);
+    }
+
+    for (i = clock->n_samples; i > 0; i--) {
+      clock->y_data[i] = clock->y_data[i - 1] - hw_delta;
+      clock->x_data[i] = clock->x_data[i - 1] - local_delta;
+    }
+  }
+
+  clock->n_samples++;
+  clock->hw_ref = *hw_ts;
+  clock->local_ref = *local_ts;
+
+  /* Get new coefficients */
+  clock->valid_coefs =
+    RGR_FindBestRobustRegression(clock->x_data, clock->y_data, clock->n_samples,
+                                 1.0e-9, &clock->offset, &raw_freq, &n_runs, &best_start);
+
+  if (!clock->valid_coefs) {
+    DEBUG_LOG(LOGF_HwClocks, "HW clock needs more samples");
+    return;
+  }
+
+  clock->frequency = raw_freq / local_freq;
+
+  /* Drop unneeded samples */
+  clock->n_samples -= best_start;
+
+  /* If the fit doesn't cross the error interval of the last sample, throw away
+     all previous samples and keep only the frequency estimate */
+  if (fabs(clock->offset) > err) {
+    DEBUG_LOG(LOGF_HwClocks, "HW clock reset offset=%e", clock->offset);
+    clock->offset = 0.0;
+    clock->n_samples = 1;
+  }
+
+  DEBUG_LOG(LOGF_HwClocks, "HW clock samples=%d offset=%e freq=%.9e raw_freq=%.9e err=%e ref_diff=%e",
+            clock->n_samples, clock->offset, clock->frequency, raw_freq, err,
+            UTI_DiffTimespecsToDouble(&clock->hw_ref, &clock->local_ref));
+}
+
+/* ================================================== */
+
+int
+HCL_CookTime(HCL_Instance clock, struct timespec *raw, struct timespec *cooked, double *err)
+{
+  double offset, elapsed;
+
+  if (!clock->valid_coefs)
+    return 0;
+
+  elapsed = UTI_DiffTimespecsToDouble(raw, &clock->hw_ref);
+  offset = clock->offset + elapsed / clock->frequency;
+  UTI_AddDoubleToTimespec(&clock->local_ref, offset, cooked);
+
+  /* Estimation of the error is not implemented yet */
+  if (err)
+    *err = 0.0;
+
+  return 1;
+}

diff --git a/hwclock.h b/hwclock.h
new file mode 100644 (file)
index 0000000..11a79b0
--- /dev/null
+++ b/hwclock.h
@@ -0,0 +1,48 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2016
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Header for tracking of hardware clocks */
+
+#ifndef GOT_HWCLOCK_H
+#define GOT_HWCLOCK_H
+
+typedef struct HCL_Instance_Record *HCL_Instance;
+
+/* Create a new HW clock instance */
+extern HCL_Instance HCL_CreateInstance(void);
+
+/* Destroy a HW clock instance */
+extern void HCL_DestroyInstance(HCL_Instance clock);
+
+/* Check if a new sample should be accumulated at this time */
+extern int HCL_NeedsNewSample(HCL_Instance clock, struct timespec *now);
+
+/* Accumulate a new sample */
+extern void HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
+                                 struct timespec *local_ts, double err);
+
+/* Convert raw hardware time to cooked local time */
+extern int HCL_CookTime(HCL_Instance clock, struct timespec *raw, struct timespec *cooked,
+                        double *err);
+
+#endif

diff --git a/logging.h b/logging.h
index 41d640eca43f9362f6b6032ee7098678c968f874..cc8beeefaa7ca20798a369bb1a99ff67b189eb70 100644 (file)
--- a/logging.h
+++ b/logging.h
@@ -116,6 +116,7 @@ typedef enum {
   LOGF_TempComp,
   LOGF_RtcLinux,
   LOGF_Refclock,
+  LOGF_HwClocks,
   LOGF_Smooth,
 } LOG_Facility;