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local: clamp frequency offset

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Don't allow frequency offset larger than 50%, the tracked time must not
stop or run backwards.
This commit is contained in:
Miroslav Lichvar 2015-04-07 14:13:41 +02:00
parent 27f8ad7fd1
commit 183a648d01
1 changed files with 24 additions and 0 deletions
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24
local.c
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@ -42,6 +42,10 @@
/* ================================================== */
/* Maximum allowed frequency offset in ppm, the time must not stop
or run backwards */
#define MAX_FREQ 500000.0
/* Variable to store the current frequency, in ppm */
static double current_freq_ppm;
@ -398,6 +402,20 @@ LCL_ReadAbsoluteFrequency(void)
}
/* ================================================== */
static double
clamp_freq(double freq)
{
if (freq <= MAX_FREQ && freq >= -MAX_FREQ)
return freq;
LOG(LOGS_WARN, LOGF_Local, "Frequency %.1f ppm exceeds allowed maximum", freq);
return freq >= MAX_FREQ ? MAX_FREQ : -MAX_FREQ;
}
/* ================================================== */
/* This involves both setting the absolute frequency with the
system-specific driver, as well as calling all notify handlers */
@ -407,6 +425,8 @@ LCL_SetAbsoluteFrequency(double afreq_ppm)
struct timeval raw, cooked;
double dfreq;
afreq_ppm = clamp_freq(afreq_ppm);
/* Apply temperature compensation */
if (temp_comp_ppm != 0.0) {
afreq_ppm = afreq_ppm * (1.0 - 1.0e-6 * temp_comp_ppm) - temp_comp_ppm;
@ -444,6 +464,8 @@ LCL_AccumulateDeltaFrequency(double dfreq)
current_freq_ppm += dfreq * (1.0e6 - current_freq_ppm);
current_freq_ppm = clamp_freq(current_freq_ppm);
/* Call the system-specific driver for setting the frequency */
current_freq_ppm = (*drv_set_freq)(current_freq_ppm);
dfreq = (current_freq_ppm - old_freq_ppm) / (1.0e6 - old_freq_ppm);
@ -542,6 +564,8 @@ LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate)
terms of the gradient of the (offset) v (local time) function. */
current_freq_ppm += dfreq * (1.0e6 - current_freq_ppm);
current_freq_ppm = clamp_freq(current_freq_ppm);
DEBUG_LOG(LOGF_Local, "old_freq=%.3fppm new_freq=%.3fppm offset=%.6fsec",
old_freq_ppm, current_freq_ppm, doffset);