2011-11-12 19:31:18 +08:00
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/**
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* @file pi.c
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* @brief Implements a Proportional Integral clock servo.
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* @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdlib.h>
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2012-09-29 02:46:00 +08:00
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#include <math.h>
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2011-11-12 19:31:18 +08:00
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2015-08-14 04:48:25 +08:00
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#include "config.h"
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2011-11-12 19:31:18 +08:00
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#include "pi.h"
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2013-06-28 23:09:14 +08:00
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#include "print.h"
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2011-11-12 19:31:18 +08:00
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#include "servo_private.h"
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2013-06-28 23:09:14 +08:00
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#define HWTS_KP_SCALE 0.7
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#define HWTS_KI_SCALE 0.3
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#define SWTS_KP_SCALE 0.1
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#define SWTS_KI_SCALE 0.001
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2011-12-13 11:57:28 +08:00
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2013-06-28 23:09:14 +08:00
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#define MAX_KP_NORM_MAX 1.0
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#define MAX_KI_NORM_MAX 2.0
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2011-11-12 19:31:18 +08:00
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2013-06-17 03:31:20 +08:00
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#define FREQ_EST_MARGIN 0.001
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2012-09-29 02:46:00 +08:00
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2013-04-11 02:07:48 +08:00
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/* These take their values from the configuration file. (see ptp4l.c) */
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2013-06-28 23:09:14 +08:00
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double configured_pi_ki_scale = 0.0;
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double configured_pi_ki_exponent = 0.4;
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double configured_pi_ki_norm_max = 0.3;
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2012-05-03 17:17:34 +08:00
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2011-11-12 19:31:18 +08:00
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struct pi_servo {
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struct servo servo;
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2013-01-15 00:09:09 +08:00
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int64_t offset[2];
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uint64_t local[2];
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2011-11-12 19:31:18 +08:00
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double drift;
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2011-12-13 11:57:28 +08:00
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double kp;
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double ki;
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2014-01-08 21:23:46 +08:00
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double last_freq;
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2011-11-12 19:31:18 +08:00
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int count;
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2015-08-14 04:48:25 +08:00
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/* configuration: */
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double configured_pi_kp;
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2015-08-14 04:54:22 +08:00
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double configured_pi_ki;
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2015-08-14 05:02:06 +08:00
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double configured_pi_kp_scale;
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2015-08-15 03:21:25 +08:00
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double configured_pi_kp_exponent;
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2015-08-15 03:25:27 +08:00
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double configured_pi_kp_norm_max;
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2011-11-12 19:31:18 +08:00
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};
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static void pi_destroy(struct servo *servo)
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{
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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free(s);
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}
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static double pi_sample(struct servo *servo,
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int64_t offset,
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uint64_t local_ts,
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2015-03-26 23:32:15 +08:00
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double weight,
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2011-11-12 19:31:18 +08:00
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enum servo_state *state)
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{
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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2014-01-08 21:23:46 +08:00
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double ki_term, ppb = s->last_freq;
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double freq_est_interval, localdiff;
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2011-11-12 19:31:18 +08:00
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switch (s->count) {
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case 0:
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s->offset[0] = offset;
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s->local[0] = local_ts;
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*state = SERVO_UNLOCKED;
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s->count = 1;
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break;
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case 1:
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s->offset[1] = offset;
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s->local[1] = local_ts;
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2013-01-15 00:09:11 +08:00
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2013-02-06 00:36:10 +08:00
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/* Make sure the first sample is older than the second. */
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if (s->local[0] >= s->local[1]) {
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2013-06-18 18:09:36 +08:00
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*state = SERVO_UNLOCKED;
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2013-02-06 00:36:10 +08:00
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s->count = 0;
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break;
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}
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2013-06-17 03:31:20 +08:00
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/* Wait long enough before estimating the frequency offset. */
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localdiff = (s->local[1] - s->local[0]) / 1e9;
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localdiff += localdiff * FREQ_EST_MARGIN;
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freq_est_interval = 0.016 / s->ki;
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if (freq_est_interval > 1000.0) {
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freq_est_interval = 1000.0;
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}
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if (localdiff < freq_est_interval) {
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*state = SERVO_UNLOCKED;
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break;
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}
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2014-01-08 22:44:37 +08:00
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/* Adjust drift by the measured frequency offset. */
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s->drift += (1e9 - s->drift) * (s->offset[1] - s->offset[0]) /
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(s->local[1] - s->local[0]);
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2014-03-14 01:34:17 +08:00
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if (s->drift < -servo->max_frequency)
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s->drift = -servo->max_frequency;
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else if (s->drift > servo->max_frequency)
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s->drift = servo->max_frequency;
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if ((servo->first_update &&
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servo->first_step_threshold &&
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servo->first_step_threshold < fabs(offset)) ||
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(servo->step_threshold &&
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servo->step_threshold < fabs(offset)))
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2013-06-20 12:30:15 +08:00
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*state = SERVO_JUMP;
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else
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*state = SERVO_LOCKED;
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2013-01-15 00:09:10 +08:00
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ppb = s->drift;
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2013-01-15 00:09:11 +08:00
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s->count = 2;
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2011-11-12 19:31:18 +08:00
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break;
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2013-01-15 00:09:11 +08:00
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case 2:
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2012-09-29 02:46:00 +08:00
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/*
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* reset the clock servo when offset is greater than the max
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* offset value. Note that the clock jump will be performed in
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2013-02-06 00:36:11 +08:00
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* step 1, so it is not necessary to have clock jump
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2012-09-29 02:46:00 +08:00
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* immediately. This allows re-calculating drift as in initial
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* clock startup.
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*/
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2014-03-14 01:34:17 +08:00
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if (servo->step_threshold &&
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servo->step_threshold < fabs(offset)) {
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2012-09-29 02:46:00 +08:00
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*state = SERVO_UNLOCKED;
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s->count = 0;
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break;
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}
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2015-03-26 23:32:17 +08:00
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ki_term = s->ki * offset * weight;
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ppb = s->kp * offset * weight + s->drift + ki_term;
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2014-03-14 01:34:17 +08:00
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if (ppb < -servo->max_frequency) {
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ppb = -servo->max_frequency;
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} else if (ppb > servo->max_frequency) {
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ppb = servo->max_frequency;
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2011-11-12 19:31:18 +08:00
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} else {
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s->drift += ki_term;
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}
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*state = SERVO_LOCKED;
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break;
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}
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2014-01-08 21:23:46 +08:00
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s->last_freq = ppb;
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2011-11-12 19:31:18 +08:00
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return ppb;
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}
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2013-05-16 22:31:45 +08:00
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static void pi_sync_interval(struct servo *servo, double interval)
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{
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2013-06-28 23:09:14 +08:00
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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2015-08-15 03:21:25 +08:00
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s->kp = s->configured_pi_kp_scale * pow(interval, s->configured_pi_kp_exponent);
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2015-08-15 03:25:27 +08:00
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if (s->kp > s->configured_pi_kp_norm_max / interval)
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s->kp = s->configured_pi_kp_norm_max / interval;
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2013-06-28 23:09:14 +08:00
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s->ki = configured_pi_ki_scale * pow(interval, configured_pi_ki_exponent);
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if (s->ki > configured_pi_ki_norm_max / interval)
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s->ki = configured_pi_ki_norm_max / interval;
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pr_debug("PI servo: sync interval %.3f kp %.3f ki %.6f",
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interval, s->kp, s->ki);
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2013-05-16 22:31:45 +08:00
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}
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2013-10-23 00:57:14 +08:00
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static void pi_reset(struct servo *servo)
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{
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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s->count = 0;
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}
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2015-08-14 04:48:25 +08:00
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struct servo *pi_servo_create(struct config *cfg, int fadj, int sw_ts)
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2011-11-12 19:31:18 +08:00
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{
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struct pi_servo *s;
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s = calloc(1, sizeof(*s));
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if (!s)
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return NULL;
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s->servo.destroy = pi_destroy;
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s->servo.sample = pi_sample;
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2013-05-16 22:31:45 +08:00
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s->servo.sync_interval = pi_sync_interval;
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2013-10-23 00:57:14 +08:00
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s->servo.reset = pi_reset;
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2012-09-21 15:27:53 +08:00
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s->drift = fadj;
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2014-01-08 21:23:46 +08:00
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s->last_freq = fadj;
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2013-06-28 23:09:14 +08:00
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s->kp = 0.0;
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s->ki = 0.0;
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2015-08-14 04:48:25 +08:00
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s->configured_pi_kp = config_get_double(cfg, NULL, "pi_proportional_const");
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2015-08-14 04:54:22 +08:00
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s->configured_pi_ki = config_get_double(cfg, NULL, "pi_integral_const");
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2015-08-14 05:02:06 +08:00
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s->configured_pi_kp_scale = config_get_double(cfg, NULL, "pi_proportional_scale");
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2015-08-15 03:21:25 +08:00
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s->configured_pi_kp_exponent =
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config_get_double(cfg, NULL, "pi_proportional_exponent");
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2015-08-15 03:25:27 +08:00
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s->configured_pi_kp_norm_max =
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config_get_double(cfg, NULL, "pi_proportional_norm_max");
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2011-11-12 19:31:18 +08:00
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2015-08-14 04:54:22 +08:00
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if (s->configured_pi_kp && s->configured_pi_ki) {
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2013-06-28 23:09:14 +08:00
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/* Use the constants as configured by the user without
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adjusting for sync interval unless they make the servo
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unstable. */
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2015-08-14 05:02:06 +08:00
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s->configured_pi_kp_scale = s->configured_pi_kp;
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2015-08-14 04:54:22 +08:00
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configured_pi_ki_scale = s->configured_pi_ki;
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2015-08-15 03:21:25 +08:00
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s->configured_pi_kp_exponent = 0.0;
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2013-06-28 23:09:14 +08:00
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configured_pi_ki_exponent = 0.0;
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2015-08-15 03:25:27 +08:00
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s->configured_pi_kp_norm_max = MAX_KP_NORM_MAX;
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2013-06-28 23:09:14 +08:00
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configured_pi_ki_norm_max = MAX_KI_NORM_MAX;
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2015-08-14 05:02:06 +08:00
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} else if (!s->configured_pi_kp_scale || !configured_pi_ki_scale) {
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2013-06-28 23:09:14 +08:00
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if (sw_ts) {
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2015-08-14 05:02:06 +08:00
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s->configured_pi_kp_scale = SWTS_KP_SCALE;
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2013-06-28 23:09:14 +08:00
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configured_pi_ki_scale = SWTS_KI_SCALE;
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} else {
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2015-08-14 05:02:06 +08:00
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s->configured_pi_kp_scale = HWTS_KP_SCALE;
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2013-06-28 23:09:14 +08:00
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configured_pi_ki_scale = HWTS_KI_SCALE;
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}
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2011-12-13 11:57:28 +08:00
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}
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2011-11-12 19:31:18 +08:00
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return &s->servo;
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}
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