1*cdfa2a7eSchristos /* $NetBSD: kern.c,v 1.5 2020/05/25 20:47:37 christos Exp $ */
2abb0f93cSkardel
3abb0f93cSkardel /*
4abb0f93cSkardel * This program simulates a first-order, type-II phase-lock loop using
5abb0f93cSkardel * actual code segments from modified kernel distributions for SunOS,
6abb0f93cSkardel * Ultrix and OSF/1 kernels. These segments do not use any licensed code.
7abb0f93cSkardel */
8abb0f93cSkardel
9abb0f93cSkardel #ifdef HAVE_CONFIG_H
10abb0f93cSkardel # include <config.h>
11abb0f93cSkardel #endif
12abb0f93cSkardel
13abb0f93cSkardel #include <stdio.h>
14abb0f93cSkardel #include <ctype.h>
15abb0f93cSkardel #include <math.h>
16abb0f93cSkardel #include <sys/time.h>
17abb0f93cSkardel
18abb0f93cSkardel #ifdef HAVE_TIMEX_H
19abb0f93cSkardel # include "timex.h"
20abb0f93cSkardel #endif
21abb0f93cSkardel
22abb0f93cSkardel /*
23abb0f93cSkardel * Phase-lock loop definitions
24abb0f93cSkardel */
25abb0f93cSkardel #define HZ 100 /* timer interrupt frequency (Hz) */
26abb0f93cSkardel #define MAXPHASE 512000 /* max phase error (us) */
27abb0f93cSkardel #define MAXFREQ 200 /* max frequency error (ppm) */
28abb0f93cSkardel #define TAU 2 /* time constant (shift 0 - 6) */
29abb0f93cSkardel #define POLL 16 /* interval between updates (s) */
30abb0f93cSkardel #define MAXSEC 1200 /* max interval between updates (s) */
31abb0f93cSkardel
32abb0f93cSkardel /*
33abb0f93cSkardel * Function declarations
34abb0f93cSkardel */
35abb0f93cSkardel void hardupdate();
36abb0f93cSkardel void hardclock();
37abb0f93cSkardel void second_overflow();
38abb0f93cSkardel
39abb0f93cSkardel /*
40abb0f93cSkardel * Kernel variables
41abb0f93cSkardel */
42abb0f93cSkardel int tick; /* timer interrupt period (us) */
43abb0f93cSkardel int fixtick; /* amortization constant (ppm) */
44abb0f93cSkardel struct timeval timex; /* ripoff of kernel time variable */
45abb0f93cSkardel
46abb0f93cSkardel /*
47abb0f93cSkardel * Phase-lock loop variables
48abb0f93cSkardel */
49abb0f93cSkardel int time_status = TIME_BAD; /* clock synchronization status */
50abb0f93cSkardel long time_offset = 0; /* time adjustment (us) */
51abb0f93cSkardel long time_constant = 0; /* pll time constant */
52abb0f93cSkardel long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */
53abb0f93cSkardel long time_precision = 1000000 / HZ; /* clock precision (us) */
54abb0f93cSkardel long time_maxerror = MAXPHASE; /* maximum error (us) */
55abb0f93cSkardel long time_esterror = MAXPHASE; /* estimated error (us) */
56abb0f93cSkardel long time_phase = 0; /* phase offset (scaled us) */
57abb0f93cSkardel long time_freq = 0; /* frequency offset (scaled ppm) */
58abb0f93cSkardel long time_adj = 0; /* tick adjust (scaled 1 / HZ) */
59abb0f93cSkardel long time_reftime = 0; /* time at last adjustment (s) */
60abb0f93cSkardel
61abb0f93cSkardel /*
62abb0f93cSkardel * Simulation variables
63abb0f93cSkardel */
64abb0f93cSkardel double timey = 0; /* simulation time (us) */
65abb0f93cSkardel long timez = 0; /* current error (us) */
66abb0f93cSkardel long poll_interval = 0; /* poll counter */
67abb0f93cSkardel
68abb0f93cSkardel /*
69abb0f93cSkardel * Simulation test program
70abb0f93cSkardel */
71abb0f93cSkardel int
main(int argc,char * argv[])72abb0f93cSkardel main(
73abb0f93cSkardel int argc,
74abb0f93cSkardel char *argv[]
75abb0f93cSkardel )
76abb0f93cSkardel {
77abb0f93cSkardel tick = 1000000 / HZ;
78abb0f93cSkardel fixtick = 1000000 % HZ;
79abb0f93cSkardel timex.tv_sec = 0;
80abb0f93cSkardel timex.tv_usec = MAXPHASE;
81abb0f93cSkardel time_freq = 0;
82abb0f93cSkardel time_constant = TAU;
83abb0f93cSkardel printf("tick %d us, fixtick %d us\n", tick, fixtick);
84abb0f93cSkardel printf(" time offset freq _offset _freq _adj\n");
85abb0f93cSkardel
86abb0f93cSkardel /*
87abb0f93cSkardel * Grind the loop until ^C
88abb0f93cSkardel */
89abb0f93cSkardel while (1) {
90abb0f93cSkardel timey += (double)(1000000) / HZ;
91abb0f93cSkardel if (timey >= 1000000)
92abb0f93cSkardel timey -= 1000000;
93abb0f93cSkardel hardclock();
94abb0f93cSkardel if (timex.tv_usec >= 1000000) {
95abb0f93cSkardel timex.tv_usec -= 1000000;
96abb0f93cSkardel timex.tv_sec++;
97abb0f93cSkardel second_overflow();
98abb0f93cSkardel poll_interval++;
99abb0f93cSkardel if (!(poll_interval % POLL)) {
100abb0f93cSkardel timez = (long)timey - timex.tv_usec;
101abb0f93cSkardel if (timez > 500000)
102abb0f93cSkardel timez -= 1000000;
103abb0f93cSkardel if (timez < -500000)
104abb0f93cSkardel timez += 1000000;
105abb0f93cSkardel hardupdate(timez);
106abb0f93cSkardel printf("%10li%10li%10.2f %08lx %08lx %08lx\n",
107abb0f93cSkardel timex.tv_sec, timez,
108abb0f93cSkardel (double)time_freq / (1 << SHIFT_KF),
109abb0f93cSkardel time_offset, time_freq, time_adj);
110abb0f93cSkardel }
111abb0f93cSkardel }
112abb0f93cSkardel }
113abb0f93cSkardel }
114abb0f93cSkardel
115abb0f93cSkardel /*
116abb0f93cSkardel * This routine simulates the ntp_adjtime() call
117abb0f93cSkardel *
118abb0f93cSkardel * For default SHIFT_UPDATE = 12, offset is limited to +-512 ms, the
119abb0f93cSkardel * maximum interval between updates is 4096 s and the maximum frequency
120abb0f93cSkardel * offset is +-31.25 ms/s.
121abb0f93cSkardel */
122abb0f93cSkardel void
hardupdate(long offset)123abb0f93cSkardel hardupdate(
124abb0f93cSkardel long offset
125abb0f93cSkardel )
126abb0f93cSkardel {
127abb0f93cSkardel long ltemp, mtemp;
128abb0f93cSkardel
129abb0f93cSkardel time_offset = offset << SHIFT_UPDATE;
130abb0f93cSkardel mtemp = timex.tv_sec - time_reftime;
131abb0f93cSkardel time_reftime = timex.tv_sec;
132abb0f93cSkardel if (mtemp > MAXSEC)
133abb0f93cSkardel mtemp = 0;
134abb0f93cSkardel
135abb0f93cSkardel /* ugly multiply should be replaced */
136abb0f93cSkardel if (offset < 0)
137abb0f93cSkardel time_freq -= (-offset * mtemp) >>
138abb0f93cSkardel (time_constant + time_constant);
139abb0f93cSkardel else
140abb0f93cSkardel time_freq += (offset * mtemp) >>
141abb0f93cSkardel (time_constant + time_constant);
142abb0f93cSkardel ltemp = time_tolerance << SHIFT_KF;
143abb0f93cSkardel if (time_freq > ltemp)
144abb0f93cSkardel time_freq = ltemp;
145abb0f93cSkardel else if (time_freq < -ltemp)
146abb0f93cSkardel time_freq = -ltemp;
147abb0f93cSkardel if (time_status == TIME_BAD)
148abb0f93cSkardel time_status = TIME_OK;
149abb0f93cSkardel }
150abb0f93cSkardel
151abb0f93cSkardel /*
152abb0f93cSkardel * This routine simulates the timer interrupt
153abb0f93cSkardel */
154abb0f93cSkardel void
hardclock(void)155abb0f93cSkardel hardclock(void)
156abb0f93cSkardel {
157abb0f93cSkardel int ltemp, time_update;
158abb0f93cSkardel
159abb0f93cSkardel time_update = tick; /* computed by adjtime() */
160abb0f93cSkardel time_phase += time_adj;
161abb0f93cSkardel if (time_phase < -FINEUSEC) {
162abb0f93cSkardel ltemp = -time_phase >> SHIFT_SCALE;
163abb0f93cSkardel time_phase += ltemp << SHIFT_SCALE;
164abb0f93cSkardel time_update -= ltemp;
165abb0f93cSkardel }
166abb0f93cSkardel else if (time_phase > FINEUSEC) {
167abb0f93cSkardel ltemp = time_phase >> SHIFT_SCALE;
168abb0f93cSkardel time_phase -= ltemp << SHIFT_SCALE;
169abb0f93cSkardel time_update += ltemp;
170abb0f93cSkardel }
171abb0f93cSkardel timex.tv_usec += time_update;
172abb0f93cSkardel }
173abb0f93cSkardel
174abb0f93cSkardel /*
175abb0f93cSkardel * This routine simulates the overflow of the microsecond field
176abb0f93cSkardel *
177abb0f93cSkardel * With SHIFT_SCALE = 23, the maximum frequency adjustment is +-256 us
178abb0f93cSkardel * per tick, or 25.6 ms/s at a clock frequency of 100 Hz. The time
179abb0f93cSkardel * contribution is shifted right a minimum of two bits, while the frequency
180abb0f93cSkardel * contribution is a right shift. Thus, overflow is prevented if the
181abb0f93cSkardel * frequency contribution is limited to half the maximum or 15.625 ms/s.
182abb0f93cSkardel */
183abb0f93cSkardel void
second_overflow(void)184abb0f93cSkardel second_overflow(void)
185abb0f93cSkardel {
186abb0f93cSkardel int ltemp;
187abb0f93cSkardel
188abb0f93cSkardel time_maxerror += time_tolerance;
189abb0f93cSkardel if (time_offset < 0) {
190abb0f93cSkardel ltemp = -time_offset >>
191abb0f93cSkardel (SHIFT_KG + time_constant);
192abb0f93cSkardel time_offset += ltemp;
193abb0f93cSkardel time_adj = -(ltemp <<
194abb0f93cSkardel (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE));
195abb0f93cSkardel } else {
196abb0f93cSkardel ltemp = time_offset >>
197abb0f93cSkardel (SHIFT_KG + time_constant);
198abb0f93cSkardel time_offset -= ltemp;
199abb0f93cSkardel time_adj = ltemp <<
200abb0f93cSkardel (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
201abb0f93cSkardel }
202abb0f93cSkardel if (time_freq < 0)
203abb0f93cSkardel time_adj -= -time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);
204abb0f93cSkardel else
205abb0f93cSkardel time_adj += time_freq >> (SHIFT_KF + SHIFT_HZ - SHIFT_SCALE);
206abb0f93cSkardel time_adj += fixtick << (SHIFT_SCALE - SHIFT_HZ);
207abb0f93cSkardel
208abb0f93cSkardel /* ugly divide should be replaced */
209abb0f93cSkardel if (timex.tv_sec % 86400 == 0) {
210abb0f93cSkardel switch (time_status) {
211abb0f93cSkardel
212abb0f93cSkardel case TIME_INS:
213abb0f93cSkardel timex.tv_sec--; /* !! */
214abb0f93cSkardel time_status = TIME_OOP;
215abb0f93cSkardel break;
216abb0f93cSkardel
217abb0f93cSkardel case TIME_DEL:
218abb0f93cSkardel timex.tv_sec++;
219abb0f93cSkardel time_status = TIME_OK;
220abb0f93cSkardel break;
221abb0f93cSkardel
222abb0f93cSkardel case TIME_OOP:
223abb0f93cSkardel time_status = TIME_OK;
224abb0f93cSkardel break;
225abb0f93cSkardel }
226abb0f93cSkardel }
227abb0f93cSkardel }
228