FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/tsc.c
1 /*-
2 * Copyright (c) 1998-2003 Poul-Henning Kamp
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29
30 #include "opt_clock.h"
31
32 #include <sys/param.h>
33 #include <sys/bus.h>
34 #include <sys/cpu.h>
35 #include <sys/malloc.h>
36 #include <sys/systm.h>
37 #include <sys/sysctl.h>
38 #include <sys/time.h>
39 #include <sys/timetc.h>
40 #include <sys/kernel.h>
41 #include <sys/power.h>
42 #include <sys/smp.h>
43 #include <machine/clock.h>
44 #include <machine/md_var.h>
45 #include <machine/specialreg.h>
46
47 #include "cpufreq_if.h"
48
49 uint64_t tsc_freq;
50 int tsc_is_broken;
51 int tsc_is_invariant;
52 u_int tsc_present;
53 static eventhandler_tag tsc_levels_tag, tsc_pre_tag, tsc_post_tag;
54
55 SYSCTL_INT(_kern_timecounter, OID_AUTO, invariant_tsc, CTLFLAG_RDTUN,
56 &tsc_is_invariant, 0, "Indicates whether the TSC is P-state invariant");
57 TUNABLE_INT("kern.timecounter.invariant_tsc", &tsc_is_invariant);
58
59 #ifdef SMP
60 static int smp_tsc;
61 SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
62 "Indicates whether the TSC is safe to use in SMP mode");
63 TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
64 #endif
65
66 static void tsc_freq_changed(void *arg, const struct cf_level *level,
67 int status);
68 static void tsc_freq_changing(void *arg, const struct cf_level *level,
69 int *status);
70 static unsigned tsc_get_timecount(struct timecounter *tc);
71 static void tsc_levels_changed(void *arg, int unit);
72
73 static struct timecounter tsc_timecounter = {
74 tsc_get_timecount, /* get_timecount */
75 0, /* no poll_pps */
76 ~0u, /* counter_mask */
77 0, /* frequency */
78 "TSC", /* name */
79 800, /* quality (adjusted in code) */
80 };
81
82 void
83 init_TSC(void)
84 {
85 u_int64_t tscval[2];
86
87 if (cpu_feature & CPUID_TSC)
88 tsc_present = 1;
89 else
90 tsc_present = 0;
91
92 if (!tsc_present)
93 return;
94
95 if (bootverbose)
96 printf("Calibrating TSC clock ... ");
97
98 tscval[0] = rdtsc();
99 DELAY(1000000);
100 tscval[1] = rdtsc();
101
102 tsc_freq = tscval[1] - tscval[0];
103 if (bootverbose)
104 printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq);
105
106 /*
107 * Inform CPU accounting about our boot-time clock rate. Once the
108 * system is finished booting, we will get the real max clock rate
109 * via tsc_freq_max(). This also will be updated if someone loads
110 * a cpufreq driver after boot that discovers a new max frequency.
111 */
112 set_cputicker(rdtsc, tsc_freq, 1);
113
114 /* Register to find out about changes in CPU frequency. */
115 tsc_pre_tag = EVENTHANDLER_REGISTER(cpufreq_pre_change,
116 tsc_freq_changing, NULL, EVENTHANDLER_PRI_FIRST);
117 tsc_post_tag = EVENTHANDLER_REGISTER(cpufreq_post_change,
118 tsc_freq_changed, NULL, EVENTHANDLER_PRI_FIRST);
119 tsc_levels_tag = EVENTHANDLER_REGISTER(cpufreq_levels_changed,
120 tsc_levels_changed, NULL, EVENTHANDLER_PRI_ANY);
121 }
122
123 void
124 init_TSC_tc(void)
125 {
126 /*
127 * We can not use the TSC if we support APM. Precise timekeeping
128 * on an APM'ed machine is at best a fools pursuit, since
129 * any and all of the time spent in various SMM code can't
130 * be reliably accounted for. Reading the RTC is your only
131 * source of reliable time info. The i8254 loses too, of course,
132 * but we need to have some kind of time...
133 * We don't know at this point whether APM is going to be used
134 * or not, nor when it might be activated. Play it safe.
135 */
136 if (power_pm_get_type() == POWER_PM_TYPE_APM) {
137 tsc_timecounter.tc_quality = -1000;
138 if (bootverbose)
139 printf("TSC timecounter disabled: APM enabled.\n");
140 }
141
142 #ifdef SMP
143 /*
144 * We can not use the TSC in SMP mode unless the TSCs on all CPUs
145 * are somehow synchronized. Some hardware configurations do
146 * this, but we have no way of determining whether this is the
147 * case, so we do not use the TSC in multi-processor systems
148 * unless the user indicated (by setting kern.timecounter.smp_tsc
149 * to 1) that he believes that his TSCs are synchronized.
150 */
151 if (mp_ncpus > 1 && !smp_tsc)
152 tsc_timecounter.tc_quality = -100;
153 #endif
154
155 if (tsc_present && tsc_freq != 0 && !tsc_is_broken) {
156 tsc_timecounter.tc_frequency = tsc_freq;
157 tc_init(&tsc_timecounter);
158 }
159 }
160
161 /*
162 * When cpufreq levels change, find out about the (new) max frequency. We
163 * use this to update CPU accounting in case it got a lower estimate at boot.
164 */
165 static void
166 tsc_levels_changed(void *arg, int unit)
167 {
168 device_t cf_dev;
169 struct cf_level *levels;
170 int count, error;
171 uint64_t max_freq;
172
173 /* Only use values from the first CPU, assuming all are equal. */
174 if (unit != 0)
175 return;
176
177 /* Find the appropriate cpufreq device instance. */
178 cf_dev = devclass_get_device(devclass_find("cpufreq"), unit);
179 if (cf_dev == NULL) {
180 printf("tsc_levels_changed() called but no cpufreq device?\n");
181 return;
182 }
183
184 /* Get settings from the device and find the max frequency. */
185 count = 64;
186 levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
187 if (levels == NULL)
188 return;
189 error = CPUFREQ_LEVELS(cf_dev, levels, &count);
190 if (error == 0 && count != 0) {
191 max_freq = (uint64_t)levels[0].total_set.freq * 1000000;
192 set_cputicker(rdtsc, max_freq, 1);
193 } else
194 printf("tsc_levels_changed: no max freq found\n");
195 free(levels, M_TEMP);
196 }
197
198 /*
199 * If the TSC timecounter is in use, veto the pending change. It may be
200 * possible in the future to handle a dynamically-changing timecounter rate.
201 */
202 static void
203 tsc_freq_changing(void *arg, const struct cf_level *level, int *status)
204 {
205
206 if (*status != 0 || timecounter != &tsc_timecounter ||
207 tsc_is_invariant)
208 return;
209
210 printf("timecounter TSC must not be in use when "
211 "changing frequencies; change denied\n");
212 *status = EBUSY;
213 }
214
215 /* Update TSC freq with the value indicated by the caller. */
216 static void
217 tsc_freq_changed(void *arg, const struct cf_level *level, int status)
218 {
219 /*
220 * If there was an error during the transition or
221 * TSC is P-state invariant, don't do anything.
222 */
223 if (status != 0 || tsc_is_invariant)
224 return;
225
226 /* Total setting for this level gives the new frequency in MHz. */
227 tsc_freq = (uint64_t)level->total_set.freq * 1000000;
228 tsc_timecounter.tc_frequency = tsc_freq;
229 }
230
231 static int
232 sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
233 {
234 int error;
235 uint64_t freq;
236
237 if (tsc_timecounter.tc_frequency == 0)
238 return (EOPNOTSUPP);
239 freq = tsc_freq;
240 error = sysctl_handle_quad(oidp, &freq, 0, req);
241 if (error == 0 && req->newptr != NULL) {
242 tsc_freq = freq;
243 tsc_timecounter.tc_frequency = tsc_freq;
244 }
245 return (error);
246 }
247
248 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_QUAD | CTLFLAG_RW,
249 0, sizeof(u_int), sysctl_machdep_tsc_freq, "QU", "");
250
251 static unsigned
252 tsc_get_timecount(struct timecounter *tc)
253 {
254 return (rdtsc());
255 }
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