FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/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: releng/7.4/sys/amd64/amd64/tsc.c 216262 2010-12-07 18:15:18Z jkim $");
29
30 #include "opt_clock.h"
31 #include "opt_kdtrace.h"
32
33 #include <sys/param.h>
34 #include <sys/bus.h>
35 #include <sys/cpu.h>
36 #include <sys/malloc.h>
37 #include <sys/systm.h>
38 #include <sys/sysctl.h>
39 #include <sys/time.h>
40 #include <sys/timetc.h>
41 #include <sys/kernel.h>
42 #include <sys/power.h>
43 #include <sys/smp.h>
44 #include <machine/clock.h>
45 #include <machine/md_var.h>
46 #include <machine/specialreg.h>
47
48 #ifdef KDTRACE_HOOKS
49 #include <sys/dtrace_bsd.h>
50 #endif
51
52 #include "cpufreq_if.h"
53
54 uint64_t tsc_freq;
55 int tsc_is_broken;
56 int tsc_is_invariant;
57 static eventhandler_tag tsc_levels_tag, tsc_pre_tag, tsc_post_tag;
58
59 SYSCTL_INT(_kern_timecounter, OID_AUTO, invariant_tsc, CTLFLAG_RDTUN,
60 &tsc_is_invariant, 0, "Indicates whether the TSC is P-state invariant");
61 TUNABLE_INT("kern.timecounter.invariant_tsc", &tsc_is_invariant);
62
63 #ifdef SMP
64 static int smp_tsc;
65 SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
66 "Indicates whether the TSC is safe to use in SMP mode");
67 TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
68 #endif
69
70 static void tsc_freq_changed(void *arg, const struct cf_level *level,
71 int status);
72 static void tsc_freq_changing(void *arg, const struct cf_level *level,
73 int *status);
74 static unsigned tsc_get_timecount(struct timecounter *tc);
75 static void tsc_levels_changed(void *arg, int unit);
76
77 static struct timecounter tsc_timecounter = {
78 tsc_get_timecount, /* get_timecount */
79 0, /* no poll_pps */
80 ~0u, /* counter_mask */
81 0, /* frequency */
82 "TSC", /* name */
83 800, /* quality (adjusted in code) */
84 };
85
86 void
87 init_TSC(void)
88 {
89 u_int64_t tscval[2];
90
91 if (bootverbose)
92 printf("Calibrating TSC clock ... ");
93
94 tscval[0] = rdtsc();
95 DELAY(1000000);
96 tscval[1] = rdtsc();
97
98 tsc_freq = tscval[1] - tscval[0];
99 if (bootverbose)
100 printf("TSC clock: %lu Hz\n", tsc_freq);
101
102 /*
103 * Inform CPU accounting about our boot-time clock rate. Once the
104 * system is finished booting, we will get the real max clock rate
105 * via tsc_freq_max(). This also will be updated if someone loads
106 * a cpufreq driver after boot that discovers a new max frequency.
107 */
108 set_cputicker(rdtsc, tsc_freq, 1);
109
110 /* Register to find out about changes in CPU frequency. */
111 tsc_pre_tag = EVENTHANDLER_REGISTER(cpufreq_pre_change,
112 tsc_freq_changing, NULL, EVENTHANDLER_PRI_FIRST);
113 tsc_post_tag = EVENTHANDLER_REGISTER(cpufreq_post_change,
114 tsc_freq_changed, NULL, EVENTHANDLER_PRI_FIRST);
115 tsc_levels_tag = EVENTHANDLER_REGISTER(cpufreq_levels_changed,
116 tsc_levels_changed, NULL, EVENTHANDLER_PRI_ANY);
117 }
118
119 void
120 init_TSC_tc(void)
121 {
122
123 #ifdef SMP
124 /*
125 * We can not use the TSC in SMP mode unless the TSCs on all CPUs
126 * are somehow synchronized. Some hardware configurations do
127 * this, but we have no way of determining whether this is the
128 * case, so we do not use the TSC in multi-processor systems
129 * unless the user indicated (by setting kern.timecounter.smp_tsc
130 * to 1) that he believes that his TSCs are synchronized.
131 */
132 if (mp_ncpus > 1 && !smp_tsc)
133 tsc_timecounter.tc_quality = -100;
134 #endif
135
136 if (tsc_freq != 0 && !tsc_is_broken) {
137 tsc_timecounter.tc_frequency = tsc_freq;
138 tc_init(&tsc_timecounter);
139 }
140 }
141
142 /*
143 * When cpufreq levels change, find out about the (new) max frequency. We
144 * use this to update CPU accounting in case it got a lower estimate at boot.
145 */
146 static void
147 tsc_levels_changed(void *arg, int unit)
148 {
149 device_t cf_dev;
150 struct cf_level *levels;
151 int count, error;
152 uint64_t max_freq;
153
154 if (tsc_is_invariant)
155 return;
156
157 /* Only use values from the first CPU, assuming all are equal. */
158 if (unit != 0)
159 return;
160
161 /* Find the appropriate cpufreq device instance. */
162 cf_dev = devclass_get_device(devclass_find("cpufreq"), unit);
163 if (cf_dev == NULL) {
164 printf("tsc_levels_changed() called but no cpufreq device?\n");
165 return;
166 }
167
168 /* Get settings from the device and find the max frequency. */
169 count = 64;
170 levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
171 if (levels == NULL)
172 return;
173 error = CPUFREQ_LEVELS(cf_dev, levels, &count);
174 if (error == 0 && count != 0) {
175 max_freq = (uint64_t)levels[0].total_set.freq * 1000000;
176 set_cputicker(rdtsc, max_freq, 1);
177 } else
178 printf("tsc_levels_changed: no max freq found\n");
179 free(levels, M_TEMP);
180 }
181
182 /*
183 * If the TSC timecounter is in use, veto the pending change. It may be
184 * possible in the future to handle a dynamically-changing timecounter rate.
185 */
186 static void
187 tsc_freq_changing(void *arg, const struct cf_level *level, int *status)
188 {
189
190 if (*status != 0 || timecounter != &tsc_timecounter ||
191 tsc_is_invariant)
192 return;
193
194 printf("timecounter TSC must not be in use when "
195 "changing frequencies; change denied\n");
196 *status = EBUSY;
197 }
198
199 /* Update TSC freq with the value indicated by the caller. */
200 static void
201 tsc_freq_changed(void *arg, const struct cf_level *level, int status)
202 {
203 /*
204 * If there was an error during the transition or
205 * TSC is P-state invariant, don't do anything.
206 */
207 if (status != 0 || tsc_is_invariant)
208 return;
209
210 /* Total setting for this level gives the new frequency in MHz. */
211 tsc_freq = (uint64_t)level->total_set.freq * 1000000;
212 tsc_timecounter.tc_frequency = tsc_freq;
213 }
214
215 static int
216 sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
217 {
218 int error;
219 uint64_t freq;
220
221 if (tsc_timecounter.tc_frequency == 0)
222 return (EOPNOTSUPP);
223 freq = tsc_freq;
224 error = sysctl_handle_quad(oidp, &freq, 0, req);
225 if (error == 0 && req->newptr != NULL) {
226 tsc_freq = freq;
227 tsc_timecounter.tc_frequency = tsc_freq;
228 }
229 return (error);
230 }
231
232 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_QUAD | CTLFLAG_RW,
233 0, sizeof(u_int), sysctl_machdep_tsc_freq, "QU", "");
234
235 static unsigned
236 tsc_get_timecount(struct timecounter *tc)
237 {
238 return (rdtsc());
239 }
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