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/5.2/sys/amd64/amd64/tsc.c 122849 2003-11-17 08:58:16Z peter $");
29
30 #include "opt_clock.h"
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/sysctl.h>
35 #include <sys/time.h>
36 #include <sys/timetc.h>
37 #include <sys/kernel.h>
38 #include <sys/power.h>
39 #include <sys/smp.h>
40 #include <machine/clock.h>
41 #include <machine/md_var.h>
42 #include <machine/specialreg.h>
43
44 uint64_t tsc_freq;
45 int tsc_is_broken;
46
47 #ifdef SMP
48 static int smp_tsc;
49 SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
50 "Indicates whether the TSC is safe to use in SMP mode");
51 TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
52 #endif
53
54 static unsigned tsc_get_timecount(struct timecounter *tc);
55
56 static struct timecounter tsc_timecounter = {
57 tsc_get_timecount, /* get_timecount */
58 0, /* no poll_pps */
59 ~0u, /* counter_mask */
60 0, /* frequency */
61 "TSC", /* name */
62 800, /* quality (adjusted in code) */
63 };
64
65 void
66 init_TSC(void)
67 {
68 u_int64_t tscval[2];
69
70 if (bootverbose)
71 printf("Calibrating TSC clock ... ");
72
73 tscval[0] = rdtsc();
74 DELAY(1000000);
75 tscval[1] = rdtsc();
76
77 tsc_freq = tscval[1] - tscval[0];
78 if (bootverbose)
79 printf("TSC clock: %lu Hz\n", tsc_freq);
80 }
81
82
83 void
84 init_TSC_tc(void)
85 {
86
87 #ifdef SMP
88 /*
89 * We can not use the TSC in SMP mode unless the TSCs on all CPUs
90 * are somehow synchronized. Some hardware configurations do
91 * this, but we have no way of determining whether this is the
92 * case, so we do not use the TSC in multi-processor systems
93 * unless the user indicated (by setting kern.timecounter.smp_tsc
94 * to 1) that he believes that his TSCs are synchronized.
95 */
96 if (mp_ncpus > 1 && !smp_tsc)
97 tsc_timecounter.tc_quality = -100;
98 #endif
99
100 if (tsc_freq != 0 && !tsc_is_broken) {
101 tsc_timecounter.tc_frequency = tsc_freq;
102 tc_init(&tsc_timecounter);
103 }
104 }
105
106 static int
107 sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
108 {
109 int error;
110 uint64_t freq;
111
112 if (tsc_timecounter.tc_frequency == 0)
113 return (EOPNOTSUPP);
114 freq = tsc_freq;
115 error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
116 if (error == 0 && req->newptr != NULL) {
117 tsc_freq = freq;
118 tsc_timecounter.tc_frequency = tsc_freq;
119 }
120 return (error);
121 }
122
123 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_LONG | CTLFLAG_RW,
124 0, sizeof(u_int), sysctl_machdep_tsc_freq, "IU", "");
125
126 static unsigned
127 tsc_get_timecount(struct timecounter *tc)
128 {
129 return (rdtsc());
130 }
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