1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990 The Regents of the University of California.
5 * Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
6 * All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * William Jolitz and Don Ahn.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include <sys/cdefs.h>
37 /* Generic x86 routines to handle delay */
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/timetc.h>
42 #include <sys/proc.h>
43 #include <sys/kernel.h>
44 #include <sys/sched.h>
45
46 #include <machine/clock.h>
47 #include <machine/cpu.h>
48 #include <x86/init.h>
49
50 static void
delay_tsc(int n)51 delay_tsc(int n)
52 {
53 uint64_t end, now;
54
55 /*
56 * Pin the current thread ensure correct behavior if the TSCs
57 * on different CPUs are not in sync.
58 */
59 sched_pin();
60 now = rdtsc();
61 end = now + tsc_freq * n / 1000000;
62 do {
63 cpu_spinwait();
64 now = rdtsc();
65 } while (now < end);
66 sched_unpin();
67 }
68
69 static int
delay_tc(int n)70 delay_tc(int n)
71 {
72 struct timecounter *tc;
73 timecounter_get_t *func;
74 uint64_t end, freq, now;
75 u_int last, mask, u;
76
77 /*
78 * Only use the TSC if it is P-state invariant. If the TSC is
79 * not P-state invariant and the CPU is not running at the
80 * "full" P-state, then the TSC will increment at some rate
81 * less than tsc_freq and delay_tsc() will wait too long.
82 */
83 if (tsc_is_invariant && tsc_freq != 0) {
84 delay_tsc(n);
85 return (1);
86 }
87 tc = timecounter;
88 if (tc->tc_quality <= 0)
89 return (0);
90 func = tc->tc_get_timecount;
91 mask = tc->tc_counter_mask;
92 freq = tc->tc_frequency;
93 now = 0;
94 end = freq * n / 1000000;
95 last = func(tc) & mask;
96 do {
97 cpu_spinwait();
98 u = func(tc) & mask;
99 if (u < last)
100 now += mask - last + u + 1;
101 else
102 now += u - last;
103 last = u;
104 } while (now < end);
105 return (1);
106 }
107
108 void
DELAY(int n)109 DELAY(int n)
110 {
111
112 TSENTER();
113 if (delay_tc(n)) {
114 TSEXIT();
115 return;
116 }
117
118 init_ops.early_delay(n);
119 TSEXIT();
120 }
121
122 void
cpu_lock_delay(void)123 cpu_lock_delay(void)
124 {
125
126 /*
127 * Use TSC to wait for a usec if present, otherwise fall back
128 * to reading from port 0x84. We can't call into timecounters
129 * for this delay since timecounters might use spin locks.
130 *
131 * Note that unlike delay_tc(), this uses the TSC even if it
132 * is not P-state invariant. For this function it is ok to
133 * wait even a few usecs.
134 */
135 if (tsc_freq != 0)
136 delay_tsc(1);
137 else
138 inb(0x84);
139 }
140