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 <[email protected]>
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 * from: @(#)clock.c 7.2 (Berkeley) 5/12/91
36 */
37
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40
41 /* Generic x86 routines to handle delay */
42
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/timetc.h>
46 #include <sys/proc.h>
47 #include <sys/kernel.h>
48 #include <sys/sched.h>
49
50 #include <machine/clock.h>
51 #include <machine/cpu.h>
52 #include <x86/init.h>
53
54 static void
delay_tsc(int n)55 delay_tsc(int n)
56 {
57 uint64_t end, now;
58
59 /*
60 * Pin the current thread ensure correct behavior if the TSCs
61 * on different CPUs are not in sync.
62 */
63 sched_pin();
64 now = rdtsc();
65 end = now + tsc_freq * n / 1000000;
66 do {
67 cpu_spinwait();
68 now = rdtsc();
69 } while (now < end);
70 sched_unpin();
71 }
72
73 static int
delay_tc(int n)74 delay_tc(int n)
75 {
76 struct timecounter *tc;
77 timecounter_get_t *func;
78 uint64_t end, freq, now;
79 u_int last, mask, u;
80
81 /*
82 * Only use the TSC if it is P-state invariant. If the TSC is
83 * not P-state invariant and the CPU is not running at the
84 * "full" P-state, then the TSC will increment at some rate
85 * less than tsc_freq and delay_tsc() will wait too long.
86 */
87 if (tsc_is_invariant && tsc_freq != 0) {
88 delay_tsc(n);
89 return (1);
90 }
91 tc = timecounter;
92 if (tc->tc_quality <= 0)
93 return (0);
94 func = tc->tc_get_timecount;
95 mask = tc->tc_counter_mask;
96 freq = tc->tc_frequency;
97 now = 0;
98 end = freq * n / 1000000;
99 last = func(tc) & mask;
100 do {
101 cpu_spinwait();
102 u = func(tc) & mask;
103 if (u < last)
104 now += mask - last + u + 1;
105 else
106 now += u - last;
107 last = u;
108 } while (now < end);
109 return (1);
110 }
111
112 void
DELAY(int n)113 DELAY(int n)
114 {
115
116 TSENTER();
117 if (delay_tc(n)) {
118 TSEXIT();
119 return;
120 }
121
122 init_ops.early_delay(n);
123 TSEXIT();
124 }
125
126 void
cpu_lock_delay(void)127 cpu_lock_delay(void)
128 {
129
130 /*
131 * Use TSC to wait for a usec if present, otherwise fall back
132 * to reading from port 0x84. We can't call into timecounters
133 * for this delay since timecounters might use spin locks.
134 *
135 * Note that unlike delay_tc(), this uses the TSC even if it
136 * is not P-state invariant. For this function it is ok to
137 * wait even a few usecs.
138 */
139 if (tsc_freq != 0)
140 delay_tsc(1);
141 else
142 inb(0x84);
143 }
144