2 * Copyright (c) 1990 The Regents of the University of California.
3 * Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
6 * This code is derived from software contributed to Berkeley by
7 * William Jolitz and Don Ahn.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * from: @(#)clock.c 7.2 (Berkeley) 5/12/91
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
39 /* Generic x86 routines to handle delay */
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/timetc.h>
45 #include <sys/kernel.h>
46 #include <sys/sched.h>
48 #include <machine/clock.h>
49 #include <machine/cpu.h>
58 * Pin the current thread ensure correct behavior if the TSCs
59 * on different CPUs are not in sync.
63 end = now + tsc_freq * n / 1000000;
74 struct timecounter *tc;
75 timecounter_get_t *func;
76 uint64_t end, freq, now;
80 * Only use the TSC if it is P-state invariant. If the TSC is
81 * not P-state invariant and the CPU is not running at the
82 * "full" P-state, then the TSC will increment at some rate
83 * less than tsc_freq and delay_tsc() will wait too long.
85 if (tsc_is_invariant && tsc_freq != 0) {
90 if (tc->tc_quality <= 0)
92 func = tc->tc_get_timecount;
93 mask = tc->tc_counter_mask;
94 freq = tc->tc_frequency;
96 end = freq * n / 1000000;
97 last = func(tc) & mask;
102 now += mask - last + u + 1;
117 init_ops.early_delay(n);
125 * Use TSC to wait for a usec if present, otherwise fall back
126 * to reading from port 0x84. We can't call into timecounters
127 * for this delay since timecounters might use spin locks.
129 * Note that unlike delay_tc(), this uses the TSC even if it
130 * is not P-state invariant. For this function it is ok to
131 * wait even a few usecs.