delay.c revision 302408 
1/*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
4 * All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * William Jolitz and Don Ahn.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
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.
20 *
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
31 * SUCH DAMAGE.
32 *
33 *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
34 */
35
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/11/sys/x86/x86/delay.c 263008 2014-03-11 10:20:42Z royger $");
38
39/* Generic x86 routines to handle delay */
40
41#include <sys/param.h>
42#include <sys/systm.h>
43#include <sys/timetc.h>
44#include <sys/proc.h>
45#include <sys/kernel.h>
46#include <sys/sched.h>
47
48#include <machine/clock.h>
49#include <machine/cpu.h>
50#include <x86/init.h>
51
52static u_int
53get_tsc(__unused struct timecounter *tc)
54{
55
56	return (rdtsc32());
57}
58
59static int
60delay_tc(int n)
61{
62	struct timecounter *tc;
63	timecounter_get_t *func;
64	uint64_t end, freq, now;
65	u_int last, mask, u;
66
67	tc = timecounter;
68	freq = atomic_load_acq_64(&tsc_freq);
69	if (tsc_is_invariant && freq != 0) {
70		func = get_tsc;
71		mask = ~0u;
72	} else {
73		if (tc->tc_quality <= 0)
74			return (0);
75		func = tc->tc_get_timecount;
76		mask = tc->tc_counter_mask;
77		freq = tc->tc_frequency;
78	}
79	now = 0;
80	end = freq * n / 1000000;
81	if (func == get_tsc)
82		sched_pin();
83	last = func(tc) & mask;
84	do {
85		cpu_spinwait();
86		u = func(tc) & mask;
87		if (u < last)
88			now += mask - last + u + 1;
89		else
90			now += u - last;
91		last = u;
92	} while (now < end);
93	if (func == get_tsc)
94		sched_unpin();
95	return (1);
96}
97
98void
99DELAY(int n)
100{
101
102	if (delay_tc(n))
103		return;
104
105	init_ops.early_delay(n);
106}
107