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 340270 2018-11-08 22:42:55Z jhb $");
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 void
53delay_tsc(int n)
54{
55	uint64_t end, now;
56
57	/*
58	 * Pin the current thread ensure correct behavior if the TSCs
59	 * on different CPUs are not in sync.
60	 */
61	sched_pin();
62	now = rdtsc();
63	end = now + tsc_freq * n / 1000000;
64	do {
65		cpu_spinwait();
66		now = rdtsc();
67	} while (now < end);
68	sched_unpin();
69}
70
71static int
72delay_tc(int n)
73{
74	struct timecounter *tc;
75	timecounter_get_t *func;
76	uint64_t end, freq, now;
77	u_int last, mask, u;
78
79	/*
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.
84	 */
85	if (tsc_is_invariant && tsc_freq != 0) {
86		delay_tsc(n);
87		return (1);
88	}
89	tc = timecounter;
90	if (tc->tc_quality <= 0)
91		return (0);
92	func = tc->tc_get_timecount;
93	mask = tc->tc_counter_mask;
94	freq = tc->tc_frequency;
95	now = 0;
96	end = freq * n / 1000000;
97	last = func(tc) & mask;
98	do {
99		cpu_spinwait();
100		u = func(tc) & mask;
101		if (u < last)
102			now += mask - last + u + 1;
103		else
104			now += u - last;
105		last = u;
106	} while (now < end);
107	return (1);
108}
109
110void
111DELAY(int n)
112{
113
114	if (delay_tc(n))
115		return;
116
117	init_ops.early_delay(n);
118}
119
120void
121cpu_lock_delay(void)
122{
123
124	/*
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.
128	 *
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.
132	 */
133	if (tsc_freq != 0)
134		delay_tsc(1);
135	else
136		inb(0x84);
137}
138