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 *	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
54static void
55delay_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
73static int
74delay_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
112void
113DELAY(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
126void
127cpu_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