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