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