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 54 static void 55 delay_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 73 static int 74 delay_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 } 111 112 void 113 DELAY(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 } 125 126 void 127 cpu_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