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 /* 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 52 static void 53 delay_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 71 static int 72 delay_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 } 109 110 void 111 DELAY(int n) 112 { 113 114 TSENTER(); 115 if (delay_tc(n)) { 116 TSEXIT(); 117 return; 118 } 119 120 init_ops.early_delay(n); 121 TSEXIT(); 122 } 123 124 void 125 cpu_lock_delay(void) 126 { 127 128 /* 129 * Use TSC to wait for a usec if present, otherwise fall back 130 * to reading from port 0x84. We can't call into timecounters 131 * for this delay since timecounters might use spin locks. 132 * 133 * Note that unlike delay_tc(), this uses the TSC even if it 134 * is not P-state invariant. For this function it is ok to 135 * wait even a few usecs. 136 */ 137 if (tsc_freq != 0) 138 delay_tsc(1); 139 else 140 inb(0x84); 141 } 142