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 50 static void 51 delay_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 69 static int 70 delay_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 } 107 108 void 109 DELAY(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 } 121 122 void 123 cpu_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