^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) // SPDX-License-Identifier: GPL-2.0+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) * This file contains the jiffies based clocksource.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) #include <linux/clocksource.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) #include <linux/jiffies.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) #include <linux/module.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) #include <linux/init.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) #include "timekeeping.h"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) /* Since jiffies uses a simple TICK_NSEC multiplier
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) * conversion, the .shift value could be zero. However
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) * this would make NTP adjustments impossible as they are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) * shift both the nominator and denominator the same
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) * amount, and give ntp adjustments in units of 1/2^8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) * The value 8 is somewhat carefully chosen, as anything
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) * larger can result in overflows. TICK_NSEC grows as HZ
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) * shrinks, so values greater than 8 overflow 32bits when
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) * HZ=100.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) #if HZ < 34
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) #define JIFFIES_SHIFT 6
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) #elif HZ < 67
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) #define JIFFIES_SHIFT 7
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) #else
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) #define JIFFIES_SHIFT 8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) #endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) static u64 jiffies_read(struct clocksource *cs)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) return (u64) jiffies;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) * The Jiffies based clocksource is the lowest common
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) * denominator clock source which should function on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) * all systems. It has the same coarse resolution as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) * the timer interrupt frequency HZ and it suffers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) * inaccuracies caused by missed or lost timer
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) * interrupts and the inability for the timer
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) * interrupt hardware to accuratly tick at the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) * requested HZ value. It is also not recommended
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) * for "tick-less" systems.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) static struct clocksource clocksource_jiffies = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) .name = "jiffies",
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) .rating = 1, /* lowest valid rating*/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) .read = jiffies_read,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) .mask = CLOCKSOURCE_MASK(32),
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) .mult = TICK_NSEC << JIFFIES_SHIFT, /* details above */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) .shift = JIFFIES_SHIFT,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) .max_cycles = 10,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(jiffies_lock);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) __cacheline_aligned_in_smp seqcount_t jiffies_seq;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) #if (BITS_PER_LONG < 64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) u64 get_jiffies_64(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) unsigned int seq;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) u64 ret;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) seq = read_seqcount_begin(&jiffies_seq);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) ret = jiffies_64;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) } while (read_seqcount_retry(&jiffies_seq, seq));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) return ret;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) EXPORT_SYMBOL(get_jiffies_64);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) #endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) EXPORT_SYMBOL(jiffies);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) static int __init init_jiffies_clocksource(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) return __clocksource_register(&clocksource_jiffies);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) core_initcall(init_jiffies_clocksource);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) struct clocksource * __init __weak clocksource_default_clock(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) return &clocksource_jiffies;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) static struct clocksource refined_jiffies;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) int register_refined_jiffies(long cycles_per_second)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) u64 nsec_per_tick, shift_hz;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) long cycles_per_tick;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) refined_jiffies = clocksource_jiffies;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) refined_jiffies.name = "refined-jiffies";
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) refined_jiffies.rating++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) /* Calc cycles per tick */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) /* shift_hz stores hz<<8 for extra accuracy */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) shift_hz = (u64)cycles_per_second << 8;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) shift_hz += cycles_per_tick/2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) do_div(shift_hz, cycles_per_tick);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) /* Calculate nsec_per_tick using shift_hz */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) nsec_per_tick = (u64)NSEC_PER_SEC << 8;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) nsec_per_tick += (u32)shift_hz/2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) do_div(nsec_per_tick, (u32)shift_hz);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) __clocksource_register(&refined_jiffies);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) }
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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