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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * You SHOULD NOT be including this unless you're vsyscall
4 * handling code or timekeeping internal code!
5 */
6
7#ifndef _LINUX_TIMEKEEPER_INTERNAL_H
8#define _LINUX_TIMEKEEPER_INTERNAL_H
9
10#include <linux/clocksource.h>
11#include <linux/jiffies.h>
12#include <linux/time.h>
13
14/**
15 * timekeeper_ids - IDs for various time keepers in the kernel
16 * @TIMEKEEPER_CORE: The central core timekeeper managing system time
17 * @TIMEKEEPER_AUX_FIRST: The first AUX timekeeper
18 * @TIMEKEEPER_AUX_LAST: The last AUX timekeeper
19 * @TIMEKEEPERS_MAX: The maximum number of timekeepers managed
20 */
21enum timekeeper_ids {
22 TIMEKEEPER_CORE,
23#ifdef CONFIG_POSIX_AUX_CLOCKS
24 TIMEKEEPER_AUX_FIRST,
25 TIMEKEEPER_AUX_LAST = TIMEKEEPER_AUX_FIRST + MAX_AUX_CLOCKS - 1,
26#endif
27 TIMEKEEPERS_MAX,
28};
29
30/**
31 * struct tk_read_base - base structure for timekeeping readout
32 * @clock: Current clocksource used for timekeeping.
33 * @mask: Bitmask for two's complement subtraction of non 64bit clocks
34 * @cycle_last: @clock cycle value at last update
35 * @mult: (NTP adjusted) multiplier for scaled math conversion
36 * @shift: Shift value for scaled math conversion
37 * @xtime_nsec: Shifted (fractional) nano seconds offset for readout
38 * @base: ktime_t (nanoseconds) base time for readout
39 * @base_real: Nanoseconds base value for clock REALTIME readout
40 *
41 * This struct has size 56 byte on 64 bit. Together with a seqcount it
42 * occupies a single 64byte cache line.
43 *
44 * The struct is separate from struct timekeeper as it is also used
45 * for the fast NMI safe accessors.
46 *
47 * @base_real is for the fast NMI safe accessor to allow reading clock
48 * realtime from any context.
49 */
50struct tk_read_base {
51 struct clocksource *clock;
52 u64 mask;
53 u64 cycle_last;
54 u32 mult;
55 u32 shift;
56 u64 xtime_nsec;
57 ktime_t base;
58 u64 base_real;
59};
60
61/**
62 * struct timekeeper - Structure holding internal timekeeping values.
63 * @tkr_mono: The readout base structure for CLOCK_MONOTONIC
64 * @xtime_sec: Current CLOCK_REALTIME time in seconds
65 * @ktime_sec: Current CLOCK_MONOTONIC time in seconds
66 * @wall_to_monotonic: CLOCK_REALTIME to CLOCK_MONOTONIC offset
67 * @offs_real: Offset clock monotonic -> clock realtime
68 * @offs_boot: Offset clock monotonic -> clock boottime
69 * @offs_tai: Offset clock monotonic -> clock tai
70 * @offs_aux: Offset clock monotonic -> clock AUX
71 * @coarse_nsec: The nanoseconds part for coarse time getters
72 * @id: The timekeeper ID
73 * @tkr_raw: The readout base structure for CLOCK_MONOTONIC_RAW
74 * @raw_sec: CLOCK_MONOTONIC_RAW time in seconds
75 * @clock_was_set_seq: The sequence number of clock was set events
76 * @cs_was_changed_seq: The sequence number of clocksource change events
77 * @clock_valid: Indicator for valid clock
78 * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset
79 * @cycle_interval: Number of clock cycles in one NTP interval
80 * @xtime_interval: Number of clock shifted nano seconds in one NTP
81 * interval.
82 * @xtime_remainder: Shifted nano seconds left over when rounding
83 * @cycle_interval
84 * @raw_interval: Shifted raw nano seconds accumulated per NTP interval.
85 * @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second
86 * @ntp_tick: The ntp_tick_length() value currently being
87 * used. This cached copy ensures we consistently
88 * apply the tick length for an entire tick, as
89 * ntp_tick_length may change mid-tick, and we don't
90 * want to apply that new value to the tick in
91 * progress.
92 * @ntp_error: Difference between accumulated time and NTP time in ntp
93 * shifted nano seconds.
94 * @ntp_error_shift: Shift conversion between clock shifted nano seconds and
95 * ntp shifted nano seconds.
96 * @ntp_err_mult: Multiplication factor for scaled math conversion
97 * @skip_second_overflow: Flag used to avoid updating NTP twice with same second
98 * @tai_offset: The current UTC to TAI offset in seconds
99 *
100 * Note: For timespec(64) based interfaces wall_to_monotonic is what
101 * we need to add to xtime (or xtime corrected for sub jiffy times)
102 * to get to monotonic time. Monotonic is pegged at zero at system
103 * boot time, so wall_to_monotonic will be negative, however, we will
104 * ALWAYS keep the tv_nsec part positive so we can use the usual
105 * normalization.
106 *
107 * wall_to_monotonic is moved after resume from suspend for the
108 * monotonic time not to jump. We need to add total_sleep_time to
109 * wall_to_monotonic to get the real boot based time offset.
110 *
111 * wall_to_monotonic is no longer the boot time, getboottime must be
112 * used instead.
113 *
114 * @monotonic_to_boottime is a timespec64 representation of @offs_boot to
115 * accelerate the VDSO update for CLOCK_BOOTTIME.
116 *
117 * @offs_aux is used by the auxiliary timekeepers which do not utilize any
118 * of the regular timekeeper offset fields.
119 *
120 * The cacheline ordering of the structure is optimized for in kernel usage of
121 * the ktime_get() and ktime_get_ts64() family of time accessors. Struct
122 * timekeeper is prepended in the core timekeeping code with a sequence count,
123 * which results in the following cacheline layout:
124 *
125 * 0: seqcount, tkr_mono
126 * 1: xtime_sec ... id
127 * 2: tkr_raw, raw_sec
128 * 3,4: Internal variables
129 *
130 * Cacheline 0,1 contain the data which is used for accessing
131 * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the
132 * data for accessing CLOCK_MONOTONIC_RAW. Cacheline 3,4 are internal
133 * variables which are only accessed during timekeeper updates once per
134 * tick.
135 */
136struct timekeeper {
137 /* Cacheline 0 (together with prepended seqcount of timekeeper core): */
138 struct tk_read_base tkr_mono;
139
140 /* Cacheline 1: */
141 u64 xtime_sec;
142 unsigned long ktime_sec;
143 struct timespec64 wall_to_monotonic;
144 ktime_t offs_real;
145 ktime_t offs_boot;
146 union {
147 ktime_t offs_tai;
148 ktime_t offs_aux;
149 };
150 u32 coarse_nsec;
151 enum timekeeper_ids id;
152
153 /* Cacheline 2: */
154 struct tk_read_base tkr_raw;
155 u64 raw_sec;
156
157 /* Cachline 3 and 4 (timekeeping internal variables): */
158 unsigned int clock_was_set_seq;
159 u8 cs_was_changed_seq;
160 u8 clock_valid;
161
162 struct timespec64 monotonic_to_boot;
163
164 u64 cycle_interval;
165 u64 xtime_interval;
166 s64 xtime_remainder;
167 u64 raw_interval;
168
169 ktime_t next_leap_ktime;
170 u64 ntp_tick;
171 s64 ntp_error;
172 u32 ntp_error_shift;
173 u32 ntp_err_mult;
174 u32 skip_second_overflow;
175 s32 tai_offset;
176};
177
178#ifdef CONFIG_GENERIC_TIME_VSYSCALL
179
180extern void update_vsyscall(struct timekeeper *tk);
181extern void update_vsyscall_tz(void);
182
183#else
184
185static inline void update_vsyscall(struct timekeeper *tk)
186{
187}
188static inline void update_vsyscall_tz(void)
189{
190}
191#endif
192
193#if defined(CONFIG_GENERIC_GETTIMEOFDAY) && defined(CONFIG_POSIX_AUX_CLOCKS)
194extern void vdso_time_update_aux(struct timekeeper *tk);
195#else
196static inline void vdso_time_update_aux(struct timekeeper *tk) { }
197#endif
198
199#endif /* _LINUX_TIMEKEEPER_INTERNAL_H */