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  * struct tk_read_base - base structure for timekeeping readout
16  * @clock:	Current clocksource used for timekeeping.
17  * @mask:	Bitmask for two's complement subtraction of non 64bit clocks
18  * @cycle_last: @clock cycle value at last update
19  * @mult:	(NTP adjusted) multiplier for scaled math conversion
20  * @shift:	Shift value for scaled math conversion
21  * @xtime_nsec: Shifted (fractional) nano seconds offset for readout
22  * @base:	ktime_t (nanoseconds) base time for readout
23  * @base_real:	Nanoseconds base value for clock REALTIME readout
24  *
25  * This struct has size 56 byte on 64 bit. Together with a seqcount it
26  * occupies a single 64byte cache line.
27  *
28  * The struct is separate from struct timekeeper as it is also used
29  * for a fast NMI safe accessors.
30  *
31  * @base_real is for the fast NMI safe accessor to allow reading clock
32  * realtime from any context.
33  */
34 struct tk_read_base {
35 	struct clocksource	*clock;
36 	u64			mask;
37 	u64			cycle_last;
38 	u32			mult;
39 	u32			shift;
40 	u64			xtime_nsec;
41 	ktime_t			base;
42 	u64			base_real;
43 };
44 
45 /**
46  * struct timekeeper - Structure holding internal timekeeping values.
47  * @tkr_mono:		The readout base structure for CLOCK_MONOTONIC
48  * @tkr_raw:		The readout base structure for CLOCK_MONOTONIC_RAW
49  * @xtime_sec:		Current CLOCK_REALTIME time in seconds
50  * @ktime_sec:		Current CLOCK_MONOTONIC time in seconds
51  * @wall_to_monotonic:	CLOCK_REALTIME to CLOCK_MONOTONIC offset
52  * @offs_real:		Offset clock monotonic -> clock realtime
53  * @offs_boot:		Offset clock monotonic -> clock boottime
54  * @offs_tai:		Offset clock monotonic -> clock tai
55  * @tai_offset:		The current UTC to TAI offset in seconds
56  * @clock_was_set_seq:	The sequence number of clock was set events
57  * @cs_was_changed_seq:	The sequence number of clocksource change events
58  * @next_leap_ktime:	CLOCK_MONOTONIC time value of a pending leap-second
59  * @raw_sec:		CLOCK_MONOTONIC_RAW  time in seconds
60  * @cycle_interval:	Number of clock cycles in one NTP interval
61  * @xtime_interval:	Number of clock shifted nano seconds in one NTP
62  *			interval.
63  * @xtime_remainder:	Shifted nano seconds left over when rounding
64  *			@cycle_interval
65  * @raw_interval:	Shifted raw nano seconds accumulated per NTP interval.
66  * @ntp_error:		Difference between accumulated time and NTP time in ntp
67  *			shifted nano seconds.
68  * @ntp_error_shift:	Shift conversion between clock shifted nano seconds and
69  *			ntp shifted nano seconds.
70  * @last_warning:	Warning ratelimiter (DEBUG_TIMEKEEPING)
71  * @underflow_seen:	Underflow warning flag (DEBUG_TIMEKEEPING)
72  * @overflow_seen:	Overflow warning flag (DEBUG_TIMEKEEPING)
73  *
74  * Note: For timespec(64) based interfaces wall_to_monotonic is what
75  * we need to add to xtime (or xtime corrected for sub jiffie times)
76  * to get to monotonic time.  Monotonic is pegged at zero at system
77  * boot time, so wall_to_monotonic will be negative, however, we will
78  * ALWAYS keep the tv_nsec part positive so we can use the usual
79  * normalization.
80  *
81  * wall_to_monotonic is moved after resume from suspend for the
82  * monotonic time not to jump. We need to add total_sleep_time to
83  * wall_to_monotonic to get the real boot based time offset.
84  *
85  * wall_to_monotonic is no longer the boot time, getboottime must be
86  * used instead.
87  */
88 struct timekeeper {
89 	struct tk_read_base	tkr_mono;
90 	struct tk_read_base	tkr_raw;
91 	u64			xtime_sec;
92 	unsigned long		ktime_sec;
93 	struct timespec64	wall_to_monotonic;
94 	ktime_t			offs_real;
95 	ktime_t			offs_boot;
96 	ktime_t			offs_tai;
97 	s32			tai_offset;
98 	unsigned int		clock_was_set_seq;
99 	u8			cs_was_changed_seq;
100 	ktime_t			next_leap_ktime;
101 	u64			raw_sec;
102 
103 	/* The following members are for timekeeping internal use */
104 	u64			cycle_interval;
105 	u64			xtime_interval;
106 	s64			xtime_remainder;
107 	u64			raw_interval;
108 	/* The ntp_tick_length() value currently being used.
109 	 * This cached copy ensures we consistently apply the tick
110 	 * length for an entire tick, as ntp_tick_length may change
111 	 * mid-tick, and we don't want to apply that new value to
112 	 * the tick in progress.
113 	 */
114 	u64			ntp_tick;
115 	/* Difference between accumulated time and NTP time in ntp
116 	 * shifted nano seconds. */
117 	s64			ntp_error;
118 	u32			ntp_error_shift;
119 	u32			ntp_err_mult;
120 	/* Flag used to avoid updating NTP twice with same second */
121 	u32			skip_second_overflow;
122 #ifdef CONFIG_DEBUG_TIMEKEEPING
123 	long			last_warning;
124 	/*
125 	 * These simple flag variables are managed
126 	 * without locks, which is racy, but they are
127 	 * ok since we don't really care about being
128 	 * super precise about how many events were
129 	 * seen, just that a problem was observed.
130 	 */
131 	int			underflow_seen;
132 	int			overflow_seen;
133 #endif
134 };
135 
136 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
137 
138 extern void update_vsyscall(struct timekeeper *tk);
139 extern void update_vsyscall_tz(void);
140 
141 #else
142 
update_vsyscall(struct timekeeper * tk)143 static inline void update_vsyscall(struct timekeeper *tk)
144 {
145 }
update_vsyscall_tz(void)146 static inline void update_vsyscall_tz(void)
147 {
148 }
149 #endif
150 
151 #endif /* _LINUX_TIMEKEEPER_INTERNAL_H */
152