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2c756feb18
Another representative use case of time sync and the correlated
clocksource (in addition to PTP noted above) is PTP synchronized
audio.
In a streaming application, as an example, samples will be sent and/or
received by multiple devices with a presentation time that is in terms
of the PTP master clock. Synchronizing the audio output on these
devices requires correlating the audio clock with the PTP master
clock. The more precise this correlation is, the better the audio
quality (i.e. out of sync audio sounds bad).
From an application standpoint, to correlate the PTP master clock with
the audio device clock, the system clock is used as a intermediate
timebase. The transforms such an application would perform are:
System Clock <-> Audio clock
System Clock <-> Network Device Clock [<-> PTP Master Clock]
Modern Intel platforms can perform a more accurate cross timestamp in
hardware (ART,audio device clock). The audio driver requires
ART->system time transforms -- the same as required for the network
driver. These platforms offload audio processing (including
cross-timestamps) to a DSP which to ensure uninterrupted audio
processing, communicates and response to the host only once every
millsecond. As a result is takes up to a millisecond for the DSP to
receive a request, the request is processed by the DSP, the audio
output hardware is polled for completion, the result is copied into
shared memory, and the host is notified. All of these operation occur
on a millisecond cadence. This transaction requires about 2 ms, but
under heavier workloads it may take up to 4 ms.
Adding a history allows these slow devices the option of providing an
ART value outside of the current interval. In this case, the callback
provided is an accessor function for the previously obtained counter
value. If get_system_device_crosststamp() receives a counter value
previous to cycle_last, it consults the history provided as an
argument in history_ref and interpolates the realtime and monotonic
raw system time using the provided counter value. If there are any
clock discontinuities, e.g. from calling settimeofday(), the monotonic
raw time is interpolated in the usual way, but the realtime clock time
is adjusted by scaling the monotonic raw adjustment.
When an accessor function is used a history argument *must* be
provided. The history is initialized using ktime_get_snapshot() and
must be called before the counter values are read.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Fixed up cycles_t/cycle_t type confusion]
Signed-off-by: John Stultz <john.stultz@linaro.org>
340 lines
7.5 KiB
C
340 lines
7.5 KiB
C
#ifndef _LINUX_TIMEKEEPING_H
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#define _LINUX_TIMEKEEPING_H
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/* Included from linux/ktime.h */
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void timekeeping_init(void);
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extern int timekeeping_suspended;
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/*
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* Get and set timeofday
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*/
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extern void do_gettimeofday(struct timeval *tv);
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extern int do_settimeofday64(const struct timespec64 *ts);
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extern int do_sys_settimeofday(const struct timespec *tv,
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const struct timezone *tz);
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/*
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* Kernel time accessors
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*/
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unsigned long get_seconds(void);
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struct timespec64 current_kernel_time64(void);
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/* does not take xtime_lock */
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struct timespec __current_kernel_time(void);
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static inline struct timespec current_kernel_time(void)
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{
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struct timespec64 now = current_kernel_time64();
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return timespec64_to_timespec(now);
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}
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/*
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* timespec based interfaces
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*/
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struct timespec64 get_monotonic_coarse64(void);
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extern void getrawmonotonic64(struct timespec64 *ts);
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extern void ktime_get_ts64(struct timespec64 *ts);
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extern time64_t ktime_get_seconds(void);
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extern time64_t ktime_get_real_seconds(void);
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extern int __getnstimeofday64(struct timespec64 *tv);
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extern void getnstimeofday64(struct timespec64 *tv);
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extern void getboottime64(struct timespec64 *ts);
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#if BITS_PER_LONG == 64
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/**
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* Deprecated. Use do_settimeofday64().
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*/
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static inline int do_settimeofday(const struct timespec *ts)
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{
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return do_settimeofday64(ts);
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}
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static inline int __getnstimeofday(struct timespec *ts)
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{
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return __getnstimeofday64(ts);
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}
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static inline void getnstimeofday(struct timespec *ts)
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{
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getnstimeofday64(ts);
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}
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static inline void ktime_get_ts(struct timespec *ts)
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{
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ktime_get_ts64(ts);
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}
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static inline void ktime_get_real_ts(struct timespec *ts)
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{
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getnstimeofday64(ts);
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}
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static inline void getrawmonotonic(struct timespec *ts)
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{
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getrawmonotonic64(ts);
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}
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static inline struct timespec get_monotonic_coarse(void)
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{
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return get_monotonic_coarse64();
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}
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static inline void getboottime(struct timespec *ts)
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{
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return getboottime64(ts);
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}
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#else
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/**
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* Deprecated. Use do_settimeofday64().
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*/
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static inline int do_settimeofday(const struct timespec *ts)
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{
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struct timespec64 ts64;
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ts64 = timespec_to_timespec64(*ts);
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return do_settimeofday64(&ts64);
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}
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static inline int __getnstimeofday(struct timespec *ts)
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{
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struct timespec64 ts64;
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int ret = __getnstimeofday64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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return ret;
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}
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static inline void getnstimeofday(struct timespec *ts)
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{
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struct timespec64 ts64;
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getnstimeofday64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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}
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static inline void ktime_get_ts(struct timespec *ts)
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{
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struct timespec64 ts64;
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ktime_get_ts64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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}
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static inline void ktime_get_real_ts(struct timespec *ts)
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{
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struct timespec64 ts64;
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getnstimeofday64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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}
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static inline void getrawmonotonic(struct timespec *ts)
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{
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struct timespec64 ts64;
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getrawmonotonic64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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}
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static inline struct timespec get_monotonic_coarse(void)
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{
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return timespec64_to_timespec(get_monotonic_coarse64());
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}
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static inline void getboottime(struct timespec *ts)
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{
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struct timespec64 ts64;
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getboottime64(&ts64);
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*ts = timespec64_to_timespec(ts64);
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}
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#endif
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#define ktime_get_real_ts64(ts) getnstimeofday64(ts)
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/*
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* ktime_t based interfaces
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*/
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enum tk_offsets {
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TK_OFFS_REAL,
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TK_OFFS_BOOT,
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TK_OFFS_TAI,
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TK_OFFS_MAX,
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};
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extern ktime_t ktime_get(void);
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extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
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extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
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extern ktime_t ktime_get_raw(void);
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extern u32 ktime_get_resolution_ns(void);
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/**
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* ktime_get_real - get the real (wall-) time in ktime_t format
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*/
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static inline ktime_t ktime_get_real(void)
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{
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return ktime_get_with_offset(TK_OFFS_REAL);
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}
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/**
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* ktime_get_boottime - Returns monotonic time since boot in ktime_t format
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*
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* This is similar to CLOCK_MONTONIC/ktime_get, but also includes the
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* time spent in suspend.
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*/
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static inline ktime_t ktime_get_boottime(void)
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{
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return ktime_get_with_offset(TK_OFFS_BOOT);
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}
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/**
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* ktime_get_clocktai - Returns the TAI time of day in ktime_t format
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*/
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static inline ktime_t ktime_get_clocktai(void)
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{
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return ktime_get_with_offset(TK_OFFS_TAI);
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}
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/**
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* ktime_mono_to_real - Convert monotonic time to clock realtime
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*/
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static inline ktime_t ktime_mono_to_real(ktime_t mono)
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{
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return ktime_mono_to_any(mono, TK_OFFS_REAL);
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}
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static inline u64 ktime_get_ns(void)
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{
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return ktime_to_ns(ktime_get());
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}
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static inline u64 ktime_get_real_ns(void)
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{
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return ktime_to_ns(ktime_get_real());
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}
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static inline u64 ktime_get_boot_ns(void)
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{
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return ktime_to_ns(ktime_get_boottime());
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}
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static inline u64 ktime_get_tai_ns(void)
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{
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return ktime_to_ns(ktime_get_clocktai());
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}
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static inline u64 ktime_get_raw_ns(void)
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{
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return ktime_to_ns(ktime_get_raw());
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}
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extern u64 ktime_get_mono_fast_ns(void);
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extern u64 ktime_get_raw_fast_ns(void);
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/*
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* Timespec interfaces utilizing the ktime based ones
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*/
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static inline void get_monotonic_boottime(struct timespec *ts)
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{
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*ts = ktime_to_timespec(ktime_get_boottime());
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}
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static inline void get_monotonic_boottime64(struct timespec64 *ts)
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{
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*ts = ktime_to_timespec64(ktime_get_boottime());
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}
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static inline void timekeeping_clocktai(struct timespec *ts)
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{
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*ts = ktime_to_timespec(ktime_get_clocktai());
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}
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/*
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* RTC specific
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*/
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extern bool timekeeping_rtc_skipsuspend(void);
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extern bool timekeeping_rtc_skipresume(void);
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extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);
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/*
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* PPS accessor
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*/
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extern void ktime_get_raw_and_real_ts64(struct timespec64 *ts_raw,
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struct timespec64 *ts_real);
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/*
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* struct system_time_snapshot - simultaneous raw/real time capture with
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* counter value
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* @cycles: Clocksource counter value to produce the system times
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* @real: Realtime system time
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* @raw: Monotonic raw system time
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* @clock_was_set_seq: The sequence number of clock was set events
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* @cs_was_changed_seq: The sequence number of clocksource change events
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*/
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struct system_time_snapshot {
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cycle_t cycles;
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ktime_t real;
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ktime_t raw;
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unsigned int clock_was_set_seq;
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u8 cs_was_changed_seq;
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};
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/*
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* struct system_device_crosststamp - system/device cross-timestamp
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* (syncronized capture)
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* @device: Device time
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* @sys_realtime: Realtime simultaneous with device time
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* @sys_monoraw: Monotonic raw simultaneous with device time
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*/
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struct system_device_crosststamp {
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ktime_t device;
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ktime_t sys_realtime;
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ktime_t sys_monoraw;
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};
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/*
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* struct system_counterval_t - system counter value with the pointer to the
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* corresponding clocksource
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* @cycles: System counter value
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* @cs: Clocksource corresponding to system counter value. Used by
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* timekeeping code to verify comparibility of two cycle values
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*/
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struct system_counterval_t {
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cycle_t cycles;
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struct clocksource *cs;
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};
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/*
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* Get cross timestamp between system clock and device clock
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*/
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extern int get_device_system_crosststamp(
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int (*get_time_fn)(ktime_t *device_time,
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struct system_counterval_t *system_counterval,
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void *ctx),
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void *ctx,
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struct system_time_snapshot *history,
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struct system_device_crosststamp *xtstamp);
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/*
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* Simultaneously snapshot realtime and monotonic raw clocks
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*/
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extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
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/*
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* Persistent clock related interfaces
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*/
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extern int persistent_clock_is_local;
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extern void read_persistent_clock(struct timespec *ts);
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extern void read_persistent_clock64(struct timespec64 *ts);
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extern void read_boot_clock64(struct timespec64 *ts);
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extern int update_persistent_clock(struct timespec now);
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extern int update_persistent_clock64(struct timespec64 now);
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#endif
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