include/linux/timecounter.h

1 /* SPDX-License-Identifier: GPL-2.0-or-later */
14 #define CYCLECOUNTER_MASK(bits) (u64)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
17  * struct cyclecounter - hardware abstraction for a free running counter
18  *	Provides completely state-free accessors to the underlying hardware.
19  *	Depending on which hardware it reads, the cycle counter may wrap
38  * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
40  *	cycle counter wrap around. Initialize with
44  *	cycle counter hardware, locking issues and reading the time
45  *	more often than the cycle counter wraps around. The nanosecond
46  *	counter will only wrap around after ~585 years.
48  * @cc:			the cycle counter used by this instance
49  * @cycle_last:		most recent cycle counter value seen by
64  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
65  * @cc:		Pointer to cycle counter.
75 	ns = (ns * cc->mult) + *frac;  in cyclecounter_cyc2ns()
77 	return ns >> cc->shift;  in cyclecounter_cyc2ns()
81  * timecounter_adjtime - Shifts the time of the clock.
86 	tc->nsec += delta;  in timecounter_adjtime()
90  * timecounter_init - initialize a time counter
91  * @tc:			Pointer to time counter which is to be initialized/reset
92  * @cc:			A cycle counter, ready to be used.
97  * the time stamp counter by the number of elapsed nanoseconds.
104  * timecounter_read - return nanoseconds elapsed since timecounter_init()
106  * @tc:          Pointer to time counter.
114  * timecounter_cyc2time - convert a cycle counter to same
117  * @tc:		Pointer to time counter.
118  * @cycle_tstamp:	a value returned by tc->cc->read()
121  * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
122  * with "max cycle count" == cs->mask+1.
124  * This allows conversion of cycle counter values which were generated