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.
20  *	around quickly. Locking rules (if necessary) have to be defined
21  *	by the implementor and user of specific instances of this API.
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.
64  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
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.
82  * @delta:	Desired change in nanoseconds.
86 	tc->nsec += delta;  in timecounter_adjtime()
90  * timecounter_init - initialize a time counter
104  * timecounter_read - return nanoseconds elapsed since timecounter_init()
108  * In other words, keeps track of time since the same epoch as
114  * timecounter_cyc2time - convert a cycle counter to same
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.
125  * in the past.