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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465// SPDX-License-Identifier: GPL-2.0+/* * Based on clocksource code. See commit 74d23cc704d1 */#include <linux/export.h>#include <linux/timecounter.h>
void timecounter_init(struct timecounter *tc, struct cyclecounter *cc, u64 start_tstamp){ tc->cc = cc; tc->cycle_last = cc->read(cc); tc->nsec = start_tstamp; tc->mask = (1ULL << cc->shift) - 1; tc->frac = 0;}EXPORT_SYMBOL_GPL(timecounter_init);
/** * timecounter_read_delta - get nanoseconds since last call of this function * @tc: Pointer to time counter * * When the underlying cycle counter runs over, this will be handled * correctly as long as it does not run over more than once between * calls. * * The first call to this function for a new time counter initializes * the time tracking and returns an undefined result. */static u64 timecounter_read_delta(struct timecounter *tc){ u64 cycle_now, cycle_delta; u64 ns_offset;
/* read cycle counter: */ cycle_now = tc->cc->read(tc->cc);
/* calculate the delta since the last timecounter_read_delta(): */ cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
/* convert to nanoseconds: */ ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta, tc->mask, &tc->frac);
/* update time stamp of timecounter_read_delta() call: */ tc->cycle_last = cycle_now;
return ns_offset;}
u64 timecounter_read(struct timecounter *tc){ u64 nsec;
/* increment time by nanoseconds since last call */ nsec = timecounter_read_delta(tc); nsec += tc->nsec; tc->nsec = nsec;
return nsec;}EXPORT_SYMBOL_GPL(timecounter_read);