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// 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);
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