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timecounter: provide a helper function to shift the time. 

Some PTP Hardware Clock drivers use a struct timecounter to represent
their clock. To adjust the time by a given offset, these drivers all
perform a two step read/write of their timecounter. However, it is
better and simpler just to adjust the offset in one step. This patch
introduces a little routine to help drivers implement the adjtime
method.

Suggested-by: Janusz Użycki <j.uzycki@elproma.com.pl>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Richard Cochran 2014-12-21 19:46:57 +01:00 committed by David S. Miller
parent 74d23cc704
commit 796c1efd6f
1 changed files with 9 additions and 0 deletions
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9
include/linux/timecounter.h
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@ -78,6 +78,15 @@ static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
return ret;
}
/**
* timecounter_adjtime - Shifts the time of the clock.
* @delta: Desired change in nanoseconds.
*/
static inline void timecounter_adjtime(struct timecounter *tc, s64 delta)
{
tc->nsec += delta;
}
/**
* timecounter_init - initialize a time counter
* @tc: Pointer to time counter which is to be initialized/reset