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Commit 260a4230 authored by John Stultz's avatar John Stultz Committed by Linus Torvalds
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[PATCH] Time: Let user request precision from current_tick_length() 



Change the current_tick_length() function so it takes an argument which
specifies how much precision to return in shifted nanoseconds.  This provides
a simple way to convert between NTPs internal nanoseconds shifted by
(SHIFT_SCALE - 10) to other shifted nanosecond units that are used by the
clocksource abstraction.

Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ad596171

arch/powerpc/kernel/time.c

+1 −1
Original line number Diff line number Diff line
@@ -534,7 +534,7 @@ static __inline__ void timer_recalc_offset(u64 cur_tb) 


	if (__USE_RTC())

		return;

	tlen = current_tick_length();

	tlen = current_tick_length(SHIFT_SCALE - 10);

	offset = cur_tb - do_gtod.varp->tb_orig_stamp;

	if (tlen == last_tick_len && offset < 0x80000000u)

		return;

include/linux/timex.h

+1 −1
Original line number Diff line number Diff line
@@ -304,7 +304,7 @@ time_interpolator_reset(void) 
#endif /* !CONFIG_TIME_INTERPOLATION */



/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */

extern u64 current_tick_length(void);

extern u64 current_tick_length(long);



extern int do_adjtimex(struct timex *);

kernel/timer.c

+17 −4
Original line number Diff line number Diff line
@@ -780,16 +780,29 @@ static void update_wall_time_one_tick(void) 
 * Return how long ticks are at the moment, that is, how much time

 * update_wall_time_one_tick will add to xtime next time we call it

 * (assuming no calls to do_adjtimex in the meantime).

 * The return value is in fixed-point nanoseconds with SHIFT_SCALE-10

 * bits to the right of the binary point.

 * The return value is in fixed-point nanoseconds shifted by the

 * specified number of bits to the right of the binary point.

 * This function has no side-effects.

 */

u64 current_tick_length(void)

u64 current_tick_length(long shift)

{

	long delta_nsec;

	u64 ret;



	/* calculate the finest interval NTP will allow.

	 *    ie: nanosecond value shifted by (SHIFT_SCALE - 10)

	 */

	delta_nsec = tick_nsec + adjtime_adjustment() * 1000;

	return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;

	ret = ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;



	/* convert from (SHIFT_SCALE - 10) to specified shift scale: */

	shift = shift - (SHIFT_SCALE - 10);

	if (shift < 0)

		ret >>= -shift;

	else

		ret <<= shift;



	return ret;

}



/* XXX - all of this timekeeping code should be later moved to time.c */