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authorjohn stultz <johnstul@us.ibm.com>2006-06-26 03:25:07 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 12:58:20 -0400
commit260a42309b31cbc54eb4b6b85649e412bcad053f (patch)
tree51efc7bb51075b0d25d0e8465d3c056e6a57fe16 /kernel
parentad596171ed635c51a9eef829187af100cbf8dcf7 (diff)
[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: John Stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/timer.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/kernel/timer.c b/kernel/timer.c
index 524c7f638365..623f9ea198d8 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -780,16 +780,29 @@ static void update_wall_time_one_tick(void)
780 * Return how long ticks are at the moment, that is, how much time 780 * Return how long ticks are at the moment, that is, how much time
781 * update_wall_time_one_tick will add to xtime next time we call it 781 * update_wall_time_one_tick will add to xtime next time we call it
782 * (assuming no calls to do_adjtimex in the meantime). 782 * (assuming no calls to do_adjtimex in the meantime).
783 * The return value is in fixed-point nanoseconds with SHIFT_SCALE-10 783 * The return value is in fixed-point nanoseconds shifted by the
784 * bits to the right of the binary point. 784 * specified number of bits to the right of the binary point.
785 * This function has no side-effects. 785 * This function has no side-effects.
786 */ 786 */
787u64 current_tick_length(void) 787u64 current_tick_length(long shift)
788{ 788{
789 long delta_nsec; 789 long delta_nsec;
790 u64 ret;
790 791
792 /* calculate the finest interval NTP will allow.
793 * ie: nanosecond value shifted by (SHIFT_SCALE - 10)
794 */
791 delta_nsec = tick_nsec + adjtime_adjustment() * 1000; 795 delta_nsec = tick_nsec + adjtime_adjustment() * 1000;
792 return ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj; 796 ret = ((u64) delta_nsec << (SHIFT_SCALE - 10)) + time_adj;
797
798 /* convert from (SHIFT_SCALE - 10) to specified shift scale: */
799 shift = shift - (SHIFT_SCALE - 10);
800 if (shift < 0)
801 ret >>= -shift;
802 else
803 ret <<= shift;
804
805 return ret;
793} 806}
794 807
795/* XXX - all of this timekeeping code should be later moved to time.c */ 808/* XXX - all of this timekeeping code should be later moved to time.c */