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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: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
john stultz 2006-06-26 00:25:07 -07:00 committed by Linus Torvalds
parent ad596171ed
commit 260a42309b
3 changed files with 19 additions and 6 deletions
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2
arch/powerpc/kernel/time.c
View File

@ -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;

2
include/linux/timex.h
View File

@ -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 *);

21
kernel/timer.c
View File

@ -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 */