forked from luck/tmp_suning_uos_patched
ntp: improve adjtimex frequency rounding
Change PPM_SCALE_INV_SHIFT so that it doesn't throw away any input bits (19 is the amount of the factor 2 in PPM_SCALE), the output frequency can then be calculated back to its input value, as the inverse divide produce a slightly larger value, which is then correctly rounded by the final shift. Reported-by: Martin Ziegler <ziegler@uni-freiburg.de> Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: John Stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
parent
5cd1c9c5cf
commit
d40e944c25
@ -82,7 +82,7 @@
|
||||
*/
|
||||
#define SHIFT_USEC 16 /* frequency offset scale (shift) */
|
||||
#define PPM_SCALE (NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
|
||||
#define PPM_SCALE_INV_SHIFT 20
|
||||
#define PPM_SCALE_INV_SHIFT 19
|
||||
#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
|
||||
PPM_SCALE + 1)
|
||||
|
||||
|
@ -406,9 +406,8 @@ int do_adjtimex(struct timex *txc)
|
||||
if (time_status & (STA_UNSYNC|STA_CLOCKERR))
|
||||
result = TIME_ERROR;
|
||||
|
||||
txc->freq = shift_right((s32)(time_freq >> PPM_SCALE_INV_SHIFT) *
|
||||
(s64)PPM_SCALE_INV,
|
||||
NTP_SCALE_SHIFT);
|
||||
txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
|
||||
(s64)PPM_SCALE_INV, NTP_SCALE_SHIFT);
|
||||
txc->maxerror = time_maxerror;
|
||||
txc->esterror = time_esterror;
|
||||
txc->status = time_status;
|
||||
|
Loading…
Reference in New Issue
Block a user