The patch titled
ntp: improve adjtimex frequency rounding
has been added to the -mm tree. Its filename is
ntp-improve-adjtimex-frequency-rounding.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
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Subject: ntp: improve adjtimex frequency rounding
From: Roman Zippel <zippel@xxxxxxxxxxxxxx>
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.
Signed-off-by: Roman Zippel <zippel@xxxxxxxxxxxxxx>
Cc: John Stultz <johnstul@xxxxxxxxxx>
Cc: Roman Zippel <zippel@xxxxxxxxxxxxxx>
Reported-by: Martin Ziegler <ziegler@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/timex.h | 2 +-
kernel/time/ntp.c | 5 ++---
2 files changed, 3 insertions(+), 4 deletions(-)
diff -puN include/linux/timex.h~ntp-improve-adjtimex-frequency-rounding include/linux/timex.h
--- a/include/linux/timex.h~ntp-improve-adjtimex-frequency-rounding
+++ a/include/linux/timex.h
@@ -83,7 +83,7 @@
*/
#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)
diff -puN kernel/time/ntp.c~ntp-improve-adjtimex-frequency-rounding kernel/time/ntp.c
--- a/kernel/time/ntp.c~ntp-improve-adjtimex-frequency-rounding
+++ a/kernel/time/ntp.c
@@ -406,9 +406,8 @@ adj_done:
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;
_
Patches currently in -mm which might be from zippel@xxxxxxxxxxxxxx are
ntp-let-update_persistent_clock-sleep.patch
timekeeping-fix-rounding-problem-during-clock-update.patch
ntp-fix-adj_offset_ss_read-bug-and-do_adjtimex-cleanup.patch
linux-timexh-cleanup-for-userspace.patch
ntp-improve-adjtimex-frequency-rounding.patch
ntp-fix-calculation-of-the-next-jiffie-to-trigger-rtc-sync.patch
clocksource-keep-track-of-original-clocksource-frequency.patch
clocksource-introduce-clocksource_forward_now.patch
clocksource-introduce-clock_monotonic_raw.patch
hfsplus-quieten-down-mounting-hfsplus-journaled-fs-read-only.patch
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