ntp: increase time_offset resolution

time_offset is already a 64bit value but its resolution barely used, so this
makes better use of it by replacing SHIFT_UPDATE with TICK_LENGTH_SHIFT.

Side note: the SHIFT_HZ in SHIFT_UPDATE was incorrect for CONFIG_NO_HZ and the
primary reason for changing time_offset to 64bit to avoid the overflow.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 7 deletions

diff --git a/include/linux/timex.h b/include/linux/timex.h
index 48c3376dce71..9fbdd12a52f1 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -76,27 +76,22 @@
 #define MAXTC           10      /* maximum time constant (shift) */
 
 /*
- * The SHIFT_UPDATE define establishes the decimal point of the
- * time_offset variable which represents the current offset with
- * respect to standard time.
- *
  * SHIFT_USEC defines the scaling (shift) of the time_freq and
  * time_tolerance variables, which represent the current frequency
  * offset and maximum frequency tolerance.
  */
-#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
 #define SHIFT_USEC 16           /* frequency offset scale (shift) */
 #define PPM_SCALE (NSEC_PER_USEC << (TICK_LENGTH_SHIFT - SHIFT_USEC))
 #define PPM_SCALE_INV_SHIFT 20
 #define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + TICK_LENGTH_SHIFT)) / \
                        PPM_SCALE + 1)
 
-#define MAXPHASE 512000L        /* max phase error (us) */
+#define MAXPHASE 500000000l     /* max phase error (ns) */
 #define MAXFREQ 500000          /* max frequency error (ns/s) */
 #define MAXFREQ_SCALED ((s64)MAXFREQ << TICK_LENGTH_SHIFT)
 #define MINSEC 256              /* min interval between updates (s) */
 #define MAXSEC 2048             /* max interval between updates (s) */
-#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
+#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
 
 /*
  * syscall interface - used (mainly by NTP daemon)