ntp: increase time_freq resolution

This changes time_freq to a 64bit value and makes it static (the only outside
user had no real need to modify it).  Intermediate values were already 64bit,
so the change isn't that big, but it saves a little in shifts by replacing
SHIFT_NSEC with TICK_LENGTH_SHIFT.  PPM_SCALE is then used to convert between
user space and kernel space representation.

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, 15 insertions, 15 deletions

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 3fc81066d7f..c6ae0c24989 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -39,7 +39,7 @@ static s64 time_offset;			/* time adjustment (ns)		*/
 static long time_constant = 2;          /* pll time constant            */
 long time_maxerror = NTP_PHASE_LIMIT;   /* maximum error (us)           */
 long time_esterror = NTP_PHASE_LIMIT;   /* estimated error (us)         */
-long time_freq;                         /* frequency offset (scaled ppm)*/
+static s64 time_freq;                   /* frequency offset (scaled ns/s)*/
 static long time_reftime;               /* time at last adjustment (s)  */
 long time_adjust;
 static long ntp_tick_adj;
@@ -49,7 +49,7 @@ static void ntp_update_frequency(void)
         u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
                                 << TICK_LENGTH_SHIFT;
         second_length += (s64)ntp_tick_adj << TICK_LENGTH_SHIFT;
-        second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
+        second_length += time_freq;
 
         tick_length_base = second_length;
 
@@ -86,16 +86,16 @@ static void ntp_update_offset(long offset)
         time_reftime = xtime.tv_sec;
 
         freq_adj = time_offset * mtemp;
-        freq_adj = shift_right(freq_adj, time_constant * 2 +
-                           (SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
+        freq_adj <<= TICK_LENGTH_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant);
         time_status &= ~STA_MODE;
         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
-                freq_adj += div_s64(time_offset << (SHIFT_NSEC - SHIFT_FLL), mtemp);
+                freq_adj += div_s64(time_offset << (TICK_LENGTH_SHIFT - SHIFT_FLL),
+                                    mtemp);
                 time_status |= STA_MODE;
         }
         freq_adj += time_freq;
-        freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
-        time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
+        freq_adj = min(freq_adj, MAXFREQ_SCALED);
+        time_freq = max(freq_adj, -MAXFREQ_SCALED);
         time_offset = div_s64(time_offset, NTP_INTERVAL_FREQ);
         time_offset <<= SHIFT_UPDATE;
 }
@@ -131,7 +131,7 @@ void second_overflow(void)
         long time_adj;
 
         /* Bump the maxerror field */
-        time_maxerror += MAXFREQ >> SHIFT_USEC;
+        time_maxerror += MAXFREQ / NSEC_PER_USEC;
         if (time_maxerror > NTP_PHASE_LIMIT) {
                 time_maxerror = NTP_PHASE_LIMIT;
                 time_status |= STA_UNSYNC;
@@ -323,10 +323,9 @@ int do_adjtimex(struct timex *txc)
                         time_status &= ~STA_NANO;
 
                 if (txc->modes & ADJ_FREQUENCY) {
-                        time_freq = min(txc->freq, MAXFREQ);
-                        time_freq = min(time_freq, -MAXFREQ);
-                        time_freq = ((s64)time_freq * NSEC_PER_USEC)
-                                        >> (SHIFT_USEC - SHIFT_NSEC);
+                        time_freq = (s64)txc->freq * PPM_SCALE;
+                        time_freq = min(time_freq, MAXFREQ_SCALED);
+                        time_freq = max(time_freq, -MAXFREQ_SCALED);
                 }
 
                 if (txc->modes & ADJ_MAXERROR)
@@ -369,14 +368,15 @@ int do_adjtimex(struct timex *txc)
                 if (!(time_status & STA_NANO))
                         txc->offset /= NSEC_PER_USEC;
         }
-        txc->freq          = (time_freq / NSEC_PER_USEC) <<
-                                (SHIFT_USEC - SHIFT_NSEC);
+        txc->freq          = shift_right((s32)(time_freq >> PPM_SCALE_INV_SHIFT) *
+                                         (s64)PPM_SCALE_INV,
+                                         TICK_LENGTH_SHIFT);
         txc->maxerror      = time_maxerror;
         txc->esterror      = time_esterror;
         txc->status        = time_status;
         txc->constant      = time_constant;
         txc->precision     = 1;
-        txc->tolerance     = MAXFREQ;
+        txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
         txc->tick          = tick_usec;
 
         /* PPS is not implemented, so these are zero */