[PATCH] ntp: convert time_freq to nsec value

This converts time_freq to a scaled nsec value and adds around 6bit of extra
resolution.  This pushes the time_freq to its 32bit limits so the calculatons
have to be done with 64bit.

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

2 files changed, 24 insertions, 14 deletions

diff --git a/include/linux/timex.h b/include/linux/timex.h
index 7715b4c0caf9..671609ee1a3d 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -91,10 +91,12 @@
 #define SHIFT_SCALE 22          /* phase scale (shift) */
 #define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
 #define SHIFT_USEC 16           /* frequency offset scale (shift) */
+#define SHIFT_NSEC 12           /* kernel frequency offset scale */
 #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
 
 #define MAXPHASE 512000L        /* max phase error (us) */
 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
+#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
 #define MINSEC 16L              /* min interval between updates (s) */
 #define MAXSEC 1200L            /* max interval between updates (s) */
 #define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index af7563f5d4e2..9137b54613e0 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -66,7 +66,7 @@ void ntp_update_frequency(void)
 {
         tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
         tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
-        tick_length_base += ((s64)time_freq * NSEC_PER_USEC) << (TICK_LENGTH_SHIFT - SHIFT_USEC);
+        tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
 
         do_div(tick_length_base, HZ);
 
@@ -200,6 +200,7 @@ void __attribute__ ((weak)) notify_arch_cmos_timer(void)
 int do_adjtimex(struct timex *txc)
 {
         long ltemp, mtemp, save_adjust;
+        s64 freq_adj;
         int result;
 
         /* In order to modify anything, you gotta be super-user! */
@@ -245,7 +246,7 @@ int do_adjtimex(struct timex *txc)
                     result = -EINVAL;
                     goto leave;
                 }
-                time_freq = txc->freq;
+                time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
             }
 
             if (txc->modes & ADJ_MAXERROR) {
@@ -278,14 +279,14 @@ int do_adjtimex(struct timex *txc)
                     time_adjust = txc->offset;
                 }
                 else if (time_status & STA_PLL) {
-                    ltemp = txc->offset;
+                    ltemp = txc->offset * NSEC_PER_USEC;
 
                     /*
                      * Scale the phase adjustment and
                      * clamp to the operating range.
                      */
-                    time_offset = min(ltemp, MAXPHASE);
-                    time_offset = max(time_offset, -MAXPHASE);
+                    time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
+                    time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
 
                     /*
                      * Select whether the frequency is to be controlled
@@ -297,24 +298,31 @@ int do_adjtimex(struct timex *txc)
                         time_reftime = xtime.tv_sec;
                     mtemp = xtime.tv_sec - time_reftime;
                     time_reftime = xtime.tv_sec;
+                    freq_adj = 0;
                     if (time_status & STA_FLL) {
                         if (mtemp >= MINSEC) {
-                            ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12);
-                            time_freq += shift_right(ltemp, SHIFT_KH);
+                            freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH);
+                            if (time_offset < 0) {
+                                freq_adj = -freq_adj;
+                                do_div(freq_adj, mtemp);
+                                freq_adj = -freq_adj;
+                            } else
+                                do_div(freq_adj, mtemp);
                         } else /* calibration interval too short (p. 12) */
                                 result = TIME_ERROR;
                     } else {    /* PLL mode */
                         if (mtemp < MAXSEC) {
-                            ltemp *= mtemp;
-                            time_freq += shift_right(ltemp,(time_constant +
+                            freq_adj = (s64)ltemp * mtemp;
+                            freq_adj = shift_right(freq_adj,(time_constant +
                                                        time_constant +
-                                                       SHIFT_KF - SHIFT_USEC));
+                                                       SHIFT_KF - SHIFT_NSEC));
                         } else /* calibration interval too long (p. 12) */
                                 result = TIME_ERROR;
                     }
-                    time_freq = min(time_freq, MAXFREQ);
-                    time_freq = max(time_freq, -MAXFREQ);
-                    time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
+                    freq_adj += time_freq;
+                    freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
+                    time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
+                    time_offset = (time_offset / HZ) << SHIFT_UPDATE;
                 } /* STA_PLL */
             } /* txc->modes & ADJ_OFFSET */
             if (txc->modes & ADJ_TICK)
@@ -330,7 +338,7 @@ leave:	if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
             txc->offset    = save_adjust;
         else
             txc->offset    = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
-        txc->freq          = time_freq;
+        txc->freq          = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
         txc->maxerror      = time_maxerror;
         txc->esterror      = time_esterror;
         txc->status        = time_status;