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Commit 04b617e7 authored by Roman Zippel's avatar Roman Zippel Committed by Linus Torvalds
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[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: default avatarRoman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 97eebe13

include/linux/timex.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/time/ntp.c

+22 −14
Original line number Diff line number Diff line
@@ -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;