[RFC][PATCH - 11/13] NTP cleanup: Introduce PPM adjustmentvariables
From: john stultz
Date: Wed Aug 10 2005 - 20:35:47 EST
All,
This patch introduces variables to keep track of the different NTP
adjustment values in PPM units. It also introduces the
ntp_get_ppm_adjustment() interface which returns shifted PPM units. The
patch also changes the ppc64 ppc_adjtimex() function to use
ntp_get_ppm_adjustment().
This will likely need careful review from the ppc64 folks. There are
some subtle differences in the calling frequency as well as between what
ntp_get_adjustment() returns and what ppc_adjtimex() used to calculate.
Any comments or feedback would be greatly appreciated.
thanks
-john
linux-2.6.13-rc6_timeofday-ntp-part11_B5.patch
============================================
diff --git a/arch/ppc64/kernel/time.c b/arch/ppc64/kernel/time.c
--- a/arch/ppc64/kernel/time.c
+++ b/arch/ppc64/kernel/time.c
@@ -106,8 +106,6 @@ extern struct timezone sys_tz;
void ppc_adjtimex(void);
-static unsigned adjusting_time = 0;
-
unsigned long ppc_proc_freq;
unsigned long ppc_tb_freq;
@@ -355,8 +353,7 @@ int timer_interrupt(struct pt_regs * reg
timer_sync_xtime(lpaca->next_jiffy_update_tb);
timer_check_rtc();
write_sequnlock(&xtime_lock);
- if ( adjusting_time && (ntp_adjtime_offset == 0) )
- ppc_adjtimex();
+ ppc_adjtimex();
}
lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy;
}
@@ -582,7 +579,7 @@ void __init time_init(void)
systemcfg->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
systemcfg->tb_to_xs = tb_to_xs;
- ntp_freq = 0;
+ ntp_clear();
xtime.tv_nsec = 0;
last_rtc_update = xtime.tv_sec;
@@ -599,7 +596,7 @@ void __init time_init(void)
* to microseconds to keep do_gettimeofday synchronized
* with ntpd.
*
- * Use the ntp_adjtime_offset, ntp_freq and ntp_offset computed by adjtimex to
+ * Use the ntp_get_ppm_adjustment computed by adjtimex to
* adjust the frequency.
*/
@@ -609,62 +606,14 @@ void ppc_adjtimex(void)
{
unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec;
unsigned long tb_ticks_per_sec_delta;
- long delta_freq, ltemp;
+ long delta_freq;
struct div_result divres;
unsigned long flags;
struct gettimeofday_vars * temp_varp;
unsigned temp_idx;
- long singleshot_ppm = 0;
- /* Compute parts per million frequency adjustment to accomplish the time adjustment
- implied by ntp_offset to be applied over the elapsed time indicated by ntp_constant.
- Use SHIFT_USEC to get it into the same units as ntp_freq. */
- if ( ntp_offset < 0 ) {
- ltemp = -ntp_offset;
- ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
- ltemp >>= SHIFT_KG + ntp_constant;
- ltemp = -ltemp;
- }
- else {
- ltemp = ntp_offset;
- ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
- ltemp >>= SHIFT_KG + ntp_constant;
- }
-
- /* If there is a single shot time adjustment in progress */
- if ( ntp_adjtime_offset ) {
-#ifdef DEBUG_PPC_ADJTIMEX
- printk("ppc_adjtimex: ");
- if ( adjusting_time == 0 )
- printk("starting ");
- printk("single shot ntp_adjtime_offset = %ld\n", ntp_adjtime_offset);
-#endif
-
- adjusting_time = 1;
-
- /* Compute parts per million frequency adjustment to match ntp_adjtime_offset */
- singleshot_ppm = tickadj * HZ;
- /*
- * The adjustment should be tickadj*HZ to match the code in
- * linux/kernel/timer.c, but experiments show that this is too
- * large. 3/4 of tickadj*HZ seems about right
- */
- singleshot_ppm -= singleshot_ppm / 4;
- /* Use SHIFT_USEC to get it into the same units as ntp_freq */
- singleshot_ppm <<= SHIFT_USEC;
- if ( ntp_adjtime_offset < 0 )
- singleshot_ppm = -singleshot_ppm;
- }
- else {
-#ifdef DEBUG_PPC_ADJTIMEX
- if ( adjusting_time )
- printk("ppc_adjtimex: ending single shot ntp_adjtime_offset\n");
-#endif
- adjusting_time = 0;
- }
-
/* Add up all of the frequency adjustments */
- delta_freq = ntp_freq + ltemp + singleshot_ppm;
+ delta_freq = ntp_get_ppm_adjustment();
/* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */
den = 1000000 * (1 << (SHIFT_USEC - 8));
@@ -678,7 +627,7 @@ void ppc_adjtimex(void)
}
#ifdef DEBUG_PPC_ADJTIMEX
- printk("ppc_adjtimex: ltemp = %ld, ntp_freq = %ld, singleshot_ppm = %ld\n", ltemp, ntp_freq, singleshot_ppm);
+ printk("ppc_adjtimex: delta_freq = %ld\n", delta_freq);
printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec);
#endif
diff --git a/include/linux/ntp.h b/include/linux/ntp.h
--- a/include/linux/ntp.h
+++ b/include/linux/ntp.h
@@ -20,17 +20,11 @@ int ntp_adjtimex(struct timex*);
int ntp_leapsecond(struct timespec now);
void ntp_clear(void);
int ntp_synced(void);
+long ntp_get_ppm_adjustment(void);
long ntp_get_fixed_ns_adjustment(void);
-
+/* these variables cannot be made static just yet */
extern int tickadj;
extern long ntp_adjtime_offset;
-/* Due to ppc64 having its own NTP code,
- * these variables cannot be made static just yet
- */
-extern long ntp_offset;
-extern long ntp_freq;
-extern long ntp_constant;
-
#endif
diff --git a/kernel/ntp.c b/kernel/ntp.c
--- a/kernel/ntp.c
+++ b/kernel/ntp.c
@@ -41,6 +41,7 @@
*
*********************************************************************/
+#include <linux/kernel.h>
#include <linux/ntp.h>
#include <linux/jiffies.h>
#include <linux/errno.h>
@@ -53,15 +54,15 @@ static long time_adj;
/* Chapter 5: Kernel Variables [RFC 1589 pg. 28] */
/* 5.1 Interface Variables */
static int ntp_status = STA_UNSYNC; /* status */
-long ntp_offset; /* usec */
-long ntp_constant = 2; /* ntp magic? */
+static long ntp_offset; /* usec */
+static long ntp_constant = 2; /* ntp magic? */
static long ntp_maxerror = NTP_PHASE_LIMIT; /* usec */
static long ntp_esterror = NTP_PHASE_LIMIT; /* usec */
static const long ntp_tolerance = MAXFREQ; /* shifted ppm */
static const long ntp_precision = 1; /* constant */
/* 5.2 Phase-Lock Loop Variables */
-long ntp_freq; /* shifted ppm */
+static long ntp_freq; /* shifted ppm */
static long ntp_reftime; /* sec */
/* Extra values */
@@ -69,11 +70,17 @@ static int ntp_state = TIME_OK;
long ntp_adjtime_offset;
static long ntp_next_adjtime_offset;
-/* lock for the above variables */
-static seqlock_t ntp_lock = SEQLOCK_UNLOCKED;
+static long singleshot_adj; /* +/- MAX_SINGLESHOT_ADJ (ppm)*/
+static long tick_adj; /* txc->tick adjustment (ppm) */
+static long offset_adj; /* offset adjustment (ppm) */
+static long shifted_ppm_sum; /* ppm<<SHIFT_USEC sum of total freq adj */
static long fixed_tick_ns_adj;
+/* lock for the above variables */
+static seqlock_t ntp_lock = SEQLOCK_UNLOCKED;
+
+#define MAX_SINGLESHOT_ADJ 500 /* (ppm) */
#define SEC_PER_DAY 86400
void ntp_advance(unsigned long interval_nsec)
@@ -81,6 +88,7 @@ void ntp_advance(unsigned long interval_
static unsigned long interval_sum = 0;
long time_adjust_step;
unsigned long flags;
+ static long ss_adj = 0;
write_seqlock_irqsave(&ntp_lock, flags);
@@ -118,11 +126,10 @@ void ntp_advance(unsigned long interval_
next_adj = min(next_adj, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
next_adj = max(next_adj, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
ntp_offset -= next_adj;
+ offset_adj = shiftR(next_adj, SHIFT_UPDATE); /* ppm */
time_adj = next_adj << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
-
time_adj += shiftR(ntp_freq, (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));
-
#if HZ == 100
/* Compensate for (HZ==100) != (1 << SHIFT_HZ).
* Add 25% and 3.125% to get 128.125;
@@ -137,9 +144,17 @@ void ntp_advance(unsigned long interval_
*/
time_adj += shiftR(time_adj,6) + shiftR(time_adj,7);
#endif
-
+ /* Set ss_adj for the next second */
+ ss_adj = min_t(unsigned long, singleshot_adj, MAX_SINGLESHOT_ADJ);
+ singleshot_adj -= ss_adj;
}
+ /* calculate total shifted ppm adjustment for the next interval */
+ shifted_ppm_sum = tick_adj<<SHIFT_USEC;
+ shifted_ppm_sum += offset_adj << SHIFT_USEC;
+ shifted_ppm_sum += ntp_freq; /* already shifted by SHIFT_USEC */
+ shifted_ppm_sum += ss_adj << SHIFT_USEC;
+
if ( (time_adjust_step = ntp_adjtime_offset) != 0 ) {
/* We are doing an adjtime thing.
@@ -332,11 +347,17 @@ int ntp_adjtimex(struct timex *txc)
/* adjtime() is independent from ntp_adjtime() */
if ((ntp_next_adjtime_offset = txc->offset) == 0)
ntp_adjtime_offset = 0;
+ singleshot_adj = txc->offset;
} else if (ntp_hardupdate(txc->offset, txc->time))
result = TIME_ERROR;
}
if (txc->modes & ADJ_TICK) {
+ /* first calculate usec/user_tick offset */
+ tick_adj = ((USEC_PER_SEC + USER_HZ/2)/USER_HZ) - txc->tick;
+ /* multiply by user_hz to get usec/sec => ppm */
+ tick_adj *= USER_HZ;
+
tick_usec = txc->tick;
tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
}
@@ -454,6 +475,9 @@ void ntp_clear(void)
ntp_status |= STA_UNSYNC;
ntp_maxerror = NTP_PHASE_LIMIT;
ntp_esterror = NTP_PHASE_LIMIT;
+ singleshot_adj = 0;
+ tick_adj = 0;
+ offset_adj =0;
write_sequnlock_irqrestore(&ntp_lock, flags);
}
@@ -467,6 +491,15 @@ int ntp_synced(void)
return !(ntp_status & STA_UNSYNC);
}
+/**
+ * ntp_get_ppm_adjustment - Returns Shifted PPM adjustment
+ *
+ */
+long ntp_get_ppm_adjustment(void)
+{
+ return shifted_ppm_sum;
+}
+
long ntp_get_fixed_ns_adjustment(void)
{
return fixed_tick_ns_adj;
-
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