X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=include%2Flinux%2Ftimex.h;h=7a082b32d8e13ac98fe5b04b962f2f44a4f9ecc7;hb=5bfec46baa3a752393433b8d89d3b2c70820f61d;hp=998a55d80acf1b1c62bd8d91755448f9a0edebd6;hpb=c29541b24fb2c6301021637229ae5347c877330a;p=safe%2Fjmp%2Flinux-2.6

diff --git a/include/linux/timex.h b/include/linux/timex.h
index 998a55d..7a082b3 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -115,13 +115,16 @@ struct timex {
 #define ADJ_OFFSET_SS_READ	0xa001	/* read-only adjtime */
 #endif
 
-/* xntp 3.4 compatibility names */
+/* NTP userland likes the MOD_ prefix better */
 #define MOD_OFFSET	ADJ_OFFSET
 #define MOD_FREQUENCY	ADJ_FREQUENCY
 #define MOD_MAXERROR	ADJ_MAXERROR
 #define MOD_ESTERROR	ADJ_ESTERROR
 #define MOD_STATUS	ADJ_STATUS
 #define MOD_TIMECONST	ADJ_TIMECONST
+#define MOD_TAI	ADJ_TAI
+#define MOD_MICRO	ADJ_MICRO
+#define MOD_NANO	ADJ_NANO
 
 
 /*
@@ -170,17 +173,37 @@ struct timex {
 #include <asm/timex.h>
 
 /*
- * SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
- * for a slightly underdamped convergence characteristic. SHIFT_KH
- * establishes the damping of the FLL and is chosen by wisdom and black
- * art.
+ * SHIFT_PLL is used as a dampening factor to define how much we
+ * adjust the frequency correction for a given offset in PLL mode.
+ * It also used in dampening the offset correction, to define how
+ * much of the current value in time_offset we correct for each
+ * second. Changing this value changes the stiffness of the ntp
+ * adjustment code. A lower value makes it more flexible, reducing
+ * NTP convergence time. A higher value makes it stiffer, increasing
+ * convergence time, but making the clock more stable.
  *
- * MAXTC establishes the maximum time constant of the PLL. With the
- * SHIFT_KG and SHIFT_KF values given and a time constant range from
- * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
- * respectively.
+ * In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
+ * However this seems to increase convergence time much too long.
+ *
+ * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
+ *
+ * In the above mailing list discussion, it seems the value of 4
+ * was appropriate for other Unix systems with HZ=100, and that
+ * SHIFT_PLL should be decreased as HZ increases. However, Linux's
+ * clock steering implementation is HZ independent.
+ *
+ * Through experimentation, a SHIFT_PLL value of 2 was found to allow
+ * for fast convergence (very similar to the NTPv3 code used prior to
+ * v2.6.19), with good clock stability.
+ *
+ *
+ * SHIFT_FLL is used as a dampening factor to define how much we
+ * adjust the frequency correction for a given offset in FLL mode.
+ * In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
+ *
+ * MAXTC establishes the maximum time constant of the PLL.
  */
-#define SHIFT_PLL	4	/* PLL frequency factor (shift) */
+#define SHIFT_PLL	2	/* PLL frequency factor (shift) */
 #define SHIFT_FLL	2	/* FLL frequency factor (shift) */
 #define MAXTC		10	/* maximum time constant (shift) */
 
@@ -190,12 +213,12 @@ struct timex {
  * offset and maximum frequency tolerance.
  */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
-#define PPM_SCALE (NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
+#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
 #define PPM_SCALE_INV_SHIFT 19
-#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
+#define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
 		       PPM_SCALE + 1)
 
-#define MAXPHASE 500000000l	/* max phase error (ns) */
+#define MAXPHASE 500000000L	/* max phase error (ns) */
 #define MAXFREQ 500000		/* max frequency error (ns/s) */
 #define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
 #define MINSEC 256		/* min interval between updates (s) */
@@ -215,9 +238,6 @@ extern int tickadj;			/* amount of adjustment per tick */
  * phase-lock loop variables
  */
 extern int time_status;		/* clock synchronization status bits */
-extern long time_maxerror;	/* maximum error */
-extern long time_esterror;	/* estimated error */
-
 extern long time_adjust;	/* The amount of adjtime left */
 
 extern void ntp_init(void);
@@ -241,11 +261,7 @@ static inline int ntp_synced(void)
 
 #define NTP_SCALE_SHIFT		32
 
-#ifdef CONFIG_NO_HZ
-#define NTP_INTERVAL_FREQ  (2)
-#else
 #define NTP_INTERVAL_FREQ  (HZ)
-#endif
 #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
 
 /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
@@ -260,6 +276,9 @@ extern int do_adjtimex(struct timex *);
 
 int read_current_timer(unsigned long *timer_val);
 
+/* The clock frequency of the i8253/i8254 PIT */
+#define PIT_TICK_RATE 1193182ul
+
 #endif /* KERNEL */
 
 #endif /* LINUX_TIMEX_H */