#ifndef _LINUX_TIMEX_H
#define _LINUX_TIMEX_H
-#include <linux/compiler.h>
#include <linux/time.h>
-#include <asm/param.h>
-
#define NTP_API 4 /* NTP API version */
/*
- * 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.
- *
- * 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.
- */
-#define SHIFT_PLL 4 /* PLL frequency factor (shift) */
-#define SHIFT_FLL 2 /* FLL frequency factor (shift) */
-#define MAXTC 10 /* maximum time constant (shift) */
-
-/*
- * SHIFT_USEC defines the scaling (shift) of the time_freq and
- * time_tolerance variables, which represent the current frequency
- * 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_INV_SHIFT 20
-#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
- PPM_SCALE + 1)
-
-#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) */
-#define MAXSEC 2048 /* max interval between updates (s) */
-#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
-
-/*
* syscall interface - used (mainly by NTP daemon)
* to discipline kernel clock oscillator
*/
#define ADJ_MICRO 0x1000 /* select microsecond resolution */
#define ADJ_NANO 0x2000 /* select nanosecond resolution */
#define ADJ_TICK 0x4000 /* tick value */
+
+#ifdef __KERNEL__
+#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */
+#define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */
+#define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */
+#else
#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
-#define ADJ_OFFSET_SS_READ 0xa001 /* read-only adjtime */
+#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
/*
#define TIME_BAD TIME_ERROR /* bw compat */
#ifdef __KERNEL__
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <linux/param.h>
+
#include <asm/timex.h>
/*
+ * 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.
+ *
+ * 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 2 /* PLL frequency factor (shift) */
+#define SHIFT_FLL 2 /* FLL frequency factor (shift) */
+#define MAXTC 10 /* maximum time constant (shift) */
+
+/*
+ * SHIFT_USEC defines the scaling (shift) of the time_freq and
+ * time_tolerance variables, which represent the current frequency
+ * offset and maximum frequency tolerance.
+ */
+#define SHIFT_USEC 16 /* frequency offset scale (shift) */
+#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)) / \
+ PPM_SCALE + 1)
+
+#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) */
+#define MAXSEC 2048 /* max interval between updates (s) */
+#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
+
+/*
* kernel variables
* Note: maximum error = NTP synch distance = dispersion + delay / 2;
* estimated error = NTP dispersion.
extern long time_adjust; /* The amount of adjtime left */
+extern void ntp_init(void);
extern void ntp_clear(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. */
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 */