[IA64] remove time interpolator
Remove time_interpolator code (This is generic code, but only user was ia64. It has been superseded by the CONFIG_GENERIC_TIME code). Signed-off-by: Bob Picco <bob.picco@hp.com> Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Peter Keilty <peter.keilty@hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Bob Picco
Tony Luck
parent
0aa366f351
commit
1f564ad6d4
@ -1,41 +0,0 @@
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Time Interpolators
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------------------
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Time interpolators are a base of time calculation between timer ticks and
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allow an accurate determination of time down to the accuracy of the time
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source in nanoseconds.
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The architecture specific code typically provides gettimeofday and
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settimeofday under Linux. The time interpolator provides both if an arch
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defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick
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operations and call the necessary functions to advance the clock.
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With the time interpolator a standardized interface exists for time
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interpolation between ticks. The provided logic is highly scalable
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and has been tested in SMP situations of up to 512 CPUs.
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If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code
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(or the device drivers - like HPET) may register time interpolators.
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These are typically defined in the following way:
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static struct time_interpolator my_interpolator {
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.frequency = MY_FREQUENCY,
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.source = TIME_SOURCE_MMIO32,
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.shift = 8, /* scaling for higher accuracy */
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.drift = -1, /* Unknown drift */
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.jitter = 0 /* time source is stable */
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};
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void time_init(void)
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{
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....
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/* Initialization of the timer *.
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my_interpolator.address = &my_timer;
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register_time_interpolator(&my_interpolator);
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....
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}
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For more details see include/linux/timex.h and kernel/timer.c.
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Christoph Lameter <christoph@lameter.com>, October 31, 2004
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@ -224,66 +224,6 @@ static inline int ntp_synced(void)
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__x < 0 ? -(-__x >> __s) : __x >> __s; \
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})
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#ifdef CONFIG_TIME_INTERPOLATION
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#define TIME_SOURCE_CPU 0
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#define TIME_SOURCE_MMIO64 1
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#define TIME_SOURCE_MMIO32 2
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#define TIME_SOURCE_FUNCTION 3
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/* For proper operations time_interpolator clocks must run slightly slower
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* than the standard clock since the interpolator may only correct by having
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* time jump forward during a tick. A slower clock is usually a side effect
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* of the integer divide of the nanoseconds in a second by the frequency.
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* The accuracy of the division can be increased by specifying a shift.
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* However, this may cause the clock not to be slow enough.
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* The interpolator will self-tune the clock by slowing down if no
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* resets occur or speeding up if the time jumps per analysis cycle
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* become too high.
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*
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* Setting jitter compensates for a fluctuating timesource by comparing
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* to the last value read from the timesource to insure that an earlier value
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* is not returned by a later call. The price to pay
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* for the compensation is that the timer routines are not as scalable anymore.
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*/
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struct time_interpolator {
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u16 source; /* time source flags */
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u8 shift; /* increases accuracy of multiply by shifting. */
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/* Note that bits may be lost if shift is set too high */
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u8 jitter; /* if set compensate for fluctuations */
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u32 nsec_per_cyc; /* set by register_time_interpolator() */
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void *addr; /* address of counter or function */
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cycles_t mask; /* mask the valid bits of the counter */
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unsigned long offset; /* nsec offset at last update of interpolator */
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u64 last_counter; /* counter value in units of the counter at last update */
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cycles_t last_cycle; /* Last timer value if TIME_SOURCE_JITTER is set */
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u64 frequency; /* frequency in counts/second */
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long drift; /* drift in parts-per-million (or -1) */
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unsigned long skips; /* skips forward */
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unsigned long ns_skipped; /* nanoseconds skipped */
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struct time_interpolator *next;
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};
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extern void register_time_interpolator(struct time_interpolator *);
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extern void unregister_time_interpolator(struct time_interpolator *);
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extern void time_interpolator_reset(void);
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extern unsigned long time_interpolator_get_offset(void);
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extern void time_interpolator_update(long delta_nsec);
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#else /* !CONFIG_TIME_INTERPOLATION */
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static inline void time_interpolator_reset(void)
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{
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}
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static inline void time_interpolator_update(long delta_nsec)
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{
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}
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#endif /* !CONFIG_TIME_INTERPOLATION */
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#define TICK_LENGTH_SHIFT 32
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#ifdef CONFIG_NO_HZ
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@ -136,7 +136,6 @@ static inline void warp_clock(void)
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write_seqlock_irq(&xtime_lock);
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wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
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xtime.tv_sec += sys_tz.tz_minuteswest * 60;
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time_interpolator_reset();
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write_sequnlock_irq(&xtime_lock);
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clock_was_set();
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}
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@ -309,92 +308,6 @@ struct timespec timespec_trunc(struct timespec t, unsigned gran)
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}
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EXPORT_SYMBOL(timespec_trunc);
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#ifdef CONFIG_TIME_INTERPOLATION
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void getnstimeofday (struct timespec *tv)
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{
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unsigned long seq,sec,nsec;
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do {
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seq = read_seqbegin(&xtime_lock);
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sec = xtime.tv_sec;
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nsec = xtime.tv_nsec+time_interpolator_get_offset();
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} while (unlikely(read_seqretry(&xtime_lock, seq)));
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while (unlikely(nsec >= NSEC_PER_SEC)) {
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nsec -= NSEC_PER_SEC;
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++sec;
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}
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tv->tv_sec = sec;
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tv->tv_nsec = nsec;
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}
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EXPORT_SYMBOL_GPL(getnstimeofday);
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int do_settimeofday (struct timespec *tv)
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{
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time_t wtm_sec, sec = tv->tv_sec;
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long wtm_nsec, nsec = tv->tv_nsec;
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if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
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return -EINVAL;
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write_seqlock_irq(&xtime_lock);
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{
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wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
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wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
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set_normalized_timespec(&xtime, sec, nsec);
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set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
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time_adjust = 0; /* stop active adjtime() */
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time_status |= STA_UNSYNC;
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time_maxerror = NTP_PHASE_LIMIT;
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time_esterror = NTP_PHASE_LIMIT;
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time_interpolator_reset();
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}
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write_sequnlock_irq(&xtime_lock);
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clock_was_set();
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return 0;
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}
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EXPORT_SYMBOL(do_settimeofday);
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void do_gettimeofday (struct timeval *tv)
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{
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unsigned long seq, nsec, usec, sec, offset;
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do {
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seq = read_seqbegin(&xtime_lock);
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offset = time_interpolator_get_offset();
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sec = xtime.tv_sec;
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nsec = xtime.tv_nsec;
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} while (unlikely(read_seqretry(&xtime_lock, seq)));
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usec = (nsec + offset) / 1000;
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while (unlikely(usec >= USEC_PER_SEC)) {
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usec -= USEC_PER_SEC;
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++sec;
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}
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tv->tv_sec = sec;
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tv->tv_usec = usec;
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/*
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* Make sure xtime.tv_sec [returned by sys_time()] always
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* follows the gettimeofday() result precisely. This
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* condition is extremely unlikely, it can hit at most
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* once per second:
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*/
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if (unlikely(xtime.tv_sec != tv->tv_sec)) {
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unsigned long flags;
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write_seqlock_irqsave(&xtime_lock, flags);
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update_wall_time();
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write_sequnlock_irqrestore(&xtime_lock, flags);
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}
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}
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EXPORT_SYMBOL(do_gettimeofday);
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#else /* CONFIG_TIME_INTERPOLATION */
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#ifndef CONFIG_GENERIC_TIME
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/*
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* Simulate gettimeofday using do_gettimeofday which only allows a timeval
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@ -410,7 +323,6 @@ void getnstimeofday(struct timespec *tv)
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}
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EXPORT_SYMBOL_GPL(getnstimeofday);
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#endif
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#endif /* CONFIG_TIME_INTERPOLATION */
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/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
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* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
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@ -116,11 +116,6 @@ void second_overflow(void)
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if (xtime.tv_sec % 86400 == 0) {
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xtime.tv_sec--;
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wall_to_monotonic.tv_sec++;
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/*
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* The timer interpolator will make time change
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* gradually instead of an immediate jump by one second
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*/
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time_interpolator_update(-NSEC_PER_SEC);
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time_state = TIME_OOP;
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printk(KERN_NOTICE "Clock: inserting leap second "
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"23:59:60 UTC\n");
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@ -130,11 +125,6 @@ void second_overflow(void)
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if ((xtime.tv_sec + 1) % 86400 == 0) {
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xtime.tv_sec++;
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wall_to_monotonic.tv_sec--;
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/*
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* Use of time interpolator for a gradual change of
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* time
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*/
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time_interpolator_update(NSEC_PER_SEC);
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time_state = TIME_WAIT;
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printk(KERN_NOTICE "Clock: deleting leap second "
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"23:59:59 UTC\n");
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@ -466,10 +466,6 @@ void update_wall_time(void)
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second_overflow();
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}
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/* interpolator bits */
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time_interpolator_update(clock->xtime_interval
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>> clock->shift);
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/* accumulate error between NTP and clock interval */
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clock->error += current_tick_length();
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clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift);
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188
kernel/timer.c
188
kernel/timer.c
@ -1349,194 +1349,6 @@ void __init init_timers(void)
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open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
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}
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#ifdef CONFIG_TIME_INTERPOLATION
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struct time_interpolator *time_interpolator __read_mostly;
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static struct time_interpolator *time_interpolator_list __read_mostly;
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static DEFINE_SPINLOCK(time_interpolator_lock);
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static inline cycles_t time_interpolator_get_cycles(unsigned int src)
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{
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unsigned long (*x)(void);
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switch (src)
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{
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case TIME_SOURCE_FUNCTION:
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x = time_interpolator->addr;
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return x();
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case TIME_SOURCE_MMIO64 :
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return readq_relaxed((void __iomem *)time_interpolator->addr);
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case TIME_SOURCE_MMIO32 :
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return readl_relaxed((void __iomem *)time_interpolator->addr);
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default: return get_cycles();
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}
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}
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static inline u64 time_interpolator_get_counter(int writelock)
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{
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unsigned int src = time_interpolator->source;
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if (time_interpolator->jitter)
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{
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cycles_t lcycle;
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cycles_t now;
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do {
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lcycle = time_interpolator->last_cycle;
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now = time_interpolator_get_cycles(src);
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if (lcycle && time_after(lcycle, now))
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return lcycle;
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/* When holding the xtime write lock, there's no need
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* to add the overhead of the cmpxchg. Readers are
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* force to retry until the write lock is released.
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*/
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if (writelock) {
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time_interpolator->last_cycle = now;
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return now;
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}
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/* Keep track of the last timer value returned. The use of cmpxchg here
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* will cause contention in an SMP environment.
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*/
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} while (unlikely(cmpxchg(&time_interpolator->last_cycle, lcycle, now) != lcycle));
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return now;
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}
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else
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return time_interpolator_get_cycles(src);
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}
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void time_interpolator_reset(void)
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{
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time_interpolator->offset = 0;
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time_interpolator->last_counter = time_interpolator_get_counter(1);
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}
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#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift)
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unsigned long time_interpolator_get_offset(void)
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{
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/* If we do not have a time interpolator set up then just return zero */
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if (!time_interpolator)
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return 0;
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return time_interpolator->offset +
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GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator);
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}
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#define INTERPOLATOR_ADJUST 65536
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#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
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void time_interpolator_update(long delta_nsec)
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{
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u64 counter;
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unsigned long offset;
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/* If there is no time interpolator set up then do nothing */
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if (!time_interpolator)
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return;
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/*
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* The interpolator compensates for late ticks by accumulating the late
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* time in time_interpolator->offset. A tick earlier than expected will
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* lead to a reset of the offset and a corresponding jump of the clock
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* forward. Again this only works if the interpolator clock is running
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* slightly slower than the regular clock and the tuning logic insures
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* that.
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*/
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counter = time_interpolator_get_counter(1);
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offset = time_interpolator->offset +
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GET_TI_NSECS(counter, time_interpolator);
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if (delta_nsec < 0 || (unsigned long) delta_nsec < offset)
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time_interpolator->offset = offset - delta_nsec;
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else {
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time_interpolator->skips++;
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time_interpolator->ns_skipped += delta_nsec - offset;
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time_interpolator->offset = 0;
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}
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time_interpolator->last_counter = counter;
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/* Tuning logic for time interpolator invoked every minute or so.
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* Decrease interpolator clock speed if no skips occurred and an offset is carried.
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* Increase interpolator clock speed if we skip too much time.
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*/
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if (jiffies % INTERPOLATOR_ADJUST == 0)
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{
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if (time_interpolator->skips == 0 && time_interpolator->offset > tick_nsec)
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time_interpolator->nsec_per_cyc--;
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if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0)
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time_interpolator->nsec_per_cyc++;
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time_interpolator->skips = 0;
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time_interpolator->ns_skipped = 0;
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}
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}
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static inline int
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is_better_time_interpolator(struct time_interpolator *new)
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{
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if (!time_interpolator)
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return 1;
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return new->frequency > 2*time_interpolator->frequency ||
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(unsigned long)new->drift < (unsigned long)time_interpolator->drift;
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}
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void
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register_time_interpolator(struct time_interpolator *ti)
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{
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unsigned long flags;
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/* Sanity check */
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BUG_ON(ti->frequency == 0 || ti->mask == 0);
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ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency;
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spin_lock(&time_interpolator_lock);
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write_seqlock_irqsave(&xtime_lock, flags);
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if (is_better_time_interpolator(ti)) {
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time_interpolator = ti;
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time_interpolator_reset();
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}
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write_sequnlock_irqrestore(&xtime_lock, flags);
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ti->next = time_interpolator_list;
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time_interpolator_list = ti;
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spin_unlock(&time_interpolator_lock);
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}
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void
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unregister_time_interpolator(struct time_interpolator *ti)
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{
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struct time_interpolator *curr, **prev;
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unsigned long flags;
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spin_lock(&time_interpolator_lock);
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prev = &time_interpolator_list;
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for (curr = *prev; curr; curr = curr->next) {
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if (curr == ti) {
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*prev = curr->next;
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break;
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}
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prev = &curr->next;
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}
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write_seqlock_irqsave(&xtime_lock, flags);
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if (ti == time_interpolator) {
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/* we lost the best time-interpolator: */
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time_interpolator = NULL;
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/* find the next-best interpolator */
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for (curr = time_interpolator_list; curr; curr = curr->next)
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if (is_better_time_interpolator(curr))
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time_interpolator = curr;
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time_interpolator_reset();
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}
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write_sequnlock_irqrestore(&xtime_lock, flags);
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spin_unlock(&time_interpolator_lock);
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}
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#endif /* CONFIG_TIME_INTERPOLATION */
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/**
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* msleep - sleep safely even with waitqueue interruptions
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* @msecs: Time in milliseconds to sleep for
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