diff options
Diffstat (limited to 'kernel/time/timekeeping.c')
| -rw-r--r-- | kernel/time/timekeeping.c | 1280 |
1 files changed, 1280 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c new file mode 100644 index 00000000..2f7b1b42 --- /dev/null +++ b/kernel/time/timekeeping.c @@ -0,0 +1,1280 @@ +/* + * linux/kernel/time/timekeeping.c + * + * Kernel timekeeping code and accessor functions + * + * This code was moved from linux/kernel/timer.c. + * Please see that file for copyright and history logs. + * + */ + +#include <linux/module.h> +#include <linux/interrupt.h> +#include <linux/percpu.h> +#include <linux/init.h> +#include <linux/mm.h> +#include <linux/sched.h> +#include <linux/syscore_ops.h> +#include <linux/clocksource.h> +#include <linux/jiffies.h> +#include <linux/time.h> +#include <linux/tick.h> +#include <linux/stop_machine.h> + +/* Structure holding internal timekeeping values. */ +struct timekeeper { + /* Current clocksource used for timekeeping. */ + struct clocksource *clock; + /* NTP adjusted clock multiplier */ + u32 mult; + /* The shift value of the current clocksource. */ + int shift; + + /* Number of clock cycles in one NTP interval. */ + cycle_t cycle_interval; + /* Number of clock shifted nano seconds in one NTP interval. */ + u64 xtime_interval; + /* shifted nano seconds left over when rounding cycle_interval */ + s64 xtime_remainder; + /* Raw nano seconds accumulated per NTP interval. */ + u32 raw_interval; + + /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */ + u64 xtime_nsec; + /* Difference between accumulated time and NTP time in ntp + * shifted nano seconds. */ + s64 ntp_error; + /* Shift conversion between clock shifted nano seconds and + * ntp shifted nano seconds. */ + int ntp_error_shift; + + /* The current time */ + struct timespec xtime; + /* + * wall_to_monotonic is what we need to add to xtime (or xtime corrected + * for sub jiffie times) to get to monotonic time. Monotonic is pegged + * at zero at system boot time, so wall_to_monotonic will be negative, + * however, we will ALWAYS keep the tv_nsec part positive so we can use + * the usual normalization. + * + * wall_to_monotonic is moved after resume from suspend for the + * monotonic time not to jump. We need to add total_sleep_time to + * wall_to_monotonic to get the real boot based time offset. + * + * - wall_to_monotonic is no longer the boot time, getboottime must be + * used instead. + */ + struct timespec wall_to_monotonic; + /* time spent in suspend */ + struct timespec total_sleep_time; + /* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */ + struct timespec raw_time; + + /* Seqlock for all timekeeper values */ + seqlock_t lock; +}; + +static struct timekeeper timekeeper; + +/* + * This read-write spinlock protects us from races in SMP while + * playing with xtime. + */ +__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); + + +/* flag for if timekeeping is suspended */ +int __read_mostly timekeeping_suspended; + + + +/** + * timekeeper_setup_internals - Set up internals to use clocksource clock. + * + * @clock: Pointer to clocksource. + * + * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment + * pair and interval request. + * + * Unless you're the timekeeping code, you should not be using this! + */ +static void timekeeper_setup_internals(struct clocksource *clock) +{ + cycle_t interval; + u64 tmp, ntpinterval; + + timekeeper.clock = clock; + clock->cycle_last = clock->read(clock); + + /* Do the ns -> cycle conversion first, using original mult */ + tmp = NTP_INTERVAL_LENGTH; + tmp <<= clock->shift; + ntpinterval = tmp; + tmp += clock->mult/2; + do_div(tmp, clock->mult); + if (tmp == 0) + tmp = 1; + + interval = (cycle_t) tmp; + timekeeper.cycle_interval = interval; + + /* Go back from cycles -> shifted ns */ + timekeeper.xtime_interval = (u64) interval * clock->mult; + timekeeper.xtime_remainder = ntpinterval - timekeeper.xtime_interval; + timekeeper.raw_interval = + ((u64) interval * clock->mult) >> clock->shift; + + timekeeper.xtime_nsec = 0; + timekeeper.shift = clock->shift; + + timekeeper.ntp_error = 0; + timekeeper.ntp_error_shift = NTP_SCALE_SHIFT - clock->shift; + + /* + * The timekeeper keeps its own mult values for the currently + * active clocksource. These value will be adjusted via NTP + * to counteract clock drifting. + */ + timekeeper.mult = clock->mult; +} + +/* Timekeeper helper functions. */ +static inline s64 timekeeping_get_ns(void) +{ + cycle_t cycle_now, cycle_delta; + struct clocksource *clock; + + /* read clocksource: */ + clock = timekeeper.clock; + cycle_now = clock->read(clock); + + /* calculate the delta since the last update_wall_time: */ + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; + + /* return delta convert to nanoseconds using ntp adjusted mult. */ + return clocksource_cyc2ns(cycle_delta, timekeeper.mult, + timekeeper.shift); +} + +static inline s64 timekeeping_get_ns_raw(void) +{ + cycle_t cycle_now, cycle_delta; + struct clocksource *clock; + + /* read clocksource: */ + clock = timekeeper.clock; + cycle_now = clock->read(clock); + + /* calculate the delta since the last update_wall_time: */ + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; + + /* return delta convert to nanoseconds. */ + return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift); +} + +/* must hold write on timekeeper.lock */ +static void timekeeping_update(bool clearntp) +{ + if (clearntp) { + timekeeper.ntp_error = 0; + ntp_clear(); + } + update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic, + timekeeper.clock, timekeeper.mult); +} + + +/** + * timekeeping_forward_now - update clock to the current time + * + * Forward the current clock to update its state since the last call to + * update_wall_time(). This is useful before significant clock changes, + * as it avoids having to deal with this time offset explicitly. + */ +static void timekeeping_forward_now(void) +{ + cycle_t cycle_now, cycle_delta; + struct clocksource *clock; + s64 nsec; + + clock = timekeeper.clock; + cycle_now = clock->read(clock); + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; + clock->cycle_last = cycle_now; + + nsec = clocksource_cyc2ns(cycle_delta, timekeeper.mult, + timekeeper.shift); + + /* If arch requires, add in gettimeoffset() */ + nsec += arch_gettimeoffset(); + + timespec_add_ns(&timekeeper.xtime, nsec); + + nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift); + timespec_add_ns(&timekeeper.raw_time, nsec); +} + +/** + * getnstimeofday - Returns the time of day in a timespec + * @ts: pointer to the timespec to be set + * + * Returns the time of day in a timespec. + */ +void getnstimeofday(struct timespec *ts) +{ + unsigned long seq; + s64 nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&timekeeper.lock); + + *ts = timekeeper.xtime; + nsecs = timekeeping_get_ns(); + + /* If arch requires, add in gettimeoffset() */ + nsecs += arch_gettimeoffset(); + + } while (read_seqretry(&timekeeper.lock, seq)); + + timespec_add_ns(ts, nsecs); +} + +EXPORT_SYMBOL(getnstimeofday); + +ktime_t ktime_get(void) +{ + unsigned int seq; + s64 secs, nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&timekeeper.lock); + secs = timekeeper.xtime.tv_sec + + timekeeper.wall_to_monotonic.tv_sec; + nsecs = timekeeper.xtime.tv_nsec + + timekeeper.wall_to_monotonic.tv_nsec; + nsecs += timekeeping_get_ns(); + /* If arch requires, add in gettimeoffset() */ + nsecs += arch_gettimeoffset(); + + } while (read_seqretry(&timekeeper.lock, seq)); + /* + * Use ktime_set/ktime_add_ns to create a proper ktime on + * 32-bit architectures without CONFIG_KTIME_SCALAR. + */ + return ktime_add_ns(ktime_set(secs, 0), nsecs); +} +EXPORT_SYMBOL_GPL(ktime_get); + +/** + * ktime_get_ts - get the monotonic clock in timespec format + * @ts: pointer to timespec variable + * + * The function calculates the monotonic clock from the realtime + * clock and the wall_to_monotonic offset and stores the result + * in normalized timespec format in the variable pointed to by @ts. + */ +void ktime_get_ts(struct timespec *ts) +{ + struct timespec tomono; + unsigned int seq; + s64 nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&timekeeper.lock); + *ts = timekeeper.xtime; + tomono = timekeeper.wall_to_monotonic; + nsecs = timekeeping_get_ns(); + /* If arch requires, add in gettimeoffset() */ + nsecs += arch_gettimeoffset(); + + } while (read_seqretry(&timekeeper.lock, seq)); + + set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec, + ts->tv_nsec + tomono.tv_nsec + nsecs); +} +EXPORT_SYMBOL_GPL(ktime_get_ts); + +#ifdef CONFIG_NTP_PPS + +/** + * getnstime_raw_and_real - get day and raw monotonic time in timespec format + * @ts_raw: pointer to the timespec to be set to raw monotonic time + * @ts_real: pointer to the timespec to be set to the time of day + * + * This function reads both the time of day and raw monotonic time at the + * same time atomically and stores the resulting timestamps in timespec + * format. + */ +void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real) +{ + unsigned long seq; + s64 nsecs_raw, nsecs_real; + + WARN_ON_ONCE(timekeeping_suspended); + + do { + u32 arch_offset; + + seq = read_seqbegin(&timekeeper.lock); + + *ts_raw = timekeeper.raw_time; + *ts_real = timekeeper.xtime; + + nsecs_raw = timekeeping_get_ns_raw(); + nsecs_real = timekeeping_get_ns(); + + /* If arch requires, add in gettimeoffset() */ + arch_offset = arch_gettimeoffset(); + nsecs_raw += arch_offset; + nsecs_real += arch_offset; + + } while (read_seqretry(&timekeeper.lock, seq)); + + timespec_add_ns(ts_raw, nsecs_raw); + timespec_add_ns(ts_real, nsecs_real); +} +EXPORT_SYMBOL(getnstime_raw_and_real); + +#endif /* CONFIG_NTP_PPS */ + +/** + * do_gettimeofday - Returns the time of day in a timeval + * @tv: pointer to the timeval to be set + * + * NOTE: Users should be converted to using getnstimeofday() + */ +void do_gettimeofday(struct timeval *tv) +{ + struct timespec now; + + getnstimeofday(&now); + tv->tv_sec = now.tv_sec; + tv->tv_usec = now.tv_nsec/1000; +} + +EXPORT_SYMBOL(do_gettimeofday); +/** + * do_settimeofday - Sets the time of day + * @tv: pointer to the timespec variable containing the new time + * + * Sets the time of day to the new time and update NTP and notify hrtimers + */ +int do_settimeofday(const struct timespec *tv) +{ + struct timespec ts_delta; + unsigned long flags; + + if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) + return -EINVAL; + + write_seqlock_irqsave(&timekeeper.lock, flags); + + timekeeping_forward_now(); + + ts_delta.tv_sec = tv->tv_sec - timekeeper.xtime.tv_sec; + ts_delta.tv_nsec = tv->tv_nsec - timekeeper.xtime.tv_nsec; + timekeeper.wall_to_monotonic = + timespec_sub(timekeeper.wall_to_monotonic, ts_delta); + + timekeeper.xtime = *tv; + timekeeping_update(true); + + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + /* signal hrtimers about time change */ + clock_was_set(); + + return 0; +} + +EXPORT_SYMBOL(do_settimeofday); + + +/** + * timekeeping_inject_offset - Adds or subtracts from the current time. + * @tv: pointer to the timespec variable containing the offset + * + * Adds or subtracts an offset value from the current time. + */ +int timekeeping_inject_offset(struct timespec *ts) +{ + unsigned long flags; + + if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC) + return -EINVAL; + + write_seqlock_irqsave(&timekeeper.lock, flags); + + timekeeping_forward_now(); + + timekeeper.xtime = timespec_add(timekeeper.xtime, *ts); + timekeeper.wall_to_monotonic = + timespec_sub(timekeeper.wall_to_monotonic, *ts); + + timekeeping_update(true); + + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + /* signal hrtimers about time change */ + clock_was_set(); + + return 0; +} +EXPORT_SYMBOL(timekeeping_inject_offset); + +/** + * change_clocksource - Swaps clocksources if a new one is available + * + * Accumulates current time interval and initializes new clocksource + */ +static int change_clocksource(void *data) +{ + struct clocksource *new, *old; + unsigned long flags; + + new = (struct clocksource *) data; + + write_seqlock_irqsave(&timekeeper.lock, flags); + + timekeeping_forward_now(); + if (!new->enable || new->enable(new) == 0) { + old = timekeeper.clock; + timekeeper_setup_internals(new); + if (old->disable) + old->disable(old); + } + timekeeping_update(true); + + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + return 0; +} + +/** + * timekeeping_notify - Install a new clock source + * @clock: pointer to the clock source + * + * This function is called from clocksource.c after a new, better clock + * source has been registered. The caller holds the clocksource_mutex. + */ +void timekeeping_notify(struct clocksource *clock) +{ + if (timekeeper.clock == clock) + return; + stop_machine(change_clocksource, clock, NULL); + tick_clock_notify(); +} + +/** + * ktime_get_real - get the real (wall-) time in ktime_t format + * + * returns the time in ktime_t format + */ +ktime_t ktime_get_real(void) +{ + struct timespec now; + + getnstimeofday(&now); + + return timespec_to_ktime(now); +} +EXPORT_SYMBOL_GPL(ktime_get_real); + +/** + * getrawmonotonic - Returns the raw monotonic time in a timespec + * @ts: pointer to the timespec to be set + * + * Returns the raw monotonic time (completely un-modified by ntp) + */ +void getrawmonotonic(struct timespec *ts) +{ + unsigned long seq; + s64 nsecs; + + do { + seq = read_seqbegin(&timekeeper.lock); + nsecs = timekeeping_get_ns_raw(); + *ts = timekeeper.raw_time; + + } while (read_seqretry(&timekeeper.lock, seq)); + + timespec_add_ns(ts, nsecs); +} +EXPORT_SYMBOL(getrawmonotonic); + + +/** + * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres + */ +int timekeeping_valid_for_hres(void) +{ + unsigned long seq; + int ret; + + do { + seq = read_seqbegin(&timekeeper.lock); + + ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; + + } while (read_seqretry(&timekeeper.lock, seq)); + + return ret; +} + +/** + * timekeeping_max_deferment - Returns max time the clocksource can be deferred + */ +u64 timekeeping_max_deferment(void) +{ + unsigned long seq; + u64 ret; + do { + seq = read_seqbegin(&timekeeper.lock); + + ret = timekeeper.clock->max_idle_ns; + + } while (read_seqretry(&timekeeper.lock, seq)); + + return ret; +} + +/** + * read_persistent_clock - Return time from the persistent clock. + * + * Weak dummy function for arches that do not yet support it. + * Reads the time from the battery backed persistent clock. + * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported. + * + * XXX - Do be sure to remove it once all arches implement it. + */ +void __attribute__((weak)) read_persistent_clock(struct timespec *ts) +{ + ts->tv_sec = 0; + ts->tv_nsec = 0; +} + +/** + * read_boot_clock - Return time of the system start. + * + * Weak dummy function for arches that do not yet support it. + * Function to read the exact time the system has been started. + * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported. + * + * XXX - Do be sure to remove it once all arches implement it. + */ +void __attribute__((weak)) read_boot_clock(struct timespec *ts) +{ + ts->tv_sec = 0; + ts->tv_nsec = 0; +} + +/* + * timekeeping_init - Initializes the clocksource and common timekeeping values + */ +void __init timekeeping_init(void) +{ + struct clocksource *clock; + unsigned long flags; + struct timespec now, boot; + + read_persistent_clock(&now); + read_boot_clock(&boot); + + seqlock_init(&timekeeper.lock); + + ntp_init(); + + write_seqlock_irqsave(&timekeeper.lock, flags); + clock = clocksource_default_clock(); + if (clock->enable) + clock->enable(clock); + timekeeper_setup_internals(clock); + + timekeeper.xtime.tv_sec = now.tv_sec; + timekeeper.xtime.tv_nsec = now.tv_nsec; + timekeeper.raw_time.tv_sec = 0; + timekeeper.raw_time.tv_nsec = 0; + if (boot.tv_sec == 0 && boot.tv_nsec == 0) { + boot.tv_sec = timekeeper.xtime.tv_sec; + boot.tv_nsec = timekeeper.xtime.tv_nsec; + } + set_normalized_timespec(&timekeeper.wall_to_monotonic, + -boot.tv_sec, -boot.tv_nsec); + timekeeper.total_sleep_time.tv_sec = 0; + timekeeper.total_sleep_time.tv_nsec = 0; + write_sequnlock_irqrestore(&timekeeper.lock, flags); +} + +/* time in seconds when suspend began */ +static struct timespec timekeeping_suspend_time; + +/** + * __timekeeping_inject_sleeptime - Internal function to add sleep interval + * @delta: pointer to a timespec delta value + * + * Takes a timespec offset measuring a suspend interval and properly + * adds the sleep offset to the timekeeping variables. + */ +static void __timekeeping_inject_sleeptime(struct timespec *delta) +{ + if (!timespec_valid(delta)) { + printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid " + "sleep delta value!\n"); + return; + } + + timekeeper.xtime = timespec_add(timekeeper.xtime, *delta); + timekeeper.wall_to_monotonic = + timespec_sub(timekeeper.wall_to_monotonic, *delta); + timekeeper.total_sleep_time = timespec_add( + timekeeper.total_sleep_time, *delta); +} + + +/** + * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values + * @delta: pointer to a timespec delta value + * + * This hook is for architectures that cannot support read_persistent_clock + * because their RTC/persistent clock is only accessible when irqs are enabled. + * + * This function should only be called by rtc_resume(), and allows + * a suspend offset to be injected into the timekeeping values. + */ +void timekeeping_inject_sleeptime(struct timespec *delta) +{ + unsigned long flags; + struct timespec ts; + + /* Make sure we don't set the clock twice */ + read_persistent_clock(&ts); + if (!(ts.tv_sec == 0 && ts.tv_nsec == 0)) + return; + + write_seqlock_irqsave(&timekeeper.lock, flags); + + timekeeping_forward_now(); + + __timekeeping_inject_sleeptime(delta); + + timekeeping_update(true); + + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + /* signal hrtimers about time change */ + clock_was_set(); +} + + +/** + * timekeeping_resume - Resumes the generic timekeeping subsystem. + * + * This is for the generic clocksource timekeeping. + * xtime/wall_to_monotonic/jiffies/etc are + * still managed by arch specific suspend/resume code. + */ +static void timekeeping_resume(void) +{ + unsigned long flags; + struct timespec ts; + + read_persistent_clock(&ts); + + clocksource_resume(); + + write_seqlock_irqsave(&timekeeper.lock, flags); + + if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) { + ts = timespec_sub(ts, timekeeping_suspend_time); + __timekeeping_inject_sleeptime(&ts); + } + /* re-base the last cycle value */ + timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock); + timekeeper.ntp_error = 0; + timekeeping_suspended = 0; + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + touch_softlockup_watchdog(); + + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); + + /* Resume hrtimers */ + hrtimers_resume(); +} + +static int timekeeping_suspend(void) +{ + unsigned long flags; + struct timespec delta, delta_delta; + static struct timespec old_delta; + + read_persistent_clock(&timekeeping_suspend_time); + + write_seqlock_irqsave(&timekeeper.lock, flags); + timekeeping_forward_now(); + timekeeping_suspended = 1; + + /* + * To avoid drift caused by repeated suspend/resumes, + * which each can add ~1 second drift error, + * try to compensate so the difference in system time + * and persistent_clock time stays close to constant. + */ + delta = timespec_sub(timekeeper.xtime, timekeeping_suspend_time); + delta_delta = timespec_sub(delta, old_delta); + if (abs(delta_delta.tv_sec) >= 2) { + /* + * if delta_delta is too large, assume time correction + * has occured and set old_delta to the current delta. + */ + old_delta = delta; + } else { + /* Otherwise try to adjust old_system to compensate */ + timekeeping_suspend_time = + timespec_add(timekeeping_suspend_time, delta_delta); + } + write_sequnlock_irqrestore(&timekeeper.lock, flags); + + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); + clocksource_suspend(); + + return 0; +} + +/* sysfs resume/suspend bits for timekeeping */ +static struct syscore_ops timekeeping_syscore_ops = { + .resume = timekeeping_resume, + .suspend = timekeeping_suspend, +}; + +static int __init timekeeping_init_ops(void) +{ + register_syscore_ops(&timekeeping_syscore_ops); + return 0; +} + +device_initcall(timekeeping_init_ops); + +/* + * If the error is already larger, we look ahead even further + * to compensate for late or lost adjustments. + */ +static __always_inline int timekeeping_bigadjust(s64 error, s64 *interval, + s64 *offset) +{ + s64 tick_error, i; + u32 look_ahead, adj; + s32 error2, mult; + + /* + * Use the current error value to determine how much to look ahead. + * The larger the error the slower we adjust for it to avoid problems + * with losing too many ticks, otherwise we would overadjust and + * produce an even larger error. The smaller the adjustment the + * faster we try to adjust for it, as lost ticks can do less harm + * here. This is tuned so that an error of about 1 msec is adjusted + * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). + */ + error2 = timekeeper.ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ); + error2 = abs(error2); + for (look_ahead = 0; error2 > 0; look_ahead++) + error2 >>= 2; + + /* + * Now calculate the error in (1 << look_ahead) ticks, but first + * remove the single look ahead already included in the error. + */ + tick_error = ntp_tick_length() >> (timekeeper.ntp_error_shift + 1); + tick_error -= timekeeper.xtime_interval >> 1; + error = ((error - tick_error) >> look_ahead) + tick_error; + + /* Finally calculate the adjustment shift value. */ + i = *interval; + mult = 1; + if (error < 0) { + error = -error; + *interval = -*interval; + *offset = -*offset; + mult = -1; + } + for (adj = 0; error > i; adj++) + error >>= 1; + + *interval <<= adj; + *offset <<= adj; + return mult << adj; +} + +/* + * Adjust the multiplier to reduce the error value, + * this is optimized for the most common adjustments of -1,0,1, + * for other values we can do a bit more work. + */ +static void timekeeping_adjust(s64 offset) +{ + s64 error, interval = timekeeper.cycle_interval; + int adj; + + /* + * The point of this is to check if the error is greater than half + * an interval. + * + * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs. + * + * Note we subtract one in the shift, so that error is really error*2. + * This "saves" dividing(shifting) interval twice, but keeps the + * (error > interval) comparison as still measuring if error is + * larger than half an interval. + * + * Note: It does not "save" on aggravation when reading the code. + */ + error = timekeeper.ntp_error >> (timekeeper.ntp_error_shift - 1); + if (error > interval) { + /* + * We now divide error by 4(via shift), which checks if + * the error is greater than twice the interval. + * If it is greater, we need a bigadjust, if its smaller, + * we can adjust by 1. + */ + error >>= 2; + /* + * XXX - In update_wall_time, we round up to the next + * nanosecond, and store the amount rounded up into + * the error. This causes the likely below to be unlikely. + * + * The proper fix is to avoid rounding up by using + * the high precision timekeeper.xtime_nsec instead of + * xtime.tv_nsec everywhere. Fixing this will take some + * time. + */ + if (likely(error <= interval)) + adj = 1; + else + adj = timekeeping_bigadjust(error, &interval, &offset); + } else if (error < -interval) { + /* See comment above, this is just switched for the negative */ + error >>= 2; + if (likely(error >= -interval)) { + adj = -1; + interval = -interval; + offset = -offset; + } else + adj = timekeeping_bigadjust(error, &interval, &offset); + } else /* No adjustment needed */ + return; + + if (unlikely(timekeeper.clock->maxadj && + (timekeeper.mult + adj > + timekeeper.clock->mult + timekeeper.clock->maxadj))) { + printk_once(KERN_WARNING + "Adjusting %s more than 11%% (%ld vs %ld)\n", + timekeeper.clock->name, (long)timekeeper.mult + adj, + (long)timekeeper.clock->mult + + timekeeper.clock->maxadj); + } + /* + * So the following can be confusing. + * + * To keep things simple, lets assume adj == 1 for now. + * + * When adj != 1, remember that the interval and offset values + * have been appropriately scaled so the math is the same. + * + * The basic idea here is that we're increasing the multiplier + * by one, this causes the xtime_interval to be incremented by + * one cycle_interval. This is because: + * xtime_interval = cycle_interval * mult + * So if mult is being incremented by one: + * xtime_interval = cycle_interval * (mult + 1) + * Its the same as: + * xtime_interval = (cycle_interval * mult) + cycle_interval + * Which can be shortened to: + * xtime_interval += cycle_interval + * + * So offset stores the non-accumulated cycles. Thus the current + * time (in shifted nanoseconds) is: + * now = (offset * adj) + xtime_nsec + * Now, even though we're adjusting the clock frequency, we have + * to keep time consistent. In other words, we can't jump back + * in time, and we also want to avoid jumping forward in time. + * + * So given the same offset value, we need the time to be the same + * both before and after the freq adjustment. + * now = (offset * adj_1) + xtime_nsec_1 + * now = (offset * adj_2) + xtime_nsec_2 + * So: + * (offset * adj_1) + xtime_nsec_1 = + * (offset * adj_2) + xtime_nsec_2 + * And we know: + * adj_2 = adj_1 + 1 + * So: + * (offset * adj_1) + xtime_nsec_1 = + * (offset * (adj_1+1)) + xtime_nsec_2 + * (offset * adj_1) + xtime_nsec_1 = + * (offset * adj_1) + offset + xtime_nsec_2 + * Canceling the sides: + * xtime_nsec_1 = offset + xtime_nsec_2 + * Which gives us: + * xtime_nsec_2 = xtime_nsec_1 - offset + * Which simplfies to: + * xtime_nsec -= offset + * + * XXX - TODO: Doc ntp_error calculation. + */ + timekeeper.mult += adj; + timekeeper.xtime_interval += interval; + timekeeper.xtime_nsec -= offset; + timekeeper.ntp_error -= (interval - offset) << + timekeeper.ntp_error_shift; +} + + +/** + * logarithmic_accumulation - shifted accumulation of cycles + * + * This functions accumulates a shifted interval of cycles into + * into a shifted interval nanoseconds. Allows for O(log) accumulation + * loop. + * + * Returns the unconsumed cycles. + */ +static cycle_t logarithmic_accumulation(cycle_t offset, int shift) +{ + u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift; + u64 raw_nsecs; + + /* If the offset is smaller than a shifted interval, do nothing */ + if (offset < timekeeper.cycle_interval<<shift) + return offset; + + /* Accumulate one shifted interval */ + offset -= timekeeper.cycle_interval << shift; + timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift; + + timekeeper.xtime_nsec += timekeeper.xtime_interval << shift; + while (timekeeper.xtime_nsec >= nsecps) { + int leap; + timekeeper.xtime_nsec -= nsecps; + timekeeper.xtime.tv_sec++; + leap = second_overflow(timekeeper.xtime.tv_sec); + timekeeper.xtime.tv_sec += leap; + timekeeper.wall_to_monotonic.tv_sec -= leap; + } + + /* Accumulate raw time */ + raw_nsecs = timekeeper.raw_interval << shift; + raw_nsecs += timekeeper.raw_time.tv_nsec; + if (raw_nsecs >= NSEC_PER_SEC) { + u64 raw_secs = raw_nsecs; + raw_nsecs = do_div(raw_secs, NSEC_PER_SEC); + timekeeper.raw_time.tv_sec += raw_secs; + } + timekeeper.raw_time.tv_nsec = raw_nsecs; + + /* Accumulate error between NTP and clock interval */ + timekeeper.ntp_error += ntp_tick_length() << shift; + timekeeper.ntp_error -= + (timekeeper.xtime_interval + timekeeper.xtime_remainder) << + (timekeeper.ntp_error_shift + shift); + + return offset; +} + + +/** + * update_wall_time - Uses the current clocksource to increment the wall time + * + */ +static void update_wall_time(void) +{ + struct clocksource *clock; + cycle_t offset; + int shift = 0, maxshift; + unsigned long flags; + + write_seqlock_irqsave(&timekeeper.lock, flags); + + /* Make sure we're fully resumed: */ + if (unlikely(timekeeping_suspended)) + goto out; + + clock = timekeeper.clock; + +#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET + offset = timekeeper.cycle_interval; +#else + offset = (clock->read(clock) - clock->cycle_last) & clock->mask; +#endif + timekeeper.xtime_nsec = (s64)timekeeper.xtime.tv_nsec << + timekeeper.shift; + + /* + * With NO_HZ we may have to accumulate many cycle_intervals + * (think "ticks") worth of time at once. To do this efficiently, + * we calculate the largest doubling multiple of cycle_intervals + * that is smaller than the offset. We then accumulate that + * chunk in one go, and then try to consume the next smaller + * doubled multiple. + */ + shift = ilog2(offset) - ilog2(timekeeper.cycle_interval); + shift = max(0, shift); + /* Bound shift to one less than what overflows tick_length */ + maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1; + shift = min(shift, maxshift); + while (offset >= timekeeper.cycle_interval) { + offset = logarithmic_accumulation(offset, shift); + if(offset < timekeeper.cycle_interval<<shift) + shift--; + } + + /* correct the clock when NTP error is too big */ + timekeeping_adjust(offset); + + /* + * Since in the loop above, we accumulate any amount of time + * in xtime_nsec over a second into xtime.tv_sec, its possible for + * xtime_nsec to be fairly small after the loop. Further, if we're + * slightly speeding the clocksource up in timekeeping_adjust(), + * its possible the required corrective factor to xtime_nsec could + * cause it to underflow. + * + * Now, we cannot simply roll the accumulated second back, since + * the NTP subsystem has been notified via second_overflow. So + * instead we push xtime_nsec forward by the amount we underflowed, + * and add that amount into the error. + * + * We'll correct this error next time through this function, when + * xtime_nsec is not as small. + */ + if (unlikely((s64)timekeeper.xtime_nsec < 0)) { + s64 neg = -(s64)timekeeper.xtime_nsec; + timekeeper.xtime_nsec = 0; + timekeeper.ntp_error += neg << timekeeper.ntp_error_shift; + } + + + /* + * Store full nanoseconds into xtime after rounding it up and + * add the remainder to the error difference. + */ + timekeeper.xtime.tv_nsec = ((s64)timekeeper.xtime_nsec >> + timekeeper.shift) + 1; + timekeeper.xtime_nsec -= (s64)timekeeper.xtime.tv_nsec << + timekeeper.shift; + timekeeper.ntp_error += timekeeper.xtime_nsec << + timekeeper.ntp_error_shift; + + /* + * Finally, make sure that after the rounding + * xtime.tv_nsec isn't larger than NSEC_PER_SEC + */ + if (unlikely(timekeeper.xtime.tv_nsec >= NSEC_PER_SEC)) { + int leap; + timekeeper.xtime.tv_nsec -= NSEC_PER_SEC; + timekeeper.xtime.tv_sec++; + leap = second_overflow(timekeeper.xtime.tv_sec); + timekeeper.xtime.tv_sec += leap; + timekeeper.wall_to_monotonic.tv_sec -= leap; + } + + timekeeping_update(false); + +out: + write_sequnlock_irqrestore(&timekeeper.lock, flags); + +} + +/** + * getboottime - Return the real time of system boot. + * @ts: pointer to the timespec to be set + * + * Returns the wall-time of boot in a timespec. + * + * This is based on the wall_to_monotonic offset and the total suspend + * time. Calls to settimeofday will affect the value returned (which + * basically means that however wrong your real time clock is at boot time, + * you get the right time here). + */ +void getboottime(struct timespec *ts) +{ + struct timespec boottime = { + .tv_sec = timekeeper.wall_to_monotonic.tv_sec + + timekeeper.total_sleep_time.tv_sec, + .tv_nsec = timekeeper.wall_to_monotonic.tv_nsec + + timekeeper.total_sleep_time.tv_nsec + }; + + set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec); +} +EXPORT_SYMBOL_GPL(getboottime); + + +/** + * get_monotonic_boottime - Returns monotonic time since boot + * @ts: pointer to the timespec to be set + * + * Returns the monotonic time since boot in a timespec. + * + * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also + * includes the time spent in suspend. + */ +void get_monotonic_boottime(struct timespec *ts) +{ + struct timespec tomono, sleep; + unsigned int seq; + s64 nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&timekeeper.lock); + *ts = timekeeper.xtime; + tomono = timekeeper.wall_to_monotonic; + sleep = timekeeper.total_sleep_time; + nsecs = timekeeping_get_ns(); + + } while (read_seqretry(&timekeeper.lock, seq)); + + set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec, + (s64)ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs); +} +EXPORT_SYMBOL_GPL(get_monotonic_boottime); + +/** + * ktime_get_boottime - Returns monotonic time since boot in a ktime + * + * Returns the monotonic time since boot in a ktime + * + * This is similar to CLOCK_MONTONIC/ktime_get, but also + * includes the time spent in suspend. + */ +ktime_t ktime_get_boottime(void) +{ + struct timespec ts; + + get_monotonic_boottime(&ts); + return timespec_to_ktime(ts); +} +EXPORT_SYMBOL_GPL(ktime_get_boottime); + +/** + * monotonic_to_bootbased - Convert the monotonic time to boot based. + * @ts: pointer to the timespec to be converted + */ +void monotonic_to_bootbased(struct timespec *ts) +{ + *ts = timespec_add(*ts, timekeeper.total_sleep_time); +} +EXPORT_SYMBOL_GPL(monotonic_to_bootbased); + +unsigned long get_seconds(void) +{ + return timekeeper.xtime.tv_sec; +} +EXPORT_SYMBOL(get_seconds); + +struct timespec __current_kernel_time(void) +{ + return timekeeper.xtime; +} + +struct timespec current_kernel_time(void) +{ + struct timespec now; + unsigned long seq; + + do { + seq = read_seqbegin(&timekeeper.lock); + + now = timekeeper.xtime; + } while (read_seqretry(&timekeeper.lock, seq)); + + return now; +} +EXPORT_SYMBOL(current_kernel_time); + +struct timespec get_monotonic_coarse(void) +{ + struct timespec now, mono; + unsigned long seq; + + do { + seq = read_seqbegin(&timekeeper.lock); + + now = timekeeper.xtime; + mono = timekeeper.wall_to_monotonic; + } while (read_seqretry(&timekeeper.lock, seq)); + + set_normalized_timespec(&now, now.tv_sec + mono.tv_sec, + now.tv_nsec + mono.tv_nsec); + return now; +} + +/* + * The 64-bit jiffies value is not atomic - you MUST NOT read it + * without sampling the sequence number in xtime_lock. + * jiffies is defined in the linker script... + */ +void do_timer(unsigned long ticks) +{ + jiffies_64 += ticks; + update_wall_time(); + calc_global_load(ticks); +} + +/** + * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic, + * and sleep offsets. + * @xtim: pointer to timespec to be set with xtime + * @wtom: pointer to timespec to be set with wall_to_monotonic + * @sleep: pointer to timespec to be set with time in suspend + */ +void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim, + struct timespec *wtom, struct timespec *sleep) +{ + unsigned long seq; + + do { + seq = read_seqbegin(&timekeeper.lock); + *xtim = timekeeper.xtime; + *wtom = timekeeper.wall_to_monotonic; + *sleep = timekeeper.total_sleep_time; + } while (read_seqretry(&timekeeper.lock, seq)); +} + +/** + * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format + */ +ktime_t ktime_get_monotonic_offset(void) +{ + unsigned long seq; + struct timespec wtom; + + do { + seq = read_seqbegin(&timekeeper.lock); + wtom = timekeeper.wall_to_monotonic; + } while (read_seqretry(&timekeeper.lock, seq)); + + return timespec_to_ktime(wtom); +} +EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset); + + +/** + * xtime_update() - advances the timekeeping infrastructure + * @ticks: number of ticks, that have elapsed since the last call. + * + * Must be called with interrupts disabled. + */ +void xtime_update(unsigned long ticks) +{ + write_seqlock(&xtime_lock); + do_timer(ticks); + write_sequnlock(&xtime_lock); +} |