/* * 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 #include #include #include #include #include #include #include #include #include #include #include /* 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; /* Offset clock monotonic -> clock realtime */ ktime_t offs_real; /* Offset clock monotonic -> clock boottime */ ktime_t offs_boot; /* 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); } static void update_rt_offset(void) { struct timespec tmp, *wtm = &timekeeper.wall_to_monotonic; set_normalized_timespec(&tmp, -wtm->tv_sec, -wtm->tv_nsec); timekeeper.offs_real = timespec_to_ktime(tmp); } /* must hold write on timekeeper.lock */ static void timekeeping_update(bool clearntp) { if (clearntp) { timekeeper.ntp_error = 0; ntp_clear(); } update_rt_offset(); 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); update_rt_offset(); 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; static void update_sleep_time(struct timespec t) { timekeeper.total_sleep_time = t; timekeeper.offs_boot = timespec_to_ktime(t); } /** * __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); update_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<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; if (leap) clock_was_set_delayed(); } /* 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<> 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; if (leap) clock_was_set_delayed(); } 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, 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)); } #ifdef CONFIG_HIGH_RES_TIMERS /** * ktime_get_update_offsets - hrtimer helper * @offs_real: pointer to storage for monotonic -> realtime offset * @offs_boot: pointer to storage for monotonic -> boottime offset * * Returns current monotonic time and updates the offsets * Called from hrtimer_interupt() or retrigger_next_event() */ ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot) { ktime_t now; unsigned int seq; u64 secs, nsecs; do { seq = read_seqbegin(&timekeeper.lock); secs = timekeeper.xtime.tv_sec; nsecs = timekeeper.xtime.tv_nsec; nsecs += timekeeping_get_ns(); /* If arch requires, add in gettimeoffset() */ nsecs += arch_gettimeoffset(); *offs_real = timekeeper.offs_real; *offs_boot = timekeeper.offs_boot; } while (read_seqretry(&timekeeper.lock, seq)); now = ktime_add_ns(ktime_set(secs, 0), nsecs); now = ktime_sub(now, *offs_real); return now; } #endif /** * 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); }