| /* |
| * 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/sysdev.h> |
| #include <linux/clocksource.h> |
| #include <linux/jiffies.h> |
| #include <linux/time.h> |
| #include <linux/tick.h> |
| |
| |
| /* |
| * This read-write spinlock protects us from races in SMP while |
| * playing with xtime and avenrun. |
| */ |
| __attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); |
| |
| EXPORT_SYMBOL(xtime_lock); |
| |
| |
| /* |
| * The current time |
| * 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 xtime __attribute__ ((aligned (16))); |
| struct timespec wall_to_monotonic __attribute__ ((aligned (16))); |
| static unsigned long total_sleep_time; /* seconds */ |
| |
| EXPORT_SYMBOL(xtime); |
| |
| |
| static struct clocksource *clock; /* pointer to current clocksource */ |
| |
| |
| #ifdef CONFIG_GENERIC_TIME |
| /** |
| * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook |
| * |
| * private function, must hold xtime_lock lock when being |
| * called. Returns the number of nanoseconds since the |
| * last call to update_wall_time() (adjusted by NTP scaling) |
| */ |
| static inline s64 __get_nsec_offset(void) |
| { |
| cycle_t cycle_now, cycle_delta; |
| s64 ns_offset; |
| |
| /* read clocksource: */ |
| cycle_now = clocksource_read(clock); |
| |
| /* calculate the delta since the last update_wall_time: */ |
| cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; |
| |
| /* convert to nanoseconds: */ |
| ns_offset = cyc2ns(clock, cycle_delta); |
| |
| return ns_offset; |
| } |
| |
| /** |
| * __get_realtime_clock_ts - Returns the time of day in a timespec |
| * @ts: pointer to the timespec to be set |
| * |
| * Returns the time of day in a timespec. Used by |
| * do_gettimeofday() and get_realtime_clock_ts(). |
| */ |
| static inline void __get_realtime_clock_ts(struct timespec *ts) |
| { |
| unsigned long seq; |
| s64 nsecs; |
| |
| do { |
| seq = read_seqbegin(&xtime_lock); |
| |
| *ts = xtime; |
| nsecs = __get_nsec_offset(); |
| |
| } while (read_seqretry(&xtime_lock, seq)); |
| |
| timespec_add_ns(ts, nsecs); |
| } |
| |
| /** |
| * 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) |
| { |
| __get_realtime_clock_ts(ts); |
| } |
| |
| EXPORT_SYMBOL(getnstimeofday); |
| |
| /** |
| * 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 get_realtime_clock_ts() |
| */ |
| void do_gettimeofday(struct timeval *tv) |
| { |
| struct timespec now; |
| |
| __get_realtime_clock_ts(&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(struct timespec *tv) |
| { |
| unsigned long flags; |
| time_t wtm_sec, sec = tv->tv_sec; |
| long wtm_nsec, nsec = tv->tv_nsec; |
| |
| if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) |
| return -EINVAL; |
| |
| write_seqlock_irqsave(&xtime_lock, flags); |
| |
| nsec -= __get_nsec_offset(); |
| |
| wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); |
| wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); |
| |
| set_normalized_timespec(&xtime, sec, nsec); |
| set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); |
| |
| clock->error = 0; |
| ntp_clear(); |
| |
| update_vsyscall(&xtime, clock); |
| |
| write_sequnlock_irqrestore(&xtime_lock, flags); |
| |
| /* signal hrtimers about time change */ |
| clock_was_set(); |
| |
| return 0; |
| } |
| |
| EXPORT_SYMBOL(do_settimeofday); |
| |
| /** |
| * change_clocksource - Swaps clocksources if a new one is available |
| * |
| * Accumulates current time interval and initializes new clocksource |
| */ |
| static void change_clocksource(void) |
| { |
| struct clocksource *new; |
| cycle_t now; |
| u64 nsec; |
| |
| new = clocksource_get_next(); |
| |
| if (clock == new) |
| return; |
| |
| now = clocksource_read(new); |
| nsec = __get_nsec_offset(); |
| timespec_add_ns(&xtime, nsec); |
| |
| clock = new; |
| clock->cycle_last = now; |
| |
| clock->error = 0; |
| clock->xtime_nsec = 0; |
| clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); |
| |
| tick_clock_notify(); |
| |
| printk(KERN_INFO "Time: %s clocksource has been installed.\n", |
| clock->name); |
| } |
| #else |
| static inline void change_clocksource(void) { } |
| #endif |
| |
| /** |
| * timekeeping_is_continuous - check to see if timekeeping is free running |
| */ |
| int timekeeping_is_continuous(void) |
| { |
| unsigned long seq; |
| int ret; |
| |
| do { |
| seq = read_seqbegin(&xtime_lock); |
| |
| ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; |
| |
| } while (read_seqretry(&xtime_lock, seq)); |
| |
| return ret; |
| } |
| |
| /** |
| * read_persistent_clock - Return time in seconds from the persistent clock. |
| * |
| * Weak dummy function for arches that do not yet support it. |
| * Returns seconds from epoch using the battery backed persistent clock. |
| * Returns zero if unsupported. |
| * |
| * XXX - Do be sure to remove it once all arches implement it. |
| */ |
| unsigned long __attribute__((weak)) read_persistent_clock(void) |
| { |
| return 0; |
| } |
| |
| /* |
| * timekeeping_init - Initializes the clocksource and common timekeeping values |
| */ |
| void __init timekeeping_init(void) |
| { |
| unsigned long flags; |
| unsigned long sec = read_persistent_clock(); |
| |
| write_seqlock_irqsave(&xtime_lock, flags); |
| |
| ntp_clear(); |
| |
| clock = clocksource_get_next(); |
| clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); |
| clock->cycle_last = clocksource_read(clock); |
| |
| xtime.tv_sec = sec; |
| xtime.tv_nsec = 0; |
| set_normalized_timespec(&wall_to_monotonic, |
| -xtime.tv_sec, -xtime.tv_nsec); |
| total_sleep_time = 0; |
| |
| write_sequnlock_irqrestore(&xtime_lock, flags); |
| } |
| |
| /* flag for if timekeeping is suspended */ |
| static int timekeeping_suspended; |
| /* time in seconds when suspend began */ |
| static unsigned long timekeeping_suspend_time; |
| |
| /** |
| * timekeeping_resume - Resumes the generic timekeeping subsystem. |
| * @dev: unused |
| * |
| * This is for the generic clocksource timekeeping. |
| * xtime/wall_to_monotonic/jiffies/etc are |
| * still managed by arch specific suspend/resume code. |
| */ |
| static int timekeeping_resume(struct sys_device *dev) |
| { |
| unsigned long flags; |
| unsigned long now = read_persistent_clock(); |
| |
| clocksource_resume(); |
| |
| write_seqlock_irqsave(&xtime_lock, flags); |
| |
| if (now && (now > timekeeping_suspend_time)) { |
| unsigned long sleep_length = now - timekeeping_suspend_time; |
| |
| xtime.tv_sec += sleep_length; |
| wall_to_monotonic.tv_sec -= sleep_length; |
| total_sleep_time += sleep_length; |
| } |
| /* re-base the last cycle value */ |
| clock->cycle_last = clocksource_read(clock); |
| clock->error = 0; |
| timekeeping_suspended = 0; |
| write_sequnlock_irqrestore(&xtime_lock, flags); |
| |
| touch_softlockup_watchdog(); |
| |
| clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); |
| |
| /* Resume hrtimers */ |
| hres_timers_resume(); |
| |
| return 0; |
| } |
| |
| static int timekeeping_suspend(struct sys_device *dev, pm_message_t state) |
| { |
| unsigned long flags; |
| |
| write_seqlock_irqsave(&xtime_lock, flags); |
| timekeeping_suspended = 1; |
| timekeeping_suspend_time = read_persistent_clock(); |
| write_sequnlock_irqrestore(&xtime_lock, flags); |
| |
| clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); |
| |
| return 0; |
| } |
| |
| /* sysfs resume/suspend bits for timekeeping */ |
| static struct sysdev_class timekeeping_sysclass = { |
| .resume = timekeeping_resume, |
| .suspend = timekeeping_suspend, |
| set_kset_name("timekeeping"), |
| }; |
| |
| static struct sys_device device_timer = { |
| .id = 0, |
| .cls = &timekeeping_sysclass, |
| }; |
| |
| static int __init timekeeping_init_device(void) |
| { |
| int error = sysdev_class_register(&timekeeping_sysclass); |
| if (!error) |
| error = sysdev_register(&device_timer); |
| return error; |
| } |
| |
| device_initcall(timekeeping_init_device); |
| |
| /* |
| * If the error is already larger, we look ahead even further |
| * to compensate for late or lost adjustments. |
| */ |
| static __always_inline int clocksource_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 adusted |
| * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). |
| */ |
| error2 = clock->error >> (TICK_LENGTH_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 = current_tick_length() >> |
| (TICK_LENGTH_SHIFT - clock->shift + 1); |
| tick_error -= clock->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 clocksource_adjust(struct clocksource *clock, s64 offset) |
| { |
| s64 error, interval = clock->cycle_interval; |
| int adj; |
| |
| error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1); |
| if (error > interval) { |
| error >>= 2; |
| if (likely(error <= interval)) |
| adj = 1; |
| else |
| adj = clocksource_bigadjust(error, &interval, &offset); |
| } else if (error < -interval) { |
| error >>= 2; |
| if (likely(error >= -interval)) { |
| adj = -1; |
| interval = -interval; |
| offset = -offset; |
| } else |
| adj = clocksource_bigadjust(error, &interval, &offset); |
| } else |
| return; |
| |
| clock->mult += adj; |
| clock->xtime_interval += interval; |
| clock->xtime_nsec -= offset; |
| clock->error -= (interval - offset) << |
| (TICK_LENGTH_SHIFT - clock->shift); |
| } |
| |
| /** |
| * update_wall_time - Uses the current clocksource to increment the wall time |
| * |
| * Called from the timer interrupt, must hold a write on xtime_lock. |
| */ |
| void update_wall_time(void) |
| { |
| cycle_t offset; |
| |
| /* Make sure we're fully resumed: */ |
| if (unlikely(timekeeping_suspended)) |
| return; |
| |
| #ifdef CONFIG_GENERIC_TIME |
| offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask; |
| #else |
| offset = clock->cycle_interval; |
| #endif |
| clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift; |
| |
| /* normally this loop will run just once, however in the |
| * case of lost or late ticks, it will accumulate correctly. |
| */ |
| while (offset >= clock->cycle_interval) { |
| /* accumulate one interval */ |
| clock->xtime_nsec += clock->xtime_interval; |
| clock->cycle_last += clock->cycle_interval; |
| offset -= clock->cycle_interval; |
| |
| if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) { |
| clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift; |
| xtime.tv_sec++; |
| second_overflow(); |
| } |
| |
| /* accumulate error between NTP and clock interval */ |
| clock->error += current_tick_length(); |
| clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift); |
| } |
| |
| /* correct the clock when NTP error is too big */ |
| clocksource_adjust(clock, offset); |
| |
| /* store full nanoseconds into xtime */ |
| xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift; |
| clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift; |
| |
| /* check to see if there is a new clocksource to use */ |
| change_clocksource(); |
| update_vsyscall(&xtime, clock); |
| } |
| |
| /** |
| * getboottime - Return the real time of system boot. |
| * @ts: pointer to the timespec to be set |
| * |
| * Returns the time of day 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) |
| { |
| set_normalized_timespec(ts, |
| - (wall_to_monotonic.tv_sec + total_sleep_time), |
| - wall_to_monotonic.tv_nsec); |
| } |
| |
| /** |
| * 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->tv_sec += total_sleep_time; |
| } |