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/*
* 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.
*/
__cacheline_aligned_in_smp DEFINE_SEQLOCK(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 */
static struct timespec xtime_cache __attribute__ ((aligned (16)));
void update_xtime_cache(u64 nsec)
{
xtime_cache = xtime;
timespec_add_ns(&xtime_cache, nsec);
}
struct clocksource *clock;
#ifdef CONFIG_GENERIC_TIME
/**
* clocksource_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 clocksource_forward_now(void)
{
cycle_t cycle_now, cycle_delta;
s64 nsec;
cycle_now = clocksource_read(clock);
cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
clock->cycle_last = cycle_now;
nsec = cyc2ns(clock, cycle_delta);
timespec_add_ns(&xtime, nsec);
nsec = ((s64)cycle_delta * clock->mult_orig) >> clock->shift;
clock->raw_time.tv_nsec += 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)
{
cycle_t cycle_now, cycle_delta;
unsigned long seq;
s64 nsecs;
do {
seq = read_seqbegin(&xtime_lock);
*ts = xtime;
/* 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: */
nsecs = cyc2ns(clock, cycle_delta);
} while (read_seqretry(&xtime_lock, seq));
timespec_add_ns(ts, nsecs);
}
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 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(struct timespec *tv)
{
struct timespec ts_delta;
unsigned long flags;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irqsave(&xtime_lock, flags);
clocksource_forward_now();
ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec;
ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec;
wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta);
xtime = *tv;
update_xtime_cache(0);
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;
new = clocksource_get_next();
if (clock == new)
return;
clocksource_forward_now();
new->raw_time = clock->raw_time;
clock = new;
clock->cycle_last = 0;
clock->cycle_last = clocksource_read(new);
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
tick_clock_notify();
/*
* We're holding xtime lock and waking up klogd would deadlock
* us on enqueue. So no printing!
printk(KERN_INFO "Time: %s clocksource has been installed.\n",
clock->name);
*/
}
#else
static inline void clocksource_forward_now(void) { }
static inline void change_clocksource(void) { }
#endif
/**
* 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;
cycle_t cycle_now, cycle_delta;
do {
seq = read_seqbegin(&xtime_lock);
/* 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: */
nsecs = ((s64)cycle_delta * clock->mult_orig) >> clock->shift;
*ts = clock->raw_time;
} while (read_seqretry(&xtime_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(&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_init();
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);
update_xtime_cache(0);
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 =
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