timekeeping: Introduce read_boot_clock
Add the new function read_boot_clock to get the exact time the system has been started. For architectures without support for exact boot time a new weak function is added that returns 0. Use the exact boot time to initialize wall_to_monotonic, or xtime if the read_boot_clock returned 0. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: John Stultz <johnstul@us.ibm.com> Cc: Daniel Walker <dwalker@fifo99.com> LKML-Reference: <20090814134811.296703241@de.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -187,6 +187,11 @@ void read_persistent_clock(struct timespec *ts)
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tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, ts);
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}
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void read_boot_clock(struct timespec *ts)
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{
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tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, ts);
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}
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static cycle_t read_tod_clock(struct clocksource *cs)
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{
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return get_clock();
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@ -243,9 +248,6 @@ void update_vsyscall_tz(void)
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*/
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void __init time_init(void)
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{
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struct timespec ts;
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unsigned long flags;
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/* Reset time synchronization interfaces. */
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etr_reset();
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stp_reset();
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@ -261,15 +263,6 @@ void __init time_init(void)
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if (clocksource_register(&clocksource_tod) != 0)
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panic("Could not register TOD clock source");
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/*
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* Reset wall_to_monotonic to the initial timestamp created
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* in head.S to get a precise value in /proc/uptime.
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*/
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write_seqlock_irqsave(&xtime_lock, flags);
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tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
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set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
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write_sequnlock_irqrestore(&xtime_lock, flags);
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/* Enable TOD clock interrupts on the boot cpu. */
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init_cpu_timer();
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@ -102,6 +102,7 @@ extern struct timespec wall_to_monotonic;
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extern seqlock_t xtime_lock;
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extern void read_persistent_clock(struct timespec *ts);
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extern void read_boot_clock(struct timespec *ts);
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extern int update_persistent_clock(struct timespec now);
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extern int no_sync_cmos_clock __read_mostly;
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void timekeeping_init(void);
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@ -501,6 +501,21 @@ void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
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ts->tv_nsec = 0;
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}
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/**
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* read_boot_clock - Return time of the system start.
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*
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* Weak dummy function for arches that do not yet support it.
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* Function to read the exact time the system has been started.
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* Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
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*
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* XXX - Do be sure to remove it once all arches implement it.
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*/
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void __attribute__((weak)) read_boot_clock(struct timespec *ts)
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{
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ts->tv_sec = 0;
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ts->tv_nsec = 0;
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}
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/*
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* timekeeping_init - Initializes the clocksource and common timekeeping values
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*/
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@ -508,9 +523,10 @@ void __init timekeeping_init(void)
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{
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struct clocksource *clock;
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unsigned long flags;
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struct timespec now;
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struct timespec now, boot;
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read_persistent_clock(&now);
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read_boot_clock(&boot);
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write_seqlock_irqsave(&xtime_lock, flags);
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@ -525,8 +541,12 @@ void __init timekeeping_init(void)
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xtime.tv_nsec = now.tv_nsec;
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raw_time.tv_sec = 0;
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raw_time.tv_nsec = 0;
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if (boot.tv_sec == 0 && boot.tv_nsec == 0) {
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boot.tv_sec = xtime.tv_sec;
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boot.tv_nsec = xtime.tv_nsec;
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}
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set_normalized_timespec(&wall_to_monotonic,
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-xtime.tv_sec, -xtime.tv_nsec);
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-boot.tv_sec, -boot.tv_nsec);
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update_xtime_cache(0);
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total_sleep_time.tv_sec = 0;
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total_sleep_time.tv_nsec = 0;
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