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Commit 23970e38 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Thomas Gleixner
Browse files

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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.296703241@de.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent d4f587c6

arch/s390/kernel/time.c

+5 −12
Original line number Diff line number Diff line
@@ -187,6 +187,11 @@ void read_persistent_clock(struct timespec *ts) 
	tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, ts);

}



void read_boot_clock(struct timespec *ts)

{

	tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, ts);

}



static cycle_t read_tod_clock(struct clocksource *cs)

{

	return get_clock();
@@ -243,9 +248,6 @@ void update_vsyscall_tz(void) 
 */

void __init time_init(void)

{

	struct timespec ts;

	unsigned long flags;



	/* Reset time synchronization interfaces. */

	etr_reset();

	stp_reset();
@@ -261,15 +263,6 @@ void __init time_init(void) 
	if (clocksource_register(&clocksource_tod) != 0)

		panic("Could not register TOD clock source");



	/*

	 * Reset wall_to_monotonic to the initial timestamp created

	 * in head.S to get a precise value in /proc/uptime.

	 */

	write_seqlock_irqsave(&xtime_lock, flags);

	tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);

	set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);

	write_sequnlock_irqrestore(&xtime_lock, flags);



	/* Enable TOD clock interrupts on the boot cpu. */

	init_cpu_timer();

include/linux/time.h

+1 −0
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ extern struct timespec wall_to_monotonic; 
extern seqlock_t xtime_lock;



extern void read_persistent_clock(struct timespec *ts);

extern void read_boot_clock(struct timespec *ts);

extern int update_persistent_clock(struct timespec now);

extern int no_sync_cmos_clock __read_mostly;

void timekeeping_init(void);

kernel/time/timekeeping.c

+22 −2
Original line number Diff line number Diff line
@@ -501,6 +501,21 @@ void __attribute__((weak)) read_persistent_clock(struct timespec *ts) 
	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

 */
@@ -508,9 +523,10 @@ void __init timekeeping_init(void) 
{

	struct clocksource *clock;

	unsigned long flags;

	struct timespec now;

	struct timespec now, boot;



	read_persistent_clock(&now);

	read_boot_clock(&boot);



	write_seqlock_irqsave(&xtime_lock, flags);
@@ -525,8 +541,12 @@ void __init timekeeping_init(void) 
	xtime.tv_nsec = now.tv_nsec;

	raw_time.tv_sec = 0;

	raw_time.tv_nsec = 0;

	if (boot.tv_sec == 0 && boot.tv_nsec == 0) {

		boot.tv_sec = xtime.tv_sec;

		boot.tv_nsec = xtime.tv_nsec;

	}

	set_normalized_timespec(&wall_to_monotonic,

		-xtime.tv_sec, -xtime.tv_nsec);

				-boot.tv_sec, -boot.tv_nsec);

	update_xtime_cache(0);

	total_sleep_time.tv_sec = 0;

	total_sleep_time.tv_nsec = 0;