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Commit 4614e6ad authored by Magnus Damm's avatar Magnus Damm Committed by Linus Torvalds
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clocksource: add enable() and disable() callbacks 



Add enable() and disable() callbacks for clocksources.

This allows us to put unused clocksources in power save mode.  The
functions clocksource_enable() and clocksource_disable() wrap the
callbacks and are inserted in the timekeeping code to enable before use
and disable after switching to a new clocksource.

Signed-off-by: default avatarMagnus Damm <damm@igel.co.jp>
Acked-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8e19608e

include/linux/clocksource.h

+31 −0
Original line number Diff line number Diff line
@@ -144,6 +144,8 @@ extern u64 timecounter_cyc2time(struct timecounter *tc, 
 *				The ideal clocksource. A must-use where

 *				available.

 * @read:		returns a cycle value, passes clocksource as argument

 * @enable:		optional function to enable the clocksource

 * @disable:		optional function to disable the clocksource

 * @mask:		bitmask for two's complement

 *			subtraction of non 64 bit counters

 * @mult:		cycle to nanosecond multiplier (adjusted by NTP)
@@ -163,6 +165,8 @@ struct clocksource { 
	struct list_head list;

	int rating;

	cycle_t (*read)(struct clocksource *cs);

	int (*enable)(struct clocksource *cs);

	void (*disable)(struct clocksource *cs);

	cycle_t mask;

	u32 mult;

	u32 mult_orig;
@@ -274,6 +278,33 @@ static inline cycle_t clocksource_read(struct clocksource *cs) 
	return cs->read(cs);

}



/**

 * clocksource_enable: - enable clocksource

 * @cs:		pointer to clocksource

 *

 * Enables the specified clocksource. The clocksource callback

 * function should start up the hardware and setup mult and field

 * members of struct clocksource to reflect hardware capabilities.

 */

static inline int clocksource_enable(struct clocksource *cs)

{

	return cs->enable ? cs->enable(cs) : 0;

}



/**

 * clocksource_disable: - disable clocksource

 * @cs:		pointer to clocksource

 *

 * Disables the specified clocksource. The clocksource callback

 * function should power down the now unused hardware block to

 * save power.

 */

static inline void clocksource_disable(struct clocksource *cs)

{

	if (cs->disable)

		cs->disable(cs);

}



/**

 * cyc2ns - converts clocksource cycles to nanoseconds

 * @cs:		Pointer to clocksource

kernel/time/timekeeping.c

+9 −3
Original line number Diff line number Diff line
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(do_settimeofday); 
 */

static void change_clocksource(void)

{

	struct clocksource *new;

	struct clocksource *new, *old;



	new = clocksource_get_next();
@@ -191,11 +191,16 @@ static void change_clocksource(void) 


	clocksource_forward_now();



	new->raw_time = clock->raw_time;

	if (clocksource_enable(new))

		return;



	new->raw_time = clock->raw_time;

	old = clock;

	clock = new;

	clocksource_disable(old);



	clock->cycle_last = 0;

	clock->cycle_last = clocksource_read(new);

	clock->cycle_last = clocksource_read(clock);

	clock->error = 0;

	clock->xtime_nsec = 0;

	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -292,6 +297,7 @@ void __init timekeeping_init(void) 
	ntp_init();



	clock = clocksource_get_next();

	clocksource_enable(clock);

	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);

	clock->cycle_last = clocksource_read(clock);