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clocksource: Add __clocksource_updatefreq_hz/khz methods

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To properly handle clocksources that change frequencies
at the clocksource->enable() point, this patch adds
a method that will update the clocksource's mult/shift and
max_idle_ns values.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1279068988-21864-12-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
John Stultz 2010-07-13 17:56:28 -07:00 committed by Thomas Gleixner
parent f12a15be63
commit 852db46d55
2 changed files with 40 additions and 10 deletions
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11
include/linux/clocksource.h
View File

@ -292,6 +292,8 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
*/
extern int
__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
extern void
__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
{
@ -303,6 +305,15 @@ static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
return __clocksource_register_scale(cs, 1000, khz);
}
static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
{
__clocksource_updatefreq_scale(cs, 1, hz);
}
static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
{
__clocksource_updatefreq_scale(cs, 1000, khz);
}
static inline void
clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)

39
kernel/time/clocksource.c
View File

@ -638,6 +638,32 @@ static void clocksource_enqueue(struct clocksource *cs)
*/
#define MAX_UPDATE_LENGTH 5 /* Seconds */
/**
* __clocksource_updatefreq_scale - Used update clocksource with new freq
* @t: clocksource to be registered
* @scale: Scale factor multiplied against freq to get clocksource hz
* @freq: clocksource frequency (cycles per second) divided by scale
*
* This should only be called from the clocksource->enable() method.
*
* This *SHOULD NOT* be called directly! Please use the
* clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
*/
void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
{
/*
* Ideally we want to use some of the limits used in
* clocksource_max_deferment, to provide a more informed
* MAX_UPDATE_LENGTH. But for now this just gets the
* register interface working properly.
*/
clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
NSEC_PER_SEC/scale,
MAX_UPDATE_LENGTH*scale);
cs->max_idle_ns = clocksource_max_deferment(cs);
}
EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
/**
* __clocksource_register_scale - Used to install new clocksources
* @t: clocksource to be registered
@ -652,17 +678,10 @@ static void clocksource_enqueue(struct clocksource *cs)
int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
{
/*
* Ideally we want to use some of the limits used in
* clocksource_max_deferment, to provide a more informed
* MAX_UPDATE_LENGTH. But for now this just gets the
* register interface working properly.
*/
clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
NSEC_PER_SEC/scale,
MAX_UPDATE_LENGTH*scale);
cs->max_idle_ns = clocksource_max_deferment(cs);
/* Intialize mult/shift and max_idle_ns */
__clocksource_updatefreq_scale(cs, scale, freq);
/* Add clocksource to the clcoksource list */
mutex_lock(&clocksource_mutex);
clocksource_enqueue(cs);
clocksource_select();