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author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-20 00:11:10 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-20 00:11:10 (GMT) |
commit | 164d44fd92e79d5bce54d0d62df9f856f7b23925 (patch) | |
tree | 9f21607849b7e684b255578ffdf41951bc31787e /kernel/time/clocksource.c | |
parent | 5bfec46baa3a752393433b8d89d3b2c70820f61d (diff) | |
parent | d7e81c269db899b800e0963dc4aceece1f82a680 (diff) | |
download | linux-164d44fd92e79d5bce54d0d62df9f856f7b23925.tar.xz |
Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
clocksource: Add clocksource_register_hz/khz interface
posix-cpu-timers: Optimize run_posix_cpu_timers()
time: Remove xtime_cache
mqueue: Convert message queue timeout to use hrtimers
hrtimers: Provide schedule_hrtimeout for CLOCK_REALTIME
timers: Introduce the concept of timer slack for legacy timers
ntp: Remove tickadj
ntp: Make time_adjust static
time: Add xtime, wall_to_monotonic to feature-removal-schedule
timer: Try to survive timer callback preempt_count leak
timer: Split out timer function call
timer: Print function name for timer callbacks modifying preemption count
time: Clean up warp_clock()
cpu-timers: Avoid iterating over all threads in fastpath_timer_check()
cpu-timers: Change SIGEV_NONE timer implementation
cpu-timers: Return correct previous timer reload value
cpu-timers: Cleanup arm_timer()
cpu-timers: Simplify RLIMIT_CPU handling
Diffstat (limited to 'kernel/time/clocksource.c')
-rw-r--r-- | kernel/time/clocksource.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 1f5dde6..f08e99c 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -625,6 +625,54 @@ static void clocksource_enqueue(struct clocksource *cs) list_add(&cs->list, entry); } + +/* + * Maximum time we expect to go between ticks. This includes idle + * tickless time. It provides the trade off between selecting a + * mult/shift pair that is very precise but can only handle a short + * period of time, vs. a mult/shift pair that can handle long periods + * of time but isn't as precise. + * + * This is a subsystem constant, and actual hardware limitations + * may override it (ie: clocksources that wrap every 3 seconds). + */ +#define MAX_UPDATE_LENGTH 5 /* Seconds */ + +/** + * __clocksource_register_scale - Used to install new clocksources + * @t: clocksource to be registered + * @scale: Scale factor multiplied against freq to get clocksource hz + * @freq: clocksource frequency (cycles per second) divided by scale + * + * Returns -EBUSY if registration fails, zero otherwise. + * + * This *SHOULD NOT* be called directly! Please use the + * clocksource_register_hz() or clocksource_register_khz helper functions. + */ +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); + + mutex_lock(&clocksource_mutex); + clocksource_enqueue(cs); + clocksource_select(); + clocksource_enqueue_watchdog(cs); + mutex_unlock(&clocksource_mutex); + return 0; +} +EXPORT_SYMBOL_GPL(__clocksource_register_scale); + + /** * clocksource_register - Used to install new clocksources * @t: clocksource to be registered |