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authorThomas Gleixner <tglx@linutronix.de>2009-11-11 14:05:29 +0000
committerThomas Gleixner <tglx@linutronix.de>2009-11-13 20:46:23 +0100
commit7d2f944a2b836c69a9d260a0a5f0d1720d57fdff (patch)
tree67766d878c650ab7ac13d155081b9c745447e24e /include
parent23af368e9a904f59256c27d371ce223d6cee0430 (diff)
downloadlinaro-lsk-7d2f944a2b836c69a9d260a0a5f0d1720d57fdff.tar.gz
clocksource: Provide a generic mult/shift factor calculation
MIPS has two functions to calculcate the mult/shift factors for clock sources and clock events at run time. ARM needs such functions as well. Implement a function which calculates the mult/shift factors based on the frequencies to which and from which is converted. The function also has a parameter to specify the minimum conversion range in seconds. This range is guaranteed not to produce a 64bit overflow when a value is multiplied with the calculated mult factor. The larger the conversion range the less becomes the conversion accuracy. Provide two inline wrappers which handle clock events and clock sources. For clock events the "from" frequency is nano seconds per second which corresponds to 1GHz and "to" is the device frequency. For clock sources "from" is the device frequency and "to" is nano seconds per second. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Mikael Pettersson <mikpe@it.uu.se> Acked-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: Linus Walleij <linus.walleij@stericsson.com> Cc: John Stultz <johnstul@us.ibm.com> LKML-Reference: <20091111134229.766673305@linutronix.de>
Diffstat (limited to 'include')
-rw-r--r--include/linux/clockchips.h7
-rw-r--r--include/linux/clocksource.h10
2 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 3b584101627..4d438b0bc10 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -130,6 +130,13 @@ extern int clockevents_program_event(struct clock_event_device *dev,
extern void clockevents_handle_noop(struct clock_event_device *dev);
+static inline void
+clockevents_calc_mult_shift(struct clock_event_device *ce, u32 freq, u32 minsec)
+{
+ return clocks_calc_mult_shift(&ce->mult, &ce->shift, NSEC_PER_SEC,
+ freq, minsec);
+}
+
#ifdef CONFIG_GENERIC_CLOCKEVENTS
extern void clockevents_notify(unsigned long reason, void *arg);
#else
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 83d2fbd81b9..f57f8825052 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -279,6 +279,16 @@ extern void clocksource_resume(void);
extern struct clocksource * __init __weak clocksource_default_clock(void);
extern void clocksource_mark_unstable(struct clocksource *cs);
+extern void
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
+
+static inline void
+clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
+{
+ return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+ NSEC_PER_SEC, minsec);
+}
+
#ifdef CONFIG_GENERIC_TIME_VSYSCALL
extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
extern void update_vsyscall_tz(void);