From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 9 Dec 2009 03:27:08 +0000 (-0800)
Subject: Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git... 
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=60d8ce2cd6c283132928c11f3fd57ff4187287e0;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

Merge branch 'timers-for-linus' of git://git./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:
  timers, init: Limit the number of per cpu calibration bootup messages
  posix-cpu-timers: optimize and document timer_create callback
  clockevents: Add missing include to pacify sparse
  x86: vmiclock: Fix printk format
  x86: Fix printk format due to variable type change
  sparc: fix printk for change of variable type
  clocksource/events: Fix fallout of generic code changes
  nohz: Allow 32-bit machines to sleep for more than 2.15 seconds
  nohz: Track last do_timer() cpu
  nohz: Prevent clocksource wrapping during idle
  nohz: Type cast printk argument
  mips: Use generic mult/shift factor calculation for clocks
  clocksource: Provide a generic mult/shift factor calculation
  clockevents: Use u32 for mult and shift factors
  nohz: Introduce arch_needs_cpu
  nohz: Reuse ktime in sub-functions of tick_check_idle.
  time: Remove xtime_cache
  time: Implement logarithmic time accumulation
---

60d8ce2cd6c283132928c11f3fd57ff4187287e0
diff --cc kernel/time/clocksource.c
index 4a310906b3e8,72a2dcbd8b48..d422c7b2236b
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@@ -105,8 -105,61 +105,61 @@@ u64 timecounter_cyc2time(struct timecou
  
  	return nsec;
  }
 -EXPORT_SYMBOL(timecounter_cyc2time);
 +EXPORT_SYMBOL_GPL(timecounter_cyc2time);
  
+ /**
+  * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
+  * @mult:	pointer to mult variable
+  * @shift:	pointer to shift variable
+  * @from:	frequency to convert from
+  * @to:		frequency to convert to
+  * @minsec:	guaranteed runtime conversion range in seconds
+  *
+  * The function evaluates the shift/mult pair for the scaled math
+  * operations of clocksources and clockevents.
+  *
+  * @to and @from are frequency values in HZ. For clock sources @to is
+  * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
+  * event @to is the counter frequency and @from is NSEC_PER_SEC.
+  *
+  * The @minsec conversion range argument controls the time frame in
+  * seconds which must be covered by the runtime conversion with the
+  * calculated mult and shift factors. This guarantees that no 64bit
+  * overflow happens when the input value of the conversion is
+  * multiplied with the calculated mult factor. Larger ranges may
+  * reduce the conversion accuracy by chosing smaller mult and shift
+  * factors.
+  */
+ void
+ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
+ {
+ 	u64 tmp;
+ 	u32 sft, sftacc= 32;
+ 
+ 	/*
+ 	 * Calculate the shift factor which is limiting the conversion
+ 	 * range:
+ 	 */
+ 	tmp = ((u64)minsec * from) >> 32;
+ 	while (tmp) {
+ 		tmp >>=1;
+ 		sftacc--;
+ 	}
+ 
+ 	/*
+ 	 * Find the conversion shift/mult pair which has the best
+ 	 * accuracy and fits the maxsec conversion range:
+ 	 */
+ 	for (sft = 32; sft > 0; sft--) {
+ 		tmp = (u64) to << sft;
+ 		do_div(tmp, from);
+ 		if ((tmp >> sftacc) == 0)
+ 			break;
+ 	}
+ 	*mult = tmp;
+ 	*shift = sft;
+ }
+ 
  /*[Clocksource internal variables]---------
   * curr_clocksource:
   *	currently selected clocksource.