clocksource: Introduce clocksource_freq2mult()

The clocksource_khz2mult() and clocksource_hz2mult() share similar
code wihch calculates a mult from the given frequency. Both implementations
in differ only in value of a frequency. This patch introduces the
clocksource_freq2mult() helper with generic implementation of
mult calculation to prevent code duplication.

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Link: http://lkml.kernel.org/r/1456542854-22104-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/clocksource.h

@@ -118,6 +118,23 @@ struct clocksource {
 /* simplify initialization of mask field */
 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 
+static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
+{
+	/*  freq = cyc/from
+	 *  mult/2^shift  = ns/cyc
+	 *  mult = ns/cyc * 2^shift
+	 *  mult = from/freq * 2^shift
+	 *  mult = from * 2^shift / freq
+	 *  mult = (from<<shift) / freq
+	 */
+	u64 tmp = ((u64)from) << shift_constant;
+
+	tmp += freq/2; /* round for do_div */
+	do_div(tmp, freq);
+
+	return (u32)tmp;
+}
+
 /**
  * clocksource_khz2mult - calculates mult from khz and shift
  * @khz:		Clocksource frequency in KHz
@@ -128,19 +145,7 @@ struct clocksource {
  */
 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 {
-	/*  khz = cyc/(Million ns)
-	 *  mult/2^shift  = ns/cyc
-	 *  mult = ns/cyc * 2^shift
-	 *  mult = 1Million/khz * 2^shift
-	 *  mult = 1000000 * 2^shift / khz
-	 *  mult = (1000000<<shift) / khz
-	 */
-	u64 tmp = ((u64)1000000) << shift_constant;
-
-	tmp += khz/2; /* round for do_div */
-	do_div(tmp, khz);
-
-	return (u32)tmp;
+	return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 }
 
 /**
@@ -154,19 +159,7 @@ static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
  */
 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 {
-	/*  hz = cyc/(Billion ns)
-	 *  mult/2^shift  = ns/cyc
-	 *  mult = ns/cyc * 2^shift
-	 *  mult = 1Billion/hz * 2^shift
-	 *  mult = 1000000000 * 2^shift / hz
-	 *  mult = (1000000000<<shift) / hz
-	 */
-	u64 tmp = ((u64)1000000000) << shift_constant;
-
-	tmp += hz/2; /* round for do_div */
-	do_div(tmp, hz);
-
-	return (u32)tmp;
+	return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 }
 
 /**