lib/math: move int_pow() from pwm_bl.c for wider use

The integer exponentiation is used in few places and might be used in
the future by other call sites.  Move it to wider use.

Link: http://lkml.kernel.org/r/20190323172531.80025-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: andy-shev

drivers/video/backlight/pwm_bl.c

@@ -155,21 +155,6 @@ static const struct backlight_ops pwm_backlight_ops = {
 #ifdef CONFIG_OF
 #define PWM_LUMINANCE_SCALE	10000 /* luminance scale */
 
-/* An integer based power function */
-static u64 int_pow(u64 base, int exp)
-{
-	u64 result = 1;
-
-	while (exp) {
-		if (exp & 1)
-			result *= base;
-		exp >>= 1;
-		base *= base;
-	}
-
-	return result;
-}
-
 /*
  * CIE lightness to PWM conversion.
  *

include/linux/kernel.h

@@ -484,6 +484,7 @@ extern int __kernel_text_address(unsigned long addr);
 extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
+u64 int_pow(u64 base, unsigned int exp);
 unsigned long int_sqrt(unsigned long);
 
 #if BITS_PER_LONG < 64

lib/math/Makefile

@@ -1,4 +1,4 @@
-obj-y += div64.o gcd.o lcm.o int_sqrt.o reciprocal_div.o
+obj-y += div64.o gcd.o lcm.o int_pow.o int_sqrt.o reciprocal_div.o
 
 obj-$(CONFIG_CORDIC)		+= cordic.o
 obj-$(CONFIG_PRIME_NUMBERS)	+= prime_numbers.o

lib/math/int_pow.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * An integer based power function
+ *
+ * Derived from drivers/video/backlight/pwm_bl.c
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+/**
+ * int_pow - computes the exponentiation of the given base and exponent
+ * @base: base which will be raised to the given power
+ * @exp: power to be raised to
+ *
+ * Computes: pow(base, exp), i.e. @base raised to the @exp power
+ */
+u64 int_pow(u64 base, unsigned int exp)
+{
+	u64 result = 1;
+
+	while (exp) {
+		if (exp & 1)
+			result *= base;
+		exp >>= 1;
+		base *= base;
+	}
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(int_pow);