[PATCH v2 3/4] backlight: pwm_bl: drop use of int_pow()

[Rasmus Villemoes]

For a fixed small exponent of 3, it is more efficient to simply use
two explicit multiplications rather than calling the int_pow() library
function: Aside from the function call overhead, its implementation
using repeated squaring means it ends up doing four 64x64
multiplications.

Reviewed-by: Daniel Thompson <daniel.thomp...@linaro.org>
Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk>
---
 drivers/video/backlight/pwm_bl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 672c5e7cfcd1..273d3fb628a0 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -179,7 +179,8 @@ static u64 cie1931(unsigned int lightness, unsigned int 
scale)
        if (lightness <= (8 * scale)) {
                retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
        } else {
-               retval = int_pow((lightness + (16 * scale)) / 116, 3);
+               retval = (lightness + (16 * scale)) / 116;
+               retval *= retval * retval;
                retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
        }
 
-- 
2.20.1