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backlight: pwm_bl: Drop use of int_pow() 

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.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Rasmus Villemoes 2019-10-08 14:03:26 +02:00 committed by Lee Jones
parent e802cbafcb
commit 407feae1ca
1 changed files with 2 additions and 1 deletions
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3
drivers/video/backlight/pwm_bl.c
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@ -180,7 +180,8 @@ 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));
}