Commit 407feae1 authored Oct 08, 2019 by Rasmus Villemoes Committed by Lee Jones Oct 14, 2019

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>

parent e802cbaf

drivers/video/backlight/pwm_bl.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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));
		}

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