From 407feae1cacaa5d00ebe686532a73ad6de747409 Mon Sep 17 00:00:00 2001
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date: Tue, 8 Oct 2019 14:03:26 +0200
Subject: backlight: pwm_bl: Drop use of int_pow()
Git-commit: 407feae1cacaa5d00ebe686532a73ad6de747409
Patch-mainline: v5.5-rc1
References: bsc#1152489
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>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
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 15d84da77ecd..ee85055146dd 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -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));
}
--
2.28.0