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.thompson@xxxxxxxxxx>
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
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
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