diff options
| author |   Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2019-10-08 14:03:26 +0200 |
|---|---|---|
| committer |   Lee Jones <lee.jones@linaro.org> | 2019-10-14 08:57:45 +0100 |
| commit | 407feae1cacaa5d00ebe686532a73ad6de747409 (patch) | |
| tree | b939ed915f984e0ebdac2a46829010ff642006db | |
| parent | backlight: pwm_bl: Eliminate a 64/32 division (diff) | |
| download | linux-dev-407feae1cacaa5d00ebe686532a73ad6de747409.tar.xz linux-dev-407feae1cacaa5d00ebe686532a73ad6de747409.zip | |
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>
| -rw-r--r-- | drivers/video/backlight/pwm_bl.c | 3 |
1 files changed, 2 insertions, 1 deletions
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)); } |