# \[PATCH 2/5\] backlight: pwm\_bl: eliminate a 64/32 division - From: Rasmus Villemoes \ - Date: 2019-09-19 14:06:35 - List: linux-fbdev - Page: https://ratatoskr.run/linux-fbdev/2019/09/5720993 - Thread: https://ratatoskr.run/linux-pwm/2019/09/5720992/t.md ```text lightness*1000 is nowhere near overflowing 32 bits, so we can just use an ordinary 32/32 division, which is much cheaper than the 64/32 done via do_div(). Signed-off-by: Rasmus Villemoes --- drivers/video/backlight/pwm_bl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index be36be1cacb7..9252d51f31b9 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -177,7 +177,7 @@ static u64 cie1931(unsigned int lightness, unsigned int scale) */ lightness *= 100; if (lightness <= (8 * scale)) { - retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9033); + retval = DIV_ROUND_CLOSEST(lightness * 10, 9033); } else { retval = int_pow((lightness + (16 * scale)) / 116, 3); retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale)); -- 2.20.1 ```