[v2,2/4] backlight: pwm_bl: eliminate a 64/32 division
diff mbox series

Message ID 20191008120327.24208-3-linux@rasmusvillemoes.dk
State New
Headers show
Series
  • backlight: pwm_bl: optimizations and small fix for cie1913
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Commit Message

Rasmus Villemoes Oct. 8, 2019, 12:03 p.m. UTC
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().

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/video/backlight/pwm_bl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Lee Jones Oct. 14, 2019, 7:27 a.m. UTC | #1
On Tue, 08 Oct 2019, Rasmus Villemoes wrote:

> 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().
> 
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
>  drivers/video/backlight/pwm_bl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

Patch
diff mbox series

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index cc44a02e95c7..672c5e7cfcd1 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));