Re: [PATCH v2 2/4] backlight: pwm_bl: eliminate a 64/32 division

[Lee Jones]

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 
> Signed-off-by: Rasmus Villemoes 
> ---
>  drivers/video/backlight/pwm_bl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
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[PATCH v2 2/4] backlight: pwm_bl: eliminate a 64/32 division

[Rasmus Villemoes]

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 
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 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));
-- 
2.20.1