The scheduler uses a (currently private) fixed_power_int() in its load
average computation for computing powers of numbers 0 < x < 1
expressed as fixed-point numbers, which is also what we want here. But
that requires the scale to be a power-of-2.
We could (and a following patch will) change to use a power-of-2 scale,
but for a fixed small exponent of 3, there's no advantage in using
repeated squaring.
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 9252d51f31b9..aee6839e024a 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
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
