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Commit 5d0c49ac authored by Derek Basehore's avatar Derek Basehore Committed by Lee Jones
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backlight: pwm_bl: Fix overflow condition 



This fixes an overflow condition that can happen with high max
brightness and period values in compute_duty_cycle. This fixes it by
using a 64 bit variable for computing the duty cycle.

Signed-off-by: default avatarDerek Basehore <dbasehore@chromium.org>
Acked-by: default avatarThierry Reding <thierry.reding@gmail.com>
Reviewed-by: default avatarBrian Norris <briannorris@chromium.org>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
parent 2bd6bf03

drivers/video/backlight/pwm_bl.c

+5 −2
Original line number Diff line number Diff line
@@ -79,14 +79,17 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb) 
static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)

{

	unsigned int lth = pb->lth_brightness;

	int duty_cycle;

	u64 duty_cycle;



	if (pb->levels)

		duty_cycle = pb->levels[brightness];

	else

		duty_cycle = brightness;



	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;

	duty_cycle *= pb->period - lth;

	do_div(duty_cycle, pb->scale);



	return duty_cycle + lth;

}



static int pwm_backlight_update_status(struct backlight_device *bl)