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authorDerek Basehore <dbasehore@chromium.org>2017-08-29 13:34:34 -0700
committerLee Jones <lee.jones@linaro.org>2017-10-13 10:41:20 +0100
commit5d0c49acebc9488e37db95f1d4a55644e545ffe7 (patch)
tree569883e84e757a23fcde534201fdd09b332be937 /drivers/video
parent2bd6bf03f4c1c59381d62c61d03f6cc3fe71f66e (diff)
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: Derek Basehore <dbasehore@chromium.org> Acked-by: Thierry Reding <thierry.reding@gmail.com> Reviewed-by: Brian Norris <briannorris@chromium.org> Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'drivers/video')
-rw-r--r--drivers/video/backlight/pwm_bl.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 9bd17682655a..1c2289ddd555 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -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)