diff options
| author | Derek Basehore <dbasehore@chromium.org> | 2017-08-29 13:34:34 -0700 |
|---|---|---|
| committer | Lee Jones <lee.jones@linaro.org> | 2017-10-13 10:41:20 +0100 |
| commit | 5d0c49acebc9488e37db95f1d4a55644e545ffe7 (patch) | |
| tree | 569883e84e757a23fcde534201fdd09b332be937 | |
| parent | 2bd6bf03f4c1c59381d62c61d03f6cc3fe71f66e (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>
| -rw-r--r-- | drivers/video/backlight/pwm_bl.c | 7 |
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) |