From: Hyong Bin Kim Date: Wed, 22 Jun 2016 11:47:21 +0000 (+0530) Subject: pwm: tegra: Avoid overflow when calculating duty cycle X-Git-Tag: v4.14-rc1~2693^2~1^2~10 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b979ed531468e9848d95a3b788dd8490927417e3;p=platform%2Fkernel%2Flinux-rpi.git pwm: tegra: Avoid overflow when calculating duty cycle duty_ns * (1 << PWM_DUTY_WIDTH) could overflow in integer calculation when the PWM rate is low. Hence do all calculation on unsigned long long to avoid overflow. Signed-off-by: Hyong Bin Kim Signed-off-by: Laxman Dewangan Signed-off-by: Thierry Reding --- diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c index 2026eaa..2471561 100644 --- a/drivers/pwm/pwm-tegra.c +++ b/drivers/pwm/pwm-tegra.c @@ -67,7 +67,7 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, int duty_ns, int period_ns) { struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip); - unsigned long long c; + unsigned long long c = duty_ns; unsigned long rate, hz; u32 val = 0; int err; @@ -77,7 +77,8 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the * nearest integer during division. */ - c = duty_ns * (1 << PWM_DUTY_WIDTH) + period_ns / 2; + c *= (1 << PWM_DUTY_WIDTH); + c += period_ns / 2; do_div(c, period_ns); val = (u32)c << PWM_DUTY_SHIFT;