Messages in this thread Patch in this message | | | From | Laxman Dewangan <> | Subject | [PATCH 3/5] pwm: tegra: fix overflow when calculating duty cycle | Date | Wed, 22 Jun 2016 17:17:21 +0530 |
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From: Hyong Bin Kim <hyongbink@nvidia.com>
duty_ns * (1 << PWM_DUTY_WIDTH) could overflow in integer calcualtion when PWM rate is low. Hence do all calculation on unsigned long long to avoid overflow.
Signed-off-by: Hyong Bin Kim <hyongbink@nvidia.com> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com> --- drivers/pwm/pwm-tegra.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c index 575ca8e..49cefd5 100644 --- a/drivers/pwm/pwm-tegra.c +++ b/drivers/pwm/pwm-tegra.c @@ -69,7 +69,7 @@ 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; @@ -79,7 +79,8 @@ 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; -- 2.1.4
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