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pwm: tegra: Avoid overflow when calculating duty cycle

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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 <hyongbink@nvidia.com>
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Hyong Bin Kim 2016-06-22 17:17:21 +05:30 committed by Thierry Reding
parent e0ee1a75f4
commit b979ed5314
1 changed files with 3 additions and 2 deletions
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5
drivers/pwm/pwm-tegra.c
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@ -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;