Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b979ed53 authored by Hyong Bin Kim's avatar Hyong Bin Kim Committed by Thierry Reding
Browse files

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: default avatarHyong Bin Kim <hyongbink@nvidia.com>
Signed-off-by: default avatarLaxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent e0ee1a75

drivers/pwm/pwm-tegra.c

+3 −2
Original line number Diff line number Diff line
@@ -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;