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 <hyongbink@nvidia.com>
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
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 @@
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 @@
* 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;