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>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
index 2026eaa932ae..247156149b44 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;