pwm: tegra: Avoid potential overflow for short periods

For very short periods, the result of the division might overflow the
unsigned long hz variable (on 32-bit architectures). Avoid that by
making it an unsigned long long. While at it, also remove an unneeded
local variable whose only purpose is to store a temporary computation.

Acked-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 9c7f180b9f3a915ec4d96729823862b16a0b651f..c040f87ee144e2a74c5fa358deaca44115688cf5 100644 (file)
--- a/drivers/pwm/pwm-tegra.c
+++ b/drivers/pwm/pwm-tegra.c
@@ -75,9 +75,8 @@ 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 = duty_ns;
-       unsigned long rate, hz;
-       unsigned long long ns100 = NSEC_PER_SEC;
+       unsigned long long c = duty_ns, hz;
+       unsigned long rate;
        u32 val = 0;
        int err;
 
@@ -98,9 +97,8 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
        rate = clk_get_rate(pc->clk) >> PWM_DUTY_WIDTH;
 
        /* Consider precision in PWM_SCALE_WIDTH rate calculation */
-       ns100 *= 100;
-       hz = DIV_ROUND_CLOSEST_ULL(ns100, period_ns);
-       rate = DIV_ROUND_CLOSEST(rate * 100, hz);
+       hz = DIV_ROUND_CLOSEST_ULL(100ULL * NSEC_PER_SEC, period_ns);
+       rate = DIV_ROUND_CLOSEST_ULL(100ULL * rate, hz);
 
        /*
         * Since the actual PWM divider is the register's frequency divider