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| author | Hyong Bin Kim <hyongbink@nvidia.com> | 2016-06-22 17:17:21 +0530 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2016-07-11 12:49:32 +0200 |
| commit | b979ed531468e9848d95a3b788dd8490927417e3 (patch) | |
| tree | 5d0c61c54f8ef8f1f1d12942a56d1bac91c6fc7a | |
| parent | e0ee1a75f412cc9f3b16127742a30baf975ec51f (diff) | |
| download | linux-stable-b979ed531468e9848d95a3b788dd8490927417e3.tar.gz linux-stable-b979ed531468e9848d95a3b788dd8490927417e3.tar.bz2 linux-stable-b979ed531468e9848d95a3b788dd8490927417e3.zip | |
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>
| -rw-r--r-- | drivers/pwm/pwm-tegra.c | 5 |
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; |