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| author | Andy Shevchenko <andriy.shevchenko@linux.intel.com> | 2017-01-28 16:10:39 +0100 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2017-01-30 08:13:19 +0100 |
| commit | 684309e5043efaaa94d9b4e65f53f7fdde1f6675 (patch) | |
| tree | 8f25bbc38fbe2e2c2ecb2c3f8b11aca68404853b /drivers/pwm/pwm-lpss.c | |
| parent | pwm: pca9685: Fix period change with same duty cycle (diff) | |
| download | linux-684309e5043efaaa94d9b4e65f53f7fdde1f6675.tar.xz linux-684309e5043efaaa94d9b4e65f53f7fdde1f6675.zip | |
pwm: lpss: Avoid potential overflow of base_unit
The resolution of base_unit is derived from base_unit_bits and thus must be
equal to (2^base_unit_bits - 1). Otherwise frequency and therefore base_unit
might potentially overflow.
Prevent the above by substracting 1 in all cases where base_unit_bits or
derivative is used.
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm/pwm-lpss.c')
| -rw-r--r-- | drivers/pwm/pwm-lpss.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 72c0bce5a75c..8642feeb8abd 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -102,7 +102,7 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm, * The equation is: * base_unit = round(base_unit_range * freq / c) */ - base_unit_range = BIT(lpwm->info->base_unit_bits); + base_unit_range = BIT(lpwm->info->base_unit_bits) - 1; freq *= base_unit_range; base_unit = DIV_ROUND_CLOSEST_ULL(freq, c); @@ -117,8 +117,8 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm, ctrl = pwm_lpss_read(pwm); ctrl &= ~PWM_ON_TIME_DIV_MASK; - ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT); - base_unit &= (base_unit_range - 1); + ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT); + base_unit &= base_unit_range; ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div; pwm_lpss_write(pwm, ctrl); |