| Message ID | 20161024144325.130353-2-andriy.shevchenko@linux.intel.com |
|---|---|
| State | Superseded |
| Headers | show |
On Mon, Oct 24, 2016 at 05:43:22PM +0300, Andy Shevchenko wrote: > 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 > derevative is used. ^^^^^^^^^^ derivative > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 72c0bce..8642fee 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);
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 derevative is used. Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> --- drivers/pwm/pwm-lpss.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)