According to the data-sheet the way the PWM controller works is that each input clock-cycle the base_unit gets added to a N bit counter and that counter overflowing determines the PWM output frequency. So assuming e.g. a 16 bit counter this means that if base_unit is set to 1, after 65535 input clock-cycles the counter has been increased from 0 to 65535 and it will overflow on the next cycle, so it will overflow after every 65536 clock cycles and thus the calculations done in pwm_lpss_prepare() should use 65536 and not 65535. This commit fixes this. Note this also aligns the calculations in pwm_lpss_prepare() with those in pwm_lpss_get_state(). Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/pwm/pwm-lpss.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index cae74ce61654..a764e062103b 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -93,7 +93,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, * The equation is: * base_unit = round(base_unit_range * freq / c) */ - base_unit_range = BIT(lpwm->info->base_unit_bits) - 1; + base_unit_range = BIT(lpwm->info->base_unit_bits); freq *= base_unit_range; base_unit = DIV_ROUND_CLOSEST_ULL(freq, c); @@ -112,7 +112,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, orig_ctrl = ctrl = pwm_lpss_read(pwm); ctrl &= ~PWM_ON_TIME_DIV_MASK; - ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT); + ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT); ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div; -- 2.26.2
