From: Mika Westerberg <mika.westerb...@linux.intel.com>
If duty_ns is large enough multiplying it by 255 overflows and results
wrong duty cycle value being programmed. For example with 10ms duty when
period is 20ms (50%) we get
255 * 10000000 / 20000000 = -87
because 255 * 10000000 overlows int. Whereas correct value should be
255 * 10000000 / 20000000 = 127
Fix this by using unsigned long long as type for on_time_div and changing
integer literals to use proper type annotation.
Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
---
drivers/pwm/pwm-lpss.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 98dc8b80b79d..be4658b42882 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -91,7 +91,7 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct
pwm_device *pwm,
int duty_ns, int period_ns)
{
struct pwm_lpss_chip *lpwm = to_lpwm(chip);
- u8 on_time_div;
+ unsigned long long on_time_div;
unsigned long c, base_unit_range;
unsigned long long base_unit, freq = NSEC_PER_SEC;
u32 ctrl;
@@ -113,7 +113,9 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct
pwm_device *pwm,
if (duty_ns <= 0)
duty_ns = 1;
- on_time_div = 255 - (255 * duty_ns / period_ns);
+ on_time_div = 255ULL * duty_ns;
+ do_div(on_time_div, period_ns);
+ on_time_div = 255ULL - on_time_div;
pm_runtime_get_sync(chip->dev);
--
1.9.1
--
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