2017-04-07 13:53 GMT+02:00 Fabrice Gasnier <fabrice.gasnier@xxxxxx>: > When prescaler (PSC) is 0, it means div factor is 1: counter clock > frequency is equal to input clk / (PSC + 1). > When reload value is 8 for example, counter counts 9 cycles, from 0 to 8. > This is handled in frequency write routine, by writing respectively: > - prescaler - 1 to PSC > - reload value - 1 to ARR > This fix does the opposite when reading the frequency from PSC and ARR: > - prescaler is PSC + 1 > - reload value is ARR + 1 > > Thus, PSC may be 0, depending on requested sampling frequency (div 1). > In this case, reading freq wrongly reports 0, instead of computing and > reporting correct value. > Remove test on !psc and !arr. > > Small test on stm32f4 (example on tim1_trgo), before this fix: > $ cd /sys/bus/iio/devices/triggerX > $ echo 10000 > sampling_frequency > $ cat sampling_frequency > 0 > > After this fix: > $ echo 10000 > sampling_frequency > $ cat sampling_frequency > 10000 > > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx> > --- > drivers/iio/trigger/stm32-timer-trigger.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c > index 994b96d..5ee362b 100644 > --- a/drivers/iio/trigger/stm32-timer-trigger.c > +++ b/drivers/iio/trigger/stm32-timer-trigger.c > @@ -152,10 +152,10 @@ static ssize_t stm32_tt_read_frequency(struct device *dev, > regmap_read(priv->regmap, TIM_PSC, &psc); > regmap_read(priv->regmap, TIM_ARR, &arr); > > - if (psc && arr && (cr1 & TIM_CR1_CEN)) { > + if (cr1 & TIM_CR1_CEN) { > freq = (unsigned long long)clk_get_rate(priv->clk); > - do_div(freq, psc); > - do_div(freq, arr); > + do_div(freq, psc + 1); > + do_div(freq, arr + 1); > } > > return sprintf(buf, "%d\n", (unsigned int)freq); > -- > 1.9.1 > Acked-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html