On Wed, 30 Oct 2024 09:28:01 +0100 Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx> wrote: > On Tue, Oct 29, 2024 at 04:18:50PM -0500, David Lechner wrote: > > Replace the call to pwm_get_state() with a call to pwm_get_state_hw() in > > the ad7606 driver. This allows reading the sampling_frequency attribute > > to return the rate the hardware is actually running at rather than the > > rate that was requested. These may differ when the hardware isn't > > capable of running at exactly the requested frequency. > > > > Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> > > --- > > > > I went ahead and made this patch since it is trivial, but it would be > > nice to get a Tested-by from Guillaume to make sure it actually works > > as expected. > > --- > > drivers/iio/adc/ad7606.c | 8 +++----- > > 1 file changed, 3 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c > > index 8b2046baaa3e..1581eb31b8f9 100644 > > --- a/drivers/iio/adc/ad7606.c > > +++ b/drivers/iio/adc/ad7606.c > > @@ -762,11 +762,9 @@ static int ad7606_read_raw(struct iio_dev *indio_dev, > > *val = st->oversampling; > > return IIO_VAL_INT; > > case IIO_CHAN_INFO_SAMP_FREQ: > > - /* > > - * TODO: return the real frequency intead of the requested one once > > - * pwm_get_state_hw comes upstream. > > - */ > > - pwm_get_state(st->cnvst_pwm, &cnvst_pwm_state); > > + ret = pwm_get_state_hw(st->cnvst_pwm, &cnvst_pwm_state); > > + if (ret < 0) > > + return ret; > > *val = DIV_ROUND_CLOSEST_ULL(NSEC_PER_SEC, cnvst_pwm_state.period); > > return IIO_VAL_INT; > > } > > Acked-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx> Probably not something we need to hurry so assuming it is fine, please send again after the merge window. > > There is a slight inconsistency compared to ad7606_set_sampling_freq(): > > ad7606_set_sampling_freq uses > > cnvst_pwm_state.period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, freq); > > . So if cnvst_pwm_state.period happens to be 3 ns then reading > the freq value yields 333333333, but if you feed freq=333333333 into > ad7606_set_sampling_freq() it sets period = 4. > > To fix that you'd better use a plain / here in ad7606_read_raw(). > (Note that with using round-closest for both there are still corner > cases, e.g. period = 31796 ns yields freq = 31450.496917851302 but > setting freq = 31450 yields 31796.50238473768 and so 31797.) Ouch. > > Best regards > Uwe
