| Message ID | 20241028160748.489596-10-u.kleine-koenig@baylibre.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | iio: adc: ad7124: Make it work on de10-nano | expand |
On Mon, 2024-10-28 at 17:07 +0100, Uwe Kleine-König wrote: > When during a measurement two channels are enabled, two measurements are > done that are reported sequencially in the DATA register. As the code > triggered by reading one of the sysfs properties expects that only one > channel is enabled it only reads the first data set which might or might > not belong to the intended channel. > > To prevent this situation disable all channels during probe. This fixes > a problem in practise because the reset default for channel 0 is > enabled. So all measurements before the first measurement on channel 0 > (which disables channel 0 at the end) might report wrong values. > > Fixes: 7b8d045e497a ("iio: adc: ad7124: allow more than 8 channels") > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> > --- Reviewed-by: Nuno Sa <nuno.sa@analog.com> > drivers/iio/adc/ad7124.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c > index a5d91933f505..749304d38415 100644 > --- a/drivers/iio/adc/ad7124.c > +++ b/drivers/iio/adc/ad7124.c > @@ -917,6 +917,9 @@ static int ad7124_setup(struct ad7124_state *st) > * set all channels to this default value. > */ > ad7124_set_channel_odr(st, i, 10); > + > + /* Disable all channels to prevent unintended conversions. */ > + ad_sd_write_reg(&st->sd, AD7124_CHANNEL(i), 2, 0); > } > > ret = ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c index a5d91933f505..749304d38415 100644 --- a/drivers/iio/adc/ad7124.c +++ b/drivers/iio/adc/ad7124.c @@ -917,6 +917,9 @@ static int ad7124_setup(struct ad7124_state *st) * set all channels to this default value. */ ad7124_set_channel_odr(st, i, 10); + + /* Disable all channels to prevent unintended conversions. */ + ad_sd_write_reg(&st->sd, AD7124_CHANNEL(i), 2, 0); } ret = ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
When during a measurement two channels are enabled, two measurements are done that are reported sequencially in the DATA register. As the code triggered by reading one of the sysfs properties expects that only one channel is enabled it only reads the first data set which might or might not belong to the intended channel. To prevent this situation disable all channels during probe. This fixes a problem in practise because the reset default for channel 0 is enabled. So all measurements before the first measurement on channel 0 (which disables channel 0 at the end) might report wrong values. Fixes: 7b8d045e497a ("iio: adc: ad7124: allow more than 8 channels") Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> --- drivers/iio/adc/ad7124.c | 3 +++ 1 file changed, 3 insertions(+)