| Message ID | 20241104101905.845737-2-u.kleine-koenig@baylibre.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | iio: adc: ad7124: Disable all channels at probe time | expand |
On Mon, 4 Nov 2024 11:19:04 +0100 Uwe Kleine-König <u.kleine-koenig@baylibre.com> 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") > Reviewed-by: Nuno Sa <nuno.sa@analog.com> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> > --- > Hello, > > this patch was part of a series before. The remaining patches are still > under discussion. As this is a fix orthogonal to the other patches of > the series (apart from the other relevant change there also being > necessary to make the ad7124 work for me) it IMHO makes sense to apply > this one already now. There are machines that don't suffer from the > other issue (i.e. the device irq becoming pending by spi traffic), so > this fix is also valuable stand alone. It's IMHO good enough to go in > before v6.12. > > The previous submission is available at > https://lore.kernel.org/linux-iio/20241028160748.489596-10-u.kleine-koenig@baylibre.com/ > > b4 ignored Nuno's Reviewed-by tag with > > NOTE: some trailers ignored due to from/email mismatches: > ! Trailer: Reviewed-by: Nuno Sa <nuno.sa@analog.com> > Msg From: Nuno Sá <noname.nuno@gmail.com> > > I wonder if other maintainers use b4 apply's -S by default, because I > often run into this issue but don't see others mentioning that. I only use -S when Nuno has given a tag. It tends to be a bit too generous on applying tags in general. Thanks for picking it up here. Sadly this has probably missed 6.12, but I have queued it up as a fix for early next cycle and marked it for stable. Thanks, Jonathan > I added the tag here anyhow. > > 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); > > base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
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") Reviewed-by: Nuno Sa <nuno.sa@analog.com> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> --- Hello, this patch was part of a series before. The remaining patches are still under discussion. As this is a fix orthogonal to the other patches of the series (apart from the other relevant change there also being necessary to make the ad7124 work for me) it IMHO makes sense to apply this one already now. There are machines that don't suffer from the other issue (i.e. the device irq becoming pending by spi traffic), so this fix is also valuable stand alone. It's IMHO good enough to go in before v6.12. The previous submission is available at https://lore.kernel.org/linux-iio/20241028160748.489596-10-u.kleine-koenig@baylibre.com/ b4 ignored Nuno's Reviewed-by tag with NOTE: some trailers ignored due to from/email mismatches: ! Trailer: Reviewed-by: Nuno Sa <nuno.sa@analog.com> Msg From: Nuno Sá <noname.nuno@gmail.com> I wonder if other maintainers use b4 apply's -S by default, because I often run into this issue but don't see others mentioning that. I added the tag here anyhow. drivers/iio/adc/ad7124.c | 3 +++ 1 file changed, 3 insertions(+) base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc