On Fri, 3 Apr 2020 15:27:15 +0200 Lars-Peter Clausen <lars@xxxxxxxxxx> wrote: > The XADC has two internal ADCs. Depending on the mode it is operating in > either one or both of them are used. The device manual calls this > continuous (one ADC) and simultaneous (both ADCs) mode. > > The meaning of the sequencing register for the aux channels changes > depending on the mode. > > In continuous mode each bit corresponds to one of the 16 aux channels. And > the single ADC will convert them one by one in order. > > In simultaneous mode the aux channels are split into two groups the first 8 > channels are assigned to the first ADC and the other 8 channels to the > second ADC. The upper 8 bits of the sequencing register are unused and the > lower 8 bits control both ADCs. This means a bit needs to be set if either > the corresponding channel from the first group or the second group (or > both) are set. > > Currently the driver does not have the special handling required for > simultaneous mode. Add it. > > Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx> Looks fine, but sounds like a fix, so when was the problem introduced? Thanks, Jonathan > --- > drivers/iio/adc/xilinx-xadc-core.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c > index 04a2a609ced4..4acababda4d5 100644 > --- a/drivers/iio/adc/xilinx-xadc-core.c > +++ b/drivers/iio/adc/xilinx-xadc-core.c > @@ -798,6 +798,16 @@ static int xadc_preenable(struct iio_dev *indio_dev) > if (ret) > goto err; > > + /* > + * In simultaneous mode the upper and lower aux channels are samples at > + * the same time. In this mode the upper 8 bits in the sequencer > + * register are don't care and the lower 8 bits control two channels > + * each. As such we must set the bit if either the channel in the lower > + * group or the upper group is enabled. > + */ > + if (seq_mode == XADC_CONF1_SEQ_SIMULTANEOUS) > + scan_mask = ((scan_mask >> 8) | scan_mask) & 0xff0000; > + > ret = xadc_write_adc_reg(xadc, XADC_REG_SEQ(1), scan_mask >> 16); > if (ret) > goto err;
