Il giorno dom 6 ott 2019 alle ore 09:55 Jonathan Cameron
<jic23@xxxxxxxxxx> ha scritto:
>
> On Mon, 23 Sep 2019 14:17:13 +0200
> Andrea Merello <andrea.merello@xxxxxxxxx> wrote:
>
> > This sensor can perform samples averaging in hardware, but currently the
> > driver leaves this setting alone (default is no averaging).
> >
> > This patch introduces a new IIO attribute that allows the user to set the
> > averaging as desired (the HW supports averaging of 2, 5, 8 or 16 samples)
> >
> > Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
>
> Sounds like oversampling combined with a lower sampling frequency, so
> there is standard ABI for that.
OK. Do you refer to "oversampling_ratio"?
The datasheet says this applies to thermocouple measure, but by doing
some testing with real HW, it seems that this setting affects both
thermocouple and cold-junction measures, so I guess it shouldn't be in
the form "in_temp_raw_oversampling_ratio"; does this sound right to
you?
> Jonathan
>
> > ---
> > drivers/iio/temperature/max31856.c | 43 ++++++++++++++++++++++++++++++
> > 1 file changed, 43 insertions(+)
> >
> > diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c
> > index d12613f7ba3c..8b2e0102fa5c 100644
> > --- a/drivers/iio/temperature/max31856.c
> > +++ b/drivers/iio/temperature/max31856.c
> > @@ -24,6 +24,8 @@
> > #define MAX31856_CR0_OCFAULT BIT(4)
> > #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
> > #define MAX31856_CR0_FILTER_50HZ BIT(0)
> > +#define MAX31856_AVERAGING_MASK GENMASK(6, 4)
> > +#define MAX31856_AVERAGING_SHIFT 4
> > #define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
> > #define MAX31856_FAULT_OVUV BIT(1)
> > #define MAX31856_FAULT_OPEN BIT(0)
> > @@ -65,6 +67,7 @@ struct max31856_data {
> > struct spi_device *spi;
> > u32 thermocouple_type;
> > bool filter_50hz;
> > + int averaging;
> > };
> >
> > static int max31856_read(struct max31856_data *data, u8 reg,
> > @@ -109,6 +112,10 @@ static int max31856_init(struct max31856_data *data)
> >
> > reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
> > reg_cr1_val |= data->thermocouple_type;
> > +
> > + reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
> > + reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
> > +
> > ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
> > if (ret)
> > return ret;
> > @@ -295,14 +302,50 @@ static ssize_t set_filter(struct device *dev,
> > return len;
> > }
> >
> > +static ssize_t show_averaging(struct device *dev,
> > + struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > + struct max31856_data *data = iio_priv(indio_dev);
> > +
> > + return sprintf(buf, "%d\n", 1 << data->averaging);
> > +}
> > +
> > +static ssize_t set_averaging(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf,
> > + size_t len)
> > +{
> > + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > + struct max31856_data *data = iio_priv(indio_dev);
> > + unsigned int nsamples;
> > + int shift;
> > + int ret;
> > +
> > + ret = kstrtouint(buf, 10, &nsamples);
> > + if (ret)
> > + return ret;
> > +
> > + shift = fls(nsamples) - 1;
> > + if (nsamples > 16 || BIT(shift) != nsamples)
> > + return -EINVAL;
> > +
> > + data->averaging = shift;
> > + max31856_init(data);
> > + return len;
> > +}
> > +
> > static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
> > static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
> > static IIO_DEVICE_ATTR(filter, 0644, show_filter, set_filter, 0);
> > +static IIO_DEVICE_ATTR(averaging, 0644, show_averaging, set_averaging, 0);
> >
> > static struct attribute *max31856_attributes[] = {
> > &iio_dev_attr_fault_ovuv.dev_attr.attr,
> > &iio_dev_attr_fault_oc.dev_attr.attr,
> > &iio_dev_attr_filter.dev_attr.attr,
> > + &iio_dev_attr_averaging.dev_attr.attr,
> > NULL,
> > };
> >
>
