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.
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,
> };
>
