On Tue, Nov 12, 2019 at 12:35 AM Andrea Merello
<andrea.merello@xxxxxxxxx> wrote:
>
> This sensor has an embedded notch filter for reducing interferences caused
> by the power mains. This filter can be tuned to reject either 50Hz or 60Hz
> (and harmonics).
>
> Currently the said setting is left alone (the sensor defaults to 60Hz).
> This patch introduces a IIO attribute that allows the user to set the said
> filter to the desired frequency.
>
> NOTE: this has been intentionally not tied to any DT property to allow
> the configuration of this setting from userspace, e.g. with a GUI or by
> reading a configuration file, or maybe reading a GPIO tied to a physical
> switch or accessing some device that can autodetect the line frequency.
>
Looks good to me. Although this ideal could be a device tree property
as well, but not a big deal.
Reviewed-by: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
> Cc: Hartmut Knaack <knaack.h@xxxxxx>
> Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Cc: Peter Meerwald-Stadler <pmeerw@xxxxxxxxxx>
> Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> Cc: Patrick Havelange <patrick.havelange@xxxxxxxxxxxxx>
> Cc: Paresh Chaudhary <paresh.chaudhary@xxxxxxxxxxxxxxxxxxx>
> Cc: Matt Weber <matthew.weber@xxxxxxxxxxxxxxxxxxx>
> Cc: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
> Cc: Chuhong Yuan <hslester96@xxxxxxxxx>
> Cc: Daniel Gomez <dagmcr@xxxxxxxxx>
> Cc: linux-iio@xxxxxxxxxxxxxxx
> Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
> ---
> drivers/iio/temperature/max31856.c | 50 ++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c
> index 73ed550e3fc9..d97ba9ee1598 100644
> --- a/drivers/iio/temperature/max31856.c
> +++ b/drivers/iio/temperature/max31856.c
> @@ -23,6 +23,7 @@
> #define MAX31856_CR0_1SHOT BIT(6)
> #define MAX31856_CR0_OCFAULT BIT(4)
> #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
> +#define MAX31856_CR0_FILTER_50HZ BIT(0)
> #define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
> #define MAX31856_FAULT_OVUV BIT(1)
> #define MAX31856_FAULT_OPEN BIT(0)
> @@ -63,6 +64,7 @@ static const struct iio_chan_spec max31856_channels[] = {
> struct max31856_data {
> struct spi_device *spi;
> u32 thermocouple_type;
> + bool filter_50hz;
> };
>
> static int max31856_read(struct max31856_data *data, u8 reg,
> @@ -123,6 +125,11 @@ static int max31856_init(struct max31856_data *data)
> reg_cr0_val &= ~MAX31856_CR0_1SHOT;
> reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
>
> + if (data->filter_50hz)
> + reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;
> + else
> + reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;
> +
> return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
> }
>
> @@ -249,12 +256,54 @@ static ssize_t show_fault_oc(struct device *dev,
> return show_fault(dev, MAX31856_FAULT_OPEN, buf);
> }
>
> +static ssize_t show_filter(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", data->filter_50hz ? 50 : 60);
> +}
> +
> +static ssize_t set_filter(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 freq;
> + int ret;
> +
> + ret = kstrtouint(buf, 10, &freq);
> + if (ret)
> + return ret;
> +
> + switch (freq) {
> + case 50:
> + data->filter_50hz = true;
> + break;
> + case 60:
> + data->filter_50hz = false;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + 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(in_temp_filter_notch_center_frequency, 0644,
> + show_filter, set_filter, 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_in_temp_filter_notch_center_frequency.dev_attr.attr,
> NULL,
> };
>
> @@ -280,6 +329,7 @@ static int max31856_probe(struct spi_device *spi)
>
> data = iio_priv(indio_dev);
> data->spi = spi;
> + data->filter_50hz = false;
>
> spi_set_drvdata(spi, indio_dev);
>
> --
> 2.17.1
>
