Re: [PATCH v2 5/5] iio: adc: ad7606: add gain calibration support

["Nuno Sá" <noname.nuno@gmail.com>]

On Fri, 2025-05-02 at 15:27 +0200, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@baylibre.com>
> 
> Add gain calibration support, using resistor values set on devicetree,
> values to be set accordingly with ADC external RFilter, as explained in
> the ad7606c-16 datasheet, rev0, page 37.
> 
> Usage example in the fdt yaml documentation.
> 
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> ---

Here!

With the the proper type for the DT properties:

Reviewed-by: Nuno Sá <nuno.sa@analog.com>

>  drivers/iio/adc/ad7606.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/iio/adc/ad7606.h |  4 ++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c
> index
> 139d8b3f9bb39dd631a71c70539005d719fb5b7b..a167f080e89c8a8d8accaff5904cce31d860edf9
> 100644
> --- a/drivers/iio/adc/ad7606.c
> +++ b/drivers/iio/adc/ad7606.c
> @@ -33,6 +33,10 @@
>  
>  #include "ad7606.h"
>  
> +#define AD7606_CALIB_GAIN_MIN	0
> +#define AD7606_CALIB_GAIN_STEP	1024
> +#define AD7606_CALIB_GAIN_MAX	(63 * AD7606_CALIB_GAIN_STEP)
> +
>  /*
>   * Scales are computed as 5000/32768 and 10000/32768 respectively,
>   * so that when applied to the raw values they provide mV values.
> @@ -125,6 +129,8 @@ static int ad7609_chan_scale_setup(struct iio_dev *indio_dev,
>  				   struct iio_chan_spec *chan);
>  static int ad7616_sw_mode_setup(struct iio_dev *indio_dev);
>  static int ad7606b_sw_mode_setup(struct iio_dev *indio_dev);
> +static int ad7606_chan_calib_gain_setup(struct iio_dev *indio_dev,
> +					struct iio_chan_spec *chan);
>  
>  const struct ad7606_chip_info ad7605_4_info = {
>  	.max_samplerate = 300 * KILO,
> @@ -180,6 +186,7 @@ const struct ad7606_chip_info ad7606b_info = {
>  	.scale_setup_cb = ad7606_16bit_chan_scale_setup,
>  	.sw_setup_cb = ad7606b_sw_mode_setup,
>  	.offload_storagebits = 32,
> +	.calib_gain_setup_cb = ad7606_chan_calib_gain_setup,
>  	.calib_offset_avail = ad7606_calib_offset_avail,
>  	.calib_phase_avail = ad7606b_calib_phase_avail,
>  };
> @@ -195,6 +202,7 @@ const struct ad7606_chip_info ad7606c_16_info = {
>  	.scale_setup_cb = ad7606c_16bit_chan_scale_setup,
>  	.sw_setup_cb = ad7606b_sw_mode_setup,
>  	.offload_storagebits = 32,
> +	.calib_gain_setup_cb = ad7606_chan_calib_gain_setup,
>  	.calib_offset_avail = ad7606_calib_offset_avail,
>  	.calib_phase_avail = ad7606c_calib_phase_avail,
>  };
> @@ -246,6 +254,7 @@ const struct ad7606_chip_info ad7606c_18_info = {
>  	.scale_setup_cb = ad7606c_18bit_chan_scale_setup,
>  	.sw_setup_cb = ad7606b_sw_mode_setup,
>  	.offload_storagebits = 32,
> +	.calib_gain_setup_cb = ad7606_chan_calib_gain_setup,
>  	.calib_offset_avail = ad7606c_18bit_calib_offset_avail,
>  	.calib_phase_avail = ad7606c_calib_phase_avail,
>  };
> @@ -357,6 +366,50 @@ static int ad7606_get_chan_config(struct iio_dev *indio_dev,
> int ch,
>  	return 0;
>  }
>  
> +static int ad7606_chan_calib_gain_setup(struct iio_dev *indio_dev,
> +					struct iio_chan_spec *chan)
> +{
> +	struct ad7606_state *st = iio_priv(indio_dev);
> +	unsigned int num_channels = st->chip_info->num_adc_channels;
> +	struct device *dev = st->dev;
> +	int ret;
> +
> +	device_for_each_child_node_scoped(dev, child) {
> +		int reg, r_gain;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			return ret;
> +
> +		/* channel number (here) is from 1 to num_channels */
> +		if (reg < 1 || reg > num_channels) {
> +			dev_warn(dev, "invalid ch number (ignoring): %d\n", reg);
> +			continue;
> +		}
> +
> +		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
> +					       &r_gain);
> +		if (ret == -EINVAL)
> +			/* Keep the default register value. */
> +			continue;
> +		if (ret)
> +			return ret;
> +
> +		if (r_gain < AD7606_CALIB_GAIN_MIN ||
> +		    r_gain > AD7606_CALIB_GAIN_MAX)
> +			return dev_err_probe(st->dev, -EINVAL,
> +					     "wrong gain calibration value.");
> +
> +		/* Chan reg is 1-based index. */
> +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> +					  r_gain / AD7606_CALIB_GAIN_STEP);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int ad7606c_18bit_chan_scale_setup(struct iio_dev *indio_dev,
>  					  struct iio_chan_spec *chan)
>  {
> @@ -1410,6 +1463,10 @@ static int ad7606_probe_channels(struct iio_dev *indio_dev)
>  				chan->info_mask_separate_available |=
>  					BIT(IIO_CHAN_INFO_CALIBBIAS) |
>  					BIT(IIO_CHAN_INFO_CALIBCONV_DELAY);
> +				ret = st->chip_info->calib_gain_setup_cb(
> +					indio_dev, chan);
> +				if (ret)
> +					return ret;
>  			}
>  
>  			/*
> diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h
> index
> 4c39de36154ffb80dfbb01bb4f812826bdc55967..e9a59d2afafd43e66137599dbd8220cd6b641e61
> 100644
> --- a/drivers/iio/adc/ad7606.h
> +++ b/drivers/iio/adc/ad7606.h
> @@ -50,6 +50,8 @@ struct ad7606_state;
>  typedef int (*ad7606_scale_setup_cb_t)(struct iio_dev *indio_dev,
>  				       struct iio_chan_spec *chan);
>  typedef int (*ad7606_sw_setup_cb_t)(struct iio_dev *indio_dev);
> +typedef int (*ad7606_calib_gain_setup_cb_t)(struct iio_dev *indio_dev,
> +					    struct iio_chan_spec *chan);
>  
>  /**
>   * struct ad7606_chip_info - chip specific information
> @@ -66,6 +68,7 @@ typedef int (*ad7606_sw_setup_cb_t)(struct iio_dev *indio_dev);
>   * @init_delay_ms:	required delay in milliseconds for initialization
>   *			after a restart
>   * @offload_storagebits: storage bits used by the offload hw implementation
> + * @calib_gain_setup_cb: callback to setup of gain calibration for each channel
>   * @calib_offset_avail: pointer to offset calibration range/limits array
>   * @calib_phase_avail:  pointer to phase calibration range/limits array
>   */
> @@ -81,6 +84,7 @@ struct ad7606_chip_info {
>  	bool				os_req_reset;
>  	unsigned long			init_delay_ms;
>  	u8				offload_storagebits;
> +	ad7606_calib_gain_setup_cb_t	calib_gain_setup_cb;
>  	const int			*calib_offset_avail;
>  	const int			(*calib_phase_avail)[2];
>  };
>