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

Angelo Dureghello
2025-05-02T13:28:23Z

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>
---
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];
};

--
2.49.0