[PATCH v5 0/5] iio: adc: add ad7606 calibration support

[PATCH v5 0/5] iio: adc: add ad7606 calibration support

[Angelo Dureghello]

Add gain, offset and phase (as a delay) calibration support, for
ad7606b, ad7606c16 and ad7606c18.

Calibration is available for devices with software mode capability. 

Offset and phase calibration is configurable by sysfs attributes, while
gain calibration value in ohms must match the external RFilter value,
when an external RFilter is available, so implemented through a specific
devicetree "adi,rfilter-ohms" property.

This patchset depends on:
https://lore.kernel.org/linux-iio/20250505131544.0a7477a2@jic23-huawei/

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
Changes in v5:
- fix tab/spaces wrong formatting on ABI doc (1/5),
- fix description in ABI doc (1/5),
- fix code multiline alignments (3/5),
- fix calibration offset calculation as oneliner expression (3/5), 
- Link to v4: https://lore.kernel.org/r/20250508-wip-bl-ad7606-calibration-v4-0-91a3f2837e6b@baylibre.com

Changes in v4:
- fix ad7606_chan_calib_gain_setup appropriately to be called once.
- Link to v3: https://lore.kernel.org/r/20250506-wip-bl-ad7606-calibration-v3-0-6eb7b6e72307@baylibre.com

Changes in v3:
- fix dt_bindings,
- change sysfs calib_delay to convdelay,
- fix sysfs documentation accordingly,
- used u32 for reg and r_gain,
- used DIV_ROUND_CLOSEST for setting r_gain,
- minor syntax fixes,
- Link to v2: https://lore.kernel.org/r/20250502-wip-bl-ad7606-calibration-v2-0-174bd0af081b@baylibre.com

Changes in v2:
- change phase_delay to calib_delay,
- fix dt_bindings,
- fix gain calibarion fdt parsing,
- fix ad7606c-18 calib offset range,
- fix calib offset calculation,
- fix calib gain range,
- Link to v1: https://lore.kernel.org/r/20250429-wip-bl-ad7606-calibration-v1-0-eb4d4821b172@baylibre.com

---
Angelo Dureghello (5):
      Documentation: ABI: IIO: add calibconv_delay documentation
      iio: core: add ADC delay calibration definition
      iio: adc: ad7606: add offset and phase calibration support
      dt-bindings: iio: adc: adi,ad7606: add gain calibration support
      iio: adc: ad7606: add gain calibration support

 Documentation/ABI/testing/sysfs-bus-iio            |  24 +++
 .../devicetree/bindings/iio/adc/adi,ad7606.yaml    |  29 +++
 drivers/iio/adc/ad7606.c                           | 221 +++++++++++++++++++++
 drivers/iio/adc/ad7606.h                           |  12 ++
 drivers/iio/industrialio-core.c                    |   1 +
 include/linux/iio/types.h                          |   1 +
 6 files changed, 288 insertions(+)
---
base-commit: 7ad2a2f59802461dd18f641482e5da808c32180b
change-id: 20250429-wip-bl-ad7606-calibration-20a396a60352

Best regards,
-- 
Angelo Dureghello <adureghello@baylibre.com>

[PATCH v5 1/5] Documentation: ABI: IIO: add calibconv_delay documentation

[Angelo Dureghello]

From: Angelo Dureghello <adureghello@baylibre.com>

Add new IIO calibconv_delay documentation.

The ad7606 implements a phase calibation feature, in nanoseconds.
Being this a time delay, using the conv_delay suffix.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 Documentation/ABI/testing/sysfs-bus-iio | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 190bfcc1e836b69622692d7c056c0092e00f1a9b..4cf482eca3d8a0a80b051fbb496f82f836ab76f8 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -559,6 +559,30 @@ Description:
 		- a small discrete set of values like "0 2 4 6 8"
 		- a range specified as "[min step max]"
 
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_convdelay
+KernelVersion:	6.16
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Delay of start of conversion from common reference point shared
+		by all channels. Can be writable when used to compensate for
+		delay variation introduced by external filters feeding a
+		simultaneous sampling ADC.
+
+		I.e., for the ad7606 ADC series, this value is intended as a
+		configurable time delay in seconds, to correct delay introduced
+		by an optional external filtering circuit.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_convdelay_available
+KernelVersion:	6.16
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Available values of convdelay. Maybe expressed as:
+
+		- a range specified as "[min step max]"
+
+		If shared across all channels, <type>_calibconv_delay_available
+		is used.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_x_calibscale
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_y_calibscale
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_z_calibscale

-- 
2.49.0

[PATCH v5 2/5] iio: core: add ADC delay calibration definition

[Angelo Dureghello]

From: Angelo Dureghello <adureghello@baylibre.com>

ADCs as ad7606 implement a phase calibration as a delay.
Add such definition, needed for ad7606.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 drivers/iio/industrialio-core.c | 1 +
 include/linux/iio/types.h       | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 178e99b111debc59a247fcc3a6037e429db3bebf..f13c3aa470d774bfe655d6a9fb00c263789db637 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -188,6 +188,7 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_CALIBAMBIENT] = "calibambient",
 	[IIO_CHAN_INFO_ZEROPOINT] = "zeropoint",
 	[IIO_CHAN_INFO_TROUGH] = "trough_raw",
+	[IIO_CHAN_INFO_CONVDELAY] = "convdelay",
 };
 /**
  * iio_device_id() - query the unique ID for the device
diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
index d89982c98368cf72c0fc30fa66ab001e48af4e8b..ad2761efcc8315e1f9907d2a7159447fb463333e 100644
--- a/include/linux/iio/types.h
+++ b/include/linux/iio/types.h
@@ -69,6 +69,7 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_CALIBAMBIENT,
 	IIO_CHAN_INFO_ZEROPOINT,
 	IIO_CHAN_INFO_TROUGH,
+	IIO_CHAN_INFO_CONVDELAY,
 };
 
 #endif /* _IIO_TYPES_H_ */

-- 
2.49.0

[PATCH v5 3/5] iio: adc: ad7606: add offset and phase calibration support

[Angelo Dureghello]

From: Angelo Dureghello <adureghello@baylibre.com>

Add support for offset and phase calibration, only for
devices that support software mode, that are:

ad7606b
ad7606c-16
ad7606c-18

Tested-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 drivers/iio/adc/ad7606.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++
 drivers/iio/adc/ad7606.h |   9 +++
 2 files changed, 169 insertions(+)

diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c
index 2aa59481c52c07537110e7fc1fd1aedbab6b098d..bb0c89fc618874f4a5948d8e537716f87127bc92 100644
--- a/drivers/iio/adc/ad7606.c
+++ b/drivers/iio/adc/ad7606.c
@@ -95,6 +95,22 @@ static const unsigned int ad7616_oversampling_avail[8] = {
 	1, 2, 4, 8, 16, 32, 64, 128,
 };
 
+static const int ad7606_calib_offset_avail[3] = {
+	-128, 1, 127,
+};
+
+static const int ad7606c_18bit_calib_offset_avail[3] = {
+	-512, 4, 508,
+};
+
+static const int ad7606b_calib_phase_avail[][2] = {
+	{ 0, 0 }, { 0, 1250 }, { 0, 318750 },
+};
+
+static const int ad7606c_calib_phase_avail[][2] = {
+	{ 0, 0 }, { 0, 1000 }, { 0, 255000 },
+};
+
 static int ad7606c_18bit_chan_scale_setup(struct iio_dev *indio_dev,
 					  struct iio_chan_spec *chan);
 static int ad7606c_16bit_chan_scale_setup(struct iio_dev *indio_dev,
@@ -164,6 +180,8 @@ 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_offset_avail = ad7606_calib_offset_avail,
+	.calib_phase_avail = ad7606b_calib_phase_avail,
 };
 EXPORT_SYMBOL_NS_GPL(ad7606b_info, "IIO_AD7606");
 
@@ -177,6 +195,8 @@ 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_offset_avail = ad7606_calib_offset_avail,
+	.calib_phase_avail = ad7606c_calib_phase_avail,
 };
 EXPORT_SYMBOL_NS_GPL(ad7606c_16_info, "IIO_AD7606");
 
@@ -226,6 +246,8 @@ 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_offset_avail = ad7606c_18bit_calib_offset_avail,
+	.calib_phase_avail = ad7606c_calib_phase_avail,
 };
 EXPORT_SYMBOL_NS_GPL(ad7606c_18_info, "IIO_AD7606");
 
@@ -683,6 +705,40 @@ static int ad7606_scan_direct(struct iio_dev *indio_dev, unsigned int ch,
 	return ret;
 }
 
+static int ad7606_get_calib_offset(struct ad7606_state *st, int ch, int *val)
+{
+	int ret;
+
+	ret = st->bops->reg_read(st, AD7606_CALIB_OFFSET(ch));
+	if (ret < 0)
+		return ret;
+
+	*val = st->chip_info->calib_offset_avail[0] +
+	       ret * st->chip_info->calib_offset_avail[1];
+
+	return 0;
+}
+
+static int ad7606_get_calib_phase(struct ad7606_state *st, int ch, int *val,
+				  int *val2)
+{
+	int ret;
+
+	ret = st->bops->reg_read(st, AD7606_CALIB_PHASE(ch));
+	if (ret < 0)
+		return ret;
+
+	*val = 0;
+
+	/*
+	 * ad7606b: phase delay from 0 to 318.75 μs in steps of 1.25 μs.
+	 * ad7606c-16/18: phase delay from 0 µs to 255 µs in steps of 1 µs.
+	 */
+	*val2 = ret * st->chip_info->calib_phase_avail[1][1];
+
+	return 0;
+}
+
 static int ad7606_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val,
@@ -717,6 +773,22 @@ static int ad7606_read_raw(struct iio_dev *indio_dev,
 		pwm_get_state(st->cnvst_pwm, &cnvst_pwm_state);
 		*val = DIV_ROUND_CLOSEST_ULL(NSEC_PER_SEC, cnvst_pwm_state.period);
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		if (!iio_device_claim_direct(indio_dev))
+			return -EBUSY;
+		ret = ad7606_get_calib_offset(st, chan->scan_index, val);
+		iio_device_release_direct(indio_dev);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CONVDELAY:
+		if (!iio_device_claim_direct(indio_dev))
+			return -EBUSY;
+		ret = ad7606_get_calib_phase(st, chan->scan_index, val, val2);
+		iio_device_release_direct(indio_dev);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT_PLUS_NANO;
 	}
 	return -EINVAL;
 }
@@ -767,6 +839,64 @@ static int ad7606_write_os_hw(struct iio_dev *indio_dev, int val)
 	return 0;
 }
 
+static int ad7606_set_calib_offset(struct ad7606_state *st, int ch, int val)
+{
+	int start_val, step_val, stop_val;
+	int offset;
+
+	start_val = st->chip_info->calib_offset_avail[0];
+	step_val = st->chip_info->calib_offset_avail[1];
+	stop_val = st->chip_info->calib_offset_avail[2];
+
+	if (val < start_val || val > stop_val)
+		return -EINVAL;
+
+	offset = (val - start_val) / step_val;
+
+	return st->bops->reg_write(st, AD7606_CALIB_OFFSET(ch), offset);
+}
+
+static int ad7606_set_calib_phase(struct ad7606_state *st, int ch, int val,
+				  int val2)
+{
+	int wreg, start_ns, step_ns, stop_ns;
+
+	if (val != 0)
+		return -EINVAL;
+
+	start_ns = st->chip_info->calib_phase_avail[0][1];
+	step_ns = st->chip_info->calib_phase_avail[1][1];
+	stop_ns = st->chip_info->calib_phase_avail[2][1];
+
+	/*
+	 * ad7606b: phase delay from 0 to 318.75 μs in steps of 1.25 μs.
+	 * ad7606c-16/18: phase delay from 0 µs to 255 µs in steps of 1 µs.
+	 */
+	if (val2 < start_ns || val2 > stop_ns)
+		return -EINVAL;
+
+	wreg = val2 / step_ns;
+
+	return st->bops->reg_write(st, AD7606_CALIB_PHASE(ch), wreg);
+}
+
+static int ad7606_write_raw_get_fmt(struct iio_dev *indio_dev,
+				    struct iio_chan_spec const *chan, long info)
+{
+	switch (info) {
+	case IIO_CHAN_INFO_SCALE:
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+	case IIO_CHAN_INFO_CALIBBIAS:
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CONVDELAY:
+		return IIO_VAL_INT_PLUS_NANO;
+	default:
+		return -EINVAL;
+	}
+}
+
 static int ad7606_write_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int val,
@@ -820,6 +950,18 @@ static int ad7606_write_raw(struct iio_dev *indio_dev,
 		if (val < 0 && val2 != 0)
 			return -EINVAL;
 		return ad7606_set_sampling_freq(st, val);
+	case IIO_CHAN_INFO_CALIBBIAS:
+		if (!iio_device_claim_direct(indio_dev))
+			return -EBUSY;
+		ret = ad7606_set_calib_offset(st, chan->scan_index, val);
+		iio_device_release_direct(indio_dev);
+		return ret;
+	case IIO_CHAN_INFO_CONVDELAY:
+		if (!iio_device_claim_direct(indio_dev))
+			return -EBUSY;
+		ret = ad7606_set_calib_phase(st, chan->scan_index, val, val2);
+		iio_device_release_direct(indio_dev);
+		return ret;
 	default:
 		return -EINVAL;
 	}
@@ -998,6 +1140,14 @@ static int ad7606_read_avail(struct iio_dev *indio_dev,
 		*type = IIO_VAL_INT_PLUS_MICRO;
 
 		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		*vals = st->chip_info->calib_offset_avail;
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_RANGE;
+	case IIO_CHAN_INFO_CONVDELAY:
+		*vals = (const int *)st->chip_info->calib_phase_avail;
+		*type = IIO_VAL_INT_PLUS_NANO;
+		return IIO_AVAIL_RANGE;
 	}
 	return -EINVAL;
 }
@@ -1060,6 +1210,7 @@ static const struct iio_info ad7606_info_sw_mode = {
 	.read_raw = &ad7606_read_raw,
 	.write_raw = &ad7606_write_raw,
 	.read_avail = &ad7606_read_avail,
+	.write_raw_get_fmt = ad7606_write_raw_get_fmt,
 	.debugfs_reg_access = &ad7606_reg_access,
 	.validate_trigger = &ad7606_validate_trigger,
 	.update_scan_mode = &ad7606_update_scan_mode,
@@ -1252,6 +1403,15 @@ static int ad7606_probe_channels(struct iio_dev *indio_dev)
 			chan->info_mask_separate_available |=
 				BIT(IIO_CHAN_INFO_SCALE);
 
+			if (st->chip_info->calib_offset_avail) {
+				chan->info_mask_separate |=
+					BIT(IIO_CHAN_INFO_CALIBBIAS) |
+					BIT(IIO_CHAN_INFO_CONVDELAY);
+				chan->info_mask_separate_available |=
+					BIT(IIO_CHAN_INFO_CALIBBIAS) |
+					BIT(IIO_CHAN_INFO_CONVDELAY);
+			}
+
 			/*
 			 * All chips with software mode support oversampling,
 			 * so we skip the oversampling_available check. And the
diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h
index 441e62c521bcbea69b4f70bb2d55f65334d22276..f613583a7fa4095115b0b28e3f8e51cd32b93524 100644
--- a/drivers/iio/adc/ad7606.h
+++ b/drivers/iio/adc/ad7606.h
@@ -40,6 +40,11 @@
 #define AD7606_RANGE_CH_ADDR(ch)	(0x03 + ((ch) >> 1))
 #define AD7606_OS_MODE			0x08
 
+#define AD7606_CALIB_GAIN(ch)		(0x09 + (ch))
+#define AD7606_CALIB_GAIN_MASK		GENMASK(5, 0)
+#define AD7606_CALIB_OFFSET(ch)		(0x11 + (ch))
+#define AD7606_CALIB_PHASE(ch)		(0x19 + (ch))
+
 struct ad7606_state;
 
 typedef int (*ad7606_scale_setup_cb_t)(struct iio_dev *indio_dev,
@@ -61,6 +66,8 @@ 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_offset_avail: pointer to offset calibration range/limits array
+ * @calib_phase_avail:  pointer to phase calibration range/limits array
  */
 struct ad7606_chip_info {
 	unsigned int			max_samplerate;
@@ -74,6 +81,8 @@ struct ad7606_chip_info {
 	bool				os_req_reset;
 	unsigned long			init_delay_ms;
 	u8				offload_storagebits;
+	const int			*calib_offset_avail;
+	const int			(*calib_phase_avail)[2];
 };
 
 /**

-- 
2.49.0

[PATCH v5 4/5] dt-bindings: iio: adc: adi,ad7606: add gain calibration support

[Angelo Dureghello]

From: Angelo Dureghello <adureghello@baylibre.com>

Add gain calibration support by a per-channel resistor value.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 .../devicetree/bindings/iio/adc/adi,ad7606.yaml    | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
index 29f12d650442b8ff2eb455306ce59a0e87867ddd..6926f5f090ad6bbbe7bfd9327dc5ae17dafcd1fd 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
@@ -204,6 +204,15 @@ patternProperties:
           considered a bipolar differential channel. Otherwise it is bipolar
           single-ended.
 
+      adi,rfilter-ohms:
+        description:
+          For ADCs that supports gain calibration, this property must be set to
+          the value of the external RFilter resistor. Proper gain error
+          correction is applied based on this value.
+        default: 0
+        minimum: 0
+        maximum: 64512
+
     required:
       - reg
       - bipolar
@@ -256,6 +265,25 @@ allOf:
       properties:
         adi,oversampling-ratio-gpios: false
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - adi,ad7605-4
+              - adi,ad7606-4
+              - adi,ad7606-6
+              - adi,ad7606-8
+              - adi,ad7607
+              - adi,ad7608
+              - adi,ad7609
+              - adi,ad7616
+    then:
+      patternProperties:
+        "^channel@[0-9a-f]+$":
+          properties:
+            adi,rfilter-ohms: false
+
   - if:
       properties:
         compatible:
@@ -398,6 +426,7 @@ examples:
                 reg = <8>;
                 diff-channels = <8 8>;
                 bipolar;
+                adi,rfilter-ohms = <2048>;
             };
 
         };

-- 
2.49.0

[PATCH v5 5/5] iio: adc: ad7606: add gain calibration support

[Angelo Dureghello]

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.

Tested-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 drivers/iio/adc/ad7606.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/iio/adc/ad7606.h |  3 +++
 2 files changed, 64 insertions(+)

diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c
index bb0c89fc618874f4a5948d8e537716f87127bc92..19802bb7ec6624203b50589b6b76085c9f2f9628 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 +129,7 @@ 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);
 
 const struct ad7606_chip_info ad7605_4_info = {
 	.max_samplerate = 300 * KILO,
@@ -180,6 +185,7 @@ 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 +201,7 @@ 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 +253,7 @@ 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 +365,52 @@ 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 ad7606_state *st = iio_priv(indio_dev);
+	unsigned int num_channels = st->chip_info->num_adc_channels;
+	struct device *dev = st->dev;
+	int ret;
+
+	/*
+	 * This function is called once, and parses all the channel nodes,
+	 * so continuing on next channel node on errors, informing of them.
+	 */
+	device_for_each_child_node_scoped(dev, child) {
+		u32 reg, r_gain;
+
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret)
+			continue;
+
+		/* Chan reg is a 1-based index. */
+		if (reg < 1 || reg > num_channels) {
+			dev_warn(dev, "wrong ch number (ignoring): %d\n", reg);
+			continue;
+		}
+
+		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
+					       &r_gain);
+		if (ret)
+			/* Keep the default register value. */
+			continue;
+
+		if (r_gain > AD7606_CALIB_GAIN_MAX) {
+			dev_warn(dev, "wrong gain calibration value");
+			continue;
+		}
+
+		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
+			DIV_ROUND_CLOSEST(r_gain, AD7606_CALIB_GAIN_STEP));
+		if (ret) {
+			dev_warn(dev, "error writing r_gain");
+			continue;
+		}
+	}
+
+	return 0;
+}
+
 static int ad7606c_18bit_chan_scale_setup(struct iio_dev *indio_dev,
 					  struct iio_chan_spec *chan)
 {
@@ -1448,6 +1502,13 @@ static int ad7606_probe_channels(struct iio_dev *indio_dev)
 	if (slow_bus)
 		channels[i] = (struct iio_chan_spec)IIO_CHAN_SOFT_TIMESTAMP(i);
 
+	/* Setting up gain calibration for all channels. */
+	if (st->sw_mode_en && st->chip_info->calib_offset_avail) {
+		ret = st->chip_info->calib_gain_setup_cb(indio_dev);
+		if (ret)
+			return ret;
+	}
+
 	indio_dev->channels = channels;
 
 	return 0;
diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h
index f613583a7fa4095115b0b28e3f8e51cd32b93524..6313eea2bd0ccf97222a50dc26d8ec65042d0db7 100644
--- a/drivers/iio/adc/ad7606.h
+++ b/drivers/iio/adc/ad7606.h
@@ -50,6 +50,7 @@ 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 ad7606_chip_info - chip specific information
@@ -66,6 +67,7 @@ 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
  * @calib_offset_avail: pointer to offset calibration range/limits array
  * @calib_phase_avail:  pointer to phase calibration range/limits array
  */
@@ -81,6 +83,7 @@ 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

Re: [PATCH v5 5/5] iio: adc: ad7606: add gain calibration support

[Andy Shevchenko]

On Mon, May 19, 2025 at 12:13:42PM +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.

...

> +	device_for_each_child_node_scoped(dev, child) {
> +		u32 reg, r_gain;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			continue;
> +
> +		/* Chan reg is a 1-based index. */
> +		if (reg < 1 || reg > num_channels) {
> +			dev_warn(dev, "wrong ch number (ignoring): %d\n", reg);
> +			continue;
> +		}

Like I said, we should leave the validation to the schema or do it correctly here.
Otherwise it's an inconsistency between DT schema validator and this check.
I.o.w. this check *allows* the b0rken DT to be handled and I think this is simply
wrong.

> +		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
> +					       &r_gain);
> +		if (ret)
> +			/* Keep the default register value. */
> +			continue;
> +
> +		if (r_gain > AD7606_CALIB_GAIN_MAX) {
> +			dev_warn(dev, "wrong gain calibration value");
> +			continue;
> +		}

Same here.

> +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> +			DIV_ROUND_CLOSEST(r_gain, AD7606_CALIB_GAIN_STEP));
> +		if (ret) {
> +			dev_warn(dev, "error writing r_gain");
> +			continue;

Not sure about this, though.

> +		}
> +	}

-- 
With Best Regards,
Andy Shevchenko