[PATCH v3 4/4] iio: adc: ad7405: add ad7405 driver

[Pop Ioan Daniel <pop.ioan-daniel@analog.com>]

Add support for the AD7405/ADUM770x, a high performance isolated ADC,
1-channel, 16-bit with a second-order Σ-Δ modulator that converts an
analog input signal into a high speed, single-bit data stream.

Signed-off-by: Pop Ioan Daniel <pop.ioan-daniel@analog.com>
---
changes in v3:
 - edit ad7405_chip_info struct instances
 - remove lock
 - add implementation for IIO_CHAN_INFO_SCALE
 - use IIO_CHAN_INFO_OVERSAMPLING_RATIO for controlling the decimation rate
 - use IIO_CHAN_INFO_SAMP_FREQ for read-only
 - remove dem_clk_get_enabled() function
 - remove chip_info variable from probe function
 - fix indentation
 - remove max_rate
 - rename ad7405_set_sampling_rate in ad7405_det_dec_rate
add adum7702 and adum7703 chip_info
 drivers/iio/adc/Kconfig  |  10 ++
 drivers/iio/adc/Makefile |   1 +
 drivers/iio/adc/ad7405.c | 276 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 287 insertions(+)
 create mode 100644 drivers/iio/adc/ad7405.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index ad06cf556785..6ed1042636d9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -251,6 +251,16 @@ config AD7380
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad7380.
 
+config AD7405
+	tristate "Analog Device AD7405 ADC Driver"
+	select IIO_BACKEND
+	help
+	  Say yes here to build support for Analog Devices AD7405, ADUM7701,
+	  ADUM7702, ADUM7703 analog to digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad7405.
+
 config AD7476
 	tristate "Analog Devices AD7476 1-channel ADCs driver and other similar devices from AD and TI"
 	depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 07d4b832c42e..8115f30b7862 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_AD7291) += ad7291.o
 obj-$(CONFIG_AD7292) += ad7292.o
 obj-$(CONFIG_AD7298) += ad7298.o
 obj-$(CONFIG_AD7380) += ad7380.o
+obj-$(CONFIG_AD7405) += ad7405.o
 obj-$(CONFIG_AD7476) += ad7476.o
 obj-$(CONFIG_AD7606_IFACE_PARALLEL) += ad7606_par.o
 obj-$(CONFIG_AD7606_IFACE_SPI) += ad7606_spi.o
diff --git a/drivers/iio/adc/ad7405.c b/drivers/iio/adc/ad7405.c
new file mode 100644
index 000000000000..1a96a283ab01
--- /dev/null
+++ b/drivers/iio/adc/ad7405.c
@@ -0,0 +1,276 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Analog Devices AD7405 driver
+ *
+ * Copyright 2025 Analog Devices Inc.
+ */
+
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/util_macros.h>
+
+#include <linux/iio/backend.h>
+#include <linux/iio/iio.h>
+
+static const unsigned int ad7405_scale_table[][2] = {
+	{640, 0},
+};
+
+static const unsigned int adum7702_scale_table[][2] = {
+	{128, 0},
+};
+
+static const unsigned int ad7405_dec_rates[] = {
+	4096, 2048, 1024, 512, 256, 128, 64, 32,
+};
+
+struct ad7405_chip_info {
+	const char *name;
+	struct iio_chan_spec channel;
+	const unsigned int (*scale_table)[2];
+};
+
+struct ad7405_state {
+	struct iio_backend *back;
+	const struct ad7405_chip_info *info;
+	unsigned int sample_frequency_tbl[ARRAY_SIZE(ad7405_dec_rates)];
+	unsigned int sample_frequency;
+	unsigned int ref_frequency;
+	unsigned int dec_rate;
+};
+
+static void ad7405_fill_samp_freq_table(struct ad7405_state *st)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(ad7405_dec_rates); i++)
+		st->sample_frequency_tbl[i] =
+			DIV_ROUND_CLOSEST_ULL(st->ref_frequency, ad7405_dec_rates[i]);
+}
+
+static int ad7405_set_dec_rate(struct iio_dev *indio_dev,
+			       const struct iio_chan_spec *chan,
+			       unsigned int dec_rate)
+{
+	struct ad7405_state *st = iio_priv(indio_dev);
+	int ret;
+
+	ret = iio_backend_oversampling_ratio_set(st->back, 0, dec_rate);
+	if (ret)
+		return ret;
+
+	st->dec_rate = dec_rate;
+
+	return 0;
+}
+
+static int ad7405_get_scale(struct ad7405_state *st, int *val, int *val2)
+{
+	unsigned int tmp;
+
+	tmp = (st->info->scale_table[0][0] * 1000000ULL) >>
+		    st->info->channel.scan_type.realbits;
+	*val = tmp / 1000000;
+	*val2 = tmp % 1000000;
+
+	return IIO_VAL_INT_PLUS_NANO;
+}
+
+static int ad7405_read_raw(struct iio_dev *indio_dev,
+			   const struct iio_chan_spec *chan, int *val,
+			   int *val2, long info)
+{
+	struct ad7405_state *st = iio_priv(indio_dev);
+
+	switch (info) {
+	case IIO_CHAN_INFO_SCALE:
+		return ad7405_get_scale(st, val, val2);
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		*val = st->dec_rate;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = DIV_ROUND_CLOSEST_ULL(st->ref_frequency, st->dec_rate);
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad7405_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int val,
+			    int val2, long info)
+{
+	switch (info) {
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		return ad7405_set_dec_rate(indio_dev, chan, val);
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		if (val < 1)
+			return -EINVAL;
+		return ad7405_set_dec_rate(indio_dev, chan, val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad7405_read_avail(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     const int **vals, int *type, int *length,
+			     long info)
+{
+	switch (info) {
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		*vals = ad7405_dec_rates;
+		*length = ARRAY_SIZE(ad7405_dec_rates);
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info ad7405_iio_info = {
+	.read_raw = &ad7405_read_raw,
+	.write_raw = &ad7405_write_raw,
+	.read_avail = &ad7405_read_avail,
+};
+
+#define AD7405_IIO_CHANNEL {					\
+	.type = IIO_VOLTAGE,					\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+	.info_mask_shared_by_all = IIO_CHAN_INFO_SAMP_FREQ |	\
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),	\
+	.info_mask_shared_by_all_available =			\
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),	\
+	.indexed = 1,						\
+	.channel = 0,						\
+	.channel2 = 1,						\
+	.differential = 1,					\
+	.scan_index = 0,					\
+	.scan_type = {						\
+		.sign = 'u',					\
+		.realbits = 16,					\
+		.storagebits = 16,				\
+	},							\
+}
+
+static const struct ad7405_chip_info ad7405_chip_info = {
+	.name = "AD7405",
+	.scale_table = ad7405_scale_table,
+	.channel = AD7405_IIO_CHANNEL,
+};
+
+static const struct ad7405_chip_info adum7701_chip_info = {
+	.name = "ADUM7701",
+	.scale_table = ad7405_scale_table,
+	.channel = AD7405_IIO_CHANNEL,
+};
+
+static const struct ad7405_chip_info adum7702_chip_info = {
+	.name = "ADUM7702",
+	.scale_table = adum7702_scale_table,
+	.channel = AD7405_IIO_CHANNEL,
+};
+
+static const struct ad7405_chip_info adum7703_chip_info = {
+	.name = "ADUM7703",
+	.scale_table = ad7405_scale_table,
+	.channel = AD7405_IIO_CHANNEL,
+};
+
+static const char * const ad7405_power_supplies[] = {
+	"vdd1",	"vdd2",
+};
+
+static int ad7405_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct iio_dev *indio_dev;
+	struct ad7405_state *st;
+	struct clk *clk;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	st->info = device_get_match_data(dev);
+	if (!st->info)
+		return dev_err_probe(dev, -EINVAL, "no chip info\n");
+
+	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(ad7405_power_supplies),
+					     ad7405_power_supplies);
+
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get and enable supplies");
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	st->ref_frequency = clk_get_rate(clk);
+	if (!st->ref_frequency)
+		return -EINVAL;
+
+	ad7405_fill_samp_freq_table(st);
+
+	indio_dev->dev.parent = dev;
+	indio_dev->name = st->info->name;
+	indio_dev->channels = &st->info->channel;
+	indio_dev->num_channels = 1;
+	indio_dev->info = &ad7405_iio_info;
+
+	st->back = devm_iio_backend_get(dev, NULL);
+	if (IS_ERR(st->back))
+		return dev_err_probe(dev, PTR_ERR(st->back),
+				     "failed to get IIO backend");
+
+	ret = iio_backend_chan_enable(st->back, 0);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_backend_request_buffer(dev, st->back, indio_dev);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_backend_enable(dev, st->back);
+	if (ret)
+		return ret;
+
+	ret = ad7405_set_dec_rate(indio_dev, &indio_dev->channels[0], 256);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+/* Match table for of_platform binding */
+static const struct of_device_id ad7405_of_match[] = {
+	{ .compatible = "adi,ad7405", .data = &ad7405_chip_info, },
+	{ .compatible = "adi,adum7701", .data = &adum7701_chip_info, },
+	{ .compatible = "adi,adum7702", .data = &adum7702_chip_info, },
+	{ .compatible = "adi,adum7703", .data = &adum7703_chip_info, },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ad7405_of_match);
+
+static struct platform_driver ad7405_driver = {
+	.driver = {
+		.name = "ad7405",
+		.owner = THIS_MODULE,
+		.of_match_table = ad7405_of_match,
+	},
+	.probe = ad7405_probe,
+};
+module_platform_driver(ad7405_driver);
+
+MODULE_AUTHOR("Dragos Bogdan <dragos.bogdan@analog.com>");
+MODULE_AUTHOR("Pop Ioan Daniel <pop.ioan-daniel@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD7405 driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_BACKEND");
-- 
2.34.1