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From: David Lechner <dlechner@baylibre.com>
To: Jonathan Cameron <jic23@kernel.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>
Cc: David Lechner <dlechner@baylibre.com>,
	Michael Hennerich <michael.hennerich@analog.com>,
	=?utf-8?q?Nuno_S=C3=A1?= <nuno.sa@analog.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-iio@vger.kernel.org,
	devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org,
	Ramona Gradinariu <ramona.gradinariu@analog.com>
Subject: [PATCH 2/3] iio: adc: ad4695: Add driver for AD4695 and similar ADCs
Date: Wed, 12 Jun 2024 14:20:41 -0500
Message-ID: <20240612-iio-adc-ad4695-v1-2-6a4ed251fc86@baylibre.com>
In-Reply-To: <20240612-iio-adc-ad4695-v1-0-6a4ed251fc86@baylibre.com>
References: <20240612-iio-adc-ad4695-v1-0-6a4ed251fc86@baylibre.com>
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This is a new driver for Analog Devices Inc. AD4695 and similar ADCs.
The initial driver supports initializing the chip including configuring
all possible LDO and reference voltage sources as well as any possible
voltage input channel wiring configuration.

Only the 4-wire SPI wiring mode where the CNV pin is tied to the CS pin
is supported at this time. And reading sample data from the ADC can only
be done in direct mode for now.

Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 MAINTAINERS              |   1 +
 drivers/iio/adc/Kconfig  |  11 +
 drivers/iio/adc/Makefile |   1 +
 drivers/iio/adc/ad4695.c | 804 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 817 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 8d15e4089d7c..611b7929e650 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1217,6 +1217,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
+F:	drivers/iio/adc/ad4695.c
 
 ANALOG DEVICES INC AD7091R DRIVER
 M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 3d91015af6ea..26c3090ff967 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -36,6 +36,17 @@ config AD4130
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad4130.
 
+config AD4695
+	tristate "Analog Device AD4695 ADC Driver"
+	depends on SPI
+	select REGMAP_SPI
+	help
+	  Say yes here to build support for Analog Devices AD4695 and similar
+	  analog to digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad4695.
+
 config AD7091R
 	tristate
 
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 37ac689a0209..5c4d79d4f939 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -7,6 +7,7 @@
 obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD4130) += ad4130.o
+obj-$(CONFIG_AD4695) += ad4695.o
 obj-$(CONFIG_AD7091R) += ad7091r-base.o
 obj-$(CONFIG_AD7091R5) += ad7091r5.o
 obj-$(CONFIG_AD7091R8) += ad7091r8.o
diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
new file mode 100644
index 000000000000..6e5a87817c86
--- /dev/null
+++ b/drivers/iio/adc/ad4695.c
@@ -0,0 +1,804 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SPI ADC driver for Analog Devices Inc. AD4695 and similar chips
+ *
+ * https://www.analog.com/en/products/ad4695.html
+ * https://www.analog.com/en/products/ad4696.html
+ * https://www.analog.com/en/products/ad4697.html
+ * https://www.analog.com/en/products/ad4698.html
+ *
+ * Copyright 2024 Analog Devices Inc.
+ * Copyright 2024 BayLibre, SAS
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/compiler.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/units.h>
+
+/* AD4695 registers */
+#define AD4695_REG_SPI_CONFIG_A			0x0000
+#define AD4695_REG_SPI_CONFIG_B			0x0001
+#define AD4695_REG_DEVICE_TYPE			0x0003
+#define AD4695_REG_SCRATCH_PAD			0x000A
+#define AD4695_REG_VENDOR_L			0x000C
+#define AD4695_REG_VENDOR_H			0x000D
+#define AD4695_REG_LOOP_MODE			0x000E
+#define AD4695_REG_SPI_CONFIG_C			0x0010
+#define AD4695_REG_SPI_STATUS			0x0011
+#define AD4695_REG_STATUS			0x0014
+#define AD4695_REG_ALERT_STATUS1		0x0015
+#define AD4695_REG_ALERT_STATUS2		0x0016
+#define AD4695_REG_CLAMP_STATUS			0x001A
+#define AD4695_REG_SETUP			0x0020
+#define AD4695_REG_REF_CTRL			0x0021
+#define AD4695_REG_SEQ_CTRL			0x0022
+#define AD4695_REG_AC_CTRL			0x0023
+#define AD4695_REG_STD_SEQ_CONFIG		0x0024
+#define AD4695_REG_GPIO_CTRL			0x0026
+#define AD4695_REG_GP_MODE			0x0027
+#define AD4695_REG_TEMP_CTRL			0x0029
+#define AD4695_REG_CONFIG_IN(n)			(0x0030 | (n))
+#define AD4695_REG_UPPER_IN(n)			(0x0040 | (2 * (n)))
+#define AD4695_REG_LOWER_IN(n)			(0x0060 | (2 * (n)))
+#define AD4695_REG_HYST_IN(n)			(0x0080 | (2 * (n)))
+#define AD4695_REG_OFFSET_IN(n)			(0x00A0 | (2 * (n)))
+#define AD4695_REG_GAIN_IN(n)			(0x00C0 | (2 * (n)))
+#define AD4695_REG_AS_SLOT(n)			(0x0100 | (n))
+#define AD4695_REG_MAX				0x017F
+
+/* Conversion mode commands */
+#define AD4695_CMD_EXIT_CNV_MODE		0x0A
+#define AD4695_CMD_TEMP_CHAN			0x0F
+#define AD4695_CMD_VOLTAGE_CHAN(n)		(0x10 | (n))
+
+/* SPI_CONFIG_A */
+#define AD4695_SW_RST_MSB		BIT(7)
+#define AD4695_SW_RST_LSB		BIT(0)
+
+/* SPI_CONFIG_B */
+#define AD4695_INST_MODE_MASK		BIT(7)
+#define AD4695_INST_MODE(x)		FIELD_PREP(AD4695_INST_MODE_MASK, (x))
+
+enum ad4695_instr_mode {
+	AD4695_INST_MODE_STREAM,
+	AD4695_INST_MODE_SINGLE,
+};
+
+/* Setup */
+#define AD4695_LDO_EN_MASK		BIT(4)
+#define AD4695_LDO_EN(x)		FIELD_PREP(AD4695_LDO_EN_MASK, (((x) ? 1 : 0)))
+#define AD4695_SPI_MODE_MASK		BIT(2)
+#define AD4695_SPI_MODE(x)		FIELD_PREP(AD4695_SPI_MODE_MASK, (x))
+#define AD4695_SPI_CYC_CTRL_MASK	BIT(1)
+#define AD4695_SPI_CYC_CTRL(x)		FIELD_PREP(AD4695_SPI_CYC_CTRL_MASK, (x))
+
+/* REF_CTRL */
+#define AD4695_OV_MODE_MASK		BIT(7)
+#define AD4695_OV_MODE(x)		FIELD_PREP(AD4695_OV_MODE_MASK, (x))
+#define AD4695_VREF_SET_MASK		GENMASK(4, 2)
+#define AD4695_VREF_SET(x)		FIELD_PREP(AD4695_VREF_SET_MASK, (x))
+#define AD4695_REFHIZ_EN_MASK		BIT(1)
+#define AD4695_REFHIZ_EN(x)		FIELD_PREP(AD4695_REFHIZ_EN_MASK, (((x) ? 1 : 0)))
+#define AD4695_REFBUF_EN_MASK		BIT(0)
+#define AD4695_REFBUF_EN(x)		FIELD_PREP(AD4695_REFBUF_EN_MASK, (((x) ? 1 : 0)))
+
+enum ad4695_ov_mode {
+	AD4695_OV_MODE_REDUCE_CURRENT,
+	AD4695_OV_MODE_DO_NOT_REDUCE_CURRENT,
+};
+
+/* SEQ_CTRL */
+#define AD4695_STD_SEQ_EN_MASK		BIT(7)
+#define AD4695_STD_SEQ_EN(x)		FIELD_PREP(AD4695_STD_SEQ_EN_MASK, (((x) ? 1 : 0)))
+#define AD4695_NUM_SLOTS_AS_MASK	GENMASK(6, 0)
+#define AD4695_NUM_SLOTS_AS(x)		FIELD_PREP(AD4695_NUM_SLOTS_AS_MASK, (x))
+
+/* CONFIG_INn */
+#define AD4695_IN_MODE_MASK		BIT(6)
+#define AD4695_IN_MODE(x)		FIELD_PREP(AD4695_IN_MODE_MASK, (((x) ? 1 : 0)))
+#define AD4695_IN_PAIR_MASK		GENMASK(5, 4)
+#define AD4695_IN_PAIR(x)		FIELD_PREP(AD4695_IN_PAIR_MASK, (x))
+#define AD4695_AINHIGHZ_EN_MASK		BIT(3)
+#define AD4695_AINHIGHZ_EN(x)		FIELD_PREP(AD4695_AINHIGHZ_EN_MASK, (((x) ? 1 : 0)))
+
+enum ad4695_in_pair {
+	AD4695_WITH_REFGND,
+	AD4695_WITH_COM,
+	AD4695_EVEN_ODD,
+};
+
+/* AS_SLOTn */
+#define AD4695_SLOT_INX_MASK		GENMASK(3, 0)
+#define AD4695_SLOT_INX(x)		FIELD_PREP(AD4695_SLOT_INX_MASK, (x))
+
+/* timing specs */
+#define AD4695_T_CONVERT_NS		415
+#define AD4695_T_WAKEUP_HW_MS		3
+#define AD4695_T_WAKEUP_SW_MS		3
+#define AD4695_T_REFBUF_MS		100
+#define AD4695_REG_ACCESS_SCLK_HZ	(10 * MEGA)
+
+/* adi,pin-paring DT property lookup table */
+static const char * const ad4695_pin_pairing[] = {
+	[AD4695_WITH_REFGND] = "refgnd",
+	[AD4695_WITH_COM] = "com",
+	[AD4695_EVEN_ODD] = "next",
+};
+
+struct ad4695_chip_info {
+	const char *name;
+	int max_sample_rate;
+	u8 num_voltage_inputs;
+};
+
+struct ad4695_channel_config {
+	bool bipolar;
+	bool highz_en;
+	unsigned int channel;
+	enum ad4695_in_pair pin_pairing;
+};
+
+struct ad4695_state {
+	struct spi_device *spi;
+	struct regmap *regmap;
+	struct gpio_desc *reset_gpio;
+	struct ad4695_channel_config *channels_cfg;
+	const struct ad4695_chip_info *chip_info;
+	/* Reference voltage. */
+	unsigned int vref_mv;
+	/* Common mode input pin voltage. */
+	unsigned int com_mv;
+	/* raw data conversion data recived */
+	u16 raw_data __aligned(IIO_DMA_MINALIGN);
+	/* Commands to send for single conversion */
+	u16 cnv_cmd;
+	u8 cnv_cmd2;
+};
+
+static const struct regmap_range ad4695_regmap_rd_ranges[] = {
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_A, AD4695_REG_SPI_CONFIG_B),
+	regmap_reg_range(AD4695_REG_DEVICE_TYPE, AD4695_REG_DEVICE_TYPE),
+	regmap_reg_range(AD4695_REG_SCRATCH_PAD, AD4695_REG_SCRATCH_PAD),
+	regmap_reg_range(AD4695_REG_VENDOR_L, AD4695_REG_LOOP_MODE),
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_C, AD4695_REG_SPI_STATUS),
+	regmap_reg_range(AD4695_REG_STATUS, AD4695_REG_ALERT_STATUS2),
+	regmap_reg_range(AD4695_REG_CLAMP_STATUS, AD4695_REG_CLAMP_STATUS),
+	regmap_reg_range(AD4695_REG_SETUP, AD4695_REG_TEMP_CTRL),
+	regmap_reg_range(AD4695_REG_CONFIG_IN(0), AD4695_REG_MAX),
+};
+
+static const struct regmap_access_table ad4695_regmap_rd_table = {
+	.yes_ranges = ad4695_regmap_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ad4695_regmap_rd_ranges),
+};
+
+static const struct regmap_range ad4695_regmap_wr_ranges[] = {
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_A, AD4695_REG_SPI_CONFIG_B),
+	regmap_reg_range(AD4695_REG_SCRATCH_PAD, AD4695_REG_SCRATCH_PAD),
+	regmap_reg_range(AD4695_REG_LOOP_MODE, AD4695_REG_LOOP_MODE),
+	regmap_reg_range(AD4695_REG_SPI_CONFIG_C, AD4695_REG_SPI_STATUS),
+	regmap_reg_range(AD4695_REG_SETUP, AD4695_REG_TEMP_CTRL),
+	regmap_reg_range(AD4695_REG_CONFIG_IN(0), AD4695_REG_MAX),
+};
+
+static const struct regmap_access_table ad4695_regmap_wr_table = {
+	.yes_ranges = ad4695_regmap_wr_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ad4695_regmap_wr_ranges),
+};
+
+static const struct regmap_config ad4695_regmap_config = {
+	.name = "ad4695",
+	.reg_bits = 16,
+	.val_bits = 8,
+	.max_register = AD4695_REG_MAX,
+	.rd_table = &ad4695_regmap_rd_table,
+	.wr_table = &ad4695_regmap_wr_table,
+	.can_multi_write = true,
+};
+
+static const struct iio_chan_spec ad4695_channel_template = {
+	.type = IIO_VOLTAGE,
+	.indexed = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_SCALE) |
+			      BIT(IIO_CHAN_INFO_OFFSET),
+	.scan_type = {
+		.realbits = 16,
+		.storagebits = 16,
+	},
+};
+
+static const struct iio_chan_spec ad4695_temp_channel_template = {
+	.address = AD4695_CMD_TEMP_CHAN,
+	.type = IIO_TEMP,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_SCALE) |
+			      BIT(IIO_CHAN_INFO_OFFSET),
+	.scan_type = {
+		.sign = 's',
+		.realbits = 16,
+		.storagebits = 16,
+	},
+};
+
+static const char * const ad4695_power_supplies[] = {
+	"avdd", "vio"
+};
+
+static const struct ad4695_chip_info ad4695_chip_info = {
+	.name = "ad4695",
+	.max_sample_rate = 500 * KILO,
+	.num_voltage_inputs = 16,
+};
+
+static const struct ad4695_chip_info ad4696_chip_info = {
+	.name = "ad4696",
+	.max_sample_rate = 1 * MEGA,
+	.num_voltage_inputs = 16,
+};
+
+static const struct ad4695_chip_info ad4697_chip_info = {
+	.name = "ad4697",
+	.max_sample_rate = 500 * KILO,
+	.num_voltage_inputs = 8,
+};
+
+static const struct ad4695_chip_info ad4698_chip_info = {
+	.name = "ad4698",
+	.max_sample_rate = 1 * MEGA,
+	.num_voltage_inputs = 8,
+};
+
+/* register convenience functions */
+
+static int ad4695_soft_reset(struct ad4695_state *st)
+{
+	int ret;
+
+	ret = regmap_set_bits(st->regmap, AD4695_REG_SPI_CONFIG_A,
+			      AD4695_SW_RST_MSB | AD4695_SW_RST_LSB);
+	if (ret)
+		return ret;
+
+	/* datasheet says we have to wait before communicating again */
+	msleep(AD4695_T_WAKEUP_SW_MS);
+
+	return 0;
+}
+
+static int ad4695_set_instr_mode(struct ad4695_state *st,
+				 enum ad4695_instr_mode mode)
+{
+	return regmap_update_bits(st->regmap, AD4695_REG_SPI_CONFIG_B,
+				  AD4695_INST_MODE_MASK, AD4695_INST_MODE(mode));
+}
+
+static int ad4695_set_ldo_en(struct ad4695_state *st, bool enable)
+{
+	return regmap_update_bits(st->regmap, AD4695_REG_SETUP,
+				  AD4695_LDO_EN_MASK, AD4695_LDO_EN(enable));
+}
+
+/**
+ * ad4695_set_single_cycle_mode - Set the device in single cycle mode
+ * @st: The AD4695 state
+ * @channel: The first channel to read
+ *
+ * As per the datasheet, to enable single cycle mode, we need to set
+ * STD_SEQ_EN=0, NUM_SLOTS_AS=0 and CYC_CTRL=1 (Table 15). Setting SPI_MODE=1
+ * triggers the first conversion using the channel in AS_SLOT0.
+ *
+ * Context: can sleep, must be called with iio_device_claim_direct held
+ * Return: 0 on success, a negative error code on failure
+ */
+static int ad4695_set_single_cycle_mode(struct ad4695_state *st,
+					unsigned int channel)
+{
+	int ret;
+
+	ret = regmap_clear_bits(st->regmap, AD4695_REG_SEQ_CTRL,
+				AD4695_STD_SEQ_EN_MASK | AD4695_NUM_SLOTS_AS_MASK);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(st->regmap, AD4695_REG_AS_SLOT(0),
+			   AD4695_SLOT_INX(channel));
+	if (ret)
+		return ret;
+
+	return regmap_set_bits(st->regmap, AD4695_REG_SETUP,
+			       AD4695_SPI_MODE_MASK | AD4695_SPI_CYC_CTRL_MASK);
+}
+
+static int ad4695_set_ov_mode(struct ad4695_state *st, enum ad4695_ov_mode mode)
+{
+	return regmap_update_bits(st->regmap, AD4695_REG_REF_CTRL,
+				  AD4695_OV_MODE_MASK, AD4695_OV_MODE(mode));
+}
+
+static int ad4695_set_ref_voltage(struct ad4695_state *st, int ref_voltage)
+{
+	u8 val;
+
+	if (ref_voltage >= 2400 && ref_voltage <= 2750)
+		val = 0;
+	else if (ref_voltage > 2750 && ref_voltage <= 3250)
+		val = 1;
+	else if (ref_voltage > 3250 && ref_voltage <= 3750)
+		val = 2;
+	else if (ref_voltage > 3750 && ref_voltage <= 4500)
+		val = 3;
+	else if (ref_voltage > 4500 && ref_voltage <= 5100)
+		val = 4;
+	else
+		return -EINVAL;
+
+	return regmap_update_bits(st->regmap, AD4695_REG_REF_CTRL,
+				  AD4695_VREF_SET_MASK, AD4695_VREF_SET(val));
+}
+
+static int ad4695_set_refhiz_en(struct ad4695_state *st, bool enable)
+{
+	return regmap_update_bits(st->regmap, AD4695_REG_REF_CTRL,
+				  AD4695_REFHIZ_EN_MASK, AD4695_REFHIZ_EN(enable));
+}
+
+static int ad4695_set_refbuf_en(struct ad4695_state *st, bool enable)
+{
+	return regmap_update_bits(st->regmap, AD4695_REG_REF_CTRL,
+				  AD4695_REFBUF_EN_MASK, AD4695_REFBUF_EN(enable));
+}
+
+static int ad4695_write_chn_cfg(struct ad4695_state *st,
+				struct ad4695_channel_config *cfg)
+{
+	u32 mask = 0, val = 0;
+
+	mask |= AD4695_IN_MODE_MASK;
+	val |= AD4695_IN_MODE(cfg->bipolar);
+
+	mask |= AD4695_IN_PAIR_MASK;
+	val |= AD4695_IN_PAIR(cfg->pin_pairing);
+
+	mask |= AD4695_AINHIGHZ_EN_MASK;
+	val |= AD4695_AINHIGHZ_EN(cfg->highz_en);
+
+	return regmap_update_bits(st->regmap, AD4695_REG_CONFIG_IN(cfg->channel),
+				  mask, val);
+}
+
+/**
+ * ad4695_read_one_sample - Read a single sample using single-cycle mode
+ * @st: The AD4695 state
+ * @address: The address of the channel to read
+ *
+ * Upon return, the sample will be stored in the raw_data field of @st.
+ *
+ * Context: can sleep, must be called with iio_device_claim_direct held
+ * Return: 0 on success, a negative error code on failure
+ */
+static int ad4695_read_one_sample(struct ad4695_state *st, unsigned int address)
+{
+	struct spi_transfer xfer[2] = { };
+	int ret;
+
+	ret = ad4695_set_single_cycle_mode(st, address);
+	if (ret)
+		return ret;
+
+	/*
+	 * Setting the first channel to the temperature channel isn't supported
+	 * in single-cycle mode, so we have to do an extra xfer to read the
+	 * temperature.
+	 */
+	if (address == AD4695_CMD_TEMP_CHAN) {
+		/* We aren't reading, so we can make this a short xfer. */
+		st->cnv_cmd2 = AD4695_CMD_TEMP_CHAN << 3;
+		xfer[0].bits_per_word = 8;
+		xfer[0].tx_buf = &st->cnv_cmd2;
+		xfer[0].len = 1;
+		xfer[0].cs_change = 1;
+		xfer[0].cs_change_delay.value = AD4695_T_CONVERT_NS;
+		xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
+
+		/* Then read the result and exit conversion mode. */
+		st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
+		xfer[1].bits_per_word = 16;
+		xfer[1].tx_buf = &st->cnv_cmd;
+		xfer[1].rx_buf = &st->raw_data;
+		xfer[1].len = 2;
+
+		return spi_sync_transfer(st->spi, xfer, 2);
+	}
+
+	/*
+	 * The conversion has already been done and we just have to read the
+	 * result and exit conversion mode.
+	 */
+	st->cnv_cmd = AD4695_CMD_EXIT_CNV_MODE << 11;
+	xfer[0].bits_per_word = 16;
+	xfer[0].tx_buf = &st->cnv_cmd;
+	xfer[0].rx_buf = &st->raw_data;
+	xfer[0].len = 2;
+
+	return spi_sync_transfer(st->spi, xfer, 1);
+}
+
+/* IIO implementation */
+
+static int ad4695_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct ad4695_state *st = iio_priv(indio_dev);
+	struct ad4695_channel_config *cfg = &st->channels_cfg[chan->scan_index];
+	u8 realbits = chan->scan_type.realbits;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
+			ret = ad4695_read_one_sample(st, chan->address);
+			if (ret)
+				return ret;
+
+			if (chan->scan_type.sign == 's')
+				*val = sign_extend32(st->raw_data, realbits - 1);
+			else
+				*val = st->raw_data;
+
+			return IIO_VAL_INT;
+		}
+		unreachable();
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			*val = st->vref_mv;
+			*val2 = chan->scan_type.realbits;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		case IIO_TEMP:
+			/* T_scale (°C) = raw * V_REF (mV) / (-1.8 mV/°C * 2^16) */
+			*val = st->vref_mv * -556;
+			*val2 = 16;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_OFFSET:
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			if (cfg->pin_pairing == AD4695_WITH_COM)
+				*val = st->com_mv * (1 << realbits) / st->vref_mv;
+			else
+				*val = 0;
+
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			/* T_offset (°C) = -725 mV / (-1.8 mV/°C) */
+			/* T_offset (raw) = T_offset (°C) * (-1.8 mV/°C) * 2^16 / V_REF (mV) */
+			*val = -47513600;
+			*val2 = st->vref_mv;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad4695_debugfs_reg_access(struct iio_dev *indio_dev, unsigned int reg,
+				     unsigned int writeval, unsigned int *readval)
+{
+	struct ad4695_state *st = iio_priv(indio_dev);
+
+	iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
+		if (readval)
+			return regmap_read(st->regmap, reg, readval);
+
+		return regmap_write(st->regmap, reg, writeval);
+	}
+
+	unreachable();
+}
+
+static const struct iio_info ad4695_info = {
+	.read_raw = &ad4695_read_raw,
+	.debugfs_reg_access = &ad4695_debugfs_reg_access,
+};
+
+static int ad4695_parse_channel_cfg(struct iio_dev *indio_dev)
+{
+	struct device *dev = indio_dev->dev.parent;
+	struct ad4695_state *st = iio_priv(indio_dev);
+	struct iio_chan_spec *iio_chan_arr;
+	struct ad4695_channel_config *chan_cfg_arr;
+	unsigned int channel, chan_idx = 0;
+	int ret;
+
+	indio_dev->num_channels = device_get_child_node_count(dev);
+	if (!indio_dev->num_channels)
+		return dev_err_probe(dev, -ENODEV, "no channel children\n");
+
+	/* Extra channel for temperature. */
+	indio_dev->num_channels++;
+
+	iio_chan_arr = devm_kcalloc(dev, indio_dev->num_channels,
+				    sizeof(*iio_chan_arr), GFP_KERNEL);
+	if (!iio_chan_arr)
+		return -ENOMEM;
+
+	chan_cfg_arr = devm_kcalloc(dev, indio_dev->num_channels,
+				    sizeof(*chan_cfg_arr), GFP_KERNEL);
+	if (!chan_cfg_arr)
+		return -ENOMEM;
+
+	indio_dev->channels = iio_chan_arr;
+	st->channels_cfg = chan_cfg_arr;
+
+	device_for_each_child_node_scoped(dev, child) {
+		struct ad4695_channel_config *chan_cfg = &st->channels_cfg[chan_idx];
+		const char *pin_pairing_str;
+
+		ret = fwnode_property_read_u32(child, "reg", &channel);
+		if (ret)
+			return dev_err_probe(dev, ret, "failed to read reg property (%s)\n",
+					     fwnode_get_name(child));
+
+		if (channel >= st->chip_info->num_voltage_inputs)
+			return dev_err_probe(dev, -EINVAL,
+				"channel id out of range, maximum %d channels allowed (%s)\n",
+				st->chip_info->num_voltage_inputs,
+				fwnode_get_name(child));
+
+		iio_chan_arr[chan_idx] = ad4695_channel_template;
+		iio_chan_arr[chan_idx].scan_index = chan_idx;
+		iio_chan_arr[chan_idx].channel = channel;
+		iio_chan_arr[chan_idx].address = AD4695_CMD_VOLTAGE_CHAN(channel);
+
+		chan_cfg->bipolar = fwnode_property_read_bool(child, "bipolar");
+		if (chan_cfg->bipolar)
+			iio_chan_arr[chan_idx].scan_type.sign = 's';
+
+		chan_cfg->highz_en = !fwnode_property_read_bool(child, "adi,no-high-z");
+
+		ret = fwnode_property_read_string(child, "adi,pin-pairing", &pin_pairing_str);
+		if (ret && ret != -EINVAL)
+			return dev_err_probe(dev, ret,
+				"failed to read adi,pin-pairing property (%s)\n",
+				fwnode_get_name(child));
+
+		if (ret == -EINVAL) {
+			/* default when property omitted */
+			chan_cfg->pin_pairing = AD4695_WITH_REFGND;
+		} else {
+			ret = sysfs_match_string(ad4695_pin_pairing, pin_pairing_str);
+			if (ret < 0)
+				return dev_err_probe(dev, ret,
+					"failed to match pin pairing: \"%s\" (%s)\n",
+					pin_pairing_str, fwnode_get_name(child));
+
+			chan_cfg->pin_pairing = ret;
+		}
+
+		if (chan_cfg->bipolar && chan_cfg->pin_pairing == AD4695_WITH_REFGND)
+			return dev_err_probe(dev, -EINVAL,
+				"bipolar mode is not available for channels with the \"refgnd\" pin pairing assignment selected (%s).\n",
+				fwnode_get_name(child));
+
+		if (chan_cfg->pin_pairing == AD4695_EVEN_ODD) {
+			if (channel % 2 == 1)
+				return dev_err_probe(dev, -EINVAL,
+					"channels with \"next\" pin pairing assignment selected must have an even index (%s)\n",
+					fwnode_get_name(child));
+
+			iio_chan_arr[chan_idx].differential = 1;
+			iio_chan_arr[chan_idx].channel2 = channel + 1;
+		}
+
+		chan_cfg->channel = channel;
+
+		ret = ad4695_write_chn_cfg(st, chan_cfg);
+		if (ret)
+			return ret;
+
+		chan_idx++;
+	}
+
+	/* Temperature channel must be next scan index after voltage channels. */
+	iio_chan_arr[chan_idx] = ad4695_temp_channel_template;
+	iio_chan_arr[chan_idx].scan_index = chan_idx;
+
+	return 0;
+}
+
+static int ad4695_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct ad4695_state *st;
+	struct iio_dev *indio_dev;
+	struct gpio_desc *cnv_gpio;
+	bool use_internal_ldo_supply;
+	bool use_internal_ref_buffer;
+	int ret;
+
+	cnv_gpio = devm_gpiod_get_optional(dev, "cnv", GPIOD_OUT_LOW);
+	if (IS_ERR(cnv_gpio))
+		return dev_err_probe(dev, PTR_ERR(cnv_gpio), "Failed to get CNV GPIO\n");
+
+	/* Driver currently requires CNV pin to be connected to SPI CS */
+	if (cnv_gpio)
+		return dev_err_probe(dev, -ENODEV, "CNV GPIO is not supported\n");
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	st->chip_info = spi_get_device_match_data(spi);
+	if (!st->chip_info)
+		return -EINVAL;
+
+	/* Registers cannot be read at the max allowable speed */
+	spi->max_speed_hz = AD4695_REG_ACCESS_SCLK_HZ;
+
+	st->regmap = devm_regmap_init_spi(spi, &ad4695_regmap_config);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap), "Failed to initialize regmap\n");
+
+	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(ad4695_power_supplies),
+					     ad4695_power_supplies);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable power supplies\n");
+
+	/* If LDO_IN supply is present, then we are using internal LDO. */
+	ret = devm_regulator_get_enable_optional(dev, "ldo-in");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to enable LDO_IN supply\n");
+
+	use_internal_ldo_supply = ret == 0;
+
+	if (!use_internal_ldo_supply) {
+		/* Otherwise we need an external VDD supply. */
+		ret = devm_regulator_get_enable(dev, "vdd");
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to enable VDD supply\n");
+	}
+
+	/* If REFIN supply is given, then we are using internal buffer */
+	ret = devm_regulator_get_enable_read_voltage(dev, "refin");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to get REFIN voltage\n");
+
+	if (ret != -ENODEV) {
+		st->vref_mv = ret / 1000;
+		use_internal_ref_buffer = true;
+	} else {
+		/* Otherwise, we need an external reference. */
+		ret = devm_regulator_get_enable_read_voltage(dev, "ref");
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to get REF voltage\n");
+
+		st->vref_mv = ret / 1000;
+		use_internal_ref_buffer = false;
+	}
+
+	ret = devm_regulator_get_enable_read_voltage(dev, "com");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "Failed to get COM voltage\n");
+
+	st->com_mv = ret == -ENODEV ? 0 : ret / 1000;
+
+	/*
+	 * Reset the device using hardware reset if available or fall back to
+	 * software reset.
+	 */
+
+	st->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(st->reset_gpio))
+		return PTR_ERR(st->reset_gpio);
+
+	if (st->reset_gpio) {
+		gpiod_set_value(st->reset_gpio, 0);
+		/* datasheet says we have to wait before communicating */
+		msleep(AD4695_T_WAKEUP_HW_MS);
+	} else {
+		ret = ad4695_soft_reset(st);
+		if (ret)
+			return ret;
+	}
+
+	ret = ad4695_set_ldo_en(st, use_internal_ldo_supply);
+	if (ret)
+		return ret;
+
+	/* configure reference supply */
+
+	if (device_property_present(dev, "adi,no-ref-current-limit")) {
+		ret = ad4695_set_ov_mode(st, AD4695_OV_MODE_DO_NOT_REDUCE_CURRENT);
+		if (ret)
+			return ret;
+	}
+
+	if (device_property_present(dev, "adi,no-ref-high-z")) {
+		if (use_internal_ref_buffer)
+			return dev_err_probe(dev, -EINVAL,
+				"Cannot disable high-Z mode for internal reference buffer\n");
+
+		ret = ad4695_set_refhiz_en(st, false);
+		if (ret)
+			return ret;
+	}
+
+	ad4695_set_ref_voltage(st, st->vref_mv);
+	if (ret)
+		return ret;
+
+	if (use_internal_ref_buffer) {
+		ret = ad4695_set_refbuf_en(st, true);
+		if (ret)
+			return ret;
+
+		/* Give the capacitor some time to charge up. */
+		msleep(AD4695_T_REFBUF_MS);
+	}
+
+	ret = ad4695_parse_channel_cfg(indio_dev);
+	if (ret)
+		return ret;
+
+	ret = ad4695_set_instr_mode(st, AD4695_INST_MODE_SINGLE);
+	if (ret)
+		return ret;
+
+	indio_dev->name = st->chip_info->name;
+	indio_dev->info = &ad4695_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id ad4695_spi_id_table[] = {
+	{ .name = "ad4695", .driver_data = (kernel_ulong_t)&ad4695_chip_info },
+	{ .name = "ad4696", .driver_data = (kernel_ulong_t)&ad4696_chip_info },
+	{ .name = "ad4697", .driver_data = (kernel_ulong_t)&ad4697_chip_info },
+	{ .name = "ad4698", .driver_data = (kernel_ulong_t)&ad4698_chip_info },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad4695_spi_id_table);
+
+static const struct of_device_id ad4695_of_match_table[] = {
+	{ .compatible = "adi,ad4695", .data = &ad4695_chip_info, },
+	{ .compatible = "adi,ad4696", .data = &ad4696_chip_info, },
+	{ .compatible = "adi,ad4697", .data = &ad4697_chip_info, },
+	{ .compatible = "adi,ad4698", .data = &ad4698_chip_info, },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad4695_of_match_table);
+
+static struct spi_driver ad4695_driver = {
+	.driver = {
+		.name = "ad4695",
+		.of_match_table = ad4695_of_match_table,
+	},
+	.probe = ad4695_probe,
+	.id_table = ad4695_spi_id_table,
+};
+module_spi_driver(ad4695_driver);
+
+MODULE_AUTHOR("Ramona Gradinariu <ramona.gradinariu@analog.com>");
+MODULE_AUTHOR("David Lechner <dlechner@baylibre.com>");
+MODULE_DESCRIPTION("Analog Devices AD4695 ADC driver");
+MODULE_LICENSE("GPL");

-- 
2.45.2