iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

The voltage ADC is peripheral of Qualcomm SPMI PMIC chips. It has
15bits resolution and register space inside PMIC accessible across
SPMI bus.

The vadc driver registers itself through IIO interface.

Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 1031 insertions, 0 deletions

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 0f79e4725763..311829a2bdf8 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -228,6 +228,20 @@ config QCOM_SPMI_IADC
 	  To compile this driver as a module, choose M here: the module will
 	  be called qcom-spmi-iadc.
 
+config QCOM_SPMI_VADC
+	tristate "Qualcomm SPMI PMIC voltage ADC"
+	depends on SPMI
+	select REGMAP_SPMI
+	help
+	  This is the IIO Voltage ADC driver for Qualcomm QPNP VADC Chip.
+
+	  The driver supports multiple channels read. The VADC is a 15-bit
+	  sigma-delta ADC. Some of the channels are internally used for
+	  calibration.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called qcom-spmi-vadc.
+
 config ROCKCHIP_SARADC
 	tristate "Rockchip SARADC driver"
 	depends on ARCH_ROCKCHIP || (ARM && COMPILE_TEST)
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 701fdb7c96aa..b0f62f789caa 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
 obj-$(CONFIG_NAU7802) += nau7802.o
 obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
+obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
 obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
new file mode 100644
index 000000000000..3211729bcb0b
--- /dev/null
+++ b/drivers/iio/adc/qcom-spmi-vadc.c
@@ -0,0 +1,1016 @@
+/*
+ * Copyright (c) 2012-2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/iio/iio.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/log2.h>
+
+#include <dt-bindings/iio/qcom,spmi-vadc.h>
+
+/* VADC register and bit definitions */
+#define VADC_REVISION2				0x1
+#define VADC_REVISION2_SUPPORTED_VADC		1
+
+#define VADC_PERPH_TYPE				0x4
+#define VADC_PERPH_TYPE_ADC			8
+
+#define VADC_PERPH_SUBTYPE			0x5
+#define VADC_PERPH_SUBTYPE_VADC			1
+
+#define VADC_STATUS1				0x8
+#define VADC_STATUS1_OP_MODE			4
+#define VADC_STATUS1_REQ_STS			BIT(1)
+#define VADC_STATUS1_EOC			BIT(0)
+#define VADC_STATUS1_REQ_STS_EOC_MASK		0x3
+
+#define VADC_MODE_CTL				0x40
+#define VADC_OP_MODE_SHIFT			3
+#define VADC_OP_MODE_NORMAL			0
+#define VADC_AMUX_TRIM_EN			BIT(1)
+#define VADC_ADC_TRIM_EN			BIT(0)
+
+#define VADC_EN_CTL1				0x46
+#define VADC_EN_CTL1_SET			BIT(7)
+
+#define VADC_ADC_CH_SEL_CTL			0x48
+
+#define VADC_ADC_DIG_PARAM			0x50
+#define VADC_ADC_DIG_DEC_RATIO_SEL_SHIFT	2
+
+#define VADC_HW_SETTLE_DELAY			0x51
+
+#define VADC_CONV_REQ				0x52
+#define VADC_CONV_REQ_SET			BIT(7)
+
+#define VADC_FAST_AVG_CTL			0x5a
+#define VADC_FAST_AVG_EN			0x5b
+#define VADC_FAST_AVG_EN_SET			BIT(7)
+
+#define VADC_ACCESS				0xd0
+#define VADC_ACCESS_DATA			0xa5
+
+#define VADC_PERH_RESET_CTL3			0xda
+#define VADC_FOLLOW_WARM_RB			BIT(2)
+
+#define VADC_DATA				0x60	/* 16 bits */
+
+#define VADC_CONV_TIME_MIN_US			2000
+#define VADC_CONV_TIME_MAX_US			2100
+
+/* Min ADC code represents 0V */
+#define VADC_MIN_ADC_CODE			0x6000
+/* Max ADC code represents full-scale range of 1.8V */
+#define VADC_MAX_ADC_CODE			0xa800
+
+#define VADC_ABSOLUTE_RANGE_UV			625000
+#define VADC_RATIOMETRIC_RANGE_UV		1800000
+
+#define VADC_DEF_PRESCALING			0 /* 1:1 */
+#define VADC_DEF_DECIMATION			0 /* 512 */
+#define VADC_DEF_HW_SETTLE_TIME			0 /* 0 us */
+#define VADC_DEF_AVG_SAMPLES			0 /* 1 sample */
+#define VADC_DEF_CALIB_TYPE			VADC_CALIB_ABSOLUTE
+
+#define VADC_DECIMATION_MIN			512
+#define VADC_DECIMATION_MAX			4096
+
+#define VADC_HW_SETTLE_DELAY_MAX		10000
+#define VADC_AVG_SAMPLES_MAX			512
+
+#define KELVINMIL_CELSIUSMIL			273150
+
+#define VADC_CHAN_MIN			VADC_USBIN
+#define VADC_CHAN_MAX			VADC_LR_MUX3_BUF_PU1_PU2_XO_THERM
+
+/*
+ * VADC_CALIB_ABSOLUTE: uses the 625mV and 1.25V as reference channels.
+ * VADC_CALIB_RATIOMETRIC: uses the reference voltage (1.8V) and GND for
+ * calibration.
+ */
+enum vadc_calibration {
+	VADC_CALIB_ABSOLUTE = 0,
+	VADC_CALIB_RATIOMETRIC
+};
+
+/**
+ * struct vadc_linear_graph - Represent ADC characteristics.
+ * @dy: numerator slope to calculate the gain.
+ * @dx: denominator slope to calculate the gain.
+ * @gnd: A/D word of the ground reference used for the channel.
+ *
+ * Each ADC device has different offset and gain parameters which are
+ * computed to calibrate the device.
+ */
+struct vadc_linear_graph {
+	s32 dy;
+	s32 dx;
+	s32 gnd;
+};
+
+/**
+ * struct vadc_prescale_ratio - Represent scaling ratio for ADC input.
+ * @num: the inverse numerator of the gain applied to the input channel.
+ * @den: the inverse denominator of the gain applied to the input channel.
+ */
+struct vadc_prescale_ratio {
+	u32 num;
+	u32 den;
+};
+
+/**
+ * struct vadc_channel_prop - VADC channel property.
+ * @channel: channel number, refer to the channel list.
+ * @calibration: calibration type.
+ * @decimation: sampling rate supported for the channel.
+ * @prescale: channel scaling performed on the input signal.
+ * @hw_settle_time: the time between AMUX being configured and the
+ *	start of conversion.
+ * @avg_samples: ability to provide single result from the ADC
+ *	that is an average of multiple measurements.
+ */
+struct vadc_channel_prop {
+	unsigned int channel;
+	enum vadc_calibration calibration;
+	unsigned int decimation;
+	unsigned int prescale;
+	unsigned int hw_settle_time;
+	unsigned int avg_samples;
+};
+
+/**
+ * struct vadc_priv - VADC private structure.
+ * @regmap: pointer to struct regmap.
+ * @dev: pointer to struct device.
+ * @base: base address for the ADC peripheral.
+ * @nchannels: number of VADC channels.
+ * @chan_props: array of VADC channel properties.
+ * @iio_chans: array of IIO channels specification.
+ * @are_ref_measured: are reference points measured.
+ * @poll_eoc: use polling instead of interrupt.
+ * @complete: VADC result notification after interrupt is received.
+ * @graph: store parameters for calibration.
+ * @lock: ADC lock for access to the peripheral.
+ */
+struct vadc_priv {
+	struct regmap		 *regmap;
+	struct device		 *dev;
+	u16			 base;
+	unsigned int		 nchannels;
+	struct vadc_channel_prop *chan_props;
+	struct iio_chan_spec	 *iio_chans;
+	bool			 are_ref_measured;
+	bool			 poll_eoc;
+	struct completion	 complete;
+	struct vadc_linear_graph graph[2];
+	struct mutex		 lock;
+};
+
+static const struct vadc_prescale_ratio vadc_prescale_ratios[] = {
+	{.num =  1, .den =  1},
+	{.num =  1, .den =  3},
+	{.num =  1, .den =  4},
+	{.num =  1, .den =  6},
+	{.num =  1, .den = 20},
+	{.num =  1, .den =  8},
+	{.num = 10, .den = 81},
+	{.num =  1, .den = 10}
+};
+
+static int vadc_read(struct vadc_priv *vadc, u16 offset, u8 *data)
+{
+	return regmap_bulk_read(vadc->regmap, vadc->base + offset, data, 1);
+}
+
+static int vadc_write(struct vadc_priv *vadc, u16 offset, u8 data)
+{
+	return regmap_write(vadc->regmap, vadc->base + offset, data);
+}
+
+static int vadc_reset(struct vadc_priv *vadc)
+{
+	u8 data;
+	int ret;
+
+	ret = vadc_write(vadc, VADC_ACCESS, VADC_ACCESS_DATA);
+	if (ret)
+		return ret;
+
+	ret = vadc_read(vadc, VADC_PERH_RESET_CTL3, &data);
+	if (ret)
+		return ret;
+
+	ret = vadc_write(vadc, VADC_ACCESS, VADC_ACCESS_DATA);
+	if (ret)
+		return ret;
+
+	data |= VADC_FOLLOW_WARM_RB;
+
+	return vadc_write(vadc, VADC_PERH_RESET_CTL3, data);
+}
+
+static int vadc_set_state(struct vadc_priv *vadc, bool state)
+{
+	return vadc_write(vadc, VADC_EN_CTL1, state ? VADC_EN_CTL1_SET : 0);
+}
+
+static void vadc_show_status(struct vadc_priv *vadc)
+{
+	u8 mode, sta1, chan, dig, en, req;
+	int ret;
+
+	ret = vadc_read(vadc, VADC_MODE_CTL, &mode);
+	if (ret)
+		return;
+
+	ret = vadc_read(vadc, VADC_ADC_DIG_PARAM, &dig);
+	if (ret)
+		return;
+
+	ret = vadc_read(vadc, VADC_ADC_CH_SEL_CTL, &chan);
+	if (ret)
+		return;
+
+	ret = vadc_read(vadc, VADC_CONV_REQ, &req);
+	if (ret)
+		return;
+
+	ret = vadc_read(vadc, VADC_STATUS1, &sta1);
+	if (ret)
+		return;
+
+	ret = vadc_read(vadc, VADC_EN_CTL1, &en);
+	if (ret)
+		return;
+
+	dev_err(vadc->dev,
+		"mode:%02x en:%02x chan:%02x dig:%02x req:%02x sta1:%02x\n",
+		mode, en, chan, dig, req, sta1);
+}
+
+static int vadc_configure(struct vadc_priv *vadc,
+			  struct vadc_channel_prop *prop)
+{
+	u8 decimation, mode_ctrl;
+	int ret;
+
+	/* Mode selection */
+	mode_ctrl = (VADC_OP_MODE_NORMAL << VADC_OP_MODE_SHIFT) |
+		     VADC_ADC_TRIM_EN | VADC_AMUX_TRIM_EN;
+	ret = vadc_write(vadc, VADC_MODE_CTL, mode_ctrl);
+	if (ret)
+		return ret;
+
+	/* Channel selection */
+	ret = vadc_write(vadc, VADC_ADC_CH_SEL_CTL, prop->channel);
+	if (ret)
+		return ret;
+
+	/* Digital parameter setup */
+	decimation = prop->decimation << VADC_ADC_DIG_DEC_RATIO_SEL_SHIFT;
+	ret = vadc_write(vadc, VADC_ADC_DIG_PARAM, decimation);
+	if (ret)
+		return ret;
+
+	/* HW settle time delay */
+	ret = vadc_write(vadc, VADC_HW_SETTLE_DELAY, prop->hw_settle_time);
+	if (ret)
+		return ret;
+
+	ret = vadc_write(vadc, VADC_FAST_AVG_CTL, prop->avg_samples);
+	if (ret)
+		return ret;
+
+	if (prop->avg_samples)
+		ret = vadc_write(vadc, VADC_FAST_AVG_EN, VADC_FAST_AVG_EN_SET);
+	else
+		ret = vadc_write(vadc, VADC_FAST_AVG_EN, 0);
+
+	return ret;
+}
+
+static int vadc_poll_wait_eoc(struct vadc_priv *vadc, unsigned int interval_us)
+{
+	unsigned int count, retry;
+	u8 sta1;
+	int ret;
+
+	retry = interval_us / VADC_CONV_TIME_MIN_US;
+
+	for (count = 0; count < retry; count++) {
+		ret = vadc_read(vadc, VADC_STATUS1, &sta1);
+		if (ret)
+			return ret;
+
+		sta1 &= VADC_STATUS1_REQ_STS_EOC_MASK;
+		if (sta1 == VADC_STATUS1_EOC)
+			return 0;
+
+		usleep_range(VADC_CONV_TIME_MIN_US, VADC_CONV_TIME_MAX_US);
+	}
+
+	vadc_show_status(vadc);
+
+	return -ETIMEDOUT;
+}
+
+static int vadc_read_result(struct vadc_priv *vadc, u16 *data)
+{
+	int ret;
+
+	ret = regmap_bulk_read(vadc->regmap, vadc->base + VADC_DATA, data, 2);
+	if (ret)
+		return ret;
+
+	*data = clamp_t(u16, *data, VADC_MIN_ADC_CODE, VADC_MAX_ADC_CODE);
+
+	return 0;
+}
+
+static struct vadc_channel_prop *vadc_get_channel(struct vadc_priv *vadc,
+						  unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < vadc->nchannels; i++)
+		if (vadc->chan_props[i].channel == num)
+			return &vadc->chan_props[i];
+
+	dev_dbg(vadc->dev, "no such channel %02x\n", num);
+
+	return NULL;
+}
+
+static int vadc_do_conversion(struct vadc_priv *vadc,
+			      struct vadc_channel_prop *prop, u16 *data)
+{
+	unsigned int timeout;
+	int ret;
+
+	mutex_lock(&vadc->lock);
+
+	ret = vadc_configure(vadc, prop);
+	if (ret)
+		goto unlock;
+
+	if (!vadc->poll_eoc)
+		reinit_completion(&vadc->complete);
+
+	ret = vadc_set_state(vadc, true);
+	if (ret)
+		goto unlock;
+
+	ret = vadc_write(vadc, VADC_CONV_REQ, VADC_CONV_REQ_SET);
+	if (ret)
+		goto err_disable;
+
+	timeout = BIT(prop->avg_samples) * VADC_CONV_TIME_MIN_US * 2;
+
+	if (vadc->poll_eoc) {
+		ret = vadc_poll_wait_eoc(vadc, timeout);
+	} else {
+		ret = wait_for_completion_timeout(&vadc->complete, timeout);
+		if (!ret) {
+			ret = -ETIMEDOUT;
+			goto err_disable;
+		}
+
+		/* Double check conversion status */
+		ret = vadc_poll_wait_eoc(vadc, VADC_CONV_TIME_MIN_US);
+		if (ret)
+			goto err_disable;
+	}
+
+	ret = vadc_read_result(vadc, data);
+
+err_disable:
+	vadc_set_state(vadc, false);
+	if (ret)
+		dev_err(vadc->dev, "conversion failed\n");
+unlock:
+	mutex_unlock(&vadc->lock);
+	return ret;
+}
+
+static int vadc_measure_ref_points(struct vadc_priv *vadc)
+{
+	struct vadc_channel_prop *prop;
+	u16 read_1, read_2;
+	int ret;
+
+	vadc->graph[VADC_CALIB_RATIOMETRIC].dx = VADC_RATIOMETRIC_RANGE_UV;
+	vadc->graph[VADC_CALIB_ABSOLUTE].dx = VADC_ABSOLUTE_RANGE_UV;
+
+	prop = vadc_get_channel(vadc, VADC_REF_1250MV);
+	ret = vadc_do_conversion(vadc, prop, &read_1);
+	if (ret)
+		goto err;
+
+	/* Try with buffered 625mV channel first */
+	prop = vadc_get_channel(vadc, VADC_SPARE1);
+	if (!prop)
+		prop = vadc_get_channel(vadc, VADC_REF_625MV);
+
+	ret = vadc_do_conversion(vadc, prop, &read_2);
+	if (ret)
+		goto err;
+
+	if (read_1 == read_2) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	vadc->graph[VADC_CALIB_ABSOLUTE].dy = read_1 - read_2;
+	vadc->graph[VADC_CALIB_ABSOLUTE].gnd = read_2;
+
+	/* Ratiometric calibration */
+	prop = vadc_get_channel(vadc, VADC_VDD_VADC);
+	ret = vadc_do_conversion(vadc, prop, &read_1);
+	if (ret)
+		goto err;
+
+	prop = vadc_get_channel(vadc, VADC_GND_REF);
+	ret = vadc_do_conversion(vadc, prop, &read_2);
+	if (ret)
+		goto err;
+
+	if (read_1 == read_2) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	vadc->graph[VADC_CALIB_RATIOMETRIC].dy = read_1 - read_2;
+	vadc->graph[VADC_CALIB_RATIOMETRIC].gnd = read_2;
+err:
+	if (ret)
+		dev_err(vadc->dev, "measure reference points failed\n");
+
+	return ret;
+}
+
+static s32 vadc_calibrate(struct vadc_priv *vadc,
+			  const struct vadc_channel_prop *prop, u16 adc_code)
+{
+	const struct vadc_prescale_ratio *prescale;
+	s32 voltage;
+
+	voltage = adc_code - vadc->graph[prop->calibration].gnd;
+	voltage *= vadc->graph[prop->calibration].dx;
+	voltage = voltage / vadc->graph[prop->calibration].dy;
+
+	if (prop->calibration == VADC_CALIB_ABSOLUTE)
+		voltage += vadc->graph[prop->calibration].dx;
+
+	if (voltage < 0)
+		voltage = 0;
+
+	prescale = &vadc_prescale_ratios[prop->prescale];
+
+	voltage = voltage * prescale->den;
+
+	return voltage / prescale->num;
+}
+
+static int vadc_decimation_from_dt(u32 value)
+{
+	if (!is_power_of_2(value) || value < VADC_DECIMATION_MIN ||
+	    value > VADC_DECIMATION_MAX)
+		return -EINVAL;
+
+	return __ffs64(value / VADC_DECIMATION_MIN);
+}
+
+static int vadc_prescaling_from_dt(u32 num, u32 den)
+{
+	unsigned int pre;
+
+	for (pre = 0; pre < ARRAY_SIZE(vadc_prescale_ratios); pre++)
+		if (vadc_prescale_ratios[pre].num == num &&
+		    vadc_prescale_ratios[pre].den == den)
+			break;
+
+	if (pre == ARRAY_SIZE(vadc_prescale_ratios))
+		return -EINVAL;
+
+	return pre;
+}
+
+static int vadc_hw_settle_time_from_dt(u32 value)
+{
+	if ((value <= 1000 && value % 100) || (value > 1000 && value % 2000))
+		return -EINVAL;
+
+	if (value <= 1000)
+		value /= 100;
+	else
+		value = value / 2000 + 10;
+
+	return value;
+}
+
+static int vadc_avg_samples_from_dt(u32 value)
+{
+	if (!is_power_of_2(value) || value > VADC_AVG_SAMPLES_MAX)
+		return -EINVAL;
+
+	return __ffs64(value);
+}
+
+static int vadc_read_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan, int *val, int *val2,
+			 long mask)
+{
+	struct vadc_priv *vadc = iio_priv(indio_dev);
+	struct vadc_channel_prop *prop;
+	u16 adc_code;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		prop = &vadc->chan_props[chan->address];
+		ret = vadc_do_conversion(vadc, prop, &adc_code);
+		if (ret)
+			break;
+
+		*val = vadc_calibrate(vadc, prop, adc_code);
+
+		/* 2mV/K, return milli Celsius */
+		*val /= 2;
+		*val -= KELVINMIL_CELSIUSMIL;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_RAW:
+		prop = &vadc->chan_props[chan->address];
+		ret = vadc_do_conversion(vadc, prop, &adc_code);
+		if (ret)
+			break;
+
+		*val = vadc_calibrate(vadc, prop, adc_code);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static int vadc_of_xlate(struct iio_dev *indio_dev,
+			 const struct of_phandle_args *iiospec)
+{
+	struct vadc_priv *vadc = iio_priv(indio_dev);
+	unsigned int i;
+
+	for (i = 0; i < vadc->nchannels; i++)
+		if (vadc->iio_chans[i].channel == iiospec->args[0])
+			return i;
+
+	return -EINVAL;
+}
+
+static const struct iio_info vadc_info = {
+	.read_raw = vadc_read_raw,
+	.of_xlate = vadc_of_xlate,
+	.driver_module = THIS_MODULE,
+};
+
+struct vadc_channels {
+	const char *datasheet_name;
+	unsigned int prescale_index;
+	enum iio_chan_type type;
+	long info_mask;
+};
+
+#define VADC_CHAN(_dname, _type, _mask, _pre)				\
+	[VADC_##_dname] = {						\
+		.datasheet_name = __stringify(_dname),			\
+		.prescale_index = _pre,					\
+		.type = _type,						\
+		.info_mask = _mask					\
+	},								\
+
+#define VADC_CHAN_TEMP(_dname, _pre)					\
+	VADC_CHAN(_dname, IIO_TEMP, BIT(IIO_CHAN_INFO_PROCESSED), _pre)	\
+
+#define VADC_CHAN_VOLT(_dname, _pre)					\
+	VADC_CHAN(_dname, IIO_VOLTAGE,					\
+		  BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),	\
+		  _pre)							\
+
+/*
+ * The array represents all possible ADC channels found in the supported PMICs.
+ * Every index in the array is equal to the channel number per datasheet. The
+ * gaps in the array should be treated as reserved channels.
+ */
+static const struct vadc_channels vadc_chans[] = {
+	VADC_CHAN_VOLT(USBIN, 4)
+	VADC_CHAN_VOLT(DCIN, 4)
+	VADC_CHAN_VOLT(VCHG_SNS, 3)
+	VADC_CHAN_VOLT(SPARE1_03, 1)
+	VADC_CHAN_VOLT(USB_ID_MV, 1)
+	VADC_CHAN_VOLT(VCOIN, 1)
+	VADC_CHAN_VOLT(VBAT_SNS, 1)
+	VADC_CHAN_VOLT(VSYS, 1)
+	VADC_CHAN_TEMP(DIE_TEMP, 0)
+	VADC_CHAN_VOLT(REF_625MV, 0)
+	VADC_CHAN_VOLT(REF_1250MV, 0)
+	VADC_CHAN_VOLT(CHG_TEMP, 0)
+	VADC_CHAN_VOLT(SPARE1, 0)
+	VADC_CHAN_VOLT(SPARE2, 0)
+	VADC_CHAN_VOLT(GND_REF, 0)
+	VADC_CHAN_VOLT(VDD_VADC, 0)
+
+	VADC_CHAN_VOLT(P_MUX1_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX2_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX3_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX4_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX5_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX6_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX7_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX8_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX9_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX10_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX11_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX12_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX13_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX14_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX15_1_1, 0)
+	VADC_CHAN_VOLT(P_MUX16_1_1, 0)
+
+	VADC_CHAN_VOLT(P_MUX1_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX2_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX3_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX4_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX5_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX6_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX7_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX8_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX9_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX10_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX11_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX12_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX13_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX14_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX15_1_3, 1)
+	VADC_CHAN_VOLT(P_MUX16_1_3, 1)
+
+	VADC_CHAN_VOLT(LR_MUX1_BAT_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX2_BAT_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_XO_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX4_AMUX_THM1, 0)
+	VADC_CHAN_VOLT(LR_MUX5_AMUX_THM2, 0)
+	VADC_CHAN_VOLT(LR_MUX6_AMUX_THM3, 0)
+	VADC_CHAN_VOLT(LR_MUX7_HW_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX8_AMUX_THM4, 0)
+	VADC_CHAN_VOLT(LR_MUX9_AMUX_THM5, 0)
+	VADC_CHAN_VOLT(LR_MUX10_USB_ID, 0)
+	VADC_CHAN_VOLT(AMUX_PU1, 0)
+	VADC_CHAN_VOLT(AMUX_PU2, 0)
+	VADC_CHAN_VOLT(LR_MUX3_BUF_XO_THERM, 0)
+
+	VADC_CHAN_VOLT(LR_MUX1_PU1_BAT_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX2_PU1_BAT_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_PU1_XO_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX4_PU1_AMUX_THM1, 0)
+	VADC_CHAN_VOLT(LR_MUX5_PU1_AMUX_THM2, 0)
+	VADC_CHAN_VOLT(LR_MUX6_PU1_AMUX_THM3, 0)
+	VADC_CHAN_VOLT(LR_MUX7_PU1_AMUX_HW_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX8_PU1_AMUX_THM4, 0)
+	VADC_CHAN_VOLT(LR_MUX9_PU1_AMUX_THM5, 0)
+	VADC_CHAN_VOLT(LR_MUX10_PU1_AMUX_USB_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_BUF_PU1_XO_THERM, 0)
+
+	VADC_CHAN_VOLT(LR_MUX1_PU2_BAT_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX2_PU2_BAT_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_PU2_XO_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX4_PU2_AMUX_THM1, 0)
+	VADC_CHAN_VOLT(LR_MUX5_PU2_AMUX_THM2, 0)
+	VADC_CHAN_VOLT(LR_MUX6_PU2_AMUX_THM3, 0)
+	VADC_CHAN_VOLT(LR_MUX7_PU2_AMUX_HW_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX8_PU2_AMUX_THM4, 0)
+	VADC_CHAN_VOLT(LR_MUX9_PU2_AMUX_THM5, 0)
+	VADC_CHAN_VOLT(LR_MUX10_PU2_AMUX_USB_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_BUF_PU2_XO_THERM, 0)
+
+	VADC_CHAN_VOLT(LR_MUX1_PU1_PU2_BAT_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX2_PU1_PU2_BAT_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_PU1_PU2_XO_THERM, 0)
+	VADC_CHAN_VOLT(LR_MUX4_PU1_PU2_AMUX_THM1, 0)
+	VADC_CHAN_VOLT(LR_MUX5_PU1_PU2_AMUX_THM2, 0)
+	VADC_CHAN_VOLT(LR_MUX6_PU1_PU2_AMUX_THM3, 0)
+	VADC_CHAN_VOLT(LR_MUX7_PU1_PU2_AMUX_HW_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX8_PU1_PU2_AMUX_THM4, 0)
+	VADC_CHAN_VOLT(LR_MUX9_PU1_PU2_AMUX_THM5, 0)
+	VADC_CHAN_VOLT(LR_MUX10_PU1_PU2_AMUX_USB_ID, 0)
+	VADC_CHAN_VOLT(LR_MUX3_BUF_PU1_PU2_XO_THERM, 0)
+};
+
+static int vadc_get_dt_channel_data(struct device *dev,
+				    struct vadc_channel_prop *prop,
+				    struct device_node *node)
+{
+	const char *name = node->name;
+	u32 chan, value, varr[2];
+	int ret;
+
+	ret = of_property_read_u32(node, "reg", &chan);
+	if (ret) {
+		dev_err(dev, "invalid channel number %s\n", name);
+		return ret;
+	}
+
+	if (chan > VADC_CHAN_MAX || chan < VADC_CHAN_MIN) {
+		dev_err(dev, "%s invalid channel number %d\n", name, chan);
+		return -EINVAL;
+	}
+
+	/* the channel has DT description */
+	prop->channel = chan;
+
+	ret = of_property_read_u32(node, "qcom,decimation", &value);
+	if (!ret) {
+		ret = vadc_decimation_from_dt(value);
+		if (ret < 0) {
+			dev_err(dev, "%02x invalid decimation %d\n",
+				chan, value);
+			return ret;
+		}
+		prop->decimation = ret;
+	} else {
+		prop->decimation = VADC_DEF_DECIMATION;
+	}
+
+	ret = of_property_read_u32_array(node, "qcom,pre-scaling", varr, 2);
+	if (!ret) {
+		ret = vadc_prescaling_from_dt(varr[0], varr[1]);
+		if (ret < 0) {
+			dev_err(dev, "%02x invalid pre-scaling <%d %d>\n",
+				chan, varr[0], varr[1]);
+			return ret;
+		}
+		prop->prescale = ret;
+	} else {
+		prop->prescale = vadc_chans[prop->channel].prescale_index;
+	}
+
+	ret = of_property_read_u32(node, "qcom,hw-settle-time", &value);
+	if (!ret) {
+		ret = vadc_hw_settle_time_from_dt(value);
+		if (ret < 0) {
+			dev_err(dev, "%02x invalid hw-settle-time %d us\n",
+				chan, value);
+			return ret;
+		}
+		prop->hw_settle_time = ret;
+	} else {
+		prop->hw_settle_time = VADC_DEF_HW_SETTLE_TIME;
+	}
+
+	ret = of_property_read_u32(node, "qcom,avg-samples", &value);
+	if (!ret) {
+		ret = vadc_avg_samples_from_dt(value);
+		if (ret < 0) {
+			dev_err(dev, "%02x invalid avg-samples %d\n",
+				chan, value);
+			return ret;
+		}
+		prop->avg_samples = ret;
+	} else {
+		prop->avg_samples = VADC_DEF_AVG_SAMPLES;
+	}
+
+	if (of_property_read_bool(node, "qcom,ratiometric"))
+		prop->calibration = VADC_CALIB_RATIOMETRIC;
+	else
+		prop->calibration = VADC_CALIB_ABSOLUTE;
+
+	dev_dbg(dev, "%02x name %s\n", chan, name);
+
+	return 0;
+}
+
+static int vadc_get_dt_data(struct vadc_priv *vadc, struct device_node *node)
+{
+	const struct vadc_channels *vadc_chan;
+	struct iio_chan_spec *iio_chan;
+	struct vadc_channel_prop prop;
+	struct device_node *child;
+	unsigned int index = 0;
+	int ret;
+
+	vadc->nchannels = of_get_available_child_count(node);
+	if (!vadc->nchannels)
+		return -EINVAL;
+
+	vadc->iio_chans = devm_kcalloc(vadc->dev, vadc->nchannels,
+				       sizeof(*vadc->iio_chans), GFP_KERNEL);
+	if (!vadc->iio_chans)
+		return -ENOMEM;
+
+	vadc->chan_props = devm_kcalloc(vadc->dev, vadc->nchannels,
+					sizeof(*vadc->chan_props), GFP_KERNEL);
+	if (!vadc->chan_props)
+		return -ENOMEM;
+
+	iio_chan = vadc->iio_chans;
+
+	for_each_available_child_of_node(node, child) {
+		ret = vadc_get_dt_channel_data(vadc->dev, &prop, child);
+		if (ret)
+			return ret;
+
+		vadc->chan_props[index] = prop;
+
+		vadc_chan = &vadc_chans[prop.channel];
+
+		iio_chan->channel = prop.channel;
+		iio_chan->datasheet_name = vadc_chan->datasheet_name;
+		iio_chan->info_mask_separate = vadc_chan->info_mask;
+		iio_chan->type = vadc_chan->type;
+		iio_chan->indexed = 1;
+		iio_chan->address = index++;
+
+		iio_chan++;
+	}
+
+	/* These channels are mandatory, they are used as reference points */
+	if (!vadc_get_channel(vadc, VADC_REF_1250MV)) {
+		dev_err(vadc->dev, "Please define 1.25V channel\n");
+		return -ENODEV;
+	}
+
+	if (!vadc_get_channel(vadc, VADC_REF_625MV)) {
+		dev_err(vadc->dev, "Please define 0.625V channel\n");
+		return -ENODEV;
+	}
+
+	if (!vadc_get_channel(vadc, VADC_VDD_VADC)) {
+		dev_err(vadc->dev, "Please define VDD channel\n");
+		return -ENODEV;
+	}
+
+	if (!vadc_get_channel(vadc, VADC_GND_REF)) {
+		dev_err(vadc->dev, "Please define GND channel\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static irqreturn_t vadc_isr(int irq, void *dev_id)
+{
+	struct vadc_priv *vadc = dev_id;
+
+	complete(&vadc->complete);
+
+	return IRQ_HANDLED;
+}
+
+static int vadc_check_revision(struct vadc_priv *vadc)
+{
+	u8 val;
+	int ret;
+
+	ret = vadc_read(vadc, VADC_PERPH_TYPE, &val);
+	if (ret)
+		return ret;
+
+	if (val < VADC_PERPH_TYPE_ADC) {
+		dev_err(vadc->dev, "%d is not ADC\n", val);
+		return -ENODEV;
+	}
+
+	ret = vadc_read(vadc, VADC_PERPH_SUBTYPE, &val);
+	if (ret)
+		return ret;
+
+	if (val < VADC_PERPH_SUBTYPE_VADC) {
+		dev_err(vadc->dev, "%d is not VADC\n", val);
+		return -ENODEV;
+	}
+
+	ret = vadc_read(vadc, VADC_REVISION2, &val);
+	if (ret)
+		return ret;
+
+	if (val < VADC_REVISION2_SUPPORTED_VADC) {
+		dev_err(vadc->dev, "revision %d not supported\n", val);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int vadc_probe(struct platform_device *pdev)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct device *dev = &pdev->dev;
+	struct iio_dev *indio_dev;
+	struct vadc_priv *vadc;
+	struct regmap *regmap;
+	int ret, irq_eoc;
+	u32 reg;
+
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (!regmap)
+		return -ENODEV;
+
+	ret = of_property_read_u32(node, "reg", &reg);
+	if (ret < 0)
+		return ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*vadc));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	vadc = iio_priv(indio_dev);
+	vadc->regmap = regmap;
+	vadc->dev = dev;
+	vadc->base = reg;
+	vadc->are_ref_measured = false;
+	init_completion(&vadc->complete);
+	mutex_init(&vadc->lock);
+
+	ret = vadc_check_revision(vadc);
+	if (ret)
+		return ret;
+
+	ret = vadc_get_dt_data(vadc, node);
+	if (ret)
+		return ret;
+
+	irq_eoc = platform_get_irq(pdev, 0);
+	if (irq_eoc < 0) {
+		if (irq_eoc == -EPROBE_DEFER || irq_eoc == -EINVAL)
+			return irq_eoc;
+		vadc->poll_eoc = true;
+	} else {
+		ret = devm_request_irq(dev, irq_eoc, vadc_isr, 0,
+				       "spmi-vadc", vadc);
+		if (ret)
+			return ret;
+	}
+
+	ret = vadc_reset(vadc);
+	if (ret) {
+		dev_err(dev, "reset failed\n");
+		return ret;
+	}
+
+	ret = vadc_measure_ref_points(vadc);
+	if (ret)
+		return ret;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->dev.of_node = node;
+	indio_dev->name = pdev->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &vadc_info;
+	indio_dev->channels = vadc->iio_chans;
+	indio_dev->num_channels = vadc->nchannels;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id vadc_match_table[] = {
+	{ .compatible = "qcom,spmi-vadc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, vadc_match_table);
+
+static struct platform_driver vadc_driver = {
+	.driver = {
+		   .name = "qcom-spmi-vadc",
+		   .of_match_table = vadc_match_table,
+	},
+	.probe = vadc_probe,
+};
+module_platform_driver(vadc_driver);
+
+MODULE_ALIAS("platform:qcom-spmi-vadc");
+MODULE_DESCRIPTION("Qualcomm SPMI PMIC voltage ADC driver");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Stanimir Varbanov <svarbanov@mm-sol.com>");
+MODULE_AUTHOR("Ivan T. Ivanov <iivanov@mm-sol.com>");