[PATCH v4 3/4] iio: adc: Add ad7124 support

[PATCH v4 3/4] iio: adc: Add ad7124 support

[Stefan Popa]

The ad7124-4 and ad7124-8 are a family of 4 and 8 channel sigma-delta ADCs
with 24-bit precision and reference.

Three power modes are available which in turn affect the output data rate:
 * Full power: 9.38 SPS to 19,200 SPS
 * Mid power: 2.34 SPS to 4800 SPS
 * Low power: 1.17 SPS to 2400 SPS

The ad7124-4 can be configured to have four differential inputs, while
ad7124-8 can have 8. Moreover, ad7124 also supports per channel
configuration. Each configuration consists of gain, reference source,
output data rate and bipolar/unipolar configuration.

Datasheets:
Link: http://www.analog.com/media/en/technical-documentation/data-sheets/AD7124-4.pdf
Link: http://www.analog.com/media/en/technical-documentation/data-sheets/ad7124-8.pdf

Signed-off-by: Stefan Popa <stefan.popa@analog.com>
---
Changes in v2:
	- Nothing changed.
Changes in v3:
	- Removed channel, address, scan_index and shift fields from
	  ad7124_channel_template.
	- Added a sanity check for val2 in ad7124_write_raw().
	- Used the "reg" property to get the channel address and "adi,diff-channels"
	  for the differential pins. The "adi,channel-number" property was removed.
	- When calling regulator_get_optional, the probe is given up in case of error,
	  but continues in case of -ENODEV.
	- clk_disable_unprepare() is called before ad_sd_cleanup_buffer_and_trigger
	  in ad7124_remove().
Changes in v4:
	- Added the .shift and .endianness fields as part of the ad7124_channel_template.
	- Made the gain configurable from the user space.
	- Removed the odr_hz and gain properties from the DT.
	- Used the bipolar and diff-channels properties defined in the new adc.txt doc.
	- Misc style fixes.

 MAINTAINERS              |   7 +
 drivers/iio/adc/Kconfig  |  11 +
 drivers/iio/adc/Makefile |   1 +
 drivers/iio/adc/ad7124.c | 676 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 695 insertions(+)
 create mode 100644 drivers/iio/adc/ad7124.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f642044..3a1bfcb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -839,6 +839,13 @@ S:	Supported
 F:	drivers/iio/dac/ad5758.c
 F:	Documentation/devicetree/bindings/iio/dac/ad5758.txt
 
+ANALOG DEVICES INC AD7124 DRIVER
+M:	Stefan Popa <stefan.popa@analog.com>
+L:	linux-iio@vger.kernel.org
+W:	http://ez.analog.com/community/linux-device-drivers
+S:	Supported
+F:	drivers/iio/adc/ad7124.c
+
 ANALOG DEVICES INC AD9389B DRIVER
 M:	Hans Verkuil <hans.verkuil@cisco.com>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a52fea8..148a10f 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -10,6 +10,17 @@ config AD_SIGMA_DELTA
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 
+config AD7124
+	tristate "Analog Devices AD7124 and similar sigma-delta ADCs driver"
+	depends on SPI_MASTER
+	select AD_SIGMA_DELTA
+	help
+	  Say yes here to build support for Analog Devices AD7124-4 and AD7124-8
+	  SPI analog to digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad7124.
+
 config AD7266
 	tristate "Analog Devices AD7265/AD7266 ADC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a6e6a0b..76168b2 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -5,6 +5,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
+obj-$(CONFIG_AD7124) += ad7124.o
 obj-$(CONFIG_AD7266) += ad7266.o
 obj-$(CONFIG_AD7291) += ad7291.o
 obj-$(CONFIG_AD7298) += ad7298.o
diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
new file mode 100644
index 0000000..64d2aa7
--- /dev/null
+++ b/drivers/iio/adc/ad7124.c
@@ -0,0 +1,676 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * AD7124 SPI ADC driver
+ *
+ * Copyright 2018 Analog Devices Inc.
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/adc/ad_sigma_delta.h>
+#include <linux/iio/sysfs.h>
+
+/* AD7124 registers */
+#define AD7124_COMMS			0x00
+#define AD7124_STATUS			0x00
+#define AD7124_ADC_CONTROL		0x01
+#define AD7124_DATA			0x02
+#define AD7124_IO_CONTROL_1		0x03
+#define AD7124_IO_CONTROL_2		0x04
+#define AD7124_ID			0x05
+#define AD7124_ERROR			0x06
+#define AD7124_ERROR_EN		0x07
+#define AD7124_MCLK_COUNT		0x08
+#define AD7124_CHANNEL(x)		(0x09 + (x))
+#define AD7124_CONFIG(x)		(0x19 + (x))
+#define AD7124_FILTER(x)		(0x21 + (x))
+#define AD7124_OFFSET(x)		(0x29 + (x))
+#define AD7124_GAIN(x)			(0x31 + (x))
+
+/* AD7124_STATUS */
+#define AD7124_STATUS_POR_FLAG_MSK	BIT(4)
+
+/* AD7124_ADC_CONTROL */
+#define AD7124_ADC_CTRL_PWR_MSK	GENMASK(7, 6)
+#define AD7124_ADC_CTRL_PWR(x)		FIELD_PREP(AD7124_ADC_CTRL_PWR_MSK, x)
+#define AD7124_ADC_CTRL_MODE_MSK	GENMASK(5, 2)
+#define AD7124_ADC_CTRL_MODE(x)	FIELD_PREP(AD7124_ADC_CTRL_MODE_MSK, x)
+
+/* AD7124_CHANNEL_X */
+#define AD7124_CHANNEL_EN_MSK		BIT(15)
+#define AD7124_CHANNEL_EN(x)		FIELD_PREP(AD7124_CHANNEL_EN_MSK, x)
+#define AD7124_CHANNEL_SETUP_MSK	GENMASK(14, 12)
+#define AD7124_CHANNEL_SETUP(x)	FIELD_PREP(AD7124_CHANNEL_SETUP_MSK, x)
+#define AD7124_CHANNEL_AINP_MSK	GENMASK(9, 5)
+#define AD7124_CHANNEL_AINP(x)		FIELD_PREP(AD7124_CHANNEL_AINP_MSK, x)
+#define AD7124_CHANNEL_AINM_MSK	GENMASK(4, 0)
+#define AD7124_CHANNEL_AINM(x)		FIELD_PREP(AD7124_CHANNEL_AINM_MSK, x)
+
+/* AD7124_CONFIG_X */
+#define AD7124_CONFIG_BIPOLAR_MSK	BIT(11)
+#define AD7124_CONFIG_BIPOLAR(x)	FIELD_PREP(AD7124_CONFIG_BIPOLAR_MSK, x)
+#define AD7124_CONFIG_REF_SEL_MSK	GENMASK(4, 3)
+#define AD7124_CONFIG_REF_SEL(x)	FIELD_PREP(AD7124_CONFIG_REF_SEL_MSK, x)
+#define AD7124_CONFIG_PGA_MSK		GENMASK(2, 0)
+#define AD7124_CONFIG_PGA(x)		FIELD_PREP(AD7124_CONFIG_PGA_MSK, x)
+
+/* AD7124_FILTER_X */
+#define AD7124_FILTER_FS_MSK		GENMASK(10, 0)
+#define AD7124_FILTER_FS(x)		FIELD_PREP(AD7124_FILTER_FS_MSK, x)
+
+enum ad7124_ids {
+	ID_AD7124_4,
+	ID_AD7124_8,
+};
+
+enum ad7124_ref_sel {
+	AD7124_REFIN1,
+	AD7124_REFIN2,
+	AD7124_INT_REF,
+	AD7124_AVDD_REF,
+};
+
+enum ad7124_power_mode {
+	AD7124_LOW_POWER,
+	AD7124_MID_POWER,
+	AD7124_FULL_POWER,
+};
+
+static const unsigned int ad7124_gain[8] = {
+	1, 2, 4, 8, 16, 32, 64, 128
+};
+
+static const int ad7124_master_clk_freq_hz[3] = {
+	[AD7124_LOW_POWER] = 76800,
+	[AD7124_MID_POWER] = 153600,
+	[AD7124_FULL_POWER] = 614400,
+};
+
+static const char * const ad7124_ref_names[] = {
+	[AD7124_REFIN1] = "refin1",
+	[AD7124_REFIN2] = "refin2",
+	[AD7124_INT_REF] = "int",
+	[AD7124_AVDD_REF] = "avdd",
+};
+
+struct ad7124_chip_info {
+	unsigned int num_inputs;
+};
+
+struct ad7124_channel_config {
+	enum ad7124_ref_sel refsel;
+	bool bipolar;
+	unsigned int ain;
+	unsigned int vref_mv;
+	unsigned int pga_bits;
+	unsigned int odr;
+};
+
+struct ad7124_state {
+	const struct ad7124_chip_info *chip_info;
+	struct ad_sigma_delta sd;
+	struct ad7124_channel_config channel_config[4];
+	struct regulator *vref[4];
+	struct clk *mclk;
+	unsigned int adc_control;
+	unsigned int num_channels;
+};
+
+static const struct iio_chan_spec ad7124_channel_template = {
+	.type = IIO_VOLTAGE,
+	.indexed = 1,
+	.differential = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+		BIT(IIO_CHAN_INFO_SCALE) |
+		BIT(IIO_CHAN_INFO_OFFSET) |
+		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+		BIT(IIO_CHAN_INFO_HARDWAREGAIN),
+	.scan_type = {
+		.sign = 'u',
+		.realbits = 24,
+		.storagebits = 32,
+		.shift = 8,
+		.endianness = IIO_BE,
+	},
+};
+
+static struct ad7124_chip_info ad7124_chip_info_tbl[] = {
+	[ID_AD7124_4] = {
+		.num_inputs = 8,
+	},
+	[ID_AD7124_8] = {
+		.num_inputs = 16,
+	},
+};
+
+static int ad7124_find_closest_match(const int *array,
+				     unsigned int size, int val)
+{
+	int i;
+
+	for (i = 0; i < size; i++) {
+		if (val <= array[i])
+			return i;
+	}
+
+	return size - 1;
+}
+
+static int ad7124_spi_write_mask(struct ad7124_state *st,
+				 unsigned int addr,
+				 unsigned long mask,
+				 unsigned int val,
+				 unsigned int bytes)
+{
+	unsigned int readval;
+	int ret;
+
+	ret = ad_sd_read_reg(&st->sd, addr, bytes, &readval);
+	if (ret < 0)
+		return ret;
+
+	readval &= ~mask;
+	readval |= val;
+
+	return ad_sd_write_reg(&st->sd, addr, bytes, readval);
+}
+
+static int ad7124_set_mode(struct ad_sigma_delta *sd,
+			   enum ad_sigma_delta_mode mode)
+{
+	struct ad7124_state *st = container_of(sd, struct ad7124_state, sd);
+
+	st->adc_control &= ~AD7124_ADC_CTRL_MODE_MSK;
+	st->adc_control |= AD7124_ADC_CTRL_MODE(mode);
+
+	return ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
+}
+
+static int ad7124_set_channel(struct ad_sigma_delta *sd, unsigned int channel)
+{
+	struct ad7124_state *st = container_of(sd, struct ad7124_state, sd);
+	unsigned int val;
+
+	val = st->channel_config[channel].ain | AD7124_CHANNEL_EN(1) |
+	      AD7124_CHANNEL_SETUP(channel);
+
+	return ad_sd_write_reg(&st->sd, AD7124_CHANNEL(channel), 2, val);
+}
+
+static const struct ad_sigma_delta_info ad7124_sigma_delta_info = {
+	.set_channel = ad7124_set_channel,
+	.set_mode = ad7124_set_mode,
+	.has_registers = true,
+	.addr_shift = 0,
+	.read_mask = BIT(6),
+	.data_reg = AD7124_DATA,
+};
+
+static int ad7124_set_channel_odr(struct ad7124_state *st,
+				  unsigned int channel,
+				  unsigned int odr)
+{
+	unsigned int fclk, odr_sel_bits;
+	int ret;
+
+	fclk = clk_get_rate(st->mclk);
+	/*
+	 * FS[10:0] = fCLK / (fADC x 32) where:
+	 * fADC is the output data rate
+	 * fCLK is the master clock frequency
+	 * FS[10:0] are the bits in the filter register
+	 * FS[10:0] can have a value from 1 to 2047
+	 */
+	odr_sel_bits = DIV_ROUND_CLOSEST(fclk, odr * 32);
+	if (odr_sel_bits < 1)
+		odr_sel_bits = 1;
+	else if (odr_sel_bits > 2047)
+		odr_sel_bits = 2047;
+
+	ret = ad7124_spi_write_mask(st, AD7124_FILTER(channel),
+				    AD7124_FILTER_FS_MSK,
+				    AD7124_FILTER_FS(odr_sel_bits), 3);
+	if (ret < 0)
+		return ret;
+	/* fADC = fCLK / (FS[10:0] x 32) */
+	st->channel_config[channel].odr =
+		DIV_ROUND_CLOSEST(fclk, odr_sel_bits * 32);
+
+	return 0;
+}
+
+static int ad7124_set_channel_gain(struct ad7124_state *st,
+				   unsigned int channel,
+				   unsigned int gain)
+{
+	unsigned int res;
+	int ret;
+
+	res = ad7124_find_closest_match(ad7124_gain,
+					ARRAY_SIZE(ad7124_gain), gain);
+	ret = ad7124_spi_write_mask(st, AD7124_CONFIG(channel),
+				    AD7124_CONFIG_PGA_MSK,
+				    AD7124_CONFIG_PGA(res), 2);
+	if (ret < 0)
+		return ret;
+
+	st->channel_config[channel].pga_bits = res;
+
+	return 0;
+}
+
+static int ad7124_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long info)
+{
+	struct ad7124_state *st = iio_priv(indio_dev);
+	int idx, ret;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		ret = ad_sigma_delta_single_conversion(indio_dev, chan, val);
+		if (ret < 0)
+			return ret;
+
+		/* After the conversion is performed, disable the channel */
+		ret = ad_sd_write_reg(&st->sd,
+				      AD7124_CHANNEL(chan->address), 2,
+				      st->channel_config[chan->address].ain |
+				      AD7124_CHANNEL_EN(0));
+		if (ret < 0)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		idx = st->channel_config[chan->address].pga_bits;
+		*val = st->channel_config[chan->address].vref_mv /
+			ad7124_gain[idx];
+		if (st->channel_config[chan->address].bipolar)
+			*val2 = chan->scan_type.realbits - 1;
+		else
+			*val2 = chan->scan_type.realbits;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_OFFSET:
+		if (st->channel_config[chan->address].bipolar) {
+			/* Code = 2^(n − 1) × ((Ain × Gain / Vref) + 1) */
+			idx = st->channel_config[chan->address].pga_bits;
+			*val = -(st->channel_config[chan->address].vref_mv /
+				 ad7124_gain[idx]);
+		} else {
+			*val = 0;
+		}
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = st->channel_config[chan->address].odr;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_HARDWAREGAIN:
+		idx = st->channel_config[chan->address].pga_bits;
+		*val = ad7124_gain[idx];
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad7124_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long info)
+{
+	struct ad7124_state *st = iio_priv(indio_dev);
+
+	if (val2 != 0)
+		return -EINVAL;
+
+	switch (info) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return ad7124_set_channel_odr(st, chan->address, val);
+	case IIO_CHAN_INFO_HARDWAREGAIN:
+		return ad7124_set_channel_gain(st, chan->address, val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static IIO_CONST_ATTR(in_voltage_gain_available, "1 2 4 8 16 32 64 128");
+
+static struct attribute *ad7124_attributes[] = {
+	&iio_const_attr_in_voltage_gain_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ad7124_attrs_group = {
+	.attrs = ad7124_attributes,
+};
+
+static const struct iio_info ad7124_info = {
+	.read_raw = ad7124_read_raw,
+	.write_raw = ad7124_write_raw,
+	.validate_trigger = ad_sd_validate_trigger,
+	.attrs = &ad7124_attrs_group,
+};
+
+static int ad7124_soft_reset(struct ad7124_state *st)
+{
+	unsigned int readval, timeout;
+	int ret;
+
+	ret = ad_sd_reset(&st->sd, 64);
+	if (ret < 0)
+		return ret;
+
+	timeout = 100;
+	do {
+		ret = ad_sd_read_reg(&st->sd, AD7124_STATUS, 1, &readval);
+		if (ret < 0)
+			return ret;
+
+		if (!(readval & AD7124_STATUS_POR_FLAG_MSK))
+			return 0;
+
+		/* The AD7124 requires typically 2ms to power up and settle */
+		usleep_range(100, 2000);
+	} while (--timeout);
+
+	dev_err(&st->sd.spi->dev, "Soft reset failed\n");
+
+	return -EIO;
+}
+
+static int ad7124_init_channel_vref(struct ad7124_state *st,
+				    unsigned int channel_number)
+{
+	unsigned int refsel = st->channel_config[channel_number].refsel;
+
+	switch (refsel) {
+	case AD7124_REFIN1:
+	case AD7124_REFIN2:
+	case AD7124_AVDD_REF:
+		if (IS_ERR(st->vref[refsel])) {
+			dev_err(&st->sd.spi->dev,
+				"Error, trying to use external voltage reference without a %s regulator.\n",
+				ad7124_ref_names[refsel]);
+				return PTR_ERR(st->vref[refsel]);
+		}
+		st->channel_config[channel_number].vref_mv =
+			regulator_get_voltage(st->vref[refsel]);
+		/* Conversion from uV to mV */
+		st->channel_config[channel_number].vref_mv /= 1000;
+		break;
+	case AD7124_INT_REF:
+		st->channel_config[channel_number].vref_mv = 2500;
+		break;
+	default:
+		dev_err(&st->sd.spi->dev, "Invalid reference %d\n", refsel);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int ad7124_of_parse_channel_config(struct iio_dev *indio_dev,
+					  struct device_node *np)
+{
+	struct ad7124_state *st = iio_priv(indio_dev);
+	struct device_node *child;
+	struct iio_chan_spec *chan;
+	unsigned int ain[2], channel = 0, tmp;
+	int ret;
+
+	st->num_channels = of_get_available_child_count(np);
+	if (!st->num_channels) {
+		dev_err(indio_dev->dev.parent, "no channel children\n");
+		return -ENODEV;
+	}
+
+	chan = devm_kcalloc(indio_dev->dev.parent, st->num_channels,
+			    sizeof(*chan), GFP_KERNEL);
+	if (!chan)
+		return -ENOMEM;
+
+	indio_dev->channels = chan;
+	indio_dev->num_channels = st->num_channels;
+
+	for_each_available_child_of_node(np, child) {
+		ret = of_property_read_u32(child, "reg", &channel);
+		if (ret)
+			goto err;
+
+		ret = of_property_read_u32_array(child, "diff-channels",
+						 ain, 2);
+		if (ret)
+			goto err;
+
+		if (ain[0] >= st->chip_info->num_inputs ||
+		    ain[1] >= st->chip_info->num_inputs) {
+			dev_err(indio_dev->dev.parent,
+				"Input pin number out of range.\n");
+			ret = -EINVAL;
+			goto err;
+		}
+		st->channel_config[channel].ain = AD7124_CHANNEL_AINP(ain[0]) |
+						  AD7124_CHANNEL_AINM(ain[1]);
+		st->channel_config[channel].bipolar =
+			of_property_read_bool(child, "bipolar");
+
+		ret = of_property_read_u32(child, "adi,reference-select", &tmp);
+		if (ret)
+			st->channel_config[channel].refsel = AD7124_INT_REF;
+		else
+			st->channel_config[channel].refsel = tmp;
+
+		*chan = ad7124_channel_template;
+		chan->address = channel;
+		chan->scan_index = channel;
+		chan->channel = ain[0];
+		chan->channel2 = ain[1];
+
+		chan++;
+	}
+
+	return 0;
+err:
+	of_node_put(child);
+
+	return ret;
+}
+
+static int ad7124_setup(struct ad7124_state *st)
+{
+	unsigned int val, fclk, power_mode;
+	int i, ret;
+
+	fclk = clk_get_rate(st->mclk);
+	if (!fclk)
+		return -EINVAL;
+
+	/* The power mode changes the master clock frequency */
+	power_mode = ad7124_find_closest_match(ad7124_master_clk_freq_hz,
+					ARRAY_SIZE(ad7124_master_clk_freq_hz),
+					fclk);
+	if (fclk != ad7124_master_clk_freq_hz[power_mode]) {
+		ret = clk_set_rate(st->mclk, fclk);
+		if (ret)
+			return ret;
+	}
+
+	/* Set the power mode */
+	st->adc_control &= ~AD7124_ADC_CTRL_PWR_MSK;
+	st->adc_control |= AD7124_ADC_CTRL_PWR(power_mode);
+	ret = ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < st->num_channels; i++) {
+		val = st->channel_config[i].ain | AD7124_CHANNEL_SETUP(i);
+		ret = ad_sd_write_reg(&st->sd, AD7124_CHANNEL(i), 2, val);
+		if (ret < 0)
+			return ret;
+
+		ret = ad7124_init_channel_vref(st, i);
+		if (ret < 0)
+			return ret;
+
+		val = AD7124_CONFIG_BIPOLAR(st->channel_config[i].bipolar) |
+		      AD7124_CONFIG_REF_SEL(st->channel_config[i].refsel);
+		ret = ad_sd_write_reg(&st->sd, AD7124_CONFIG(i), 2, val);
+		if (ret < 0)
+			return ret;
+		/*
+		 * 9.38 SPS is the minimum output data rate supported
+		 * regardless of the selected power mode. Round it up to 10 and
+		 * set all the enabled channels to this default value.
+		 */
+		ret = ad7124_set_channel_odr(st, i, 10);
+		if (ret < 0)
+			return ret;
+	}
+
+	return ret;
+}
+
+static int ad7124_probe(struct spi_device *spi)
+{
+	const struct spi_device_id *id;
+	struct ad7124_state *st;
+	struct iio_dev *indio_dev;
+	int i, ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	id = spi_get_device_id(spi);
+	st->chip_info = &ad7124_chip_info_tbl[id->driver_data];
+
+	ad_sd_init(&st->sd, indio_dev, spi, &ad7124_sigma_delta_info);
+
+	spi_set_drvdata(spi, indio_dev);
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &ad7124_info;
+
+	ret = ad7124_of_parse_channel_config(indio_dev, spi->dev.of_node);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < ARRAY_SIZE(st->vref); i++) {
+		if (i == AD7124_INT_REF)
+			continue;
+
+		st->vref[i] = devm_regulator_get_optional(&spi->dev,
+						ad7124_ref_names[i]);
+		if (PTR_ERR(st->vref[i]) == -ENODEV)
+			continue;
+		else if (IS_ERR(st->vref[i]))
+			return PTR_ERR(st->vref[i]);
+
+		ret = regulator_enable(st->vref[i]);
+		if (ret)
+			return ret;
+	}
+
+	st->mclk = devm_clk_get(&spi->dev, "mclk");
+	if (IS_ERR(st->mclk)) {
+		ret = PTR_ERR(st->mclk);
+		goto error_regulator_disable;
+	}
+
+	ret = clk_prepare_enable(st->mclk);
+	if (ret < 0)
+		goto error_regulator_disable;
+
+	ret = ad7124_soft_reset(st);
+	if (ret < 0)
+		goto error_clk_disable_unprepare;
+
+	ret = ad7124_setup(st);
+	if (ret < 0)
+		goto error_clk_disable_unprepare;
+
+	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
+	if (ret < 0)
+		goto error_clk_disable_unprepare;
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0) {
+		dev_err(&spi->dev, "Failed to register iio device\n");
+		goto error_remove_trigger;
+	}
+
+	return 0;
+
+error_remove_trigger:
+	ad_sd_cleanup_buffer_and_trigger(indio_dev);
+error_clk_disable_unprepare:
+	clk_disable_unprepare(st->mclk);
+error_regulator_disable:
+	for (i = ARRAY_SIZE(st->vref) - 1; i >= 0; i--) {
+		if (!IS_ERR_OR_NULL(st->vref[i]))
+			regulator_disable(st->vref[i]);
+	}
+
+	return ret;
+}
+
+static int ad7124_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct ad7124_state *st = iio_priv(indio_dev);
+	int i;
+
+	iio_device_unregister(indio_dev);
+	ad_sd_cleanup_buffer_and_trigger(indio_dev);
+	clk_disable_unprepare(st->mclk);
+
+	for (i = ARRAY_SIZE(st->vref) - 1; i >= 0; i--) {
+		if (!IS_ERR_OR_NULL(st->vref[i]))
+			regulator_disable(st->vref[i]);
+	}
+
+	return 0;
+}
+
+static const struct spi_device_id ad7124_id_table[] = {
+	{ "ad7124-4", ID_AD7124_4 },
+	{ "ad7124-8", ID_AD7124_8 },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ad7124_id_table);
+
+static const struct of_device_id ad7124_of_match[] = {
+	{ .compatible = "adi,ad7124-4" },
+	{ .compatible = "adi,ad7124-8" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ad7124_of_match);
+
+static struct spi_driver ad71124_driver = {
+	.driver = {
+		.name = "ad7124",
+		.of_match_table = ad7124_of_match,
+	},
+	.probe = ad7124_probe,
+	.remove	= ad7124_remove,
+	.id_table = ad7124_id_table,
+};
+module_spi_driver(ad71124_driver);
+
+MODULE_AUTHOR("Stefan Popa <stefan.popa@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD7124 SPI driver");
+MODULE_LICENSE("GPL");
-- 
2.7.4

Re: [PATCH v4 3/4] iio: adc: Add ad7124 support

[Jonathan Cameron]

On Fri, 9 Nov 2018 17:41:46 +0200
Stefan Popa <stefan.popa@analog.com> wrote:

> The ad7124-4 and ad7124-8 are a family of 4 and 8 channel sigma-delta ADCs
> with 24-bit precision and reference.
>=20
> Three power modes are available which in turn affect the output data rate:
>  * Full power: 9.38 SPS to 19,200 SPS
>  * Mid power: 2.34 SPS to 4800 SPS
>  * Low power: 1.17 SPS to 2400 SPS
>=20
> The ad7124-4 can be configured to have four differential inputs, while
> ad7124-8 can have 8. Moreover, ad7124 also supports per channel
> configuration. Each configuration consists of gain, reference source,
> output data rate and bipolar/unipolar configuration.

One question around the offset.
Voltage =3D (raw value + offset) * scale.
So I think the offset should simply be half the raw value range, not depend=
ent
on the current gain?

Perhaps I'm missing something.

The other thing that I think needs to be dropped is the use of hardware gai=
n.
It was never intended for this use case and means we effectively have two
interfaces for the same thing.  Scale and hardwaregain.

Otherwise, looking very nice.

Jonathan

>=20
> Datasheets:
> Link: http://www.analog.com/media/en/technical-documentation/data-sheets/=
AD7124-4.pdf
> Link: http://www.analog.com/media/en/technical-documentation/data-sheets/=
ad7124-8.pdf
>=20
> Signed-off-by: Stefan Popa <stefan.popa@analog.com>
> ---
> Changes in v2:
> 	- Nothing changed.
> Changes in v3:
> 	- Removed channel, address, scan_index and shift fields from
> 	  ad7124_channel_template.
> 	- Added a sanity check for val2 in ad7124_write_raw().
> 	- Used the "reg" property to get the channel address and "adi,diff-chann=
els"
> 	  for the differential pins. The "adi,channel-number" property was remov=
ed.
> 	- When calling regulator_get_optional, the probe is given up in case of =
error,
> 	  but continues in case of -ENODEV.
> 	- clk_disable_unprepare() is called before ad_sd_cleanup_buffer_and_trig=
ger
> 	  in ad7124_remove().
> Changes in v4:
> 	- Added the .shift and .endianness fields as part of the ad7124_channel_=
template.
> 	- Made the gain configurable from the user space.
> 	- Removed the odr_hz and gain properties from the DT.
> 	- Used the bipolar and diff-channels properties defined in the new adc.t=
xt doc.
> 	- Misc style fixes.
>=20
>  MAINTAINERS              |   7 +
>  drivers/iio/adc/Kconfig  |  11 +
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad7124.c | 676 +++++++++++++++++++++++++++++++++++++++++=
++++++
>  4 files changed, 695 insertions(+)
>  create mode 100644 drivers/iio/adc/ad7124.c
>=20
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f642044..3a1bfcb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -839,6 +839,13 @@ S:	Supported
>  F:	drivers/iio/dac/ad5758.c
>  F:	Documentation/devicetree/bindings/iio/dac/ad5758.txt
> =20
> +ANALOG DEVICES INC AD7124 DRIVER
> +M:	Stefan Popa <stefan.popa@analog.com>
> +L:	linux-iio@vger.kernel.org
> +W:	http://ez.analog.com/community/linux-device-drivers
> +S:	Supported
> +F:	drivers/iio/adc/ad7124.c
> +
>  ANALOG DEVICES INC AD9389B DRIVER
>  M:	Hans Verkuil <hans.verkuil@cisco.com>
>  L:	linux-media@vger.kernel.org
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index a52fea8..148a10f 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -10,6 +10,17 @@ config AD_SIGMA_DELTA
>  	select IIO_BUFFER
>  	select IIO_TRIGGERED_BUFFER
> =20
> +config AD7124
> +	tristate "Analog Devices AD7124 and similar sigma-delta ADCs driver"
> +	depends on SPI_MASTER
> +	select AD_SIGMA_DELTA
> +	help
> +	  Say yes here to build support for Analog Devices AD7124-4 and AD7124-8
> +	  SPI analog to digital converters (ADC).
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ad7124.
> +
>  config AD7266
>  	tristate "Analog Devices AD7265/AD7266 ADC driver"
>  	depends on SPI_MASTER
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index a6e6a0b..76168b2 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -5,6 +5,7 @@
> =20
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_AD_SIGMA_DELTA) +=3D ad_sigma_delta.o
> +obj-$(CONFIG_AD7124) +=3D ad7124.o
>  obj-$(CONFIG_AD7266) +=3D ad7266.o
>  obj-$(CONFIG_AD7291) +=3D ad7291.o
>  obj-$(CONFIG_AD7298) +=3D ad7298.o
> diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
> new file mode 100644
> index 0000000..64d2aa7
> --- /dev/null
> +++ b/drivers/iio/adc/ad7124.c
> @@ -0,0 +1,676 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * AD7124 SPI ADC driver
> + *
> + * Copyright 2018 Analog Devices Inc.
> + */
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/adc/ad_sigma_delta.h>
> +#include <linux/iio/sysfs.h>
> +
> +/* AD7124 registers */
> +#define AD7124_COMMS			0x00
> +#define AD7124_STATUS			0x00
> +#define AD7124_ADC_CONTROL		0x01
> +#define AD7124_DATA			0x02
> +#define AD7124_IO_CONTROL_1		0x03
> +#define AD7124_IO_CONTROL_2		0x04
> +#define AD7124_ID			0x05
> +#define AD7124_ERROR			0x06
> +#define AD7124_ERROR_EN		0x07
> +#define AD7124_MCLK_COUNT		0x08
> +#define AD7124_CHANNEL(x)		(0x09 + (x))
> +#define AD7124_CONFIG(x)		(0x19 + (x))
> +#define AD7124_FILTER(x)		(0x21 + (x))
> +#define AD7124_OFFSET(x)		(0x29 + (x))
> +#define AD7124_GAIN(x)			(0x31 + (x))
> +
> +/* AD7124_STATUS */
> +#define AD7124_STATUS_POR_FLAG_MSK	BIT(4)
> +
> +/* AD7124_ADC_CONTROL */
> +#define AD7124_ADC_CTRL_PWR_MSK	GENMASK(7, 6)
> +#define AD7124_ADC_CTRL_PWR(x)		FIELD_PREP(AD7124_ADC_CTRL_PWR_MSK, x)
> +#define AD7124_ADC_CTRL_MODE_MSK	GENMASK(5, 2)
> +#define AD7124_ADC_CTRL_MODE(x)	FIELD_PREP(AD7124_ADC_CTRL_MODE_MSK, x)
> +
> +/* AD7124_CHANNEL_X */
> +#define AD7124_CHANNEL_EN_MSK		BIT(15)
> +#define AD7124_CHANNEL_EN(x)		FIELD_PREP(AD7124_CHANNEL_EN_MSK, x)
> +#define AD7124_CHANNEL_SETUP_MSK	GENMASK(14, 12)
> +#define AD7124_CHANNEL_SETUP(x)	FIELD_PREP(AD7124_CHANNEL_SETUP_MSK, x)
> +#define AD7124_CHANNEL_AINP_MSK	GENMASK(9, 5)
> +#define AD7124_CHANNEL_AINP(x)		FIELD_PREP(AD7124_CHANNEL_AINP_MSK, x)
> +#define AD7124_CHANNEL_AINM_MSK	GENMASK(4, 0)
> +#define AD7124_CHANNEL_AINM(x)		FIELD_PREP(AD7124_CHANNEL_AINM_MSK, x)
> +
> +/* AD7124_CONFIG_X */
> +#define AD7124_CONFIG_BIPOLAR_MSK	BIT(11)
> +#define AD7124_CONFIG_BIPOLAR(x)	FIELD_PREP(AD7124_CONFIG_BIPOLAR_MSK, x)
> +#define AD7124_CONFIG_REF_SEL_MSK	GENMASK(4, 3)
> +#define AD7124_CONFIG_REF_SEL(x)	FIELD_PREP(AD7124_CONFIG_REF_SEL_MSK, x)
> +#define AD7124_CONFIG_PGA_MSK		GENMASK(2, 0)
> +#define AD7124_CONFIG_PGA(x)		FIELD_PREP(AD7124_CONFIG_PGA_MSK, x)
> +
> +/* AD7124_FILTER_X */
> +#define AD7124_FILTER_FS_MSK		GENMASK(10, 0)
> +#define AD7124_FILTER_FS(x)		FIELD_PREP(AD7124_FILTER_FS_MSK, x)
> +
> +enum ad7124_ids {
> +	ID_AD7124_4,
> +	ID_AD7124_8,
> +};
> +
> +enum ad7124_ref_sel {
> +	AD7124_REFIN1,
> +	AD7124_REFIN2,
> +	AD7124_INT_REF,
> +	AD7124_AVDD_REF,
> +};
> +
> +enum ad7124_power_mode {
> +	AD7124_LOW_POWER,
> +	AD7124_MID_POWER,
> +	AD7124_FULL_POWER,
> +};
> +
> +static const unsigned int ad7124_gain[8] =3D {
> +	1, 2, 4, 8, 16, 32, 64, 128
> +};
> +
> +static const int ad7124_master_clk_freq_hz[3] =3D {
> +	[AD7124_LOW_POWER] =3D 76800,
> +	[AD7124_MID_POWER] =3D 153600,
> +	[AD7124_FULL_POWER] =3D 614400,
> +};
> +
> +static const char * const ad7124_ref_names[] =3D {
> +	[AD7124_REFIN1] =3D "refin1",
> +	[AD7124_REFIN2] =3D "refin2",
> +	[AD7124_INT_REF] =3D "int",
> +	[AD7124_AVDD_REF] =3D "avdd",
> +};
> +
> +struct ad7124_chip_info {
> +	unsigned int num_inputs;
> +};
> +
> +struct ad7124_channel_config {
> +	enum ad7124_ref_sel refsel;
> +	bool bipolar;
> +	unsigned int ain;
> +	unsigned int vref_mv;
> +	unsigned int pga_bits;
> +	unsigned int odr;
> +};
> +
> +struct ad7124_state {
> +	const struct ad7124_chip_info *chip_info;
> +	struct ad_sigma_delta sd;
> +	struct ad7124_channel_config channel_config[4];
> +	struct regulator *vref[4];
> +	struct clk *mclk;
> +	unsigned int adc_control;
> +	unsigned int num_channels;
> +};
> +
> +static const struct iio_chan_spec ad7124_channel_template =3D {
> +	.type =3D IIO_VOLTAGE,
> +	.indexed =3D 1,
> +	.differential =3D 1,
> +	.info_mask_separate =3D BIT(IIO_CHAN_INFO_RAW) |
> +		BIT(IIO_CHAN_INFO_SCALE) |
> +		BIT(IIO_CHAN_INFO_OFFSET) |
> +		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
> +		BIT(IIO_CHAN_INFO_HARDWAREGAIN),
> +	.scan_type =3D {
> +		.sign =3D 'u',
> +		.realbits =3D 24,
> +		.storagebits =3D 32,
> +		.shift =3D 8,
> +		.endianness =3D IIO_BE,
> +	},
> +};

...
> +static int ad7124_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long info)
> +{
> +	struct ad7124_state *st =3D iio_priv(indio_dev);
> +	int idx, ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret =3D ad_sigma_delta_single_conversion(indio_dev, chan, val);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* After the conversion is performed, disable the channel */
> +		ret =3D ad_sd_write_reg(&st->sd,
> +				      AD7124_CHANNEL(chan->address), 2,
> +				      st->channel_config[chan->address].ain |
> +				      AD7124_CHANNEL_EN(0));
> +		if (ret < 0)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		idx =3D st->channel_config[chan->address].pga_bits;
> +		*val =3D st->channel_config[chan->address].vref_mv /
> +			ad7124_gain[idx];

Given the gains are all a power of 2.  You 'could' apply them to
*val2 instead?  Might give better precision. I haven't checked!

> +		if (st->channel_config[chan->address].bipolar)
> +			*val2 =3D chan->scan_type.realbits - 1;
> +		else
> +			*val2 =3D chan->scan_type.realbits;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	case IIO_CHAN_INFO_OFFSET:
> +		if (st->channel_config[chan->address].bipolar) {
> +			/* Code =3D 2^(n =E2=88=92 1) =C3=97 ((Ain =C3=97 Gain / Vref) + 1) */
> +			idx =3D st->channel_config[chan->address].pga_bits;
> +			*val =3D -(st->channel_config[chan->address].vref_mv /
> +				 ad7124_gain[idx]);
This one surprised me.  Offset is applied before gain and I think this part
is symmetric when bipolar, so I think should just be based on the raw adc
counts as half the full range?

> +		} else {
> +			*val =3D 0;
> +		}
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val =3D st->channel_config[chan->address].odr;
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_HARDWAREGAIN:
> +		idx =3D st->channel_config[chan->address].pga_bits;
> +		*val =3D ad7124_gain[idx];
Hmm. Normally hardwaregain is reserved for those cases where scale
doesn't work.  Scale is definitely the preferred option and it'll
take a pretty persuasive argument to convince me otherwise.

Normally hardware gain is when it is is actually effecting the
measurement (so things like light intensity for time of flight
sensors).

> +
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +

...