iio: potentiostat: add LMP91000 support

Add support for the LMP91000 potentiostat which is used for chemical
sensing applications.
Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt

+* Texas Instruments LMP91000 potentiostat
+
+http://www.ti.com/lit/ds/symlink/lmp91000.pdf
+
+Required properties:
+
+  - compatible: should be "ti,lmp91000"
+  - reg: the I2C address of the device
+  - io-channels: the phandle of the iio provider
+
+  - ti,external-tia-resistor: if the property ti,tia-gain-ohm is not defined this
+    needs to be set to signal that an external resistor value is being used.
+
+Optional properties:
+
+  - ti,tia-gain-ohm: ohm value of the internal resistor for the transimpedance
+    amplifier. Must be 2750, 3500, 7000, 14000, 35000, 120000, or 350000 ohms.
+
+  - ti,rload-ohm: ohm value of the internal resistor load applied to the gas
+    sensor. Must be 10, 33, 50, or 100 (default) ohms.
+
+Example:
+
+lmp91000@48 {
+	compatible = "ti,lmp91000";
+	reg = <0x48>;
+	ti,tia-gain-ohm = <7500>;
+	ti,rload = <100>;
+	io-channels = <&adc>;
+};

drivers/iio/Kconfig

@@ -87,6 +87,7 @@ if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
 endif #IIO_TRIGGER
 source "drivers/iio/potentiometer/Kconfig"
+source "drivers/iio/potentiostat/Kconfig"
 source "drivers/iio/pressure/Kconfig"
 source "drivers/iio/proximity/Kconfig"
 source "drivers/iio/temperature/Kconfig"

drivers/iio/Makefile

@@ -29,6 +29,7 @@ obj-y += light/
 obj-y += magnetometer/
 obj-y += orientation/
 obj-y += potentiometer/
+obj-y += potentiostat/
 obj-y += pressure/
 obj-y += proximity/
 obj-y += temperature/

drivers/iio/potentiostat/Kconfig

+#
+# Potentiostat drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Digital potentiostats"
+
+config LMP91000
+	tristate "Texas Instruments LMP91000 potentiostat driver"
+	depends on I2C
+	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_BUFFER_CB
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for the Texas Instruments
+	  LMP91000 digital potentiostat chip.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called lmp91000
+
+endmenu

drivers/iio/potentiostat/Makefile

+#
+# Makefile for industrial I/O potentiostat drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_LMP91000) += lmp91000.o

drivers/iio/potentiostat/lmp91000.c

+/*
+ * lmp91000.c - Support for Texas Instruments digital potentiostats
+ *
+ * Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * TODO: bias voltage + polarity control, and multiple chip support
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#define LMP91000_REG_LOCK		0x01
+#define LMP91000_REG_TIACN		0x10
+#define LMP91000_REG_TIACN_GAIN_SHIFT	2
+
+#define LMP91000_REG_REFCN		0x11
+#define LMP91000_REG_REFCN_EXT_REF	0x20
+#define LMP91000_REG_REFCN_50_ZERO	0x80
+
+#define LMP91000_REG_MODECN		0x12
+#define LMP91000_REG_MODECN_3LEAD	0x03
+#define LMP91000_REG_MODECN_TEMP	0x07
+
+#define LMP91000_DRV_NAME	"lmp91000"
+
+static const int lmp91000_tia_gain[] = { 0, 2750, 3500, 7000, 14000, 35000,
+					 120000, 350000 };
+
+static const int lmp91000_rload[] = { 10, 33, 50, 100 };
+
+#define LMP91000_TEMP_BASE	-40
+
+static const u16 lmp91000_temp_lut[] = {
+	1875, 1867, 1860, 1852, 1844, 1836, 1828, 1821, 1813, 1805,
+	1797, 1789, 1782, 1774, 1766, 1758, 1750, 1742, 1734, 1727,
+	1719, 1711, 1703, 1695, 1687, 1679, 1671, 1663, 1656, 1648,
+	1640, 1632, 1624, 1616, 1608, 1600, 1592, 1584, 1576, 1568,
+	1560, 1552, 1544, 1536, 1528, 1520, 1512, 1504, 1496, 1488,
+	1480, 1472, 1464, 1456, 1448, 1440, 1432, 1424, 1415, 1407,
+	1399, 1391, 1383, 1375, 1367, 1359, 1351, 1342, 1334, 1326,
+	1318, 1310, 1302, 1293, 1285, 1277, 1269, 1261, 1253, 1244,
+	1236, 1228, 1220, 1212, 1203, 1195, 1187, 1179, 1170, 1162,
+	1154, 1146, 1137, 1129, 1121, 1112, 1104, 1096, 1087, 1079,
+	1071, 1063, 1054, 1046, 1038, 1029, 1021, 1012, 1004,  996,
+	 987,  979,  971,  962,  954,  945,  937,  929,  920,  912,
+	 903,  895,  886,  878,  870,  861 };
+
+static const struct regmap_config lmp91000_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+struct lmp91000_data {
+	struct regmap *regmap;
+	struct device *dev;
+
+	struct iio_trigger *trig;
+	struct iio_cb_buffer *cb_buffer;
+	struct iio_channel *adc_chan;
+
+	struct completion completion;
+	u8 chan_select;
+
+	u32 buffer[4]; /* 64-bit data + 64-bit timestamp */
+};
+
+static const struct iio_chan_spec lmp91000_channels[] = {
+	{ /* chemical channel mV */
+		.type = IIO_VOLTAGE,
+		.channel = 0,
+		.address = LMP91000_REG_MODECN_3LEAD,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_OFFSET) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+		},
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(1),
+	{ /* temperature channel mV */
+		.type = IIO_TEMP,
+		.channel = 1,
+		.address = LMP91000_REG_MODECN_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.scan_index = -1,
+	},
+};
+
+static int lmp91000_read(struct lmp91000_data *data, int channel, int *val)
+{
+	int state, ret;
+
+	ret = regmap_read(data->regmap, LMP91000_REG_MODECN, &state);
+	if (ret)
+		return -EINVAL;
+
+	ret = regmap_write(data->regmap, LMP91000_REG_MODECN, channel);
+	if (ret)
+		return -EINVAL;
+
+	/* delay till first temperature reading is complete */
+	if ((state != channel) && (channel == LMP91000_REG_MODECN_TEMP))
+		usleep_range(3000, 4000);
+
+	data->chan_select = channel != LMP91000_REG_MODECN_3LEAD;
+
+	iio_trigger_poll_chained(data->trig);
+
+	ret = wait_for_completion_timeout(&data->completion, HZ);
+	reinit_completion(&data->completion);
+
+	if (!ret)
+		return -ETIMEDOUT;
+
+	*val = data->buffer[data->chan_select];
+
+	return 0;
+}
+
+static irqreturn_t lmp91000_buffer_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct lmp91000_data *data = iio_priv(indio_dev);
+	int ret, val;
+
+	memset(data->buffer, 0, sizeof(data->buffer));
+
+	ret = lmp91000_read(data, LMP91000_REG_MODECN_3LEAD, &val);
+	if (!ret) {
+		data->buffer[0] = val;
+		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+						   iio_get_time_ns(indio_dev));
+	}
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int lmp91000_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+	case IIO_CHAN_INFO_PROCESSED: {
+		int ret = iio_channel_start_all_cb(data->cb_buffer);
+
+		if (ret)
+			return ret;
+
+		ret = lmp91000_read(data, chan->address, val);
+
+		iio_channel_stop_all_cb(data->cb_buffer);
+
+		if (ret)
+			return ret;
+
+		if (mask == IIO_CHAN_INFO_PROCESSED) {
+			int tmp, i;
+
+			ret = iio_convert_raw_to_processed(data->adc_chan,
+							   *val, &tmp, 1);
+			if (ret)
+				return ret;
+
+			for (i = 0; i < ARRAY_SIZE(lmp91000_temp_lut); i++)
+				if (lmp91000_temp_lut[i] < tmp)
+					break;
+
+			*val = (LMP91000_TEMP_BASE + i) * 1000;
+		}
+		return IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_OFFSET:
+		return iio_read_channel_offset(data->adc_chan, val, val2);
+	case IIO_CHAN_INFO_SCALE:
+		return iio_read_channel_scale(data->adc_chan, val, val2);
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info lmp91000_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = lmp91000_read_raw,
+};
+
+static int lmp91000_read_config(struct lmp91000_data *data)
+{
+	struct device *dev = data->dev;
+	struct device_node *np = dev->of_node;
+	unsigned int reg, val;
+	int i, ret;
+
+	ret = of_property_read_u32(np, "ti,tia-gain-ohm", &val);
+	if (ret) {
+		if (of_property_read_bool(np, "ti,external-tia-resistor"))
+			val = 0;
+		else {
+			dev_err(dev, "no ti,tia-gain-ohm defined");
+			return ret;
+		}
+	}
+
+	ret = -EINVAL;
+	for (i = 0; i < ARRAY_SIZE(lmp91000_tia_gain); i++) {
+		if (lmp91000_tia_gain[i] == val) {
+			reg = i << LMP91000_REG_TIACN_GAIN_SHIFT;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (ret) {
+		dev_err(dev, "invalid ti,tia-gain-ohm %d\n", val);
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "ti,rload-ohm", &val);
+	if (ret) {
+		val = 100;
+		dev_info(dev, "no ti,rload-ohm defined, default to %d\n", val);
+	}
+
+	ret = -EINVAL;
+	for (i = 0; i < ARRAY_SIZE(lmp91000_rload); i++) {
+		if (lmp91000_rload[i] == val) {
+			reg |= i;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (ret) {
+		dev_err(dev, "invalid ti,rload-ohm %d\n", val);
+		return ret;
+	}
+
+	regmap_write(data->regmap, LMP91000_REG_LOCK, 0);
+	regmap_write(data->regmap, LMP91000_REG_TIACN, reg);
+	regmap_write(data->regmap, LMP91000_REG_REFCN, LMP91000_REG_REFCN_EXT_REF
+					| LMP91000_REG_REFCN_50_ZERO);
+	regmap_write(data->regmap, LMP91000_REG_LOCK, 1);
+
+	return 0;
+}
+
+static int lmp91000_buffer_cb(const void *val, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	data->buffer[data->chan_select] = *((int *)val);
+	complete_all(&data->completion);
+
+	return 0;
+}
+
+static const struct iio_trigger_ops lmp91000_trigger_ops = {
+	.owner = THIS_MODULE,
+};
+
+
+static int lmp91000_buffer_preenable(struct iio_dev *indio_dev)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	return iio_channel_start_all_cb(data->cb_buffer);
+}
+
+static int lmp91000_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	iio_channel_stop_all_cb(data->cb_buffer);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops lmp91000_buffer_setup_ops = {
+	.preenable = lmp91000_buffer_preenable,
+	.postenable = iio_triggered_buffer_postenable,
+	.predisable = lmp91000_buffer_predisable,
+};
+
+static int lmp91000_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct lmp91000_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	indio_dev->info = &lmp91000_info;
+	indio_dev->channels = lmp91000_channels;
+	indio_dev->num_channels = ARRAY_SIZE(lmp91000_channels);
+	indio_dev->name = LMP91000_DRV_NAME;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	i2c_set_clientdata(client, indio_dev);
+
+	data = iio_priv(indio_dev);
+	data->dev = dev;
+	data->regmap = devm_regmap_init_i2c(client, &lmp91000_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(dev, "regmap initialization failed.\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	data->trig = devm_iio_trigger_alloc(data->dev, "%s-mux%d",
+					    indio_dev->name, indio_dev->id);
+	if (!data->trig) {
+		dev_err(dev, "cannot allocate iio trigger.\n");
+		return -ENOMEM;
+	}
+
+	data->trig->ops = &lmp91000_trigger_ops;
+	data->trig->dev.parent = dev;
+	init_completion(&data->completion);
+
+	ret = lmp91000_read_config(data);
+	if (ret)
+		return ret;
+
+	ret = iio_trigger_set_immutable(iio_channel_cb_get_iio_dev(data->cb_buffer),
+					data->trig);
+	if (ret) {
+		dev_err(dev, "cannot set immutable trigger.\n");
+		return ret;
+	}
+
+	ret = iio_trigger_register(data->trig);
+	if (ret) {
+		dev_err(dev, "cannot register iio trigger.\n");
+		return ret;
+	}
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+					 &lmp91000_buffer_handler,
+					 &lmp91000_buffer_setup_ops);
+	if (ret)
+		goto error_unreg_trigger;
+
+	data->cb_buffer = iio_channel_get_all_cb(dev, &lmp91000_buffer_cb,
+						 indio_dev);
+
+	if (IS_ERR(data->cb_buffer)) {
+		if (PTR_ERR(data->cb_buffer) == -ENODEV)
+			ret = -EPROBE_DEFER;
+		else
+			ret = PTR_ERR(data->cb_buffer);
+
+		goto error_unreg_buffer;
+	}
+
+	data->adc_chan = iio_channel_cb_get_channels(data->cb_buffer);
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto error_unreg_cb_buffer;
+
+	return 0;
+
+error_unreg_cb_buffer:
+	iio_channel_release_all_cb(data->cb_buffer);
+
+error_unreg_buffer:
+	iio_triggered_buffer_cleanup(indio_dev);
+
+error_unreg_trigger:
+	iio_trigger_unregister(data->trig);
+
+	return ret;
+}
+
+static int lmp91000_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	iio_channel_stop_all_cb(data->cb_buffer);
+	iio_channel_release_all_cb(data->cb_buffer);
+
+	iio_triggered_buffer_cleanup(indio_dev);
+	iio_trigger_unregister(data->trig);
+
+	return 0;
+}
+
+static const struct of_device_id lmp91000_of_match[] = {
+	{ .compatible = "ti,lmp91000", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lmp91000_of_match);
+
+static const struct i2c_device_id lmp91000_id[] = {
+	{ "lmp91000", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, lmp91000_id);
+
+static struct i2c_driver lmp91000_driver = {
+	.driver = {
+		.name = LMP91000_DRV_NAME,
+		.of_match_table = of_match_ptr(lmp91000_of_match),
+	},
+	.probe = lmp91000_probe,
+	.remove = lmp91000_remove,
+	.id_table = lmp91000_id,
+};
+module_i2c_driver(lmp91000_driver);
+
+MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
+MODULE_DESCRIPTION("LMP91000 digital potentiostat");
+MODULE_LICENSE("GPL");