hwmon: add driver for TI ADS1118

Add new driver for Texas Instruments ADS1118 and and ADS1018. This driver works with ADS1018, because of code borrowed from asd1015, which is similar, but I can only test ADS1118

Signed-off-by Joshua Clayton <[email protected]>

---
  drivers/hwmon/Kconfig   |  11 ++
  drivers/hwmon/Makefile  |   1 +
  drivers/hwmon/ads1118.c | 516 ++++++++++++++++++++++++++++++++++++++++++++++++
  3 files changed, 528 insertions(+)

create mode 100644 drivers/hwmon/ads1118.c

drivers/hwmon/Kconfig +11 -0

index ff94007..cadde38 100644
@@ -1459,6 +1459,17 @@ config SENSORS_ADS1015
  	  This driver can also be built as a module.  If so, the module
  	  will be called ads1015.
 
+config SENSORS_ADS1118
+	tristate "Texas Instruments ADS1018/ADS1118"
+	depends on SPI
+	help
+	  If you say yes here you get support for Texas Instruments
+	  ADS1118 16-bit 4-input ADC device and temperature sensor,
+	  and the 12-bit ADS1018.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called ads1118.
+
  config SENSORS_ADS7828
  	tristate "Texas Instruments ADS7828 and compatibles"
  	depends on I2C

drivers/hwmon/Makefile +1 -0

index 2ef5b7c..a3b4b2e 100644
@@ -34,6 +34,7 @@ obj-$(CONFIG_SENSORS_ADM1029)	+= adm1029.o
  obj-$(CONFIG_SENSORS_ADM1031)	+= adm1031.o
  obj-$(CONFIG_SENSORS_ADM9240)	+= adm9240.o
  obj-$(CONFIG_SENSORS_ADS1015)	+= ads1015.o
+obj-$(CONFIG_SENSORS_ADS1118)	+= ads1118.o
  obj-$(CONFIG_SENSORS_ADS7828)	+= ads7828.o
  obj-$(CONFIG_SENSORS_ADS7871)	+= ads7871.o
  obj-$(CONFIG_SENSORS_ADT7X10)	+= adt7x10.o

drivers/hwmon/ads1118.c new file +516 -0

new file mode 100644
index 0000000..65ee337
@@ -0,0 +1,516 @@
+/*
+ * ads1118.c - hwmon driver for Texas Instruments ADS1118 16-bit 4-input ADC
+ * / temperature sensor, and Texas Instruments ADS1018, a faster, 12-bit
+ * chip  of the same family.
+ *
+ * Author: Joshua Clayton
+ *
+ * Loosely based on ads1015.c by Dirk Eibach and others
+ *
+ * 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.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+struct ads_table {
+	unsigned int rates[8];
+	unsigned int divisor;
+};
+
+struct ads_channel {
+	unsigned int delay_ms;
+	int pga;
+	u16 cfg;
+	bool enabled;
+};
+
+/* PGA fullscale voltages in microvolts */
+static const unsigned int fullscale_table[8] = {
+	6144000, 4096000, 2048000, 1024000, 512000, 256000, 256000, 256000 };
+
+static const struct ads_table ads1018_table = {
+	.rates = {128, 250, 490, 920, 1600, 2400, 3300, 3300},
+	.divisor = 0x7ff0,
+};
+
+static const struct ads_table ads1118_table = {
+	.rates = {8, 16, 32, 64, 128, 250, 475, 860},
+	.divisor = 0x7fff,
+};
+
+#define ADS1118_NUM_CHANS 5
+#define ADS1118_TEMP_CHAN 4
+
+struct ads1118 {
+	struct device *hwmon_dev;
+	struct device *dev;
+	struct mutex update_lock; /* mutex protect updates */
+	struct ads_channel channel_data[ADS1118_NUM_CHANS];
+	const struct ads_table *ref;
+};
+
+/*
+ * NOTE: the bit offsets in the datasheet are 16 bit big
+ * endian. I've swapped upper and lower bytes in the defines
+ * so no twiddling is needed when sending the cfg to the device.
+ */
+#define ADS1118_MODE	0	/* single shot mode */
+#define ADS1118_PGA	1	/* programmmed gain */
+#define ADS1118_MUX	4	/* input channel */
+#define ADS1118_SS	7	/* start a conversion */
+#define ADS1118_NOP	8	/* validation pattern */
+#define ADS1118_PULL_UP	11	/* pullup resistor on MISO */
+#define ADS1118_TS_MODE	12	/* temperature sensor mode */
+#define ADS1118_DR	13	/* data rate table index */
+
+#define ADS1118_ADC_CFG (BIT(ADS1118_MODE) | BIT(ADS1118_SS) | \
+		(0x3 << ADS1118_NOP) | BIT(ADS1118_PULL_UP))
+#define ADS1118_TEMP_CFG (ADS1118_ADC_CFG | BIT(ADS1118_TS_MODE))
+
+/* MUX values for AINN (second input or ground) */
+#define ADS1118_MUX_AINN1 0
+#define ADS1118_MUX_AINN3 1
+#define ADS1118_MUX_AINN_GND 4
+
+#define ADS1118_DEFAULT_PGA 0
+#define ADS1118_DEFAULT_DR 7
+
+static inline void ads1118_set_cfg(u16 *cfg, u16 value, int offset)
+{
+	*cfg &= ~(0x07 << offset);
+	*cfg |= ((value & 0x07) << offset);
+}
+
+static int ads1118_channel_set_pga(struct ads_channel *chan, u32 fullscale)
+{
+	int i;
+
+	for (i = 7; i >= 0; --i)
+		if (fullscale_table[i] == fullscale)
+			break;
+
+	if (i < 0)
+		return -EINVAL;
+
+	chan->pga = fullscale / 1000;
+	ads1118_set_cfg(&chan->cfg, i, ADS1118_PGA);
+
+	return 0;
+}
+
+static int ads1118_chan_set_mux(struct ads_channel *chan, u16 in1, u16 in2)
+{
+	switch (in1) {
+	case 0:
+		if (in2 == ADS1118_MUX_AINN1)
+			break;
+	case 1:
+	case 2:
+		if (in2 == ADS1118_MUX_AINN3)
+			break;
+	case 3:
+		if (in2 == ADS1118_MUX_AINN_GND)
+			break;
+	default:
+		return -EINVAL;
+	}
+
+	ads1118_set_cfg(&chan->cfg, in1 + in2, ADS1118_MUX);
+
+	return 0;
+}
+
+static int ads1118_chan_set_rate(struct ads1118 *ads,
+				 struct ads_channel *chan, u32 rate)
+{
+	int i;
+
+	for (i = 7; i >= 0; --i)
+		if (ads->ref->rates[i] == rate)
+			break;
+
+	if (i < 0)
+		return -EINVAL;
+
+	chan->delay_ms = DIV_ROUND_UP(1000, rate);
+	ads1118_set_cfg(&chan->cfg, i, ADS1118_DR);
+
+	return 0;
+}
+
+static int ads1118_read_adc(struct ads1118 *ads, struct ads_channel *chan,
+			    s16 *value)
+{
+	int ret;
+	u16 buf;
+	struct spi_device *spi = to_spi_device(ads->dev);
+
+	mutex_lock(&ads->update_lock);
+
+	ret = spi_write(spi, &chan->cfg, sizeof(chan->cfg));
+	if (ret < 0)
+		goto err_unlock;
+
+	/* wait until conversion finished */
+	msleep(chan->delay_ms);
+
+	ret = spi_read(spi, &buf, sizeof(buf));
+	if (ret)
+		dev_info(&spi->dev, "error reading: %d\n", ret);
+
+	*value = (s16)be16_to_cpu(buf);
+
+err_unlock:
+	mutex_unlock(&ads->update_lock);
+	return ret;
+}
+
+static ssize_t show_in(struct device *dev, struct device_attribute *da,
+	char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ads1118 *ads = dev_get_drvdata(dev);
+	struct ads_channel *chan = &ads->channel_data[attr->index];
+	s16 read_value;
+	int microvolts;
+	int ret;
+
+	ret = ads1118_read_adc(ads, chan, &read_value);
+	if (ret < 0)
+		return ret;
+
+	microvolts = DIV_ROUND_CLOSEST(read_value * chan->pga,
+				       ads->ref->divisor);
+
+	return sprintf(buf, "%d\n", microvolts);
+}
+
+static ssize_t show_temp(struct device *dev, struct device_attribute *da,
+			 char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ads1118 *ads = dev_get_drvdata(dev);
+	struct ads_channel *chan = &ads->channel_data[attr->index];
+	s16 read_value;
+	int ret;
+
+	ret = ads1118_read_adc(ads, chan, &read_value);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * The ads1118 datasheet indicates 32nds of degree steps, but
+	 * 14 bits left justified means a divisor of 128.
+	 */
+	return sprintf(buf, "%d\n", (((int)read_value) * 1000) >> 7);
+}
+
+static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_in, NULL, 0);
+static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_in, NULL, 1);
+static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_in, NULL, 2);
+static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_in, NULL, 3);
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL,
+		ADS1118_TEMP_CHAN);
+
+static struct attribute *ads1118_attributes[] = {
+	&sensor_dev_attr_in0_input.dev_attr.attr,
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in3_input.dev_attr.attr,
+
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL
+};
+
+static umode_t ads1118_attrs_visible(struct kobject *kobj,
+				     struct attribute *attr, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct ads1118 *ads = dev_get_drvdata(dev);
+
+	if (ads->channel_data[n].enabled)
+		return attr->mode;
+
+	return 0;
+}
+
+static const struct attribute_group ads1118_attr_group = {
+	.attrs = ads1118_attributes,
+	.is_visible = ads1118_attrs_visible,
+};
+
+static const struct attribute_group *groups[] = {
+	&ads1118_attr_group,
+	NULL
+};
+
+#ifdef CONFIG_OF
+static int ads1118_of_get_chan(struct device *dev, struct device_node *node)
+{
+	u32 chan_i;
+
+	if (!of_device_is_available(node))
+		return -EINVAL;
+
+	if (of_property_read_u32(node, "reg", &chan_i)) {
+		dev_err(dev, "reg value missing in %s\n", node->full_name);
+		return -EINVAL;
+	}
+
+	if (chan_i >= ADS1118_TEMP_CHAN) {
+		dev_err(dev, "reg value %d out of range in %s\n",
+				chan_i, node->full_name);
+		return -EINVAL;
+	}
+
+	return (int)chan_i;
+}
+
+static int ads1118_of_get_chan_pga(struct device *dev,
+				   struct device_node *node,
+				   struct ads_channel *chan)
+{
+	int ret;
+	u32 fullscale;
+
+	ret = of_property_read_u32(node, "ti,fullscale", &fullscale);
+	if (ret == -EINVAL) {
+		fullscale = fullscale_table[ADS1118_DEFAULT_PGA];
+	} else if (ret) {
+		dev_err(dev, "bad ti,fullscale on %s: should be u32\n",
+			node->full_name);
+		return ret;
+	}
+
+	ret = ads1118_channel_set_pga(chan, fullscale);
+	if (ret)
+		dev_err(dev, "bad ti,fullscale on %s: invalid value\n",
+			node->full_name);
+
+	return ret;
+}
+
+static int ads1118_of_get_chan_datarate(struct ads1118 *ads,
+					 struct device_node *node,
+					 struct ads_channel *chan)
+{
+	int ret;
+	u32 rate;
+
+	ret = of_property_read_u32(node, "ti,datarate", &rate);
+	if (ret == -EINVAL) {
+		rate = ads->ref->rates[ADS1118_DEFAULT_DR];
+	} else if (ret) {
+		dev_err(ads->dev, "bad ti,datarate on %s: should be u32\n",
+			node->full_name);
+		return ret;
+	}
+
+	ret = ads1118_chan_set_rate(ads, chan, rate);
+	if (ret)
+		dev_err(ads->dev, "bad ti,datarate on %s: invalid value\n",
+			node->full_name);
+
+	return ret;
+}
+
+static int ads1118_of_get_chan_mux(struct device *dev,
+				    struct device_node *node,
+				    struct ads_channel *chan,
+				    int chan_i)
+{
+	int ret;
+	u32 de;
+	u16 in2;
+
+	ret = of_property_read_u32(node, "ti,differential-endpoint", &de);
+	if (ret == -EINVAL) {
+		in2 = ADS1118_MUX_AINN_GND;
+		goto set_mux;
+	} else if (ret) {
+		dev_err(dev, "bad ti,differential-endpoint on %s: should be a u32\n",
+			node->full_name);
+		return ret;
+	}
+
+	switch (de) {
+	case 1:
+		in2 = ADS1118_MUX_AINN1;
+		break;
+	case 3:
+		in2 = ADS1118_MUX_AINN3;
+		break;
+	default:
+		dev_err(dev, "bad ti,differential-endpoint %d on %s\n",
+			de, node->full_name);
+		return -EINVAL;
+	}
+
+set_mux:
+	ret = ads1118_chan_set_mux(chan, (u16)chan_i, in2);
+	if (ret)
+		dev_err(dev, "bad ti,differential-endpoint pair %d, %d on %s\n",
+			chan_i, de, node->full_name);
+
+	return ret;
+}
+
+static void ads1118_of_cfg_chan(struct ads1118 *ads, struct device_node *node)
+{
+	int ret;
+	int chan_i;
+	struct ads_channel *chan;
+
+	chan_i = ads1118_of_get_chan(ads->dev, node);
+	if (chan_i < 0)
+		return;
+
+	chan = &ads->channel_data[chan_i];
+	chan->cfg = ADS1118_ADC_CFG;
+	ret = ads1118_of_get_chan_pga(ads->dev, node, chan);
+	if (ret)
+		return;
+
+	ret = ads1118_of_get_chan_datarate(ads, node, chan);
+	if (ret)
+		return;
+
+	ret = ads1118_of_get_chan_mux(ads->dev, node, chan, chan_i);
+	if (ret)
+		return;
+
+	chan->enabled = true;
+}
+
+static void ads1118_of_get_pullup(struct ads1118 *ads)
+{
+	int i;
+
+	if (of_find_property(ads->dev->of_node, "ti,pullup-disable", NULL))
+		for (i = 0; i < ADS1118_NUM_CHANS; ++i)
+			ads->channel_data[i].cfg &= ~(BIT(ADS1118_PULL_UP));
+}
+#endif
+
+static void ads1118_temp_chan_enable(struct ads1118 *ads)
+{
+	struct ads_channel *chan = &ads->channel_data[ADS1118_TEMP_CHAN];
+	unsigned int rate = ads->ref->rates[ADS1118_DEFAULT_DR];
+
+	chan->cfg = ADS1118_TEMP_CFG;
+	ads1118_chan_set_rate(ads, chan, rate);
+	chan->enabled = true;
+}
+
+static int ads1118_get_cfg(struct ads1118 *ads)
+{
+	struct device_node *node;
+
+#ifndef CONFIG_OF
+	return -EINVAL;
+#else
+	if (!ads->dev->of_node
+	    || !of_get_next_child(ads->dev->of_node, NULL))
+		return -EINVAL;
+
+	if (of_find_property(ads->dev->of_node, "ti,tempsensor", NULL))
+		ads1118_temp_chan_enable(ads);
+
+	ads1118_of_get_pullup(ads);
+
+	for_each_child_of_node(ads->dev->of_node, node) {
+		ads1118_of_cfg_chan(ads, node);
+	}
+
+	return 0;
+#endif
+}
+
+static void ads1118_enable_all(struct ads1118 *ads)
+{
+	unsigned int i;
+	unsigned int fullscale = fullscale_table[ADS1118_DEFAULT_PGA];
+	unsigned int rate = ads->ref->rates[ADS1118_DEFAULT_DR];
+
+	ads1118_temp_chan_enable(ads);
+
+	for (i = 0; i < ADS1118_TEMP_CHAN; ++i) {
+		struct ads_channel *chan = &ads->channel_data[i];
+
+		chan->cfg = ADS1118_ADC_CFG;
+		ads1118_channel_set_pga(chan, fullscale);
+		ads1118_chan_set_rate(ads, chan, rate);
+		ads1118_chan_set_mux(chan, (u16)i, ADS1118_MUX_AINN_GND);
+		chan->enabled = true;
+	}
+}
+
+static const struct of_device_id ads_1x18_ids[] = {
+	{ .compatible = "ti,ads1018", .data = &ads1018_table, },
+	{ .compatible = "ti,ads1118", .data = &ads1118_table, },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, ads_1x18_ids);
+
+static int ads1118_probe(struct spi_device *spi)
+{
+	const struct of_device_id *of_id;
+	struct ads1118 *ads;
+	int err;
+
+	ads = devm_kzalloc(&spi->dev, sizeof(struct ads1118),
+			    GFP_KERNEL);
+	if (!ads)
+		return -ENOMEM;
+
+	of_id = of_match_device(ads_1x18_ids, &spi->dev);
+	if (!of_id)
+		return -EINVAL;
+
+	ads->ref = of_id->data;
+	ads->dev = &spi->dev;
+	mutex_init(&ads->update_lock);
+	err = ads1118_get_cfg(ads);
+	if (err)
+		ads1118_enable_all(ads);
+
+	ads->hwmon_dev =
+		devm_hwmon_device_register_with_groups(ads->dev, "ads11118",
+						       ads, groups);
+	if (IS_ERR(ads->hwmon_dev)) {
+		err = PTR_ERR(ads->hwmon_dev);
+		dev_err(ads->dev, "error initializing hwmon: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static struct spi_driver ads1118_driver = {
+	.driver = {
+		.name = "ads1118",
+		.of_match_table = ads_1x18_ids,
+	},
+	.probe = ads1118_probe,
+};
+
+module_spi_driver(ads1118_driver);
+
+MODULE_AUTHOR("Joshua Clayton <[email protected]>");
+MODULE_DESCRIPTION("ADS1118 driver");
+MODULE_LICENSE("GPL");

Quoted 4 lines · Joshua Clayton

Add new driver for Texas Instruments ADS1118 and and ADS1018. This driver works with ADS1018, because of code borrowed from asd1015, which is similar, but I can only test ADS1118

Browsing through the datasheet, I think this should probably be implemented as iio driver (and iio already has a driver for ads1015).

Jonathan, what do you think ?

Thanks,
Guenter

Greetings Guenter,

Thank you for reviewing my submission.

Quoted 9 lines · Guenter Roeck

Quoted 4 lines · Joshua Clayton

Add new driver for Texas Instruments ADS1118 and and ADS1018. This driver works with ADS1018, because of code borrowed from asd1015, which is similar, but I can only test ADS1118

Browsing through the datasheet, I think this should probably be implemented as iio driver (and iio already has a driver for ads1015).

Quoted 5 lines

Jonathan, what do you think ?

Thanks,
Guenter

No response from Jonathan as yet, but I am willing to rework the driver when I have some time. It might be weeks before I can start, though.

Quoted 16 lines · Joshua Clayton

Greetings Guenter,

Thank you for reviewing my submission.

Quoted 11 lines · Guenter Roeck

Quoted 4 lines · Joshua Clayton

Add new driver for Texas Instruments ADS1118 and and ADS1018. This driver works with ADS1018, because of code borrowed from asd1015, which is similar, but I can only test ADS1118

Browsing through the datasheet, I think this should probably be implemented as iio driver (and iio already has a driver for ads1015).

Jonathan, what do you think ?

Quoted 6 lines

Quoted 3 lines

Thanks,
Guenter

No response from Jonathan as yet, but I am willing to rework the driver when I have some time. It might be weeks before I can start, though.

Changing the subject - maybe it helps to get Jonathan's attention.

Guenter

Signature · 3 lines

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Greetings Guenter,

Thank you for reviewing my submission.

Quoted 9 lines · Guenter Roeck

Quoted 4 lines · Joshua Clayton

Add new driver for Texas Instruments ADS1118 and and ADS1018. This driver works with ADS1018, because of code borrowed from asd1015, which is similar, but I can only test ADS1118

Browsing through the datasheet, I think this should probably be implemented as iio driver (and iio already has a driver for ads1015).

Quoted 5 lines

Jonathan, what do you think ?

Thanks,
Guenter

No response from Jonathan as yet, but I am willing to rework the driver when I have some time. It might be weeks before I can start, though.

I am not very familiar with the iio subsystem, (actually had never heard of it before receiving your response). Learning it might be beneficial, as it looks like a good fit for an in house driver, which I'd like to eventually upstream.

If an hwmon driver is adequate, I have new patches that address kbuild and endianness issues in the first version.

~Joshua Clayton
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ads1118 is a 4 input 16 bit adc with a buit-in temperature gauge

Signed-off-by Joshua Clayton <[email protected]>

---
 .../devicetree/bindings/hwmon/ads1118.txt          | 81 ++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/ads1118.txt

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +14 -0

new file mode 100644
index 0000000..41c66dc
@@ -0,0 +1,81 @@
+ADS1118 (SPI)
+
+The ADS1118 is 16-bit analog to digital converter with 4 inputs and a
+temperature sensor.
+The ADS1018 is a 12-bit version of the chip.
+
+The inputs can be single ended or differential pair combinations.
+
+Each channel, 0 - 4 may be configured as a single ended adc input.
+Channel 0 may be configured differentially with channel 1.
+Channels 0, 1, or 2 may be configured differentially with channel 3.
+
+To set up a differential pair, the lower channel should be have
+the ti,differential-endpoint property set to the higher channel in the pair.

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +8 -0

+
+The sensor contains an internal pullup register to keep the data output
+high when not in use. This may be disabled, but is enabled by default.
+
+1) The /ads1118 node
+
+  Required properties:
+

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +14 -0

+			reg = <0>;
+			ti,fullscale = <6144000>;
+			ti,datarate = <860>;
+			ti,differential-endpoint = <1>;
+		};
+		voltage1 at 3 {
+			reg = <3>;
+			ti,fullscale = <6144000>;
+			ti,datarate = <475>;
+		};
+	};
+
+For the above example, The temperature sensor is enabled as well as
+channels 0 and 1 in differential mode, and channel 3 single ended.

Signature · 1 line

2.7.4

Quoted 28 lines · Joshua Clayton

ads1118 is a 4 input 16 bit adc with a buit-in temperature gauge

Signed-off-by Joshua Clayton <[email protected]>

---
 .../devicetree/bindings/hwmon/ads1118.txt          | 81 ++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/ads1118.txt

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +14 -0

new file mode 100644
index 0000000..41c66dc
@@ -0,0 +1,81 @@
+ADS1118 (SPI)
+
+The ADS1118 is 16-bit analog to digital converter with 4 inputs and a
+temperature sensor.
+The ADS1018 is a 12-bit version of the chip.
+
+The inputs can be single ended or differential pair combinations.
+
+Each channel, 0 - 4 may be configured as a single ended adc input.
+Channel 0 may be configured differentially with channel 1.
+Channels 0, 1, or 2 may be configured differentially with channel 3.
+
+To set up a differential pair, the lower channel should be have
+the ti,differential-endpoint property set to the higher channel in the pair.

Documentation/devicetree/bindings/hwmon/ads1118.txt line 24

Quoted 10 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +10 -0

+
+Each channel can be configured individually:
+ - fullscale voltage range values are +/- microvolts
+    6144000, 4096000, 2048000, 1024000, 512000, or 256000
+
+ - data_rate in samples per second
+    - for the ads1018:
+      128, 250, 490, 920, 1600, 2400, or 3300
+    - for the ads1118:
+      8, 16, 32, 64, 128, 250, or 860

Would be better if these are documented with the property itself.

Quoted 8 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +8 -0

+
+The sensor contains an internal pullup register to keep the data output
+high when not in use. This may be disabled, but is enabled by default.
+
+1) The /ads1118 node
+
+  Required properties:
+

Documentation/devicetree/bindings/hwmon/ads1118.txt line 42

Quoted 10 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +10 -0

+   - compatible : must be "ti,ads1018" or "ti,ads1118"
+   - spi-cpha : spi phase set to 1 (spi polarity is 0)
+   - reg : the spi chipselect address
+   - #address-cells : must be <1>
+   - #size-cells : must be <0>
+
+  Optional properties:
+
+   - ti,tempsensor: enable the temperature sensor
+   - ti,pullup-disable: disable the internal pullup resistor

Explicitly state these are boolean.

Documentation/devicetree/bindings/hwmon/ads1118.txt line 54

Quoted 12 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +12 -0

+
+  The node contains child nodes for each channel that the platform uses.
+
+2) channel nodes
+
+  Required properties:
+
+   - reg : the channel number (0, 1, 2, or 3)
+
+  Optional properties:
+
+   - ti,differential-endpoint: differential second endpoint.

Type?

Documentation/devicetree/bindings/hwmon/ads1118.txt line 55

Quoted 2 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +1 -0

+   - ti,fullscale: fullscale range in +/- microvolts

Add standard unit suffix.

Documentation/devicetree/bindings/hwmon/ads1118.txt line 56

Quoted 2 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +1 -0

+   - ti,datarate : the converter data rate in samples / second

Perhaps "-hz" here?

Documentation/devicetree/bindings/hwmon/ads1118.txt line 67

Quoted 12 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +11 -0

+
+  Example ADS1118 node:
+
+	ads1118 at 0 {
+		compatible = "ti,ads1118";
+		spi-max-frequency = <2450000>;
+		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		ti,tempsensor;
+		voltage0 at 0 {

Perhaps channel at 0. Either way, drop the first 0.

Quoted 15 lines

Documentation/devicetree/bindings/hwmon/ads1118.txt new file +14 -0

+			reg = <0>;
+			ti,fullscale = <6144000>;
+			ti,datarate = <860>;
+			ti,differential-endpoint = <1>;
+		};
+		voltage1 at 3 {
+			reg = <3>;
+			ti,fullscale = <6144000>;
+			ti,datarate = <475>;
+		};
+	};
+
+For the above example, The temperature sensor is enabled as well as
+channels 0 and 1 in differential mode, and channel 3 single ended.