iio: adc: Add TI ADS8688

This patch adds support for the Texas Intruments ADS8688 ADC.

Signed-off-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
Reviewed-by: Martin Hundebøll <martin.hundeboll@prevas.dk>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -341,6 +341,16 @@ config TI_ADC128S052
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-adc128s052.
 
+config TI_ADS8688
+	tristate "Texas Instruments ADS8688"
+	depends on SPI && OF
+	help
+	  If you say yes here you get support for Texas Instruments ADS8684 and
+	  and ADS8688 ADC chips
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ti-ads8688.
+
 config TI_AM335X_ADC
 	tristate "TI's AM335X ADC driver"
 	depends on MFD_TI_AM335X_TSCADC

drivers/iio/adc/Makefile

@@ -33,6 +33,7 @@ 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
+obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
 obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
 obj-$(CONFIG_TWL6030_GPADC) += twl6030-gpadc.o

drivers/iio/adc/ti-ads8688.c

@@ -0,0 +1,486 @@
+/*
+ * Copyright (C) 2015 Prevas A/S
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/spi/spi.h>
+#include <linux/regulator/consumer.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define ADS8688_CMD_REG(x)		(x << 8)
+#define ADS8688_CMD_REG_NOOP		0x00
+#define ADS8688_CMD_REG_RST		0x85
+#define ADS8688_CMD_REG_MAN_CH(chan)	(0xC0 | (4 * chan))
+#define ADS8688_CMD_DONT_CARE_BITS	16
+
+#define ADS8688_PROG_REG(x)		(x << 9)
+#define ADS8688_PROG_REG_RANGE_CH(chan)	(0x05 + chan)
+#define ADS8688_PROG_WR_BIT		BIT(8)
+#define ADS8688_PROG_DONT_CARE_BITS	8
+
+#define ADS8688_REG_PLUSMINUS25VREF	0
+#define ADS8688_REG_PLUSMINUS125VREF	1
+#define ADS8688_REG_PLUSMINUS0625VREF	2
+#define ADS8688_REG_PLUS25VREF		5
+#define ADS8688_REG_PLUS125VREF		6
+
+#define ADS8688_VREF_MV			4096
+#define ADS8688_REALBITS		16
+
+/*
+ * enum ads8688_range - ADS8688 reference voltage range
+ * @ADS8688_PLUSMINUS25VREF: Device is configured for input range ±2.5 * VREF
+ * @ADS8688_PLUSMINUS125VREF: Device is configured for input range ±1.25 * VREF
+ * @ADS8688_PLUSMINUS0625VREF: Device is configured for input range ±0.625 * VREF
+ * @ADS8688_PLUS25VREF: Device is configured for input range 0 - 2.5 * VREF
+ * @ADS8688_PLUS125VREF: Device is configured for input range 0 - 1.25 * VREF
+ */
+enum ads8688_range {
+	ADS8688_PLUSMINUS25VREF,
+	ADS8688_PLUSMINUS125VREF,
+	ADS8688_PLUSMINUS0625VREF,
+	ADS8688_PLUS25VREF,
+	ADS8688_PLUS125VREF,
+};
+
+struct ads8688_chip_info {
+	const struct iio_chan_spec *channels;
+	unsigned int num_channels;
+};
+
+struct ads8688_state {
+	struct mutex			lock;
+	const struct ads8688_chip_info	*chip_info;
+	struct spi_device		*spi;
+	struct regulator		*reg;
+	unsigned int			vref_mv;
+	enum ads8688_range		range[8];
+	union {
+		__be32 d32;
+		u8 d8[4];
+	} data[2] ____cacheline_aligned;
+};
+
+enum ads8688_id {
+	ID_ADS8684,
+	ID_ADS8688,
+};
+
+struct ads8688_ranges {
+	enum ads8688_range range;
+	unsigned int scale;
+	int offset;
+	u8 reg;
+};
+
+static const struct ads8688_ranges ads8688_range_def[5] = {
+	{
+		.range = ADS8688_PLUSMINUS25VREF,
+		.scale = 76295,
+		.offset = -(1 << (ADS8688_REALBITS - 1)),
+		.reg = ADS8688_REG_PLUSMINUS25VREF,
+	}, {
+		.range = ADS8688_PLUSMINUS125VREF,
+		.scale = 38148,
+		.offset = -(1 << (ADS8688_REALBITS - 1)),
+		.reg = ADS8688_REG_PLUSMINUS125VREF,
+	}, {
+		.range = ADS8688_PLUSMINUS0625VREF,
+		.scale = 19074,
+		.offset = -(1 << (ADS8688_REALBITS - 1)),
+		.reg = ADS8688_REG_PLUSMINUS0625VREF,
+	}, {
+		.range = ADS8688_PLUS25VREF,
+		.scale = 38148,
+		.offset = 0,
+		.reg = ADS8688_REG_PLUS25VREF,
+	}, {
+		.range = ADS8688_PLUS125VREF,
+		.scale = 19074,
+		.offset = 0,
+		.reg = ADS8688_REG_PLUS125VREF,
+	}
+};
+
+static ssize_t ads8688_show_scales(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct ads8688_state *st = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "0.%09u 0.%09u 0.%09u\n",
+		       ads8688_range_def[0].scale * st->vref_mv,
+		       ads8688_range_def[1].scale * st->vref_mv,
+		       ads8688_range_def[2].scale * st->vref_mv);
+}
+
+static ssize_t ads8688_show_offsets(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d %d\n", ads8688_range_def[0].offset,
+		       ads8688_range_def[3].offset);
+}
+
+static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO,
+		       ads8688_show_scales, NULL, 0);
+static IIO_DEVICE_ATTR(in_voltage_offset_available, S_IRUGO,
+		       ads8688_show_offsets, NULL, 0);
+
+static struct attribute *ads8688_attributes[] = {
+	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage_offset_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ads8688_attribute_group = {
+	.attrs = ads8688_attributes,
+};
+
+#define ADS8688_CHAN(index)					\
+{								\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.channel = index,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)		\
+			      | BIT(IIO_CHAN_INFO_SCALE)	\
+			      | BIT(IIO_CHAN_INFO_OFFSET),	\
+}
+
+static const struct iio_chan_spec ads8684_channels[] = {
+	ADS8688_CHAN(0),
+	ADS8688_CHAN(1),
+	ADS8688_CHAN(2),
+	ADS8688_CHAN(3),
+};
+
+static const struct iio_chan_spec ads8688_channels[] = {
+	ADS8688_CHAN(0),
+	ADS8688_CHAN(1),
+	ADS8688_CHAN(2),
+	ADS8688_CHAN(3),
+	ADS8688_CHAN(4),
+	ADS8688_CHAN(5),
+	ADS8688_CHAN(6),
+	ADS8688_CHAN(7),
+};
+
+static int ads8688_prog_write(struct iio_dev *indio_dev, unsigned int addr,
+			      unsigned int val)
+{
+	struct ads8688_state *st = iio_priv(indio_dev);
+	u32 tmp;
+
+	tmp = ADS8688_PROG_REG(addr) | ADS8688_PROG_WR_BIT | val;
+	tmp <<= ADS8688_PROG_DONT_CARE_BITS;
+	st->data[0].d32 = cpu_to_be32(tmp);
+
+	return spi_write(st->spi, &st->data[0].d8[1], 3);
+}
+
+static int ads8688_reset(struct iio_dev *indio_dev)
+{
+	struct ads8688_state *st = iio_priv(indio_dev);
+	u32 tmp;
+
+	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_RST);
+	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
+	st->data[0].d32 = cpu_to_be32(tmp);
+
+	return spi_write(st->spi, &st->data[0].d8[0], 4);
+}
+
+static int ads8688_read(struct iio_dev *indio_dev, unsigned int chan)
+{
+	struct ads8688_state *st = iio_priv(indio_dev);
+	int ret;
+	u32 tmp;
+	struct spi_transfer t[] = {
+		{
+			.tx_buf = &st->data[0].d8[0],
+			.len = 4,
+			.cs_change = 1,
+		}, {
+			.tx_buf = &st->data[1].d8[0],
+			.rx_buf = &st->data[1].d8[0],
+			.len = 4,
+		},
+	};
+
+	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_MAN_CH(chan));
+	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
+	st->data[0].d32 = cpu_to_be32(tmp);
+
+	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_NOOP);
+	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
+	st->data[1].d32 = cpu_to_be32(tmp);
+
+	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
+	if (ret < 0)
+		return ret;
+
+	return be32_to_cpu(st->data[1].d32) & 0xffff;
+}
+
+static int ads8688_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long m)
+{
+	int ret, offset;
+	unsigned long scale_mv;
+
+	struct ads8688_state *st = iio_priv(indio_dev);
+
+	mutex_lock(&st->lock);
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		ret = ads8688_read(indio_dev, chan->channel);
+		mutex_unlock(&st->lock);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		scale_mv = st->vref_mv;
+		scale_mv *= ads8688_range_def[st->range[chan->channel]].scale;
+		*val = 0;
+		*val2 = scale_mv;
+		mutex_unlock(&st->lock);
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_OFFSET:
+		offset = ads8688_range_def[st->range[chan->channel]].offset;
+		*val = offset;
+		mutex_unlock(&st->lock);
+		return IIO_VAL_INT;
+	}
+	mutex_unlock(&st->lock);
+
+	return -EINVAL;
+}
+
+static int ads8688_write_reg_range(struct iio_dev *indio_dev,
+				   struct iio_chan_spec const *chan,
+				   enum ads8688_range range)
+{
+	unsigned int tmp;
+	int ret;
+
+	tmp = ADS8688_PROG_REG_RANGE_CH(chan->channel);
+	ret = ads8688_prog_write(indio_dev, tmp, range);
+
+	return ret;
+}
+
+static int ads8688_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct ads8688_state *st = iio_priv(indio_dev);
+	unsigned int scale = 0;
+	int ret = -EINVAL, i, offset = 0;
+
+	mutex_lock(&st->lock);
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		/* If the offset is 0 the ±2.5 * VREF mode is not available */
+		offset = ads8688_range_def[st->range[chan->channel]].offset;
+		if (offset == 0 && val2 == ads8688_range_def[0].scale * st->vref_mv) {
+			mutex_unlock(&st->lock);
+			return -EINVAL;
+		}
+
+		/* Lookup new mode */
+		for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
+			if (val2 == ads8688_range_def[i].scale * st->vref_mv &&
+			    offset == ads8688_range_def[i].offset) {
+				ret = ads8688_write_reg_range(indio_dev, chan,
+					ads8688_range_def[i].reg);
+				break;
+			}
+		break;
+	case IIO_CHAN_INFO_OFFSET:
+		/*
+		 * There are only two available offsets:
+		 * 0 and -(1 << (ADS8688_REALBITS - 1))
+		 */
+		if (!(ads8688_range_def[0].offset == val ||
+		    ads8688_range_def[3].offset == val)) {
+			mutex_unlock(&st->lock);
+			return -EINVAL;
+		}
+
+		/*
+		 * If the device are in ±2.5 * VREF mode, it's not allowed to
+		 * switch to a mode where the offset is 0
+		 */
+		if (val == 0 &&
+		    st->range[chan->channel] == ADS8688_PLUSMINUS25VREF) {
+			mutex_unlock(&st->lock);
+			return -EINVAL;
+		}
+
+		scale = ads8688_range_def[st->range[chan->channel]].scale;
+
+		/* Lookup new mode */
+		for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
+			if (val == ads8688_range_def[i].offset &&
+			    scale == ads8688_range_def[i].scale) {
+				ret = ads8688_write_reg_range(indio_dev, chan,
+					ads8688_range_def[i].reg);
+				break;
+			}
+		break;
+	}
+
+	if (!ret)
+		st->range[chan->channel] = ads8688_range_def[i].range;
+
+	mutex_unlock(&st->lock);
+
+	return ret;
+}
+
+static int ads8688_write_raw_get_fmt(struct iio_dev *indio_dev,
+				     struct iio_chan_spec const *chan,
+				     long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_OFFSET:
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info ads8688_info = {
+	.read_raw = &ads8688_read_raw,
+	.write_raw = &ads8688_write_raw,
+	.write_raw_get_fmt = &ads8688_write_raw_get_fmt,
+	.attrs = &ads8688_attribute_group,
+	.driver_module = THIS_MODULE,
+};
+
+static const struct ads8688_chip_info ads8688_chip_info_tbl[] = {
+	[ID_ADS8684] = {
+		.channels = ads8684_channels,
+		.num_channels = ARRAY_SIZE(ads8684_channels),
+	},
+	[ID_ADS8688] = {
+		.channels = ads8688_channels,
+		.num_channels = ARRAY_SIZE(ads8688_channels),
+	},
+};
+
+static int ads8688_probe(struct spi_device *spi)
+{
+	struct ads8688_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (indio_dev == NULL)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
+	if (!IS_ERR(st->reg)) {
+		ret = regulator_enable(st->reg);
+		if (ret)
+			return ret;
+
+		ret = regulator_get_voltage(st->reg);
+		if (ret < 0)
+			goto error_out;
+
+		st->vref_mv = ret / 1000;
+	} else {
+		/* Use internal reference */
+		st->vref_mv = ADS8688_VREF_MV;
+	}
+
+	st->chip_info =	&ads8688_chip_info_tbl[spi_get_device_id(spi)->driver_data];
+
+	spi->mode = SPI_MODE_1;
+
+	spi_set_drvdata(spi, indio_dev);
+
+	st->spi = spi;
+
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = st->chip_info->channels;
+	indio_dev->num_channels = st->chip_info->num_channels;
+	indio_dev->info = &ads8688_info;
+
+	ads8688_reset(indio_dev);
+
+	mutex_init(&st->lock);
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto error_out;
+
+	return 0;
+
+error_out:
+	if (!IS_ERR_OR_NULL(st->reg))
+		regulator_disable(st->reg);
+
+	return ret;
+}
+
+static int ads8688_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct ads8688_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	if (!IS_ERR_OR_NULL(st->reg))
+		regulator_disable(st->reg);
+
+	return 0;
+}
+
+static const struct spi_device_id ads8688_id[] = {
+	{"ads8684", ID_ADS8684},
+	{"ads8688", ID_ADS8688},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ads8688_id);
+
+static const struct of_device_id ads8688_of_match[] = {
+	{ .compatible = "ti,ads8684" },
+	{ .compatible = "ti,ads8688" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ads8688_of_match);
+
+static struct spi_driver ads8688_driver = {
+	.driver = {
+		.name	= "ads8688",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ads8688_probe,
+	.remove		= ads8688_remove,
+	.id_table	= ads8688_id,
+};
+module_spi_driver(ads8688_driver);
+
+MODULE_AUTHOR("Sean Nyekjaer <sean.nyekjaer@prevas.dk>");
+MODULE_DESCRIPTION("Texas Instruments ADS8688 driver");
+MODULE_LICENSE("GPL v2");