--- /dev/null
+/*
+ * 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");
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