--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ADS8344 16-bit 8-Channel ADC driver
+ *
+ * Author: Gregory CLEMENT <gregory.clement@bootlin.com>
+ *
+ * Datasheet: http://www.ti.com/lit/ds/symlink/ads8344.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define ADS8344_START BIT(7)
+#define ADS8344_SINGLE_END BIT(2)
+#define ADS8344_CHANNEL(channel) ((channel) << 4)
+#define ADS8344_CLOCK_INTERNAL 0x2 /* PD1 = 1 and PD0 = 0 */
+
+struct ads8344 {
+ struct spi_device *spi;
+ struct regulator *reg;
+ /*
+ * Lock protecting access to adc->tx_buff and rx_buff,
+ * especially from concurrent read on sysfs file.
+ */
+ struct mutex lock;
+
+ u8 tx_buf ____cacheline_aligned;
+ u16 rx_buf;
+};
+
+#define ADS8344_VOLTAGE_CHANNEL(chan, si) \
+ { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = chan, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ }
+
+#define ADS8344_VOLTAGE_CHANNEL_DIFF(chan1, chan2, si) \
+ { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = (chan1), \
+ .channel2 = (chan2), \
+ .differential = 1, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ }
+
+static const struct iio_chan_spec ads8344_channels[] = {
+ ADS8344_VOLTAGE_CHANNEL(0, 0),
+ ADS8344_VOLTAGE_CHANNEL(1, 4),
+ ADS8344_VOLTAGE_CHANNEL(2, 1),
+ ADS8344_VOLTAGE_CHANNEL(3, 5),
+ ADS8344_VOLTAGE_CHANNEL(4, 2),
+ ADS8344_VOLTAGE_CHANNEL(5, 6),
+ ADS8344_VOLTAGE_CHANNEL(6, 3),
+ ADS8344_VOLTAGE_CHANNEL(7, 7),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(0, 1, 8),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(2, 3, 9),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(4, 5, 10),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(6, 7, 11),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(1, 0, 12),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(3, 2, 13),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(5, 4, 14),
+ ADS8344_VOLTAGE_CHANNEL_DIFF(7, 6, 15),
+};
+
+static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
+ bool differential)
+{
+ struct spi_device *spi = adc->spi;
+ int ret;
+
+ adc->tx_buf = ADS8344_START;
+ if (!differential)
+ adc->tx_buf |= ADS8344_SINGLE_END;
+ adc->tx_buf |= ADS8344_CHANNEL(channel);
+ adc->tx_buf |= ADS8344_CLOCK_INTERNAL;
+
+ ret = spi_write(spi, &adc->tx_buf, 1);
+ if (ret)
+ return ret;
+
+ udelay(9);
+
+ ret = spi_read(spi, &adc->rx_buf, 2);
+ if (ret)
+ return ret;
+
+ return adc->rx_buf;
+}
+
+static int ads8344_read_raw(struct iio_dev *iio,
+ struct iio_chan_spec const *channel, int *value,
+ int *shift, long mask)
+{
+ struct ads8344 *adc = iio_priv(iio);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&adc->lock);
+ *value = ads8344_adc_conversion(adc, channel->scan_index,
+ channel->differential);
+ mutex_unlock(&adc->lock);
+ if (*value < 0)
+ return *value;
+
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *value = regulator_get_voltage(adc->reg);
+ if (*value < 0)
+ return *value;
+
+ /* convert regulator output voltage to mV */
+ *value /= 1000;
+ *shift = 16;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ads8344_info = {
+ .read_raw = ads8344_read_raw,
+};
+
+static int ads8344_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct ads8344 *adc;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ adc = iio_priv(indio_dev);
+ adc->spi = spi;
+ mutex_init(&adc->lock);
+
+ indio_dev->name = dev_name(&spi->dev);
+ indio_dev->dev.parent = &spi->dev;
+ indio_dev->dev.of_node = spi->dev.of_node;
+ indio_dev->info = &ads8344_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = ads8344_channels;
+ indio_dev->num_channels = ARRAY_SIZE(ads8344_channels);
+
+ adc->reg = devm_regulator_get(&spi->dev, "vref");
+ if (IS_ERR(adc->reg))
+ return PTR_ERR(adc->reg);
+
+ ret = regulator_enable(adc->reg);
+ if (ret)
+ return ret;
+
+ spi_set_drvdata(spi, indio_dev);
+
+ ret = iio_device_register(indio_dev);
+ if (ret) {
+ regulator_disable(adc->reg);
+ return ret;
+ }
+
+ return 0;
+}
+
+static int ads8344_remove(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev = spi_get_drvdata(spi);
+ struct ads8344 *adc = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+ regulator_disable(adc->reg);
+
+ return 0;
+}
+
+static const struct of_device_id ads8344_of_match[] = {
+ { .compatible = "ti,ads8344", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, ads8344_of_match);
+
+static struct spi_driver ads8344_driver = {
+ .driver = {
+ .name = "ads8344",
+ .of_match_table = ads8344_of_match,
+ },
+ .probe = ads8344_probe,
+ .remove = ads8344_remove,
+};
+module_spi_driver(ads8344_driver);
+
+MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@bootlin.com>");
+MODULE_DESCRIPTION("ADS8344 driver");
+MODULE_LICENSE("GPL");
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