max11100.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * iio/adc/max11100.c
  4 * Maxim max11100 ADC Driver with IIO interface
  5 *
  6 * Copyright (C) 2016-17 Renesas Electronics Corporation
  7 * Copyright (C) 2016-17 Jacopo Mondi
  8 */
  9#include <linux/delay.h>
 10#include <linux/kernel.h>
 11#include <linux/mod_devicetable.h>
 12#include <linux/module.h>
 13#include <linux/regulator/consumer.h>
 14#include <linux/spi/spi.h>
 15#include <linux/unaligned.h>
 16
 17#include <linux/iio/iio.h>
 18#include <linux/iio/driver.h>
 19
 20/*
 21 * LSB is the ADC single digital step
 22 * 1 LSB = (vref_mv / 2 ^ 16)
 23 *
 24 * LSB is used to calculate analog voltage value
 25 * from the number of ADC steps count
 26 *
 27 * Ain = (count * LSB)
 28 */
 29#define MAX11100_LSB_DIV		(1 << 16)
 30
 31struct max11100_state {
 32	struct regulator *vref_reg;
 33	struct spi_device *spi;
 34
 35	/*
 36	 * DMA (thus cache coherency maintenance) may require the
 37	 * transfer buffers to live in their own cache lines.
 38	 */
 39	u8 buffer[3] __aligned(IIO_DMA_MINALIGN);
 40};
 41
 42static const struct iio_chan_spec max11100_channels[] = {
 43	{ /* [0] */
 44		.type = IIO_VOLTAGE,
 45		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 46				      BIT(IIO_CHAN_INFO_SCALE),
 47	},
 48};
 49
 50static int max11100_read_single(struct iio_dev *indio_dev, int *val)
 51{
 52	int ret;
 53	struct max11100_state *state = iio_priv(indio_dev);
 54
 55	ret = spi_read(state->spi, state->buffer, sizeof(state->buffer));
 56	if (ret) {
 57		dev_err(&indio_dev->dev, "SPI transfer failed\n");
 58		return ret;
 59	}
 60
 61	/* the first 8 bits sent out from ADC must be 0s */
 62	if (state->buffer[0]) {
 63		dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
 64		return -EINVAL;
 65	}
 66
 67	*val = get_unaligned_be16(&state->buffer[1]);
 68
 69	return 0;
 70}
 71
 72static int max11100_read_raw(struct iio_dev *indio_dev,
 73			     struct iio_chan_spec const *chan,
 74			     int *val, int *val2, long info)
 75{
 76	int ret, vref_uv;
 77	struct max11100_state *state = iio_priv(indio_dev);
 78
 79	switch (info) {
 80	case IIO_CHAN_INFO_RAW:
 81		ret = max11100_read_single(indio_dev, val);
 82		if (ret)
 83			return ret;
 84
 85		return IIO_VAL_INT;
 86
 87	case IIO_CHAN_INFO_SCALE:
 88		vref_uv = regulator_get_voltage(state->vref_reg);
 89		if (vref_uv < 0)
 90			/* dummy regulator "get_voltage" returns -EINVAL */
 91			return -EINVAL;
 92
 93		*val =  vref_uv / 1000;
 94		*val2 = MAX11100_LSB_DIV;
 95		return IIO_VAL_FRACTIONAL;
 96	}
 97
 98	return -EINVAL;
 99}
100
101static const struct iio_info max11100_info = {
102	.read_raw = max11100_read_raw,
103};
104
105static void max11100_regulator_disable(void *reg)
106{
107	regulator_disable(reg);
108}
109
110static int max11100_probe(struct spi_device *spi)
111{
112	int ret;
113	struct iio_dev *indio_dev;
114	struct max11100_state *state;
115
116	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
117	if (!indio_dev)
118		return -ENOMEM;
119
120	state = iio_priv(indio_dev);
121	state->spi = spi;
122
123	indio_dev->name = "max11100";
124	indio_dev->info = &max11100_info;
125	indio_dev->modes = INDIO_DIRECT_MODE;
126	indio_dev->channels = max11100_channels;
127	indio_dev->num_channels = ARRAY_SIZE(max11100_channels);
128
129	state->vref_reg = devm_regulator_get(&spi->dev, "vref");
130	if (IS_ERR(state->vref_reg))
131		return PTR_ERR(state->vref_reg);
132
133	ret = regulator_enable(state->vref_reg);
134	if (ret)
135		return ret;
136
137	ret = devm_add_action_or_reset(&spi->dev, max11100_regulator_disable,
138				       state->vref_reg);
139	if (ret)
140		return ret;
141
142	return devm_iio_device_register(&spi->dev, indio_dev);
143}
144
145static const struct of_device_id max11100_ids[] = {
146	{ .compatible = "maxim,max11100" },
147	{ }
148};
149MODULE_DEVICE_TABLE(of, max11100_ids);
150
151static struct spi_driver max11100_driver = {
152	.driver = {
153		.name	= "max11100",
154		.of_match_table = max11100_ids,
155	},
156	.probe		= max11100_probe,
157};
158
159module_spi_driver(max11100_driver);
160
161MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
162MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
163MODULE_LICENSE("GPL v2");