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
16#include <linux/iio/iio.h>
17#include <linux/iio/driver.h>
18
19/*
20 * LSB is the ADC single digital step
21 * 1 LSB = (vref_mv / 2 ^ 16)
22 *
23 * LSB is used to calculate analog voltage value
24 * from the number of ADC steps count
25 *
26 * Ain = (count * LSB)
27 */
28#define MAX11100_LSB_DIV		(1 << 16)
29
30struct max11100_state {
31	struct regulator *vref_reg;
32	struct spi_device *spi;
33
34	/*
35	 * DMA (thus cache coherency maintenance) requires the
36	 * transfer buffers to live in their own cache lines.
37	 */
38	u8 buffer[3] ____cacheline_aligned;
39};
40
41static const struct iio_chan_spec max11100_channels[] = {
42	{ /* [0] */
43		.type = IIO_VOLTAGE,
44		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
45				      BIT(IIO_CHAN_INFO_SCALE),
46	},
47};
48
49static int max11100_read_single(struct iio_dev *indio_dev, int *val)
50{
51	int ret;
52	struct max11100_state *state = iio_priv(indio_dev);
53
54	ret = spi_read(state->spi, state->buffer, sizeof(state->buffer));
55	if (ret) {
56		dev_err(&indio_dev->dev, "SPI transfer failed\n");
57		return ret;
58	}
59
60	/* the first 8 bits sent out from ADC must be 0s */
61	if (state->buffer[0]) {
62		dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
63		return -EINVAL;
64	}
65
66	*val = (state->buffer[1] << 8) | state->buffer[2];
67
68	return 0;
69}
70
71static int max11100_read_raw(struct iio_dev *indio_dev,
72			     struct iio_chan_spec const *chan,
73			     int *val, int *val2, long info)
74{
75	int ret, vref_uv;
76	struct max11100_state *state = iio_priv(indio_dev);
77
78	switch (info) {
79	case IIO_CHAN_INFO_RAW:
80		ret = max11100_read_single(indio_dev, val);
81		if (ret)
82			return ret;
83
84		return IIO_VAL_INT;
85
86	case IIO_CHAN_INFO_SCALE:
87		vref_uv = regulator_get_voltage(state->vref_reg);
88		if (vref_uv < 0)
89			/* dummy regulator "get_voltage" returns -EINVAL */
90			return -EINVAL;
91
92		*val =  vref_uv / 1000;
93		*val2 = MAX11100_LSB_DIV;
94		return IIO_VAL_FRACTIONAL;
95	}
96
97	return -EINVAL;
98}
99
100static const struct iio_info max11100_info = {
101	.read_raw = max11100_read_raw,
102};
103
104static int max11100_probe(struct spi_device *spi)
105{
106	int ret;
107	struct iio_dev *indio_dev;
108	struct max11100_state *state;
109
110	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
111	if (!indio_dev)
112		return -ENOMEM;
113
114	spi_set_drvdata(spi, indio_dev);
115
116	state = iio_priv(indio_dev);
117	state->spi = spi;
118
119	indio_dev->name = "max11100";
120	indio_dev->info = &max11100_info;
121	indio_dev->modes = INDIO_DIRECT_MODE;
122	indio_dev->channels = max11100_channels;
123	indio_dev->num_channels = ARRAY_SIZE(max11100_channels);
124
125	state->vref_reg = devm_regulator_get(&spi->dev, "vref");
126	if (IS_ERR(state->vref_reg))
127		return PTR_ERR(state->vref_reg);
128
129	ret = regulator_enable(state->vref_reg);
130	if (ret)
131		return ret;
132
133	ret = iio_device_register(indio_dev);
134	if (ret)
135		goto disable_regulator;
136
137	return 0;
138
139disable_regulator:
140	regulator_disable(state->vref_reg);
141
142	return ret;
143}
144
145static int max11100_remove(struct spi_device *spi)
146{
147	struct iio_dev *indio_dev = spi_get_drvdata(spi);
148	struct max11100_state *state = iio_priv(indio_dev);
149
150	iio_device_unregister(indio_dev);
151	regulator_disable(state->vref_reg);
152
153	return 0;
154}
155
156static const struct of_device_id max11100_ids[] = {
157	{.compatible = "maxim,max11100"},
158	{ },
159};
160MODULE_DEVICE_TABLE(of, max11100_ids);
161
162static struct spi_driver max11100_driver = {
163	.driver = {
164		.name	= "max11100",
165		.of_match_table = max11100_ids,
166	},
167	.probe		= max11100_probe,
168	.remove		= max11100_remove,
169};
170
171module_spi_driver(max11100_driver);
172
173MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
174MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
175MODULE_LICENSE("GPL v2");
176