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 <asm/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");
164