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
31 struct 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
42 static 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
max11100_read_single(struct iio_dev * indio_dev,int * val)50 static 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
max11100_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long info)72 static 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
101 static const struct iio_info max11100_info = {
102 .read_raw = max11100_read_raw,
103 };
104
max11100_regulator_disable(void * reg)105 static void max11100_regulator_disable(void *reg)
106 {
107 regulator_disable(reg);
108 }
109
max11100_probe(struct spi_device * spi)110 static 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
145 static const struct of_device_id max11100_ids[] = {
146 {.compatible = "maxim,max11100"},
147 { },
148 };
149 MODULE_DEVICE_TABLE(of, max11100_ids);
150
151 static struct spi_driver max11100_driver = {
152 .driver = {
153 .name = "max11100",
154 .of_match_table = max11100_ids,
155 },
156 .probe = max11100_probe,
157 };
158
159 module_spi_driver(max11100_driver);
160
161 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
162 MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
163 MODULE_LICENSE("GPL v2");
164