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8a80a71d AL |
1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* | |
3 | * MAX1241 low-power, 12-bit serial ADC | |
4 | * | |
5 | * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf | |
6 | */ | |
7 | ||
8 | #include <linux/delay.h> | |
9 | #include <linux/gpio/consumer.h> | |
10 | #include <linux/iio/iio.h> | |
11 | #include <linux/module.h> | |
12 | #include <linux/regulator/consumer.h> | |
13 | #include <linux/spi/spi.h> | |
14 | ||
15 | #define MAX1241_VAL_MASK GENMASK(11, 0) | |
16 | #define MAX1241_SHUTDOWN_DELAY_USEC 4 | |
17 | ||
18 | enum max1241_id { | |
19 | max1241, | |
20 | }; | |
21 | ||
22 | struct max1241 { | |
23 | struct spi_device *spi; | |
24 | struct mutex lock; | |
8a80a71d AL |
25 | struct regulator *vref; |
26 | struct gpio_desc *shutdown; | |
27 | ||
9d7019e4 | 28 | __be16 data __aligned(IIO_DMA_MINALIGN); |
8a80a71d AL |
29 | }; |
30 | ||
31 | static const struct iio_chan_spec max1241_channels[] = { | |
32 | { | |
33 | .type = IIO_VOLTAGE, | |
34 | .indexed = 1, | |
35 | .channel = 0, | |
36 | .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | | |
37 | BIT(IIO_CHAN_INFO_SCALE), | |
38 | }, | |
39 | }; | |
40 | ||
41 | static int max1241_read(struct max1241 *adc) | |
42 | { | |
43 | struct spi_transfer xfers[] = { | |
44 | /* | |
45 | * Begin conversion by bringing /CS low for at least | |
46 | * tconv us. | |
47 | */ | |
48 | { | |
49 | .len = 0, | |
50 | .delay.value = 8, | |
51 | .delay.unit = SPI_DELAY_UNIT_USECS, | |
52 | }, | |
53 | /* | |
54 | * Then read two bytes of data in our RX buffer. | |
55 | */ | |
56 | { | |
57 | .rx_buf = &adc->data, | |
58 | .len = 2, | |
59 | }, | |
60 | }; | |
61 | ||
62 | return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers)); | |
63 | } | |
64 | ||
65 | static int max1241_read_raw(struct iio_dev *indio_dev, | |
66 | struct iio_chan_spec const *chan, | |
67 | int *val, int *val2, long mask) | |
68 | { | |
69 | int ret, vref_uV; | |
70 | struct max1241 *adc = iio_priv(indio_dev); | |
71 | ||
72 | switch (mask) { | |
73 | case IIO_CHAN_INFO_RAW: | |
74 | mutex_lock(&adc->lock); | |
75 | ||
76 | if (adc->shutdown) { | |
77 | gpiod_set_value(adc->shutdown, 0); | |
78 | udelay(MAX1241_SHUTDOWN_DELAY_USEC); | |
79 | ret = max1241_read(adc); | |
80 | gpiod_set_value(adc->shutdown, 1); | |
81 | } else | |
82 | ret = max1241_read(adc); | |
83 | ||
84 | if (ret) { | |
85 | mutex_unlock(&adc->lock); | |
86 | return ret; | |
87 | } | |
88 | ||
89 | *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK; | |
90 | ||
91 | mutex_unlock(&adc->lock); | |
92 | return IIO_VAL_INT; | |
93 | case IIO_CHAN_INFO_SCALE: | |
94 | vref_uV = regulator_get_voltage(adc->vref); | |
95 | ||
96 | if (vref_uV < 0) | |
97 | return vref_uV; | |
98 | ||
99 | *val = vref_uV / 1000; | |
100 | *val2 = 12; | |
101 | ||
102 | return IIO_VAL_FRACTIONAL_LOG2; | |
103 | default: | |
104 | return -EINVAL; | |
105 | } | |
106 | } | |
107 | ||
108 | static const struct iio_info max1241_info = { | |
109 | .read_raw = max1241_read_raw, | |
110 | }; | |
111 | ||
8a80a71d AL |
112 | static void max1241_disable_vref_action(void *data) |
113 | { | |
114 | struct max1241 *adc = data; | |
115 | struct device *dev = &adc->spi->dev; | |
116 | int err; | |
117 | ||
118 | err = regulator_disable(adc->vref); | |
119 | if (err) | |
120 | dev_err(dev, "could not disable vref regulator.\n"); | |
121 | } | |
122 | ||
123 | static int max1241_probe(struct spi_device *spi) | |
124 | { | |
125 | struct device *dev = &spi->dev; | |
126 | struct iio_dev *indio_dev; | |
127 | struct max1241 *adc; | |
128 | int ret; | |
129 | ||
130 | indio_dev = devm_iio_device_alloc(dev, sizeof(*adc)); | |
131 | if (!indio_dev) | |
132 | return -ENOMEM; | |
133 | ||
134 | adc = iio_priv(indio_dev); | |
135 | adc->spi = spi; | |
136 | mutex_init(&adc->lock); | |
137 | ||
f55c8e66 | 138 | ret = devm_regulator_get_enable(dev, "vdd"); |
8a80a71d | 139 | if (ret) |
f55c8e66 MV |
140 | return dev_err_probe(dev, ret, |
141 | "failed to get/enable vdd regulator\n"); | |
8a80a71d AL |
142 | |
143 | adc->vref = devm_regulator_get(dev, "vref"); | |
070a83ff CH |
144 | if (IS_ERR(adc->vref)) |
145 | return dev_err_probe(dev, PTR_ERR(adc->vref), | |
146 | "failed to get vref regulator\n"); | |
8a80a71d AL |
147 | |
148 | ret = regulator_enable(adc->vref); | |
149 | if (ret) | |
150 | return ret; | |
151 | ||
152 | ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc); | |
153 | if (ret) { | |
154 | dev_err(dev, "could not set up vref regulator cleanup action\n"); | |
155 | return ret; | |
156 | } | |
157 | ||
158 | adc->shutdown = devm_gpiod_get_optional(dev, "shutdown", | |
159 | GPIOD_OUT_HIGH); | |
160 | if (IS_ERR(adc->shutdown)) | |
070a83ff CH |
161 | return dev_err_probe(dev, PTR_ERR(adc->shutdown), |
162 | "cannot get shutdown gpio\n"); | |
8a80a71d AL |
163 | |
164 | if (adc->shutdown) | |
165 | dev_dbg(dev, "shutdown pin passed, low-power mode enabled"); | |
166 | else | |
167 | dev_dbg(dev, "no shutdown pin passed, low-power mode disabled"); | |
168 | ||
169 | indio_dev->name = spi_get_device_id(spi)->name; | |
8a80a71d AL |
170 | indio_dev->info = &max1241_info; |
171 | indio_dev->modes = INDIO_DIRECT_MODE; | |
172 | indio_dev->channels = max1241_channels; | |
173 | indio_dev->num_channels = ARRAY_SIZE(max1241_channels); | |
174 | ||
175 | return devm_iio_device_register(dev, indio_dev); | |
176 | } | |
177 | ||
178 | static const struct spi_device_id max1241_id[] = { | |
179 | { "max1241", max1241 }, | |
180 | {} | |
181 | }; | |
182 | ||
183 | static const struct of_device_id max1241_dt_ids[] = { | |
184 | { .compatible = "maxim,max1241" }, | |
185 | {} | |
186 | }; | |
187 | MODULE_DEVICE_TABLE(of, max1241_dt_ids); | |
188 | ||
189 | static struct spi_driver max1241_spi_driver = { | |
190 | .driver = { | |
191 | .name = "max1241", | |
192 | .of_match_table = max1241_dt_ids, | |
193 | }, | |
194 | .probe = max1241_probe, | |
195 | .id_table = max1241_id, | |
196 | }; | |
197 | module_spi_driver(max1241_spi_driver); | |
198 | ||
199 | MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>"); | |
200 | MODULE_DESCRIPTION("MAX1241 ADC driver"); | |
201 | MODULE_LICENSE("GPL v2"); |