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;
25 struct regulator *vdd;
26 struct regulator *vref;
27 struct gpio_desc *shutdown;
28
29 __be16 data ____cacheline_aligned;
30 };
31
32 static const struct iio_chan_spec max1241_channels[] = {
33 {
34 .type = IIO_VOLTAGE,
35 .indexed = 1,
36 .channel = 0,
37 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
38 BIT(IIO_CHAN_INFO_SCALE),
39 },
40 };
41
max1241_read(struct max1241 * adc)42 static int max1241_read(struct max1241 *adc)
43 {
44 struct spi_transfer xfers[] = {
45 /*
46 * Begin conversion by bringing /CS low for at least
47 * tconv us.
48 */
49 {
50 .len = 0,
51 .delay.value = 8,
52 .delay.unit = SPI_DELAY_UNIT_USECS,
53 },
54 /*
55 * Then read two bytes of data in our RX buffer.
56 */
57 {
58 .rx_buf = &adc->data,
59 .len = 2,
60 },
61 };
62
63 return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
64 }
65
max1241_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)66 static int max1241_read_raw(struct iio_dev *indio_dev,
67 struct iio_chan_spec const *chan,
68 int *val, int *val2, long mask)
69 {
70 int ret, vref_uV;
71 struct max1241 *adc = iio_priv(indio_dev);
72
73 switch (mask) {
74 case IIO_CHAN_INFO_RAW:
75 mutex_lock(&adc->lock);
76
77 if (adc->shutdown) {
78 gpiod_set_value(adc->shutdown, 0);
79 udelay(MAX1241_SHUTDOWN_DELAY_USEC);
80 ret = max1241_read(adc);
81 gpiod_set_value(adc->shutdown, 1);
82 } else
83 ret = max1241_read(adc);
84
85 if (ret) {
86 mutex_unlock(&adc->lock);
87 return ret;
88 }
89
90 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
91
92 mutex_unlock(&adc->lock);
93 return IIO_VAL_INT;
94 case IIO_CHAN_INFO_SCALE:
95 vref_uV = regulator_get_voltage(adc->vref);
96
97 if (vref_uV < 0)
98 return vref_uV;
99
100 *val = vref_uV / 1000;
101 *val2 = 12;
102
103 return IIO_VAL_FRACTIONAL_LOG2;
104 default:
105 return -EINVAL;
106 }
107 }
108
109 static const struct iio_info max1241_info = {
110 .read_raw = max1241_read_raw,
111 };
112
max1241_disable_vdd_action(void * data)113 static void max1241_disable_vdd_action(void *data)
114 {
115 struct max1241 *adc = data;
116 struct device *dev = &adc->spi->dev;
117 int err;
118
119 err = regulator_disable(adc->vdd);
120 if (err)
121 dev_err(dev, "could not disable vdd regulator.\n");
122 }
123
max1241_disable_vref_action(void * data)124 static void max1241_disable_vref_action(void *data)
125 {
126 struct max1241 *adc = data;
127 struct device *dev = &adc->spi->dev;
128 int err;
129
130 err = regulator_disable(adc->vref);
131 if (err)
132 dev_err(dev, "could not disable vref regulator.\n");
133 }
134
max1241_probe(struct spi_device * spi)135 static int max1241_probe(struct spi_device *spi)
136 {
137 struct device *dev = &spi->dev;
138 struct iio_dev *indio_dev;
139 struct max1241 *adc;
140 int ret;
141
142 indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
143 if (!indio_dev)
144 return -ENOMEM;
145
146 adc = iio_priv(indio_dev);
147 adc->spi = spi;
148 mutex_init(&adc->lock);
149
150 spi_set_drvdata(spi, indio_dev);
151
152 adc->vdd = devm_regulator_get(dev, "vdd");
153 if (IS_ERR(adc->vdd)) {
154 dev_err(dev, "failed to get vdd regulator\n");
155 return PTR_ERR(adc->vdd);
156 }
157
158 ret = regulator_enable(adc->vdd);
159 if (ret)
160 return ret;
161
162 ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc);
163 if (ret) {
164 dev_err(dev, "could not set up vdd regulator cleanup action\n");
165 return ret;
166 }
167
168 adc->vref = devm_regulator_get(dev, "vref");
169 if (IS_ERR(adc->vref)) {
170 dev_err(dev, "failed to get vref regulator\n");
171 return PTR_ERR(adc->vref);
172 }
173
174 ret = regulator_enable(adc->vref);
175 if (ret)
176 return ret;
177
178 ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
179 if (ret) {
180 dev_err(dev, "could not set up vref regulator cleanup action\n");
181 return ret;
182 }
183
184 adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
185 GPIOD_OUT_HIGH);
186 if (IS_ERR(adc->shutdown))
187 return PTR_ERR(adc->shutdown);
188
189 if (adc->shutdown)
190 dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
191 else
192 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
193
194 indio_dev->name = spi_get_device_id(spi)->name;
195 indio_dev->info = &max1241_info;
196 indio_dev->modes = INDIO_DIRECT_MODE;
197 indio_dev->channels = max1241_channels;
198 indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
199
200 return devm_iio_device_register(dev, indio_dev);
201 }
202
203 static const struct spi_device_id max1241_id[] = {
204 { "max1241", max1241 },
205 {}
206 };
207
208 static const struct of_device_id max1241_dt_ids[] = {
209 { .compatible = "maxim,max1241" },
210 {}
211 };
212 MODULE_DEVICE_TABLE(of, max1241_dt_ids);
213
214 static struct spi_driver max1241_spi_driver = {
215 .driver = {
216 .name = "max1241",
217 .of_match_table = max1241_dt_ids,
218 },
219 .probe = max1241_probe,
220 .id_table = max1241_id,
221 };
222 module_spi_driver(max1241_spi_driver);
223
224 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
225 MODULE_DESCRIPTION("MAX1241 ADC driver");
226 MODULE_LICENSE("GPL v2");
227