1 // SPDX-License-Identifier: GPL-2.0-only
3 * MAX1241 low-power, 12-bit serial ADC
5 * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
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>
15 #define MAX1241_VAL_MASK GENMASK(11, 0)
16 #define MAX1241_SHUTDOWN_DELAY_USEC 4
23 struct spi_device *spi;
25 struct regulator *vdd;
26 struct regulator *vref;
27 struct gpio_desc *shutdown;
29 __be16 data ____cacheline_aligned;
32 static const struct iio_chan_spec max1241_channels[] = {
37 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
38 BIT(IIO_CHAN_INFO_SCALE),
42 static int max1241_read(struct max1241 *adc)
44 struct spi_transfer xfers[] = {
46 * Begin conversion by bringing /CS low for at least
52 .delay.unit = SPI_DELAY_UNIT_USECS,
55 * Then read two bytes of data in our RX buffer.
63 return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
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)
71 struct max1241 *adc = iio_priv(indio_dev);
74 case IIO_CHAN_INFO_RAW:
75 mutex_lock(&adc->lock);
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);
83 ret = max1241_read(adc);
86 mutex_unlock(&adc->lock);
90 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
92 mutex_unlock(&adc->lock);
94 case IIO_CHAN_INFO_SCALE:
95 vref_uV = regulator_get_voltage(adc->vref);
100 *val = vref_uV / 1000;
103 return IIO_VAL_FRACTIONAL_LOG2;
109 static const struct iio_info max1241_info = {
110 .read_raw = max1241_read_raw,
113 static void max1241_disable_vdd_action(void *data)
115 struct max1241 *adc = data;
116 struct device *dev = &adc->spi->dev;
119 err = regulator_disable(adc->vdd);
121 dev_err(dev, "could not disable vdd regulator.\n");
124 static void max1241_disable_vref_action(void *data)
126 struct max1241 *adc = data;
127 struct device *dev = &adc->spi->dev;
130 err = regulator_disable(adc->vref);
132 dev_err(dev, "could not disable vref regulator.\n");
135 static int max1241_probe(struct spi_device *spi)
137 struct device *dev = &spi->dev;
138 struct iio_dev *indio_dev;
142 indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
146 adc = iio_priv(indio_dev);
148 mutex_init(&adc->lock);
150 spi_set_drvdata(spi, indio_dev);
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);
158 ret = regulator_enable(adc->vdd);
162 ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc);
164 dev_err(dev, "could not set up vdd regulator cleanup action\n");
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);
174 ret = regulator_enable(adc->vref);
178 ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
180 dev_err(dev, "could not set up vref regulator cleanup action\n");
184 adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
186 if (IS_ERR(adc->shutdown))
187 return PTR_ERR(adc->shutdown);
190 dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
192 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
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);
200 return devm_iio_device_register(dev, indio_dev);
203 static const struct spi_device_id max1241_id[] = {
204 { "max1241", max1241 },
208 static const struct of_device_id max1241_dt_ids[] = {
209 { .compatible = "maxim,max1241" },
212 MODULE_DEVICE_TABLE(of, max1241_dt_ids);
214 static struct spi_driver max1241_spi_driver = {
217 .of_match_table = max1241_dt_ids,
219 .probe = max1241_probe,
220 .id_table = max1241_id,
222 module_spi_driver(max1241_spi_driver);
224 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
225 MODULE_DESCRIPTION("MAX1241 ADC driver");
226 MODULE_LICENSE("GPL v2");