max1241.c

  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
 18enum max1241_id {
 19	max1241,
 20};
 21
 22struct max1241 {
 23	struct spi_device *spi;
 24	struct mutex lock;
 25	struct regulator *vref;
 26	struct gpio_desc *shutdown;
 27
 28	__be16 data __aligned(IIO_DMA_MINALIGN);
 29};
 30
 31static 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
 41static 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
 65static 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
108static const struct iio_info max1241_info = {
109	.read_raw = max1241_read_raw,
110};
111
112static 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
123static 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
138	ret = devm_regulator_get_enable(dev, "vdd");
139	if (ret)
140		return dev_err_probe(dev, ret,
141				     "failed to get/enable vdd regulator\n");
142
143	adc->vref = devm_regulator_get(dev, "vref");
144	if (IS_ERR(adc->vref))
145		return dev_err_probe(dev, PTR_ERR(adc->vref),
146				     "failed to get vref regulator\n");
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))
161		return dev_err_probe(dev, PTR_ERR(adc->shutdown),
162				     "cannot get shutdown gpio\n");
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;
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
178static const struct spi_device_id max1241_id[] = {
179	{ "max1241", max1241 },
180	{ }
181};
182
183static const struct of_device_id max1241_dt_ids[] = {
184	{ .compatible = "maxim,max1241" },
185	{ }
186};
187MODULE_DEVICE_TABLE(of, max1241_dt_ids);
188
189static 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};
197module_spi_driver(max1241_spi_driver);
198
199MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
200MODULE_DESCRIPTION("MAX1241 ADC driver");
201MODULE_LICENSE("GPL v2");