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 *vdd;
 26	struct regulator *vref;
 27	struct gpio_desc *shutdown;
 28
 29	__be16 data ____cacheline_aligned;
 30};
 31
 32static 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
 42static 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
 66static 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
109static const struct iio_info max1241_info = {
110	.read_raw = max1241_read_raw,
111};
112
113static 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
124static 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
135static 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
203static const struct spi_device_id max1241_id[] = {
204	{ "max1241", max1241 },
205	{}
206};
207
208static const struct of_device_id max1241_dt_ids[] = {
209	{ .compatible = "maxim,max1241" },
210	{}
211};
212MODULE_DEVICE_TABLE(of, max1241_dt_ids);
213
214static 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};
222module_spi_driver(max1241_spi_driver);
223
224MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
225MODULE_DESCRIPTION("MAX1241 ADC driver");
226MODULE_LICENSE("GPL v2");