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(spi: 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(desc: adc->shutdown, value: 0);
78 udelay(MAX1241_SHUTDOWN_DELAY_USEC);
79 ret = max1241_read(adc);
80 gpiod_set_value(desc: adc->shutdown, value: 1);
81 } else
82 ret = max1241_read(adc);
83
84 if (ret) {
85 mutex_unlock(lock: &adc->lock);
86 return ret;
87 }
88
89 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
90
91 mutex_unlock(lock: &adc->lock);
92 return IIO_VAL_INT;
93 case IIO_CHAN_INFO_SCALE:
94 vref_uV = regulator_get_voltage(regulator: 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(regulator: 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(parent: dev, sizeof_priv: 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, id: "vdd");
139 if (ret)
140 return dev_err_probe(dev, err: ret,
141 fmt: "failed to get/enable vdd regulator\n");
142
143 adc->vref = devm_regulator_get(dev, id: "vref");
144 if (IS_ERR(ptr: adc->vref))
145 return dev_err_probe(dev, err: PTR_ERR(ptr: adc->vref),
146 fmt: "failed to get vref regulator\n");
147
148 ret = regulator_enable(regulator: 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, con_id: "shutdown",
159 flags: GPIOD_OUT_HIGH);
160 if (IS_ERR(ptr: adc->shutdown))
161 return dev_err_probe(dev, err: PTR_ERR(ptr: adc->shutdown),
162 fmt: "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(sdev: 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");
202

source code of linux/drivers/iio/adc/max1241.c