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 *vref; |
26 | struct gpio_desc *shutdown; |
27 | |
28 | __be16 data __aligned(IIO_DMA_MINALIGN); |
29 | }; |
30 | |
31 | static 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 | |
41 | static 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 | |
65 | static 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 | |
108 | static const struct iio_info max1241_info = { |
109 | .read_raw = max1241_read_raw, |
110 | }; |
111 | |
112 | static 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 | |
123 | static 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 | |
178 | static const struct spi_device_id max1241_id[] = { |
179 | { "max1241" , max1241 }, |
180 | {} |
181 | }; |
182 | |
183 | static const struct of_device_id max1241_dt_ids[] = { |
184 | { .compatible = "maxim,max1241" }, |
185 | {} |
186 | }; |
187 | MODULE_DEVICE_TABLE(of, max1241_dt_ids); |
188 | |
189 | static 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 | }; |
197 | module_spi_driver(max1241_spi_driver); |
198 | |
199 | MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>" ); |
200 | MODULE_DESCRIPTION("MAX1241 ADC driver" ); |
201 | MODULE_LICENSE("GPL v2" ); |
202 | |