xref: /openbmc/linux/drivers/iio/adc/ad7292.c (revision ff7f85e3)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Analog Devices AD7292 SPI ADC driver
4  *
5  * Copyright 2019 Analog Devices Inc.
6  */
7 
8 #include <linux/bitfield.h>
9 #include <linux/device.h>
10 #include <linux/module.h>
11 #include <linux/of.h>
12 #include <linux/regulator/consumer.h>
13 #include <linux/spi/spi.h>
14 
15 #include <linux/iio/iio.h>
16 
17 #define ADI_VENDOR_ID 0x0018
18 
19 /* AD7292 registers definition */
20 #define AD7292_REG_VENDOR_ID		0x00
21 #define AD7292_REG_CONF_BANK		0x05
22 #define AD7292_REG_CONV_COMM		0x0E
23 #define AD7292_REG_ADC_CH(x)		(0x10 + (x))
24 
25 /* AD7292 configuration bank subregisters definition */
26 #define AD7292_BANK_REG_VIN_RNG0	0x10
27 #define AD7292_BANK_REG_VIN_RNG1	0x11
28 #define AD7292_BANK_REG_SAMP_MODE	0x12
29 
30 #define AD7292_RD_FLAG_MSK(x)		(BIT(7) | ((x) & 0x3F))
31 
32 /* AD7292_REG_ADC_CONVERSION */
33 #define AD7292_ADC_DATA_MASK		GENMASK(15, 6)
34 #define AD7292_ADC_DATA(x)		FIELD_GET(AD7292_ADC_DATA_MASK, x)
35 
36 /* AD7292_CHANNEL_SAMPLING_MODE */
37 #define AD7292_CH_SAMP_MODE(reg, ch)	(((reg) >> 8) & BIT(ch))
38 
39 /* AD7292_CHANNEL_VIN_RANGE */
40 #define AD7292_CH_VIN_RANGE(reg, ch)	((reg) & BIT(ch))
41 
42 #define AD7292_VOLTAGE_CHAN(_chan)					\
43 {									\
44 	.type = IIO_VOLTAGE,						\
45 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
46 			      BIT(IIO_CHAN_INFO_SCALE),			\
47 	.indexed = 1,							\
48 	.channel = _chan,						\
49 }
50 
51 static const struct iio_chan_spec ad7292_channels[] = {
52 	AD7292_VOLTAGE_CHAN(0),
53 	AD7292_VOLTAGE_CHAN(1),
54 	AD7292_VOLTAGE_CHAN(2),
55 	AD7292_VOLTAGE_CHAN(3),
56 	AD7292_VOLTAGE_CHAN(4),
57 	AD7292_VOLTAGE_CHAN(5),
58 	AD7292_VOLTAGE_CHAN(6),
59 	AD7292_VOLTAGE_CHAN(7)
60 };
61 
62 static const struct iio_chan_spec ad7292_channels_diff[] = {
63 	{
64 		.type = IIO_VOLTAGE,
65 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
66 		.indexed = 1,
67 		.differential = 1,
68 		.channel = 0,
69 		.channel2 = 1,
70 	},
71 	AD7292_VOLTAGE_CHAN(2),
72 	AD7292_VOLTAGE_CHAN(3),
73 	AD7292_VOLTAGE_CHAN(4),
74 	AD7292_VOLTAGE_CHAN(5),
75 	AD7292_VOLTAGE_CHAN(6),
76 	AD7292_VOLTAGE_CHAN(7)
77 };
78 
79 struct ad7292_state {
80 	struct spi_device *spi;
81 	struct regulator *reg;
82 	unsigned short vref_mv;
83 
84 	__be16 d16 __aligned(IIO_DMA_MINALIGN);
85 	u8 d8[2];
86 };
87 
ad7292_spi_reg_read(struct ad7292_state * st,unsigned int addr)88 static int ad7292_spi_reg_read(struct ad7292_state *st, unsigned int addr)
89 {
90 	int ret;
91 
92 	st->d8[0] = AD7292_RD_FLAG_MSK(addr);
93 
94 	ret = spi_write_then_read(st->spi, st->d8, 1, &st->d16, 2);
95 	if (ret < 0)
96 		return ret;
97 
98 	return be16_to_cpu(st->d16);
99 }
100 
ad7292_spi_subreg_read(struct ad7292_state * st,unsigned int addr,unsigned int sub_addr,unsigned int len)101 static int ad7292_spi_subreg_read(struct ad7292_state *st, unsigned int addr,
102 				  unsigned int sub_addr, unsigned int len)
103 {
104 	unsigned int shift = 16 - (8 * len);
105 	int ret;
106 
107 	st->d8[0] = AD7292_RD_FLAG_MSK(addr);
108 	st->d8[1] = sub_addr;
109 
110 	ret = spi_write_then_read(st->spi, st->d8, 2, &st->d16, len);
111 	if (ret < 0)
112 		return ret;
113 
114 	return (be16_to_cpu(st->d16) >> shift);
115 }
116 
ad7292_single_conversion(struct ad7292_state * st,unsigned int chan_addr)117 static int ad7292_single_conversion(struct ad7292_state *st,
118 				    unsigned int chan_addr)
119 {
120 	int ret;
121 
122 	struct spi_transfer t[] = {
123 		{
124 			.tx_buf = &st->d8,
125 			.len = 4,
126 			.delay = {
127 				.value = 6,
128 				.unit = SPI_DELAY_UNIT_USECS
129 			},
130 		}, {
131 			.rx_buf = &st->d16,
132 			.len = 2,
133 		},
134 	};
135 
136 	st->d8[0] = chan_addr;
137 	st->d8[1] = AD7292_RD_FLAG_MSK(AD7292_REG_CONV_COMM);
138 
139 	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
140 
141 	if (ret < 0)
142 		return ret;
143 
144 	return be16_to_cpu(st->d16);
145 }
146 
ad7292_vin_range_multiplier(struct ad7292_state * st,int channel)147 static int ad7292_vin_range_multiplier(struct ad7292_state *st, int channel)
148 {
149 	int samp_mode, range0, range1, factor = 1;
150 
151 	/*
152 	 * Every AD7292 ADC channel may have its input range adjusted according
153 	 * to the settings at the ADC sampling mode and VIN range subregisters.
154 	 * For a given channel, the minimum input range is equal to Vref, and it
155 	 * may be increased by a multiplier factor of 2 or 4 according to the
156 	 * following rule:
157 	 * If channel is being sampled with respect to AGND:
158 	 *	factor = 4 if VIN range0 and VIN range1 equal 0
159 	 *	factor = 2 if only one of VIN ranges equal 1
160 	 *	factor = 1 if both VIN range0 and VIN range1 equal 1
161 	 * If channel is being sampled with respect to AVDD:
162 	 *	factor = 4 if VIN range0 and VIN range1 equal 0
163 	 *	Behavior is undefined if any of VIN range doesn't equal 0
164 	 */
165 
166 	samp_mode = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
167 					   AD7292_BANK_REG_SAMP_MODE, 2);
168 
169 	if (samp_mode < 0)
170 		return samp_mode;
171 
172 	range0 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
173 					AD7292_BANK_REG_VIN_RNG0, 2);
174 
175 	if (range0 < 0)
176 		return range0;
177 
178 	range1 = ad7292_spi_subreg_read(st, AD7292_REG_CONF_BANK,
179 					AD7292_BANK_REG_VIN_RNG1, 2);
180 
181 	if (range1 < 0)
182 		return range1;
183 
184 	if (AD7292_CH_SAMP_MODE(samp_mode, channel)) {
185 		/* Sampling with respect to AGND */
186 		if (!AD7292_CH_VIN_RANGE(range0, channel))
187 			factor *= 2;
188 
189 		if (!AD7292_CH_VIN_RANGE(range1, channel))
190 			factor *= 2;
191 
192 	} else {
193 		/* Sampling with respect to AVDD */
194 		if (AD7292_CH_VIN_RANGE(range0, channel) ||
195 		    AD7292_CH_VIN_RANGE(range1, channel))
196 			return -EPERM;
197 
198 		factor = 4;
199 	}
200 
201 	return factor;
202 }
203 
ad7292_read_raw(struct iio_dev * indio_dev,const struct iio_chan_spec * chan,int * val,int * val2,long info)204 static int ad7292_read_raw(struct iio_dev *indio_dev,
205 			   const struct iio_chan_spec *chan,
206 			   int *val, int *val2, long info)
207 {
208 	struct ad7292_state *st = iio_priv(indio_dev);
209 	unsigned int ch_addr;
210 	int ret;
211 
212 	switch (info) {
213 	case IIO_CHAN_INFO_RAW:
214 		ch_addr = AD7292_REG_ADC_CH(chan->channel);
215 		ret = ad7292_single_conversion(st, ch_addr);
216 		if (ret < 0)
217 			return ret;
218 
219 		*val = AD7292_ADC_DATA(ret);
220 
221 		return IIO_VAL_INT;
222 	case IIO_CHAN_INFO_SCALE:
223 		/*
224 		 * To convert a raw value to standard units, the IIO defines
225 		 * this formula: Scaled value = (raw + offset) * scale.
226 		 * For the scale to be a correct multiplier for (raw + offset),
227 		 * it must be calculated as the input range divided by the
228 		 * number of possible distinct input values. Given the ADC data
229 		 * is 10 bit long, it may assume 2^10 distinct values.
230 		 * Hence, scale = range / 2^10. The IIO_VAL_FRACTIONAL_LOG2
231 		 * return type indicates to the IIO API to divide *val by 2 to
232 		 * the power of *val2 when returning from read_raw.
233 		 */
234 
235 		ret = ad7292_vin_range_multiplier(st, chan->channel);
236 		if (ret < 0)
237 			return ret;
238 
239 		*val = st->vref_mv * ret;
240 		*val2 = 10;
241 		return IIO_VAL_FRACTIONAL_LOG2;
242 	default:
243 		break;
244 	}
245 	return -EINVAL;
246 }
247 
248 static const struct iio_info ad7292_info = {
249 	.read_raw = ad7292_read_raw,
250 };
251 
ad7292_regulator_disable(void * data)252 static void ad7292_regulator_disable(void *data)
253 {
254 	struct ad7292_state *st = data;
255 
256 	regulator_disable(st->reg);
257 }
258 
ad7292_probe(struct spi_device * spi)259 static int ad7292_probe(struct spi_device *spi)
260 {
261 	struct ad7292_state *st;
262 	struct iio_dev *indio_dev;
263 	struct device_node *child;
264 	bool diff_channels = false;
265 	int ret;
266 
267 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
268 	if (!indio_dev)
269 		return -ENOMEM;
270 
271 	st = iio_priv(indio_dev);
272 	st->spi = spi;
273 
274 	ret = ad7292_spi_reg_read(st, AD7292_REG_VENDOR_ID);
275 	if (ret != ADI_VENDOR_ID) {
276 		dev_err(&spi->dev, "Wrong vendor id 0x%x\n", ret);
277 		return -EINVAL;
278 	}
279 
280 	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
281 	if (!IS_ERR(st->reg)) {
282 		ret = regulator_enable(st->reg);
283 		if (ret) {
284 			dev_err(&spi->dev,
285 				"Failed to enable external vref supply\n");
286 			return ret;
287 		}
288 
289 		ret = devm_add_action_or_reset(&spi->dev,
290 					       ad7292_regulator_disable, st);
291 		if (ret)
292 			return ret;
293 
294 		ret = regulator_get_voltage(st->reg);
295 		if (ret < 0)
296 			return ret;
297 
298 		st->vref_mv = ret / 1000;
299 	} else {
300 		/* Use the internal voltage reference. */
301 		st->vref_mv = 1250;
302 	}
303 
304 	indio_dev->name = spi_get_device_id(spi)->name;
305 	indio_dev->modes = INDIO_DIRECT_MODE;
306 	indio_dev->info = &ad7292_info;
307 
308 	for_each_available_child_of_node(spi->dev.of_node, child) {
309 		diff_channels = of_property_read_bool(child, "diff-channels");
310 		if (diff_channels) {
311 			of_node_put(child);
312 			break;
313 		}
314 	}
315 
316 	if (diff_channels) {
317 		indio_dev->num_channels = ARRAY_SIZE(ad7292_channels_diff);
318 		indio_dev->channels = ad7292_channels_diff;
319 	} else {
320 		indio_dev->num_channels = ARRAY_SIZE(ad7292_channels);
321 		indio_dev->channels = ad7292_channels;
322 	}
323 
324 	return devm_iio_device_register(&spi->dev, indio_dev);
325 }
326 
327 static const struct spi_device_id ad7292_id_table[] = {
328 	{ "ad7292", 0 },
329 	{}
330 };
331 MODULE_DEVICE_TABLE(spi, ad7292_id_table);
332 
333 static const struct of_device_id ad7292_of_match[] = {
334 	{ .compatible = "adi,ad7292" },
335 	{ },
336 };
337 MODULE_DEVICE_TABLE(of, ad7292_of_match);
338 
339 static struct spi_driver ad7292_driver = {
340 	.driver = {
341 		.name = "ad7292",
342 		.of_match_table = ad7292_of_match,
343 	},
344 	.probe = ad7292_probe,
345 	.id_table = ad7292_id_table,
346 };
347 module_spi_driver(ad7292_driver);
348 
349 MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt1@gmail.com>");
350 MODULE_DESCRIPTION("Analog Devices AD7292 ADC driver");
351 MODULE_LICENSE("GPL v2");
352