1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * IIO driver for Texas Instruments ADS7924 ADC, 12-bit, 4-Channels, I2C
4  *
5  * Author: Hugo Villeneuve <hvilleneuve@dimonoff.com>
6  * Copyright 2022 DimOnOff
7  *
8  * based on iio/adc/ti-ads1015.c
9  * Copyright (c) 2016, Intel Corporation.
10  *
11  * Datasheet: https://www.ti.com/lit/gpn/ads7924
12  */
13 
14 #include <linux/bitfield.h>
15 #include <linux/delay.h>
16 #include <linux/gpio/consumer.h>
17 #include <linux/init.h>
18 #include <linux/irq.h>
19 #include <linux/i2c.h>
20 #include <linux/module.h>
21 #include <linux/mutex.h>
22 #include <linux/regmap.h>
23 #include <linux/regulator/consumer.h>
24 
25 #include <linux/iio/iio.h>
26 #include <linux/iio/types.h>
27 
28 #define ADS7924_CHANNELS	 4
29 #define ADS7924_BITS		12
30 #define ADS7924_DATA_SHIFT	 4
31 
32 /* Registers. */
33 #define ADS7924_MODECNTRL_REG	0x00
34 #define ADS7924_INTCNTRL_REG	0x01
35 #define ADS7924_DATA0_U_REG	0x02
36 #define ADS7924_DATA0_L_REG	0x03
37 #define ADS7924_DATA1_U_REG	0x04
38 #define ADS7924_DATA1_L_REG	0x05
39 #define ADS7924_DATA2_U_REG	0x06
40 #define ADS7924_DATA2_L_REG	0x07
41 #define ADS7924_DATA3_U_REG	0x08
42 #define ADS7924_DATA3_L_REG	0x09
43 #define ADS7924_ULR0_REG	0x0A
44 #define ADS7924_LLR0_REG	0x0B
45 #define ADS7924_ULR1_REG	0x0C
46 #define ADS7924_LLR1_REG	0x0D
47 #define ADS7924_ULR2_REG	0x0E
48 #define ADS7924_LLR2_REG	0x0F
49 #define ADS7924_ULR3_REG	0x10
50 #define ADS7924_LLR3_REG	0x11
51 #define ADS7924_INTCONFIG_REG	0x12
52 #define ADS7924_SLPCONFIG_REG	0x13
53 #define ADS7924_ACQCONFIG_REG	0x14
54 #define ADS7924_PWRCONFIG_REG	0x15
55 #define ADS7924_RESET_REG	0x16
56 
57 /*
58  * Register address INC bit: when set to '1', the register address is
59  * automatically incremented after every register read which allows convenient
60  * reading of multiple registers. Set INC to '0' when reading a single register.
61  */
62 #define ADS7924_AUTO_INCREMENT_BIT	BIT(7)
63 
64 #define ADS7924_MODECNTRL_MODE_MASK	GENMASK(7, 2)
65 
66 #define ADS7924_MODECNTRL_SEL_MASK	GENMASK(1, 0)
67 
68 #define ADS7924_CFG_INTPOL_BIT		1
69 #define ADS7924_CFG_INTTRIG_BIT		0
70 
71 #define ADS7924_CFG_INTPOL_MASK		BIT(ADS7924_CFG_INTPOL_BIT)
72 #define ADS7924_CFG_INTTRIG_MASK	BIT(ADS7924_CFG_INTTRIG_BIT)
73 
74 /* Interrupt pin polarity */
75 #define ADS7924_CFG_INTPOL_LOW		0
76 #define ADS7924_CFG_INTPOL_HIGH		1
77 
78 /* Interrupt pin signaling */
79 #define ADS7924_CFG_INTTRIG_LEVEL	0
80 #define ADS7924_CFG_INTTRIG_EDGE	1
81 
82 /* Mode control values */
83 #define ADS7924_MODECNTRL_IDLE			0x00
84 #define ADS7924_MODECNTRL_AWAKE			0x20
85 #define ADS7924_MODECNTRL_MANUAL_SINGLE		0x30
86 #define ADS7924_MODECNTRL_MANUAL_SCAN		0x32
87 #define ADS7924_MODECNTRL_AUTO_SINGLE		0x31
88 #define ADS7924_MODECNTRL_AUTO_SCAN		0x33
89 #define ADS7924_MODECNTRL_AUTO_SINGLE_SLEEP	0x39
90 #define ADS7924_MODECNTRL_AUTO_SCAN_SLEEP	0x3B
91 #define ADS7924_MODECNTRL_AUTO_BURST_SLEEP	0x3F
92 
93 #define ADS7924_ACQTIME_MASK	GENMASK(4, 0)
94 
95 #define ADS7924_PWRUPTIME_MASK	GENMASK(4, 0)
96 
97 /*
98  * The power-up time is allowed to elapse whenever the device has been shutdown
99  * in idle mode. Power-up time can allow external circuits, such as an
100  * operational amplifier, between the MUXOUT and ADCIN pins to turn on.
101  * The nominal time programmed by the PUTIME[4:0] register bits is given by:
102  *     t PU = PWRUPTIME[4:0] × 2 μs
103  * If a power-up time is not required, set the bits to '0' to effectively bypass.
104  */
105 #define ADS7924_PWRUPTIME_US 0 /* Bypass (0us). */
106 
107 /*
108  * Acquisition Time according to ACQTIME[4:0] register bits.
109  * The Acquisition Time is given by:
110  *     t ACQ = (ACQTIME[4:0] × 2 μs) + 6 μs
111  * Using default value of 0 for ACQTIME[4:0] results in a minimum acquisition
112  * time of 6us.
113  */
114 #define ADS7924_ACQTIME_US 6
115 
116 /* The conversion time is always 4μs and cannot be programmed by the user. */
117 #define ADS7924_CONVTIME_US 4
118 
119 #define ADS7924_TOTAL_CONVTIME_US (ADS7924_PWRUPTIME_US + ADS7924_ACQTIME_US + \
120 				   ADS7924_CONVTIME_US)
121 
122 #define ADS7924_V_CHAN(_chan, _addr) {				\
123 	.type = IIO_VOLTAGE,					\
124 	.indexed = 1,						\
125 	.channel = _chan,					\
126 	.address = _addr,					\
127 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 		\
128 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
129 	.datasheet_name = "AIN"#_chan,				\
130 }
131 
132 struct ads7924_data {
133 	struct device *dev;
134 	struct regmap *regmap;
135 	struct regulator *vref_reg;
136 
137 	/* GPIO descriptor for device hard-reset pin. */
138 	struct gpio_desc *reset_gpio;
139 
140 	/*
141 	 * Protects ADC ops, e.g: concurrent sysfs/buffered
142 	 * data reads, configuration updates
143 	 */
144 	struct mutex lock;
145 
146 	/*
147 	 * Set to true when the ADC is switched to the continuous-conversion
148 	 * mode and exits from a power-down state. This flag is used to avoid
149 	 * getting the stale result from the conversion register.
150 	 */
151 	bool conv_invalid;
152 };
153 
ads7924_is_writeable_reg(struct device * dev,unsigned int reg)154 static bool ads7924_is_writeable_reg(struct device *dev, unsigned int reg)
155 {
156 	switch (reg) {
157 	case ADS7924_MODECNTRL_REG:
158 	case ADS7924_INTCNTRL_REG:
159 	case ADS7924_ULR0_REG:
160 	case ADS7924_LLR0_REG:
161 	case ADS7924_ULR1_REG:
162 	case ADS7924_LLR1_REG:
163 	case ADS7924_ULR2_REG:
164 	case ADS7924_LLR2_REG:
165 	case ADS7924_ULR3_REG:
166 	case ADS7924_LLR3_REG:
167 	case ADS7924_INTCONFIG_REG:
168 	case ADS7924_SLPCONFIG_REG:
169 	case ADS7924_ACQCONFIG_REG:
170 	case ADS7924_PWRCONFIG_REG:
171 	case ADS7924_RESET_REG:
172 		return true;
173 	default:
174 		return false;
175 	}
176 }
177 
178 static const struct regmap_config ads7924_regmap_config = {
179 	.reg_bits = 8,
180 	.val_bits = 8,
181 	.max_register = ADS7924_RESET_REG,
182 	.writeable_reg = ads7924_is_writeable_reg,
183 };
184 
185 static const struct iio_chan_spec ads7924_channels[] = {
186 	ADS7924_V_CHAN(0, ADS7924_DATA0_U_REG),
187 	ADS7924_V_CHAN(1, ADS7924_DATA1_U_REG),
188 	ADS7924_V_CHAN(2, ADS7924_DATA2_U_REG),
189 	ADS7924_V_CHAN(3, ADS7924_DATA3_U_REG),
190 };
191 
ads7924_get_adc_result(struct ads7924_data * data,struct iio_chan_spec const * chan,int * val)192 static int ads7924_get_adc_result(struct ads7924_data *data,
193 				  struct iio_chan_spec const *chan, int *val)
194 {
195 	int ret;
196 	__be16 be_val;
197 
198 	if (chan->channel < 0 || chan->channel >= ADS7924_CHANNELS)
199 		return -EINVAL;
200 
201 	if (data->conv_invalid) {
202 		int conv_time;
203 
204 		conv_time = ADS7924_TOTAL_CONVTIME_US;
205 		/* Allow 10% for internal clock inaccuracy. */
206 		conv_time += conv_time / 10;
207 		usleep_range(conv_time, conv_time + 1);
208 		data->conv_invalid = false;
209 	}
210 
211 	ret = regmap_raw_read(data->regmap, ADS7924_AUTO_INCREMENT_BIT |
212 			      chan->address, &be_val, sizeof(be_val));
213 	if (ret)
214 		return ret;
215 
216 	*val = be16_to_cpu(be_val) >> ADS7924_DATA_SHIFT;
217 
218 	return 0;
219 }
220 
ads7924_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)221 static int ads7924_read_raw(struct iio_dev *indio_dev,
222 			    struct iio_chan_spec const *chan, int *val,
223 			    int *val2, long mask)
224 {
225 	int ret, vref_uv;
226 	struct ads7924_data *data = iio_priv(indio_dev);
227 
228 	switch (mask) {
229 	case IIO_CHAN_INFO_RAW:
230 		mutex_lock(&data->lock);
231 		ret = ads7924_get_adc_result(data, chan, val);
232 		mutex_unlock(&data->lock);
233 		if (ret < 0)
234 			return ret;
235 
236 		return IIO_VAL_INT;
237 	case IIO_CHAN_INFO_SCALE:
238 		vref_uv = regulator_get_voltage(data->vref_reg);
239 		if (vref_uv < 0)
240 			return vref_uv;
241 
242 		*val =  vref_uv / 1000; /* Convert reg voltage to mV */
243 		*val2 = ADS7924_BITS;
244 		return IIO_VAL_FRACTIONAL_LOG2;
245 	default:
246 		return -EINVAL;
247 	}
248 }
249 
250 static const struct iio_info ads7924_info = {
251 	.read_raw = ads7924_read_raw,
252 };
253 
ads7924_get_channels_config(struct i2c_client * client,struct iio_dev * indio_dev)254 static int ads7924_get_channels_config(struct i2c_client *client,
255 				       struct iio_dev *indio_dev)
256 {
257 	struct ads7924_data *priv = iio_priv(indio_dev);
258 	struct device *dev = priv->dev;
259 	struct fwnode_handle *node;
260 	int num_channels = 0;
261 
262 	device_for_each_child_node(dev, node) {
263 		u32 pval;
264 		unsigned int channel;
265 
266 		if (fwnode_property_read_u32(node, "reg", &pval)) {
267 			dev_err(dev, "invalid reg on %pfw\n", node);
268 			continue;
269 		}
270 
271 		channel = pval;
272 		if (channel >= ADS7924_CHANNELS) {
273 			dev_err(dev, "invalid channel index %d on %pfw\n",
274 				channel, node);
275 			continue;
276 		}
277 
278 		num_channels++;
279 	}
280 
281 	if (!num_channels)
282 		return -EINVAL;
283 
284 	return 0;
285 }
286 
ads7924_set_conv_mode(struct ads7924_data * data,int mode)287 static int ads7924_set_conv_mode(struct ads7924_data *data, int mode)
288 {
289 	int ret;
290 	unsigned int mode_field;
291 	struct device *dev = data->dev;
292 
293 	/*
294 	 * When switching between modes, be sure to first select the Awake mode
295 	 * and then switch to the desired mode. This procedure ensures the
296 	 * internal control logic is properly synchronized.
297 	 */
298 	if (mode != ADS7924_MODECNTRL_IDLE) {
299 		mode_field = FIELD_PREP(ADS7924_MODECNTRL_MODE_MASK,
300 					ADS7924_MODECNTRL_AWAKE);
301 
302 		ret = regmap_update_bits(data->regmap, ADS7924_MODECNTRL_REG,
303 					 ADS7924_MODECNTRL_MODE_MASK,
304 					 mode_field);
305 		if (ret) {
306 			dev_err(dev, "failed to set awake mode (%pe)\n",
307 				ERR_PTR(ret));
308 			return ret;
309 		}
310 	}
311 
312 	mode_field = FIELD_PREP(ADS7924_MODECNTRL_MODE_MASK, mode);
313 
314 	ret = regmap_update_bits(data->regmap, ADS7924_MODECNTRL_REG,
315 				 ADS7924_MODECNTRL_MODE_MASK, mode_field);
316 	if (ret)
317 		dev_err(dev, "failed to set mode %d (%pe)\n", mode,
318 			ERR_PTR(ret));
319 
320 	return ret;
321 }
322 
ads7924_reset(struct iio_dev * indio_dev)323 static int ads7924_reset(struct iio_dev *indio_dev)
324 {
325 	struct ads7924_data *data = iio_priv(indio_dev);
326 
327 	if (data->reset_gpio) {
328 		gpiod_set_value(data->reset_gpio, 1); /* Assert. */
329 		/* Educated guess: assert time not specified in datasheet... */
330 		mdelay(100);
331 		gpiod_set_value(data->reset_gpio, 0); /* Deassert. */
332 		return 0;
333 	}
334 
335 	/*
336 	 * A write of 10101010 to this register will generate a
337 	 * software reset of the ADS7924.
338 	 */
339 	return regmap_write(data->regmap, ADS7924_RESET_REG, 0b10101010);
340 };
341 
ads7924_reg_disable(void * data)342 static void ads7924_reg_disable(void *data)
343 {
344 	regulator_disable(data);
345 }
346 
ads7924_set_idle_mode(void * data)347 static void ads7924_set_idle_mode(void *data)
348 {
349 	ads7924_set_conv_mode(data, ADS7924_MODECNTRL_IDLE);
350 }
351 
ads7924_probe(struct i2c_client * client)352 static int ads7924_probe(struct i2c_client *client)
353 {
354 	struct iio_dev *indio_dev;
355 	struct ads7924_data *data;
356 	struct device *dev = &client->dev;
357 	int ret;
358 
359 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
360 	if (!indio_dev)
361 		return dev_err_probe(dev, -ENOMEM,
362 				     "failed to allocate iio device\n");
363 
364 	data = iio_priv(indio_dev);
365 
366 	data->dev = dev;
367 
368 	/* Initialize the reset GPIO as output with an initial value of 0. */
369 	data->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
370 	if (IS_ERR(data->reset_gpio))
371 		return dev_err_probe(dev, PTR_ERR(data->reset_gpio),
372 				     "failed to get request reset GPIO\n");
373 
374 	mutex_init(&data->lock);
375 
376 	indio_dev->name = "ads7924";
377 	indio_dev->modes = INDIO_DIRECT_MODE;
378 
379 	indio_dev->channels = ads7924_channels;
380 	indio_dev->num_channels = ARRAY_SIZE(ads7924_channels);
381 	indio_dev->info = &ads7924_info;
382 
383 	ret = ads7924_get_channels_config(client, indio_dev);
384 	if (ret < 0)
385 		return dev_err_probe(dev, ret,
386 				     "failed to get channels configuration\n");
387 
388 	data->regmap = devm_regmap_init_i2c(client, &ads7924_regmap_config);
389 	if (IS_ERR(data->regmap))
390 		return dev_err_probe(dev, PTR_ERR(data->regmap),
391 				     "failed to init regmap\n");
392 
393 	data->vref_reg = devm_regulator_get(dev, "vref");
394 	if (IS_ERR(data->vref_reg))
395 		return dev_err_probe(dev, PTR_ERR(data->vref_reg),
396 				     "failed to get vref regulator\n");
397 
398 	ret = regulator_enable(data->vref_reg);
399 	if (ret)
400 		return dev_err_probe(dev, ret,
401 				     "failed to enable regulator\n");
402 
403 	ret = devm_add_action_or_reset(dev, ads7924_reg_disable, data->vref_reg);
404 	if (ret)
405 		return dev_err_probe(dev, ret,
406 				     "failed to add regulator disable action\n");
407 
408 	ret = ads7924_reset(indio_dev);
409 	if (ret < 0)
410 		return dev_err_probe(dev, ret,
411 				     "failed to reset device\n");
412 
413 	ret = ads7924_set_conv_mode(data, ADS7924_MODECNTRL_AUTO_SCAN);
414 	if (ret)
415 		return dev_err_probe(dev, ret,
416 				     "failed to set conversion mode\n");
417 
418 	ret = devm_add_action_or_reset(dev, ads7924_set_idle_mode, data);
419 	if (ret)
420 		return dev_err_probe(dev, ret,
421 				     "failed to add idle mode action\n");
422 
423 	/* Use minimum signal acquire time. */
424 	ret = regmap_update_bits(data->regmap, ADS7924_ACQCONFIG_REG,
425 				 ADS7924_ACQTIME_MASK,
426 				 FIELD_PREP(ADS7924_ACQTIME_MASK, 0));
427 	if (ret < 0)
428 		return dev_err_probe(dev, ret,
429 				     "failed to configure signal acquire time\n");
430 
431 	/* Disable power-up time. */
432 	ret = regmap_update_bits(data->regmap, ADS7924_PWRCONFIG_REG,
433 				 ADS7924_PWRUPTIME_MASK,
434 				 FIELD_PREP(ADS7924_PWRUPTIME_MASK, 0));
435 	if (ret < 0)
436 		return dev_err_probe(dev, ret,
437 				     "failed to configure power-up time\n");
438 
439 	data->conv_invalid = true;
440 
441 	ret = devm_iio_device_register(dev, indio_dev);
442 	if (ret < 0)
443 		return dev_err_probe(dev, ret,
444 				     "failed to register IIO device\n");
445 
446 	return 0;
447 }
448 
449 static const struct i2c_device_id ads7924_id[] = {
450 	{ "ads7924", 0 },
451 	{}
452 };
453 MODULE_DEVICE_TABLE(i2c, ads7924_id);
454 
455 static const struct of_device_id ads7924_of_match[] = {
456 	{ .compatible = "ti,ads7924", },
457 	{}
458 };
459 MODULE_DEVICE_TABLE(of, ads7924_of_match);
460 
461 static struct i2c_driver ads7924_driver = {
462 	.driver = {
463 		.name = "ads7924",
464 		.of_match_table = ads7924_of_match,
465 	},
466 	.probe		= ads7924_probe,
467 	.id_table	= ads7924_id,
468 };
469 
470 module_i2c_driver(ads7924_driver);
471 
472 MODULE_AUTHOR("Hugo Villeneuve <hvilleneuve@dimonoff.com>");
473 MODULE_DESCRIPTION("Texas Instruments ADS7924 ADC I2C driver");
474 MODULE_LICENSE("GPL");
475