1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Analog Devices AD5110 digital potentiometer driver
4  *
5  * Copyright (C) 2021 Mugilraj Dhavachelvan <dmugil2000@gmail.com>
6  *
7  * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5110_5112_5114.pdf
8  */
9 
10 #include <linux/bitfield.h>
11 #include <linux/delay.h>
12 #include <linux/device.h>
13 #include <linux/i2c.h>
14 #include <linux/module.h>
15 
16 #include <linux/iio/iio.h>
17 #include <linux/iio/sysfs.h>
18 
19 /* AD5110 commands */
20 #define AD5110_EEPROM_WR	1
21 #define AD5110_RDAC_WR		2
22 #define AD5110_SHUTDOWN	3
23 #define AD5110_RESET		4
24 #define AD5110_RDAC_RD		5
25 #define AD5110_EEPROM_RD	6
26 
27 /* AD5110_EEPROM_RD data */
28 #define AD5110_WIPER_POS	0
29 #define AD5110_RESISTOR_TOL	1
30 
31 #define AD5110_WIPER_RESISTANCE	70
32 
33 struct ad5110_cfg {
34 	int max_pos;
35 	int kohms;
36 	int shift;
37 };
38 
39 enum ad5110_type {
40 	AD5110_10,
41 	AD5110_80,
42 	AD5112_05,
43 	AD5112_10,
44 	AD5112_80,
45 	AD5114_10,
46 	AD5114_80,
47 };
48 
49 static const struct ad5110_cfg ad5110_cfg[] = {
50 	[AD5110_10] = { .max_pos = 128, .kohms = 10 },
51 	[AD5110_80] = { .max_pos = 128, .kohms = 80 },
52 	[AD5112_05] = { .max_pos = 64, .kohms = 5, .shift = 1 },
53 	[AD5112_10] = { .max_pos = 64, .kohms = 10, .shift = 1 },
54 	[AD5112_80] = { .max_pos = 64, .kohms = 80, .shift = 1 },
55 	[AD5114_10] = { .max_pos = 32, .kohms = 10, .shift = 2 },
56 	[AD5114_80] = { .max_pos = 32, .kohms = 80, .shift = 2 },
57 };
58 
59 struct ad5110_data {
60 	struct i2c_client       *client;
61 	s16			tol;		/* resistor tolerance */
62 	bool			enable;
63 	struct mutex            lock;
64 	const struct ad5110_cfg	*cfg;
65 	/*
66 	 * DMA (thus cache coherency maintenance) may require the
67 	 * transfer buffers to live in their own cache lines.
68 	 */
69 	u8			buf[2] __aligned(IIO_DMA_MINALIGN);
70 };
71 
72 static const struct iio_chan_spec ad5110_channels[] = {
73 	{
74 		.type = IIO_RESISTANCE,
75 		.output = 1,
76 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_OFFSET) |
77 					BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_ENABLE),
78 	},
79 };
80 
81 static int ad5110_read(struct ad5110_data *data, u8 cmd, int *val)
82 {
83 	int ret;
84 
85 	mutex_lock(&data->lock);
86 	data->buf[0] = cmd;
87 	data->buf[1] = *val;
88 
89 	ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
90 	if (ret < 0) {
91 		goto error;
92 	} else if (ret != sizeof(data->buf)) {
93 		ret = -EIO;
94 		goto error;
95 	}
96 
97 	ret = i2c_master_recv_dmasafe(data->client, data->buf, 1);
98 	if (ret < 0) {
99 		goto error;
100 	} else if (ret != 1) {
101 		ret = -EIO;
102 		goto error;
103 	}
104 
105 	*val = data->buf[0];
106 	ret = 0;
107 
108 error:
109 	mutex_unlock(&data->lock);
110 	return ret;
111 }
112 
113 static int ad5110_write(struct ad5110_data *data, u8 cmd, u8 val)
114 {
115 	int ret;
116 
117 	mutex_lock(&data->lock);
118 	data->buf[0] = cmd;
119 	data->buf[1] = val;
120 
121 	ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
122 	if (ret < 0) {
123 		goto error;
124 	} else if (ret != sizeof(data->buf)) {
125 		ret = -EIO;
126 		goto error;
127 	}
128 
129 	ret = 0;
130 
131 error:
132 	mutex_unlock(&data->lock);
133 	return ret;
134 }
135 
136 static int ad5110_resistor_tol(struct ad5110_data *data, u8 cmd, int val)
137 {
138 	int ret;
139 
140 	ret = ad5110_read(data, cmd, &val);
141 	if (ret)
142 		return ret;
143 
144 	data->tol = data->cfg->kohms * (val & GENMASK(6, 0)) * 10 / 8;
145 	if (!(val & BIT(7)))
146 		data->tol *= -1;
147 
148 	return 0;
149 }
150 
151 static ssize_t store_eeprom_show(struct device *dev,
152 				  struct device_attribute *attr,
153 				  char *buf)
154 {
155 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
156 	struct ad5110_data *data = iio_priv(indio_dev);
157 	int val = AD5110_WIPER_POS;
158 	int ret;
159 
160 	ret = ad5110_read(data, AD5110_EEPROM_RD, &val);
161 	if (ret)
162 		return ret;
163 
164 	val = val >> data->cfg->shift;
165 	return iio_format_value(buf, IIO_VAL_INT, 1, &val);
166 }
167 
168 static ssize_t store_eeprom_store(struct device *dev,
169 				   struct device_attribute *attr,
170 				   const char *buf, size_t len)
171 {
172 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
173 	struct ad5110_data *data = iio_priv(indio_dev);
174 	int ret;
175 
176 	ret = ad5110_write(data, AD5110_EEPROM_WR, 0);
177 	if (ret) {
178 		dev_err(&data->client->dev, "RDAC to EEPROM write failed\n");
179 		return ret;
180 	}
181 
182 	/* The storing of EEPROM data takes approximately 18 ms. */
183 	msleep(20);
184 
185 	return len;
186 }
187 
188 static IIO_DEVICE_ATTR_RW(store_eeprom, 0);
189 
190 static struct attribute *ad5110_attributes[] = {
191 	&iio_dev_attr_store_eeprom.dev_attr.attr,
192 	NULL
193 };
194 
195 static const struct attribute_group ad5110_attribute_group = {
196 	.attrs = ad5110_attributes,
197 };
198 
199 static int ad5110_read_raw(struct iio_dev *indio_dev,
200 			   struct iio_chan_spec const *chan,
201 			   int *val, int *val2, long mask)
202 {
203 	struct ad5110_data *data = iio_priv(indio_dev);
204 	int ret;
205 
206 	switch (mask) {
207 	case IIO_CHAN_INFO_RAW:
208 		ret = ad5110_read(data, AD5110_RDAC_RD, val);
209 		if (ret)
210 			return ret;
211 
212 		*val = *val >> data->cfg->shift;
213 		return IIO_VAL_INT;
214 	case IIO_CHAN_INFO_OFFSET:
215 		*val = AD5110_WIPER_RESISTANCE * data->cfg->max_pos;
216 		*val2 = 1000 * data->cfg->kohms + data->tol;
217 		return IIO_VAL_FRACTIONAL;
218 	case IIO_CHAN_INFO_SCALE:
219 		*val = 1000 * data->cfg->kohms + data->tol;
220 		*val2 = data->cfg->max_pos;
221 		return IIO_VAL_FRACTIONAL;
222 	case IIO_CHAN_INFO_ENABLE:
223 		*val = data->enable;
224 		return IIO_VAL_INT;
225 	default:
226 		return -EINVAL;
227 	}
228 }
229 
230 static int ad5110_write_raw(struct iio_dev *indio_dev,
231 			    struct iio_chan_spec const *chan,
232 			    int val, int val2, long mask)
233 {
234 	struct ad5110_data *data = iio_priv(indio_dev);
235 	int ret;
236 
237 	switch (mask) {
238 	case IIO_CHAN_INFO_RAW:
239 		if (val > data->cfg->max_pos || val < 0)
240 			return -EINVAL;
241 
242 		return ad5110_write(data, AD5110_RDAC_WR, val << data->cfg->shift);
243 	case IIO_CHAN_INFO_ENABLE:
244 		if (val < 0 || val > 1)
245 			return -EINVAL;
246 		if (data->enable == val)
247 			return 0;
248 		ret = ad5110_write(data, AD5110_SHUTDOWN, val ? 0 : 1);
249 		if (ret)
250 			return ret;
251 		data->enable = val;
252 		return 0;
253 	default:
254 		return -EINVAL;
255 	}
256 }
257 
258 static const struct iio_info ad5110_info = {
259 	.read_raw = ad5110_read_raw,
260 	.write_raw = ad5110_write_raw,
261 	.attrs = &ad5110_attribute_group,
262 };
263 
264 #define AD5110_COMPATIBLE(of_compatible, cfg) {	\
265 			.compatible = of_compatible,	\
266 			.data = &ad5110_cfg[cfg],	\
267 }
268 
269 static const struct of_device_id ad5110_of_match[] = {
270 	AD5110_COMPATIBLE("adi,ad5110-10", AD5110_10),
271 	AD5110_COMPATIBLE("adi,ad5110-80", AD5110_80),
272 	AD5110_COMPATIBLE("adi,ad5112-05", AD5112_05),
273 	AD5110_COMPATIBLE("adi,ad5112-10", AD5112_10),
274 	AD5110_COMPATIBLE("adi,ad5112-80", AD5112_80),
275 	AD5110_COMPATIBLE("adi,ad5114-10", AD5114_10),
276 	AD5110_COMPATIBLE("adi,ad5114-80", AD5114_80),
277 	{ }
278 };
279 MODULE_DEVICE_TABLE(of, ad5110_of_match);
280 
281 static const struct i2c_device_id ad5110_id[] = {
282 	{ "ad5110-10", AD5110_10 },
283 	{ "ad5110-80", AD5110_80 },
284 	{ "ad5112-05", AD5112_05 },
285 	{ "ad5112-10", AD5112_10 },
286 	{ "ad5112-80", AD5112_80 },
287 	{ "ad5114-10", AD5114_10 },
288 	{ "ad5114-80", AD5114_80 },
289 	{ }
290 };
291 MODULE_DEVICE_TABLE(i2c, ad5110_id);
292 
293 static int ad5110_probe(struct i2c_client *client)
294 {
295 	struct device *dev = &client->dev;
296 	struct iio_dev *indio_dev;
297 	struct ad5110_data *data;
298 	int ret;
299 
300 	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
301 	if (!indio_dev)
302 		return -ENOMEM;
303 
304 	data = iio_priv(indio_dev);
305 	data->client = client;
306 	mutex_init(&data->lock);
307 	data->enable = 1;
308 	data->cfg = device_get_match_data(dev);
309 
310 	/* refresh RDAC register with EEPROM */
311 	ret = ad5110_write(data, AD5110_RESET, 0);
312 	if (ret) {
313 		dev_err(dev, "Refresh RDAC with EEPROM failed\n");
314 		return ret;
315 	}
316 
317 	ret = ad5110_resistor_tol(data, AD5110_EEPROM_RD, AD5110_RESISTOR_TOL);
318 	if (ret) {
319 		dev_err(dev, "Read resistor tolerance failed\n");
320 		return ret;
321 	}
322 
323 	indio_dev->modes = INDIO_DIRECT_MODE;
324 	indio_dev->info = &ad5110_info;
325 	indio_dev->channels = ad5110_channels;
326 	indio_dev->num_channels = ARRAY_SIZE(ad5110_channels);
327 	indio_dev->name = client->name;
328 
329 	return devm_iio_device_register(dev, indio_dev);
330 }
331 
332 static struct i2c_driver ad5110_driver = {
333 	.driver = {
334 		.name	= "ad5110",
335 		.of_match_table = ad5110_of_match,
336 	},
337 	.probe_new	= ad5110_probe,
338 	.id_table	= ad5110_id,
339 };
340 module_i2c_driver(ad5110_driver);
341 
342 MODULE_AUTHOR("Mugilraj Dhavachelvan <dmugil2000@gmail.com>");
343 MODULE_DESCRIPTION("AD5110 digital potentiometer");
344 MODULE_LICENSE("GPL v2");
345