summaryrefslogtreecommitdiffstats
path: root/drivers/iio/dac/dpot-dac.c
blob: be61c3b01e8b1afe9555fe8f51c1ae116e4b999f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
// SPDX-License-Identifier: GPL-2.0
/*
 * IIO DAC emulation driver using a digital potentiometer
 *
 * Copyright (C) 2016 Axentia Technologies AB
 *
 * Author: Peter Rosin <peda@axentia.se>
 */

/*
 * It is assumed that the dpot is used as a voltage divider between the
 * current dpot wiper setting and the maximum resistance of the dpot. The
 * divided voltage is provided by a vref regulator.
 *
 *                   .------.
 *    .-----------.  |      |
 *    | vref      |--'    .---.
 *    | regulator |--.    |   |
 *    '-----------'  |    | d |
 *                   |    | p |
 *                   |    | o |  wiper
 *                   |    | t |<---------+
 *                   |    |   |
 *                   |    '---'       dac output voltage
 *                   |      |
 *                   '------+------------+
 */

#include <linux/err.h>
#include <linux/iio/consumer.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regulator/consumer.h>

struct dpot_dac {
	struct regulator *vref;
	struct iio_channel *dpot;
	u32 max_ohms;
};

static const struct iio_chan_spec dpot_dac_iio_channel = {
	.type = IIO_VOLTAGE,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
			    | BIT(IIO_CHAN_INFO_SCALE),
	.info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),
	.output = 1,
	.indexed = 1,
};

static int dpot_dac_read_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int *val, int *val2, long mask)
{
	struct dpot_dac *dac = iio_priv(indio_dev);
	int ret;
	unsigned long long tmp;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		return iio_read_channel_raw(dac->dpot, val);

	case IIO_CHAN_INFO_SCALE:
		ret = iio_read_channel_scale(dac->dpot, val, val2);
		switch (ret) {
		case IIO_VAL_FRACTIONAL_LOG2:
			tmp = *val * 1000000000LL;
			do_div(tmp, dac->max_ohms);
			tmp *= regulator_get_voltage(dac->vref) / 1000;
			do_div(tmp, 1000000000LL);
			*val = tmp;
			return ret;
		case IIO_VAL_INT:
			/*
			 * Convert integer scale to fractional scale by
			 * setting the denominator (val2) to one, and...
			 */
			*val2 = 1;
			ret = IIO_VAL_FRACTIONAL;
			fallthrough;
		case IIO_VAL_FRACTIONAL:
			*val *= regulator_get_voltage(dac->vref) / 1000;
			*val2 *= dac->max_ohms;
			break;
		}

		return ret;
	}

	return -EINVAL;
}

static int dpot_dac_read_avail(struct iio_dev *indio_dev,
			       struct iio_chan_spec const *chan,
			       const int **vals, int *type, int *length,
			       long mask)
{
	struct dpot_dac *dac = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		*type = IIO_VAL_INT;
		return iio_read_avail_channel_raw(dac->dpot, vals, length);
	}

	return -EINVAL;
}

static int dpot_dac_write_raw(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan,
			      int val, int val2, long mask)
{
	struct dpot_dac *dac = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		return iio_write_channel_raw(dac->dpot, val);
	}

	return -EINVAL;
}

static const struct iio_info dpot_dac_info = {
	.read_raw = dpot_dac_read_raw,
	.read_avail = dpot_dac_read_avail,
	.write_raw = dpot_dac_write_raw,
};

static int dpot_dac_channel_max_ohms(struct iio_dev *indio_dev)
{
	struct device *dev = &indio_dev->dev;
	struct dpot_dac *dac = iio_priv(indio_dev);
	unsigned long long tmp;
	int ret;
	int val;
	int val2;
	int max;

	ret = iio_read_max_channel_raw(dac->dpot, &max);
	if (ret < 0) {
		dev_err(dev, "dpot does not indicate its raw maximum value\n");
		return ret;
	}

	switch (iio_read_channel_scale(dac->dpot, &val, &val2)) {
	case IIO_VAL_INT:
		return max * val;
	case IIO_VAL_FRACTIONAL:
		tmp = (unsigned long long)max * val;
		do_div(tmp, val2);
		return tmp;
	case IIO_VAL_FRACTIONAL_LOG2:
		tmp = val * 1000000000LL * max >> val2;
		do_div(tmp, 1000000000LL);
		return tmp;
	default:
		dev_err(dev, "dpot has a scale that is too weird\n");
	}

	return -EINVAL;
}

static int dpot_dac_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct iio_dev *indio_dev;
	struct dpot_dac *dac;
	enum iio_chan_type type;
	int ret;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*dac));
	if (!indio_dev)
		return -ENOMEM;

	platform_set_drvdata(pdev, indio_dev);
	dac = iio_priv(indio_dev);

	indio_dev->name = dev_name(dev);
	indio_dev->info = &dpot_dac_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = &dpot_dac_iio_channel;
	indio_dev->num_channels = 1;

	dac->vref = devm_regulator_get(dev, "vref");
	if (IS_ERR(dac->vref)) {
		if (PTR_ERR(dac->vref) != -EPROBE_DEFER)
			dev_err(&pdev->dev, "failed to get vref regulator\n");
		return PTR_ERR(dac->vref);
	}

	dac->dpot = devm_iio_channel_get(dev, "dpot");
	if (IS_ERR(dac->dpot)) {
		if (PTR_ERR(dac->dpot) != -EPROBE_DEFER)
			dev_err(dev, "failed to get dpot input channel\n");
		return PTR_ERR(dac->dpot);
	}

	ret = iio_get_channel_type(dac->dpot, &type);
	if (ret < 0)
		return ret;

	if (type != IIO_RESISTANCE) {
		dev_err(dev, "dpot is of the wrong type\n");
		return -EINVAL;
	}

	ret = dpot_dac_channel_max_ohms(indio_dev);
	if (ret < 0)
		return ret;
	dac->max_ohms = ret;

	ret = regulator_enable(dac->vref);
	if (ret) {
		dev_err(dev, "failed to enable the vref regulator\n");
		return ret;
	}

	ret = iio_device_register(indio_dev);
	if (ret) {
		dev_err(dev, "failed to register iio device\n");
		goto disable_reg;
	}

	return 0;

disable_reg:
	regulator_disable(dac->vref);
	return ret;
}

static int dpot_dac_remove(struct platform_device *pdev)
{
	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
	struct dpot_dac *dac = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);
	regulator_disable(dac->vref);

	return 0;
}

static const struct of_device_id dpot_dac_match[] = {
	{ .compatible = "dpot-dac" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, dpot_dac_match);

static struct platform_driver dpot_dac_driver = {
	.probe = dpot_dac_probe,
	.remove = dpot_dac_remove,
	.driver = {
		.name = "iio-dpot-dac",
		.of_match_table = dpot_dac_match,
	},
};
module_platform_driver(dpot_dac_driver);

MODULE_DESCRIPTION("DAC emulation driver using a digital potentiometer");
MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
MODULE_LICENSE("GPL v2");