1// SPDX-License-Identifier: GPL-2.0
2/*
3 * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
4 *
5 * Datasheet:
6 * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
7 *
8 * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
9 */
10#include <linux/bitfield.h>
11#include <linux/i2c.h>
12#include <linux/iio/iio.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/mutex.h>
16#include <linux/regulator/consumer.h>
17
18#define LTC2309_ADC_RESOLUTION	12
19
20#define LTC2309_DIN_CH_MASK	GENMASK(7, 4)
21#define LTC2309_DIN_SDN		BIT(7)
22#define LTC2309_DIN_OSN		BIT(6)
23#define LTC2309_DIN_S1		BIT(5)
24#define LTC2309_DIN_S0		BIT(4)
25#define LTC2309_DIN_UNI		BIT(3)
26#define LTC2309_DIN_SLEEP	BIT(2)
27
28/**
29 * struct ltc2309 - internal device data structure
30 * @dev:	Device reference
31 * @client:	I2C reference
32 * @vref:	External reference source
33 * @lock:	Lock to serialize data access
34 * @vref_mv:	Internal voltage reference
35 */
36struct ltc2309 {
37	struct device		*dev;
38	struct i2c_client	*client;
39	struct regulator	*vref;
40	struct mutex		lock; /* serialize data access */
41	int			vref_mv;
42};
43
44/* Order matches expected channel address, See datasheet Table 1. */
45enum ltc2309_channels {
46	LTC2309_CH0_CH1 = 0,
47	LTC2309_CH2_CH3,
48	LTC2309_CH4_CH5,
49	LTC2309_CH6_CH7,
50	LTC2309_CH1_CH0,
51	LTC2309_CH3_CH2,
52	LTC2309_CH5_CH4,
53	LTC2309_CH7_CH6,
54	LTC2309_CH0,
55	LTC2309_CH2,
56	LTC2309_CH4,
57	LTC2309_CH6,
58	LTC2309_CH1,
59	LTC2309_CH3,
60	LTC2309_CH5,
61	LTC2309_CH7,
62};
63
64#define LTC2309_CHAN(_chan, _addr) {				\
65	.type = IIO_VOLTAGE,					\
66	.indexed = 1,						\
67	.address = _addr,					\
68	.channel = _chan,					\
69	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
70	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
71}
72
73#define LTC2309_DIFF_CHAN(_chan, _chan2, _addr) {		\
74	.type = IIO_VOLTAGE,					\
75	.differential = 1,					\
76	.indexed = 1,						\
77	.address = _addr,					\
78	.channel = _chan,					\
79	.channel2 = _chan2,					\
80	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
81	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
82}
83
84static const struct iio_chan_spec ltc2309_channels[] = {
85	LTC2309_CHAN(0, LTC2309_CH0),
86	LTC2309_CHAN(1, LTC2309_CH1),
87	LTC2309_CHAN(2, LTC2309_CH2),
88	LTC2309_CHAN(3, LTC2309_CH3),
89	LTC2309_CHAN(4, LTC2309_CH4),
90	LTC2309_CHAN(5, LTC2309_CH5),
91	LTC2309_CHAN(6, LTC2309_CH6),
92	LTC2309_CHAN(7, LTC2309_CH7),
93	LTC2309_DIFF_CHAN(0, 1, LTC2309_CH0_CH1),
94	LTC2309_DIFF_CHAN(2, 3, LTC2309_CH2_CH3),
95	LTC2309_DIFF_CHAN(4, 5, LTC2309_CH4_CH5),
96	LTC2309_DIFF_CHAN(6, 7, LTC2309_CH6_CH7),
97	LTC2309_DIFF_CHAN(1, 0, LTC2309_CH1_CH0),
98	LTC2309_DIFF_CHAN(3, 2, LTC2309_CH3_CH2),
99	LTC2309_DIFF_CHAN(5, 4, LTC2309_CH5_CH4),
100	LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
101};
102
103static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
104				    unsigned long address, int *val)
105{
106	int ret;
107	u16 buf;
108	u8 din;
109
110	din = FIELD_PREP(LTC2309_DIN_CH_MASK, address & 0x0f) |
111		FIELD_PREP(LTC2309_DIN_UNI, 1) |
112		FIELD_PREP(LTC2309_DIN_SLEEP, 0);
113
114	ret = i2c_smbus_write_byte(ltc2309->client, din);
115	if (ret < 0) {
116		dev_err(ltc2309->dev, "i2c command failed: %pe\n",
117			ERR_PTR(ret));
118		return ret;
119	}
120
121	ret = i2c_master_recv(ltc2309->client, (char *)&buf, 2);
122	if (ret < 0) {
123		dev_err(ltc2309->dev, "i2c read failed: %pe\n", ERR_PTR(ret));
124		return ret;
125	}
126
127	*val = be16_to_cpu(buf) >> 4;
128
129	return ret;
130}
131
132static int ltc2309_read_raw(struct iio_dev *indio_dev,
133			    struct iio_chan_spec const *chan, int *val,
134			    int *val2, long mask)
135{
136	struct ltc2309 *ltc2309 = iio_priv(indio_dev);
137	int ret;
138
139	switch (mask) {
140	case IIO_CHAN_INFO_RAW:
141		mutex_lock(&ltc2309->lock);
142		ret = ltc2309_read_raw_channel(ltc2309, chan->address, val);
143		mutex_unlock(&ltc2309->lock);
144		if (ret < 0)
145			return -EINVAL;
146		return IIO_VAL_INT;
147	case IIO_CHAN_INFO_SCALE:
148		*val = ltc2309->vref_mv;
149		*val2 = LTC2309_ADC_RESOLUTION;
150		return IIO_VAL_FRACTIONAL_LOG2;
151	default:
152		return -EINVAL;
153	}
154}
155
156static const struct iio_info ltc2309_info = {
157	.read_raw = ltc2309_read_raw,
158};
159
160static void ltc2309_regulator_disable(void *regulator)
161{
162	regulator_disable(regulator);
163}
164
165static int ltc2309_probe(struct i2c_client *client)
166{
167	struct iio_dev *indio_dev;
168	struct ltc2309 *ltc2309;
169	int ret;
170
171	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
172	if (!indio_dev)
173		return -ENOMEM;
174
175	ltc2309 = iio_priv(indio_dev);
176	ltc2309->dev = &indio_dev->dev;
177	ltc2309->client = client;
178	ltc2309->vref_mv = 4096; /* Default to the internal ref */
179
180	indio_dev->name = "ltc2309";
181	indio_dev->modes = INDIO_DIRECT_MODE;
182	indio_dev->channels = ltc2309_channels;
183	indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
184	indio_dev->info = &ltc2309_info;
185
186	ltc2309->vref = devm_regulator_get_optional(&client->dev, "vref");
187	if (IS_ERR(ltc2309->vref)) {
188		ret = PTR_ERR(ltc2309->vref);
189		if (ret == -ENODEV)
190			ltc2309->vref = NULL;
191		else
192			return ret;
193	}
194
195	if (ltc2309->vref) {
196		ret = regulator_enable(ltc2309->vref);
197		if (ret)
198			return dev_err_probe(ltc2309->dev, ret,
199					     "failed to enable vref\n");
200
201		ret = devm_add_action_or_reset(ltc2309->dev,
202					       ltc2309_regulator_disable,
203					       ltc2309->vref);
204		if (ret) {
205			return dev_err_probe(ltc2309->dev, ret,
206					     "failed to add regulator_disable action: %d\n",
207					     ret);
208		}
209
210		ret = regulator_get_voltage(ltc2309->vref);
211		if (ret < 0)
212			return ret;
213
214		ltc2309->vref_mv = ret / 1000;
215	}
216
217	mutex_init(&ltc2309->lock);
218
219	return devm_iio_device_register(&client->dev, indio_dev);
220}
221
222static const struct of_device_id ltc2309_of_match[] = {
223	{ .compatible = "lltc,ltc2309" },
224	{ }
225};
226MODULE_DEVICE_TABLE(of, ltc2309_of_match);
227
228static const struct i2c_device_id ltc2309_id[] = {
229	{ "ltc2309" },
230	{ }
231};
232MODULE_DEVICE_TABLE(i2c, ltc2309_id);
233
234static struct i2c_driver ltc2309_driver = {
235	.driver = {
236		.name = "ltc2309",
237		.of_match_table = ltc2309_of_match,
238	},
239	.probe		= ltc2309_probe,
240	.id_table	= ltc2309_id,
241};
242module_i2c_driver(ltc2309_driver);
243
244MODULE_AUTHOR("Liam Beguin <liambeguin@gmail.com>");
245MODULE_DESCRIPTION("Linear Technology LTC2309 ADC");
246MODULE_LICENSE("GPL v2");
247