1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
4 *
5 * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
6 */
7#include <linux/module.h>
8#include <linux/mod_devicetable.h>
9#include <linux/spi/spi.h>
10
11#include <linux/iio/sysfs.h>
12#include <linux/iio/iio.h>
13
14#define MAX5487_WRITE_WIPER_A	(0x01 << 8)
15#define MAX5487_WRITE_WIPER_B	(0x02 << 8)
16
17/* copy both wiper regs to NV regs */
18#define MAX5487_COPY_AB_TO_NV	(0x23 << 8)
19/* copy both NV regs to wiper regs */
20#define MAX5487_COPY_NV_TO_AB	(0x33 << 8)
21
22#define MAX5487_MAX_POS		255
23
24struct max5487_data {
25	struct spi_device *spi;
26	int kohms;
27};
28
29#define MAX5487_CHANNEL(ch, addr) {				\
30	.type = IIO_RESISTANCE,					\
31	.indexed = 1,						\
32	.output = 1,						\
33	.channel = ch,						\
34	.address = addr,					\
35	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
36	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
37}
38
39static const struct iio_chan_spec max5487_channels[] = {
40	MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
41	MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
42};
43
44static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
45{
46	return spi_write(spi, (const void *) &cmd, sizeof(u16));
47}
48
49static int max5487_read_raw(struct iio_dev *indio_dev,
50			    struct iio_chan_spec const *chan,
51			    int *val, int *val2, long mask)
52{
53	struct max5487_data *data = iio_priv(indio_dev);
54
55	if (mask != IIO_CHAN_INFO_SCALE)
56		return -EINVAL;
57
58	*val = 1000 * data->kohms;
59	*val2 = MAX5487_MAX_POS;
60
61	return IIO_VAL_FRACTIONAL;
62}
63
64static int max5487_write_raw(struct iio_dev *indio_dev,
65			     struct iio_chan_spec const *chan,
66			     int val, int val2, long mask)
67{
68	struct max5487_data *data = iio_priv(indio_dev);
69
70	if (mask != IIO_CHAN_INFO_RAW)
71		return -EINVAL;
72
73	if (val < 0 || val > MAX5487_MAX_POS)
74		return -EINVAL;
75
76	return max5487_write_cmd(data->spi, chan->address | val);
77}
78
79static const struct iio_info max5487_info = {
80	.read_raw = max5487_read_raw,
81	.write_raw = max5487_write_raw,
82};
83
84static int max5487_spi_probe(struct spi_device *spi)
85{
86	struct iio_dev *indio_dev;
87	struct max5487_data *data;
88	const struct spi_device_id *id = spi_get_device_id(spi);
89	int ret;
90
91	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
92	if (!indio_dev)
93		return -ENOMEM;
94
95	spi_set_drvdata(spi, indio_dev);
96	data = iio_priv(indio_dev);
97
98	data->spi = spi;
99	data->kohms = id->driver_data;
100
101	indio_dev->info = &max5487_info;
102	indio_dev->name = id->name;
103	indio_dev->modes = INDIO_DIRECT_MODE;
104	indio_dev->channels = max5487_channels;
105	indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
106
107	/* restore both wiper regs from NV regs */
108	ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
109	if (ret < 0)
110		return ret;
111
112	return iio_device_register(indio_dev);
113}
114
115static void max5487_spi_remove(struct spi_device *spi)
116{
117	struct iio_dev *indio_dev = spi_get_drvdata(spi);
118	int ret;
119
120	iio_device_unregister(indio_dev);
121
122	/* save both wiper regs to NV regs */
123	ret = max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
124	if (ret)
125		dev_warn(&spi->dev, "Failed to save wiper regs to NV regs\n");
126}
127
128static const struct spi_device_id max5487_id[] = {
129	{ "MAX5487", 10 },
130	{ "MAX5488", 50 },
131	{ "MAX5489", 100 },
132	{ }
133};
134MODULE_DEVICE_TABLE(spi, max5487_id);
135
136static const struct acpi_device_id max5487_acpi_match[] = {
137	{ "MAX5487", 10 },
138	{ "MAX5488", 50 },
139	{ "MAX5489", 100 },
140	{ },
141};
142MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
143
144static struct spi_driver max5487_driver = {
145	.driver = {
146		.name = "max5487",
147		.acpi_match_table = max5487_acpi_match,
148	},
149	.id_table = max5487_id,
150	.probe = max5487_spi_probe,
151	.remove = max5487_spi_remove
152};
153module_spi_driver(max5487_driver);
154
155MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
156MODULE_DESCRIPTION("max5487 SPI driver");
157MODULE_LICENSE("GPL v2");
158