1 /*
2  * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
3  *
4  * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  */
11 #include <linux/module.h>
12 #include <linux/spi/spi.h>
13 #include <linux/acpi.h>
14 
15 #include <linux/iio/sysfs.h>
16 #include <linux/iio/iio.h>
17 
18 #define MAX5487_WRITE_WIPER_A	(0x01 << 8)
19 #define MAX5487_WRITE_WIPER_B	(0x02 << 8)
20 
21 /* copy both wiper regs to NV regs */
22 #define MAX5487_COPY_AB_TO_NV	(0x23 << 8)
23 /* copy both NV regs to wiper regs */
24 #define MAX5487_COPY_NV_TO_AB	(0x33 << 8)
25 
26 #define MAX5487_MAX_POS		255
27 
28 struct max5487_data {
29 	struct spi_device *spi;
30 	int kohms;
31 };
32 
33 #define MAX5487_CHANNEL(ch, addr) {				\
34 	.type = IIO_RESISTANCE,					\
35 	.indexed = 1,						\
36 	.output = 1,						\
37 	.channel = ch,						\
38 	.address = addr,					\
39 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
40 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
41 }
42 
43 static const struct iio_chan_spec max5487_channels[] = {
44 	MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
45 	MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
46 };
47 
48 static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
49 {
50 	return spi_write(spi, (const void *) &cmd, sizeof(u16));
51 }
52 
53 static int max5487_read_raw(struct iio_dev *indio_dev,
54 			    struct iio_chan_spec const *chan,
55 			    int *val, int *val2, long mask)
56 {
57 	struct max5487_data *data = iio_priv(indio_dev);
58 
59 	if (mask != IIO_CHAN_INFO_SCALE)
60 		return -EINVAL;
61 
62 	*val = 1000 * data->kohms;
63 	*val2 = MAX5487_MAX_POS;
64 
65 	return IIO_VAL_FRACTIONAL;
66 }
67 
68 static int max5487_write_raw(struct iio_dev *indio_dev,
69 			     struct iio_chan_spec const *chan,
70 			     int val, int val2, long mask)
71 {
72 	struct max5487_data *data = iio_priv(indio_dev);
73 
74 	if (mask != IIO_CHAN_INFO_RAW)
75 		return -EINVAL;
76 
77 	if (val < 0 || val > MAX5487_MAX_POS)
78 		return -EINVAL;
79 
80 	return max5487_write_cmd(data->spi, chan->address | val);
81 }
82 
83 static const struct iio_info max5487_info = {
84 	.read_raw = max5487_read_raw,
85 	.write_raw = max5487_write_raw,
86 	.driver_module = THIS_MODULE,
87 };
88 
89 static int max5487_spi_probe(struct spi_device *spi)
90 {
91 	struct iio_dev *indio_dev;
92 	struct max5487_data *data;
93 	const struct spi_device_id *id = spi_get_device_id(spi);
94 	int ret;
95 
96 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
97 	if (!indio_dev)
98 		return -ENOMEM;
99 
100 	dev_set_drvdata(&spi->dev, indio_dev);
101 	data = iio_priv(indio_dev);
102 
103 	data->spi = spi;
104 	data->kohms = id->driver_data;
105 
106 	indio_dev->info = &max5487_info;
107 	indio_dev->name = id->name;
108 	indio_dev->dev.parent = &spi->dev;
109 	indio_dev->modes = INDIO_DIRECT_MODE;
110 	indio_dev->channels = max5487_channels;
111 	indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
112 
113 	/* restore both wiper regs from NV regs */
114 	ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
115 	if (ret < 0)
116 		return ret;
117 
118 	return iio_device_register(indio_dev);
119 }
120 
121 static int max5487_spi_remove(struct spi_device *spi)
122 {
123 	struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
124 
125 	iio_device_unregister(indio_dev);
126 
127 	/* save both wiper regs to NV regs */
128 	return max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
129 }
130 
131 static const struct spi_device_id max5487_id[] = {
132 	{ "MAX5487", 10 },
133 	{ "MAX5488", 50 },
134 	{ "MAX5489", 100 },
135 	{ }
136 };
137 MODULE_DEVICE_TABLE(spi, max5487_id);
138 
139 static const struct acpi_device_id max5487_acpi_match[] = {
140 	{ "MAX5487", 10 },
141 	{ "MAX5488", 50 },
142 	{ "MAX5489", 100 },
143 	{ },
144 };
145 MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
146 
147 static struct spi_driver max5487_driver = {
148 	.driver = {
149 		.name = "max5487",
150 		.owner = THIS_MODULE,
151 		.acpi_match_table = ACPI_PTR(max5487_acpi_match),
152 	},
153 	.id_table = max5487_id,
154 	.probe = max5487_spi_probe,
155 	.remove = max5487_spi_remove
156 };
157 module_spi_driver(max5487_driver);
158 
159 MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
160 MODULE_DESCRIPTION("max5487 SPI driver");
161 MODULE_LICENSE("GPL v2");
162