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/spi/spi.h>
9 #include <linux/acpi.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 
24 struct 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 
39 static 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 
44 static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
45 {
46 	return spi_write(spi, (const void *) &cmd, sizeof(u16));
47 }
48 
49 static 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 
64 static 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 
79 static const struct iio_info max5487_info = {
80 	.read_raw = max5487_read_raw,
81 	.write_raw = max5487_write_raw,
82 };
83 
84 static 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 
115 static 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 
128 static const struct spi_device_id max5487_id[] = {
129 	{ "MAX5487", 10 },
130 	{ "MAX5488", 50 },
131 	{ "MAX5489", 100 },
132 	{ }
133 };
134 MODULE_DEVICE_TABLE(spi, max5487_id);
135 
136 static const struct acpi_device_id max5487_acpi_match[] = {
137 	{ "MAX5487", 10 },
138 	{ "MAX5488", 50 },
139 	{ "MAX5489", 100 },
140 	{ },
141 };
142 MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
143 
144 static struct spi_driver max5487_driver = {
145 	.driver = {
146 		.name = "max5487",
147 		.acpi_match_table = ACPI_PTR(max5487_acpi_match),
148 	},
149 	.id_table = max5487_id,
150 	.probe = max5487_spi_probe,
151 	.remove = max5487_spi_remove
152 };
153 module_spi_driver(max5487_driver);
154 
155 MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
156 MODULE_DESCRIPTION("max5487 SPI driver");
157 MODULE_LICENSE("GPL v2");
158