1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver
4  * Copyright 2016 Rockwell Collins
5  *
6  * Datasheet:
7  * https://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
8  */
9 
10 #include <linux/iio/iio.h>
11 #include <linux/iio/sysfs.h>
12 #include <linux/module.h>
13 #include <linux/mod_devicetable.h>
14 #include <linux/property.h>
15 #include <linux/spi/spi.h>
16 
17 /* write wiper reg */
18 #define MAX5481_WRITE_WIPER (0 << 4)
19 /* copy wiper reg to NV reg */
20 #define MAX5481_COPY_AB_TO_NV (2 << 4)
21 /* copy NV reg to wiper reg */
22 #define MAX5481_COPY_NV_TO_AB (3 << 4)
23 
24 #define MAX5481_MAX_POS    1023
25 
26 enum max5481_variant {
27 	max5481,
28 	max5482,
29 	max5483,
30 	max5484,
31 };
32 
33 struct max5481_cfg {
34 	int kohms;
35 };
36 
37 static const struct max5481_cfg max5481_cfg[] = {
38 	[max5481] = { .kohms =  10, },
39 	[max5482] = { .kohms =  50, },
40 	[max5483] = { .kohms =  10, },
41 	[max5484] = { .kohms =  50, },
42 };
43 
44 struct max5481_data {
45 	struct spi_device *spi;
46 	const struct max5481_cfg *cfg;
47 	u8 msg[3] __aligned(IIO_DMA_MINALIGN);
48 };
49 
50 #define MAX5481_CHANNEL {					\
51 	.type = IIO_RESISTANCE,					\
52 	.indexed = 1,						\
53 	.output = 1,						\
54 	.channel = 0,						\
55 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
56 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
57 }
58 
59 static const struct iio_chan_spec max5481_channels[] = {
60 	MAX5481_CHANNEL,
61 };
62 
63 static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val)
64 {
65 	struct spi_device *spi = data->spi;
66 
67 	data->msg[0] = cmd;
68 
69 	switch (cmd) {
70 	case MAX5481_WRITE_WIPER:
71 		data->msg[1] = val >> 2;
72 		data->msg[2] = (val & 0x3) << 6;
73 		return spi_write(spi, data->msg, 3);
74 
75 	case MAX5481_COPY_AB_TO_NV:
76 	case MAX5481_COPY_NV_TO_AB:
77 		return spi_write(spi, data->msg, 1);
78 
79 	default:
80 		return -EIO;
81 	}
82 }
83 
84 static int max5481_read_raw(struct iio_dev *indio_dev,
85 		struct iio_chan_spec const *chan,
86 		int *val, int *val2, long mask)
87 {
88 	struct max5481_data *data = iio_priv(indio_dev);
89 
90 	if (mask != IIO_CHAN_INFO_SCALE)
91 		return -EINVAL;
92 
93 	*val = 1000 * data->cfg->kohms;
94 	*val2 = MAX5481_MAX_POS;
95 
96 	return IIO_VAL_FRACTIONAL;
97 }
98 
99 static int max5481_write_raw(struct iio_dev *indio_dev,
100 		struct iio_chan_spec const *chan,
101 		int val, int val2, long mask)
102 {
103 	struct max5481_data *data = iio_priv(indio_dev);
104 
105 	if (mask != IIO_CHAN_INFO_RAW)
106 		return -EINVAL;
107 
108 	if (val < 0 || val > MAX5481_MAX_POS)
109 		return -EINVAL;
110 
111 	return max5481_write_cmd(data, MAX5481_WRITE_WIPER, val);
112 }
113 
114 static const struct iio_info max5481_info = {
115 	.read_raw = max5481_read_raw,
116 	.write_raw = max5481_write_raw,
117 };
118 
119 static const struct of_device_id max5481_match[] = {
120 	{ .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] },
121 	{ .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] },
122 	{ .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] },
123 	{ .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] },
124 	{ }
125 };
126 MODULE_DEVICE_TABLE(of, max5481_match);
127 
128 static void max5481_wiper_save(void *data)
129 {
130 	max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
131 }
132 
133 static int max5481_probe(struct spi_device *spi)
134 {
135 	struct iio_dev *indio_dev;
136 	struct max5481_data *data;
137 	const struct spi_device_id *id = spi_get_device_id(spi);
138 	int ret;
139 
140 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
141 	if (!indio_dev)
142 		return -ENOMEM;
143 
144 	data = iio_priv(indio_dev);
145 
146 	data->spi = spi;
147 
148 	data->cfg = device_get_match_data(&spi->dev);
149 	if (!data->cfg)
150 		data->cfg = &max5481_cfg[id->driver_data];
151 
152 	indio_dev->name = id->name;
153 	indio_dev->modes = INDIO_DIRECT_MODE;
154 
155 	/* variant specific configuration */
156 	indio_dev->info = &max5481_info;
157 	indio_dev->channels = max5481_channels;
158 	indio_dev->num_channels = ARRAY_SIZE(max5481_channels);
159 
160 	/* restore wiper from NV */
161 	ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0);
162 	if (ret < 0)
163 		return ret;
164 
165 	ret = devm_add_action(&spi->dev, max5481_wiper_save, data);
166 	if (ret < 0)
167 		return ret;
168 
169 	return devm_iio_device_register(&spi->dev, indio_dev);
170 }
171 
172 static const struct spi_device_id max5481_id_table[] = {
173 	{ "max5481", max5481 },
174 	{ "max5482", max5482 },
175 	{ "max5483", max5483 },
176 	{ "max5484", max5484 },
177 	{ }
178 };
179 MODULE_DEVICE_TABLE(spi, max5481_id_table);
180 
181 static struct spi_driver max5481_driver = {
182 	.driver = {
183 		.name  = "max5481",
184 		.of_match_table = max5481_match,
185 	},
186 	.probe = max5481_probe,
187 	.id_table = max5481_id_table,
188 };
189 
190 module_spi_driver(max5481_driver);
191 
192 MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>");
193 MODULE_DESCRIPTION("max5481 SPI driver");
194 MODULE_LICENSE("GPL v2");
195