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
max5481_write_cmd(struct max5481_data * data,u8 cmd,u16 val)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
max5481_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)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
max5481_write_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int val,int val2,long mask)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
max5481_wiper_save(void * data)128 static void max5481_wiper_save(void *data)
129 {
130 max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
131 }
132
max5481_probe(struct spi_device * spi)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