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