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] ____cacheline_aligned; 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 int max5481_probe(struct spi_device *spi) 129 { 130 struct iio_dev *indio_dev; 131 struct max5481_data *data; 132 const struct spi_device_id *id = spi_get_device_id(spi); 133 int ret; 134 135 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data)); 136 if (!indio_dev) 137 return -ENOMEM; 138 139 dev_set_drvdata(&spi->dev, indio_dev); 140 data = iio_priv(indio_dev); 141 142 data->spi = spi; 143 144 data->cfg = device_get_match_data(&spi->dev); 145 if (!data->cfg) 146 data->cfg = &max5481_cfg[id->driver_data]; 147 148 indio_dev->name = id->name; 149 indio_dev->modes = INDIO_DIRECT_MODE; 150 151 /* variant specific configuration */ 152 indio_dev->info = &max5481_info; 153 indio_dev->channels = max5481_channels; 154 indio_dev->num_channels = ARRAY_SIZE(max5481_channels); 155 156 /* restore wiper from NV */ 157 ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0); 158 if (ret < 0) 159 return ret; 160 161 return iio_device_register(indio_dev); 162 } 163 164 static int max5481_remove(struct spi_device *spi) 165 { 166 struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev); 167 struct max5481_data *data = iio_priv(indio_dev); 168 169 iio_device_unregister(indio_dev); 170 171 /* save wiper reg to NV reg */ 172 return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0); 173 } 174 175 static const struct spi_device_id max5481_id_table[] = { 176 { "max5481", max5481 }, 177 { "max5482", max5482 }, 178 { "max5483", max5483 }, 179 { "max5484", max5484 }, 180 { } 181 }; 182 MODULE_DEVICE_TABLE(spi, max5481_id_table); 183 184 static struct spi_driver max5481_driver = { 185 .driver = { 186 .name = "max5481", 187 .of_match_table = max5481_match, 188 }, 189 .probe = max5481_probe, 190 .remove = max5481_remove, 191 .id_table = max5481_id_table, 192 }; 193 194 module_spi_driver(max5481_driver); 195 196 MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>"); 197 MODULE_DESCRIPTION("max5481 SPI driver"); 198 MODULE_LICENSE("GPL v2"); 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