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