diff options
Diffstat (limited to 'drivers/iio/potentiometer/max5481.c')
| -rw-r--r-- | drivers/iio/potentiometer/max5481.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/drivers/iio/potentiometer/max5481.c b/drivers/iio/potentiometer/max5481.c new file mode 100644 index 000000000..b40e5ac21 --- /dev/null +++ b/drivers/iio/potentiometer/max5481.c @@ -0,0 +1,194 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver + * Copyright 2016 Rockwell Collins + * + * Datasheet: + * https://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf + */ + +#include <linux/iio/iio.h> +#include <linux/iio/sysfs.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/property.h> +#include <linux/spi/spi.h> + +/* write wiper reg */ +#define MAX5481_WRITE_WIPER (0 << 4) +/* copy wiper reg to NV reg */ +#define MAX5481_COPY_AB_TO_NV (2 << 4) +/* copy NV reg to wiper reg */ +#define MAX5481_COPY_NV_TO_AB (3 << 4) + +#define MAX5481_MAX_POS 1023 + +enum max5481_variant { + max5481, + max5482, + max5483, + max5484, +}; + +struct max5481_cfg { + int kohms; +}; + +static const struct max5481_cfg max5481_cfg[] = { + [max5481] = { .kohms = 10, }, + [max5482] = { .kohms = 50, }, + [max5483] = { .kohms = 10, }, + [max5484] = { .kohms = 50, }, +}; + +struct max5481_data { + struct spi_device *spi; + const struct max5481_cfg *cfg; + u8 msg[3] __aligned(IIO_DMA_MINALIGN); +}; + +#define MAX5481_CHANNEL { \ + .type = IIO_RESISTANCE, \ + .indexed = 1, \ + .output = 1, \ + .channel = 0, \ + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \ +} + +static const struct iio_chan_spec max5481_channels[] = { + MAX5481_CHANNEL, +}; + +static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val) +{ + struct spi_device *spi = data->spi; + + data->msg[0] = cmd; + + switch (cmd) { + case MAX5481_WRITE_WIPER: + data->msg[1] = val >> 2; + data->msg[2] = (val & 0x3) << 6; + return spi_write(spi, data->msg, 3); + + case MAX5481_COPY_AB_TO_NV: + case MAX5481_COPY_NV_TO_AB: + return spi_write(spi, data->msg, 1); + + default: + return -EIO; + } +} + +static int max5481_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int *val, int *val2, long mask) +{ + struct max5481_data *data = iio_priv(indio_dev); + + if (mask != IIO_CHAN_INFO_SCALE) + return -EINVAL; + + *val = 1000 * data->cfg->kohms; + *val2 = MAX5481_MAX_POS; + + return IIO_VAL_FRACTIONAL; +} + +static int max5481_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int val, int val2, long mask) +{ + struct max5481_data *data = iio_priv(indio_dev); + + if (mask != IIO_CHAN_INFO_RAW) + return -EINVAL; + + if (val < 0 || val > MAX5481_MAX_POS) + return -EINVAL; + + return max5481_write_cmd(data, MAX5481_WRITE_WIPER, val); +} + +static const struct iio_info max5481_info = { + .read_raw = max5481_read_raw, + .write_raw = max5481_write_raw, +}; + +static const struct of_device_id max5481_match[] = { + { .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] }, + { .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] }, + { .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] }, + { .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] }, + { } +}; +MODULE_DEVICE_TABLE(of, max5481_match); + +static void max5481_wiper_save(void *data) +{ + max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0); +} + +static int max5481_probe(struct spi_device *spi) +{ + struct iio_dev *indio_dev; + struct max5481_data *data; + const struct spi_device_id *id = spi_get_device_id(spi); + int ret; + + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data)); + if (!indio_dev) + return -ENOMEM; + + data = iio_priv(indio_dev); + + data->spi = spi; + + data->cfg = device_get_match_data(&spi->dev); + if (!data->cfg) + data->cfg = &max5481_cfg[id->driver_data]; + + indio_dev->name = id->name; + indio_dev->modes = INDIO_DIRECT_MODE; + + /* variant specific configuration */ + indio_dev->info = &max5481_info; + indio_dev->channels = max5481_channels; + indio_dev->num_channels = ARRAY_SIZE(max5481_channels); + + /* restore wiper from NV */ + ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0); + if (ret < 0) + return ret; + + ret = devm_add_action(&spi->dev, max5481_wiper_save, data); + if (ret < 0) + return ret; + + return devm_iio_device_register(&spi->dev, indio_dev); +} + +static const struct spi_device_id max5481_id_table[] = { + { "max5481", max5481 }, + { "max5482", max5482 }, + { "max5483", max5483 }, + { "max5484", max5484 }, + { } +}; +MODULE_DEVICE_TABLE(spi, max5481_id_table); + +static struct spi_driver max5481_driver = { + .driver = { + .name = "max5481", + .of_match_table = max5481_match, + }, + .probe = max5481_probe, + .id_table = max5481_id_table, +}; + +module_spi_driver(max5481_driver); + +MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>"); +MODULE_DESCRIPTION("max5481 SPI driver"); +MODULE_LICENSE("GPL v2"); |