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// 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");
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