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iio: max5481: Add support for Maxim digital potentiometers 

Add implementation for Maxim Integrated 5481, 5482, 5483,
and 5484 digital potentiometer devices.

Datasheet:
http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf

Signed-off-by: Maury Anderson <maury.anderson@rockwellcollins.com>
Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Slawomir Stepien <sst@poczta.fm>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Matt Weber 2017-01-26 21:26:15 +01:00 committed by Jonathan Cameron
parent ba34b3a2df
commit df1fd2de11
4 changed files with 258 additions and 0 deletions
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23
Documentation/devicetree/bindings/iio/potentiometer/max5481.txt Normal file
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@ -0,0 +1,23 @@
* Maxim Linear-Taper Digital Potentiometer MAX5481-MAX5484
The node for this driver must be a child node of a SPI controller, hence
all mandatory properties described in
Documentation/devicetree/bindings/spi/spi-bus.txt
must be specified.
Required properties:
- compatible: Must be one of the following, depending on the
model:
"maxim,max5481"
"maxim,max5482"
"maxim,max5483"
"maxim,max5484"
Example:
max548x: max548x@0 {
compatible = "maxim,max5482";
spi-max-frequency = <7000000>;
reg = <0>; /* chip-select */
};

11
drivers/iio/potentiometer/Kconfig
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@ -15,6 +15,17 @@ config DS1803
To compile this driver as a module, choose M here: the
module will be called ds1803.
config MAX5481
tristate "Maxim MAX5481-MAX5484 Digital Potentiometer driver"
depends on SPI
help
Say yes here to build support for the Maxim
MAX5481, MAX5482, MAX5483, MAX5484 digital potentiometer
chips.
To compile this driver as a module, choose M here: the
module will be called max5481.
config MAX5487
tristate "Maxim MAX5487/MAX5488/MAX5489 Digital Potentiometer driver"
depends on SPI

1
drivers/iio/potentiometer/Makefile
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@ -4,6 +4,7 @@
# When adding new entries keep the list in alphabetical order
obj-$(CONFIG_DS1803) += ds1803.o
obj-$(CONFIG_MAX5481) += max5481.o
obj-$(CONFIG_MAX5487) += max5487.o
obj-$(CONFIG_MCP4131) += mcp4131.o
obj-$(CONFIG_MCP4531) += mcp4531.o

223
drivers/iio/potentiometer/max5481.c Normal file
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@ -0,0 +1,223 @@
/*
* Maxim Integrated MAX5481-MAX5484 digital potentiometer driver
* Copyright 2016 Rockwell Collins
*
* Datasheet:
* http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the gnu general public license version 2 as
* published by the free software foundation.
*
*/
#include <linux/acpi.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.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] ____cacheline_aligned;
};
#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,
.driver_module = THIS_MODULE,
};
#if defined(CONFIG_OF)
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);
#endif
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);
const struct of_device_id *match;
int ret;
indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
dev_set_drvdata(&spi->dev, indio_dev);
data = iio_priv(indio_dev);
data->spi = spi;
match = of_match_device(of_match_ptr(max5481_match), &spi->dev);
if (match)
data->cfg = of_device_get_match_data(&spi->dev);
else
data->cfg = &max5481_cfg[id->driver_data];
indio_dev->name = id->name;
indio_dev->dev.parent = &spi->dev;
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;
return iio_device_register(indio_dev);
}
static int max5481_remove(struct spi_device *spi)
{
struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
struct max5481_data *data = iio_priv(indio_dev);
iio_device_unregister(indio_dev);
/* save wiper reg to NV reg */
return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
}
static const struct spi_device_id max5481_id_table[] = {
{ "max5481", max5481 },
{ "max5482", max5482 },
{ "max5483", max5483 },
{ "max5484", max5484 },
{ }
};
MODULE_DEVICE_TABLE(spi, max5481_id_table);
#if defined(CONFIG_ACPI)
static const struct acpi_device_id max5481_acpi_match[] = {
{ "max5481", max5481 },
{ "max5482", max5482 },
{ "max5483", max5483 },
{ "max5484", max5484 },
{ }
};
MODULE_DEVICE_TABLE(acpi, max5481_acpi_match);
#endif
static struct spi_driver max5481_driver = {
.driver = {
.name = "max5481",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(max5481_match),
.acpi_match_table = ACPI_PTR(max5481_acpi_match),
},
.probe = max5481_probe,
.remove = max5481_remove,
.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");