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iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation Amplifier

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This adds support for LTC6373 36 V Fully-Differential Programmable-Gain
Instrumentation Amplifier with 25 pA Input Bias Current.
The user can program the gain to one of seven available settings through
a 3-bit parallel interface (A2 to A0).

Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240220153553.2432-6-mitrutzceclan@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Dumitru Ceclan 2024-02-20 17:34:53 +02:00 committed by Jonathan Cameron
parent 09ac57ac01
commit a0e7a2b703
1 changed files with 120 additions and 4 deletions
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124
drivers/iio/amplifiers/hmc425a.c
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@ -2,9 +2,10 @@
/*
* HMC425A and similar Gain Amplifiers
*
* Copyright 2020 Analog Devices Inc.
* Copyright 2020, 2024 Analog Devices Inc.
*/
#include <linux/bits.h>
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/err.h>
@ -12,6 +13,7 @@
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/kernel.h>
#include <linux/math.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
@ -20,10 +22,24 @@
#include <linux/regulator/consumer.h>
#include <linux/sysfs.h>
/*
* The LTC6373 amplifier supports configuring gain using GPIO's with the following
* values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
*
* Except for the shutdown value, all can be converted to dB using 20 * log10(x)
* From here, it is observed that all values are multiples of the '2' gain setting,
* with the correspondent of 6.020dB.
*/
#define LTC6373_CONVERSION_CONSTANT 6020
#define LTC6373_MIN_GAIN_CODE 0x6
#define LTC6373_CONVERSION_MASK GENMASK(2, 0)
#define LTC6373_SHUTDOWN GENMASK(2, 0)
enum hmc425a_type {
ID_HMC425A,
ID_HMC540S,
ID_ADRF5740
ID_ADRF5740,
ID_LTC6373,
};
struct hmc425a_chip_info {
@ -34,6 +50,8 @@ struct hmc425a_chip_info {
int gain_min;
int gain_max;
int default_gain;
int powerdown_val;
bool has_powerdown;
int (*gain_dB_to_code)(int gain, int *code);
int (*code_to_gain_dB)(int code, int *val, int *val2);
@ -44,6 +62,7 @@ struct hmc425a_state {
const struct hmc425a_chip_info *chip_info;
struct gpio_descs *gpios;
u32 gain;
bool powerdown;
};
static int gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
@ -58,6 +77,8 @@ static int gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *cod
if (gain > inf->gain_max || gain < inf->gain_min)
return -EINVAL;
if (st->powerdown)
return -EPERM;
return st->chip_info->gain_dB_to_code(gain, code);
}
@ -83,8 +104,17 @@ static int adrf5740_gain_dB_to_code(int gain, int *code)
return 0;
}
static int ltc6373_gain_dB_to_code(int gain, int *code)
{
*code = ~(DIV_ROUND_CLOSEST(gain, LTC6373_CONVERSION_CONSTANT) + 3)
& LTC6373_CONVERSION_MASK;
return 0;
}
static int code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2)
{
if (st->powerdown)
return -EPERM;
return st->chip_info->code_to_gain_dB(st->gain, val, val2);
}
@ -114,6 +144,16 @@ static int adrf5740_code_to_gain_dB(int code, int *val, int *val2)
return 0;
}
static int ltc6373_code_to_gain_dB(int code, int *val, int *val2)
{
int gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
LTC6373_CONVERSION_CONSTANT;
*val = gain / 1000;
*val2 = (gain % 1000) * 1000;
return 0;
}
static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
{
struct hmc425a_state *st = iio_priv(indio_dev);
@ -192,6 +232,48 @@ static const struct iio_info hmc425a_info = {
.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
};
static ssize_t ltc6373_read_powerdown(struct iio_dev *indio_dev,
uintptr_t private,
const struct iio_chan_spec *chan,
char *buf)
{
struct hmc425a_state *st = iio_priv(indio_dev);
return sysfs_emit(buf, "%d\n", st->powerdown);
}
static ssize_t ltc6373_write_powerdown(struct iio_dev *indio_dev,
uintptr_t private,
const struct iio_chan_spec *chan,
const char *buf,
size_t len)
{
struct hmc425a_state *st = iio_priv(indio_dev);
bool powerdown;
int code, ret;
ret = kstrtobool(buf, &powerdown);
if (ret)
return ret;
mutex_lock(&st->lock);
st->powerdown = powerdown;
code = (powerdown) ? LTC6373_SHUTDOWN : st->gain;
hmc425a_write(indio_dev, code);
mutex_unlock(&st->lock);
return len;
}
static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
{
.name = "powerdown",
.read = ltc6373_read_powerdown,
.write = ltc6373_write_powerdown,
.shared = IIO_SEPARATE,
},
{}
};
#define HMC425A_CHAN(_channel) \
{ \
.type = IIO_VOLTAGE, \
@ -201,10 +283,24 @@ static const struct iio_info hmc425a_info = {
.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
}
#define LTC6373_CHAN(_channel) \
{ \
.type = IIO_VOLTAGE, \
.output = 1, \
.indexed = 1, \
.channel = _channel, \
.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
.ext_info = ltc6373_ext_info, \
}
static const struct iio_chan_spec hmc425a_channels[] = {
HMC425A_CHAN(0),
};
static const struct iio_chan_spec ltc6373_channels[] = {
LTC6373_CHAN(0),
};
static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
[ID_HMC425A] = {
.name = "hmc425a",
@ -239,6 +335,19 @@ static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
.gain_dB_to_code = adrf5740_gain_dB_to_code,
.code_to_gain_dB = adrf5740_code_to_gain_dB,
},
[ID_LTC6373] = {
.name = "ltc6373",
.channels = ltc6373_channels,
.num_channels = ARRAY_SIZE(ltc6373_channels),
.num_gpios = 3,
.gain_min = -12041, /* gain setting x0.25*/
.gain_max = 24082, /* gain setting x16 */
.default_gain = LTC6373_MIN_GAIN_CODE,
.powerdown_val = LTC6373_SHUTDOWN,
.has_powerdown = true,
.gain_dB_to_code = ltc6373_gain_dB_to_code,
.code_to_gain_dB = ltc6373_code_to_gain_dB,
},
};
static int hmc425a_probe(struct platform_device *pdev)
@ -279,8 +388,13 @@ static int hmc425a_probe(struct platform_device *pdev)
indio_dev->info = &hmc425a_info;
indio_dev->modes = INDIO_DIRECT_MODE;
/* Set default gain */
hmc425a_write(indio_dev, st->gain);
if (st->chip_info->has_powerdown) {
st->powerdown = true;
hmc425a_write(indio_dev, st->chip_info->powerdown_val);
} else {
/* Set default gain */
hmc425a_write(indio_dev, st->gain);
}
return devm_iio_device_register(&pdev->dev, indio_dev);
}
@ -293,6 +407,8 @@ static const struct of_device_id hmc425a_of_match[] = {
.data = &hmc425a_chip_info_tbl[ID_HMC540S]},
{ .compatible = "adi,adrf5740",
.data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
{ .compatible = "adi,ltc6373",
.data = &hmc425a_chip_info_tbl[ID_LTC6373]},
{}
};
MODULE_DEVICE_TABLE(of, hmc425a_of_match);