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// SPDX-License-Identifier: GPL-2.0-only
/*
* MAX1241 low-power, 12-bit serial ADC
*
* Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
*/
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>
#define MAX1241_VAL_MASK GENMASK(11, 0)
#define MAX1241_SHUTDOWN_DELAY_USEC 4
enum max1241_id {
max1241,
};
struct max1241 {
struct spi_device *spi;
struct mutex lock;
struct regulator *vref;
struct gpio_desc *shutdown;
__be16 data __aligned(IIO_DMA_MINALIGN);
};
static const struct iio_chan_spec max1241_channels[] = {
{
.type = IIO_VOLTAGE,
.indexed = 1,
.channel = 0,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
},
};
static int max1241_read(struct max1241 *adc)
{
struct spi_transfer xfers[] = {
/*
* Begin conversion by bringing /CS low for at least
* tconv us.
*/
{
.len = 0,
.delay.value = 8,
.delay.unit = SPI_DELAY_UNIT_USECS,
},
/*
* Then read two bytes of data in our RX buffer.
*/
{
.rx_buf = &adc->data,
.len = 2,
},
};
return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
}
static int max1241_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
int ret, vref_uV;
struct max1241 *adc = iio_priv(indio_dev);
switch (mask) {
case IIO_CHAN_INFO_RAW:
mutex_lock(&adc->lock);
if (adc->shutdown) {
gpiod_set_value(adc->shutdown, 0);
udelay(MAX1241_SHUTDOWN_DELAY_USEC);
ret = max1241_read(adc);
gpiod_set_value(adc->shutdown, 1);
} else
ret = max1241_read(adc);
if (ret) {
mutex_unlock(&adc->lock);
return ret;
}
*val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
mutex_unlock(&adc->lock);
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
vref_uV = regulator_get_voltage(adc->vref);
if (vref_uV < 0)
return vref_uV;
*val = vref_uV / 1000;
*val2 = 12;
return IIO_VAL_FRACTIONAL_LOG2;
default:
return -EINVAL;
}
}
static const struct iio_info max1241_info = {
.read_raw = max1241_read_raw,
};
static void max1241_disable_vref_action(void *data)
{
struct max1241 *adc = data;
struct device *dev = &adc->spi->dev;
int err;
err = regulator_disable(adc->vref);
if (err)
dev_err(dev, "could not disable vref regulator.\n");
}
static int max1241_probe(struct spi_device *spi)
{
struct device *dev = &spi->dev;
struct iio_dev *indio_dev;
struct max1241 *adc;
int ret;
indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
if (!indio_dev)
return -ENOMEM;
adc = iio_priv(indio_dev);
adc->spi = spi;
mutex_init(&adc->lock);
ret = devm_regulator_get_enable(dev, "vdd");
if (ret)
return dev_err_probe(dev, ret,
"failed to get/enable vdd regulator\n");
adc->vref = devm_regulator_get(dev, "vref");
if (IS_ERR(adc->vref))
return dev_err_probe(dev, PTR_ERR(adc->vref),
"failed to get vref regulator\n");
ret = regulator_enable(adc->vref);
if (ret)
return ret;
ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
if (ret) {
dev_err(dev, "could not set up vref regulator cleanup action\n");
return ret;
}
adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
GPIOD_OUT_HIGH);
if (IS_ERR(adc->shutdown))
return dev_err_probe(dev, PTR_ERR(adc->shutdown),
"cannot get shutdown gpio\n");
if (adc->shutdown)
dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
else
dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
indio_dev->name = spi_get_device_id(spi)->name;
indio_dev->info = &max1241_info;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = max1241_channels;
indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
return devm_iio_device_register(dev, indio_dev);
}
static const struct spi_device_id max1241_id[] = {
{ "max1241", max1241 },
{ }
};
static const struct of_device_id max1241_dt_ids[] = {
{ .compatible = "maxim,max1241" },
{ }
};
MODULE_DEVICE_TABLE(of, max1241_dt_ids);
static struct spi_driver max1241_spi_driver = {
.driver = {
.name = "max1241",
.of_match_table = max1241_dt_ids,
},
.probe = max1241_probe,
.id_table = max1241_id,
};
module_spi_driver(max1241_spi_driver);
MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
MODULE_DESCRIPTION("MAX1241 ADC driver");
MODULE_LICENSE("GPL v2");
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