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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) Linumiz 2021
*
* max31865.c - Maxim MAX31865 RTD-to-Digital Converter sensor driver
*
* Author: Navin Sankar Velliangiri <navin@linumiz.com>
*/
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/spi/spi.h>
#include <asm/unaligned.h>
/*
* The MSB of the register value determines whether the following byte will
* be written or read. If it is 0, read will follow and if it is 1, write
* will follow.
*/
#define MAX31865_RD_WR_BIT BIT(7)
#define MAX31865_CFG_VBIAS BIT(7)
#define MAX31865_CFG_1SHOT BIT(5)
#define MAX31865_3WIRE_RTD BIT(4)
#define MAX31865_FAULT_STATUS_CLEAR BIT(1)
#define MAX31865_FILTER_50HZ BIT(0)
/* The MAX31865 registers */
#define MAX31865_CFG_REG 0x00
#define MAX31865_RTD_MSB 0x01
#define MAX31865_FAULT_STATUS 0x07
#define MAX31865_FAULT_OVUV BIT(2)
static const char max31865_show_samp_freq[] = "50 60";
static const struct iio_chan_spec max31865_channels[] = {
{ /* RTD Temperature */
.type = IIO_TEMP,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE)
},
};
struct max31865_data {
struct spi_device *spi;
struct mutex lock;
bool filter_50hz;
bool three_wire;
u8 buf[2] ____cacheline_aligned;
};
static int max31865_read(struct max31865_data *data, u8 reg,
unsigned int read_size)
{
return spi_write_then_read(data->spi, &reg, 1, data->buf, read_size);
}
static int max31865_write(struct max31865_data *data, size_t len)
{
return spi_write(data->spi, data->buf, len);
}
static int enable_bias(struct max31865_data *data)
{
u8 cfg;
int ret;
ret = max31865_read(data, MAX31865_CFG_REG, 1);
if (ret)
return ret;
cfg = data->buf[0];
data->buf[0] = MAX31865_CFG_REG | MAX31865_RD_WR_BIT;
data->buf[1] = cfg | MAX31865_CFG_VBIAS;
return max31865_write(data, 2);
}
static int disable_bias(struct max31865_data *data)
{
u8 cfg;
int ret;
ret = max31865_read(data, MAX31865_CFG_REG, 1);
if (ret)
return ret;
cfg = data->buf[0];
cfg &= ~MAX31865_CFG_VBIAS;
data->buf[0] = MAX31865_CFG_REG | MAX31865_RD_WR_BIT;
data->buf[1] = cfg;
return max31865_write(data, 2);
}
static int max31865_rtd_read(struct max31865_data *data, int *val)
{
u8 reg;
int ret;
/* Enable BIAS to start the conversion */
ret = enable_bias(data);
if (ret)
return ret;
/* wait 10.5ms before initiating the conversion */
msleep(11);
ret = max31865_read(data, MAX31865_CFG_REG, 1);
if (ret)
return ret;
reg = data->buf[0];
reg |= MAX31865_CFG_1SHOT | MAX31865_FAULT_STATUS_CLEAR;
data->buf[0] = MAX31865_CFG_REG | MAX31865_RD_WR_BIT;
data->buf[1] = reg;
ret = max31865_write(data, 2);
if (ret)
return ret;
if (data->filter_50hz) {
/* 50Hz filter mode requires 62.5ms to complete */
msleep(63);
} else {
/* 60Hz filter mode requires 52ms to complete */
msleep(52);
}
ret = max31865_read(data, MAX31865_RTD_MSB, 2);
if (ret)
return ret;
*val = get_unaligned_be16(&data->buf) >> 1;
return disable_bias(data);
}
static int max31865_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct max31865_data *data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW:
mutex_lock(&data->lock);
ret = max31865_rtd_read(data, val);
mutex_unlock(&data->lock);
if (ret)
return ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
/* Temp. Data resolution is 0.03125 degree centigrade */
*val = 31;
*val2 = 250000; /* 1000 * 0.03125 */
return IIO_VAL_INT_PLUS_MICRO;
default:
return -EINVAL;
}
}
static int max31865_init(struct max31865_data *data)
{
u8 cfg;
int ret;
ret = max31865_read(data, MAX31865_CFG_REG, 1);
if (ret)
return ret;
cfg = data->buf[0];
if (data->three_wire)
/* 3-wire RTD connection */
cfg |= MAX31865_3WIRE_RTD;
if (data->filter_50hz)
/* 50Hz noise rejection filter */
cfg |= MAX31865_FILTER_50HZ;
data->buf[0] = MAX31865_CFG_REG | MAX31865_RD_WR_BIT;
data->buf[1] = cfg;
return max31865_write(data, 2);
}
static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
{
int ret;
bool fault;
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31865_data *data = iio_priv(indio_dev);
ret = max31865_read(data, MAX31865_FAULT_STATUS, 1);
if (ret)
return ret;
fault = data->buf[0] & faultbit;
return sysfs_emit(buf, "%d\n", fault);
}
static ssize_t show_fault_ovuv(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return show_fault(dev, MAX31865_FAULT_OVUV, buf);
}
static ssize_t show_filter(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31865_data *data = iio_priv(indio_dev);
return sysfs_emit(buf, "%d\n", data->filter_50hz ? 50 : 60);
}
static ssize_t set_filter(struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t len)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31865_data *data = iio_priv(indio_dev);
unsigned int freq;
int ret;
ret = kstrtouint(buf, 10, &freq);
if (ret)
return ret;
switch (freq) {
case 50:
data->filter_50hz = true;
break;
case 60:
data->filter_50hz = false;
break;
default:
return -EINVAL;
}
mutex_lock(&data->lock);
ret = max31865_init(data);
mutex_unlock(&data->lock);
if (ret)
return ret;
return len;
}
static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(max31865_show_samp_freq);
static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
static IIO_DEVICE_ATTR(in_filter_notch_center_frequency, 0644,
show_filter, set_filter, 0);
static struct attribute *max31865_attributes[] = {
&iio_dev_attr_fault_ovuv.dev_attr.attr,
&iio_const_attr_sampling_frequency_available.dev_attr.attr,
&iio_dev_attr_in_filter_notch_center_frequency.dev_attr.attr,
NULL,
};
static const struct attribute_group max31865_group = {
.attrs = max31865_attributes,
};
static const struct iio_info max31865_info = {
.read_raw = max31865_read_raw,
.attrs = &max31865_group,
};
static int max31865_probe(struct spi_device *spi)
{
const struct spi_device_id *id = spi_get_device_id(spi);
struct iio_dev *indio_dev;
struct max31865_data *data;
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->filter_50hz = false;
mutex_init(&data->lock);
indio_dev->info = &max31865_info;
indio_dev->name = id->name;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = max31865_channels;
indio_dev->num_channels = ARRAY_SIZE(max31865_channels);
if (of_property_read_bool(spi->dev.of_node, "maxim,3-wire")) {
/* select 3 wire */
data->three_wire = 1;
} else {
/* select 2 or 4 wire */
data->three_wire = 0;
}
ret = max31865_init(data);
if (ret) {
dev_err(&spi->dev, "error: Failed to configure max31865\n");
return ret;
}
return devm_iio_device_register(&spi->dev, indio_dev);
}
static const struct spi_device_id max31865_id[] = {
{ "max31865", 0 },
{ }
};
MODULE_DEVICE_TABLE(spi, max31865_id);
static const struct of_device_id max31865_of_match[] = {
{ .compatible = "maxim,max31865" },
{ }
};
MODULE_DEVICE_TABLE(of, max31865_of_match);
static struct spi_driver max31865_driver = {
.driver = {
.name = "max31865",
.of_match_table = max31865_of_match,
},
.probe = max31865_probe,
.id_table = max31865_id,
};
module_spi_driver(max31865_driver);
MODULE_AUTHOR("Navin Sankar Velliangiri <navin@linumiz.com>");
MODULE_DESCRIPTION("Maxim MAX31865 RTD-to-Digital Converter sensor driver");
MODULE_LICENSE("GPL v2");