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linux-next/drivers/hwmon/max127.c
Tao Ren 8efd10147c hwmon: (max127) Add Maxim MAX127 hardware monitoring driver
Add hardware monitoring driver for the Maxim MAX127 chip.

MAX127 min/max range handling code is inspired by the max197 driver.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Link: https://lore.kernel.org/r/20201123185658.7632-2-rentao.bupt@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2020-12-02 17:42:24 -08:00

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// SPDX-License-Identifier: GPL-2.0+
/*
* Hardware monitoring driver for MAX127.
*
* Copyright (c) 2020 Facebook Inc.
*/
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/module.h>
/*
* MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
* Format" for details.
*/
#define MAX127_CTRL_START BIT(7)
#define MAX127_CTRL_SEL_SHIFT 4
#define MAX127_CTRL_RNG BIT(3)
#define MAX127_CTRL_BIP BIT(2)
#define MAX127_CTRL_PD1 BIT(1)
#define MAX127_CTRL_PD0 BIT(0)
#define MAX127_NUM_CHANNELS 8
#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
/*
* MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
* and Polarity Selection" for details.
*/
#define MAX127_FULL_RANGE 10000 /* 10V */
#define MAX127_HALF_RANGE 5000 /* 5V */
/*
* MAX127 returns 2 bytes at read:
* - the first byte contains data[11:4].
* - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
* Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
* for details.
*/
#define MAX127_DATA_LEN 2
#define MAX127_DATA_SHIFT 4
#define MAX127_SIGN_BIT BIT(11)
struct max127_data {
struct mutex lock;
struct i2c_client *client;
u8 ctrl_byte[MAX127_NUM_CHANNELS];
};
static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
{
int status;
struct i2c_msg msg = {
.addr = client->addr,
.flags = 0,
.len = sizeof(ctrl_byte),
.buf = &ctrl_byte,
};
status = i2c_transfer(client->adapter, &msg, 1);
if (status < 0)
return status;
if (status != 1)
return -EIO;
return 0;
}
static int max127_read_channel(struct i2c_client *client, long *val)
{
int status;
u8 i2c_data[MAX127_DATA_LEN];
struct i2c_msg msg = {
.addr = client->addr,
.flags = I2C_M_RD,
.len = sizeof(i2c_data),
.buf = i2c_data,
};
status = i2c_transfer(client->adapter, &msg, 1);
if (status < 0)
return status;
if (status != 1)
return -EIO;
*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
((u16)i2c_data[0] << MAX127_DATA_SHIFT);
return 0;
}
static long max127_process_raw(u8 ctrl_byte, long raw)
{
long scale, weight;
/*
* MAX127's data coding is binary in unipolar mode with 1 LSB =
* (Full-Scale/4096) and twos complement binary in bipolar mode
* with 1 LSB = [(2 x |FS|)/4096].
* Refer to MAX127 datasheet, "Transfer Function" section for
* details.
*/
scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
MAX127_HALF_RANGE;
if (ctrl_byte & MAX127_CTRL_BIP) {
weight = (raw & MAX127_SIGN_BIT);
raw &= ~MAX127_SIGN_BIT;
raw -= weight;
raw *= 2;
}
return raw * scale / 4096;
}
static int max127_read_input(struct max127_data *data, int channel, long *val)
{
long raw;
int status;
struct i2c_client *client = data->client;
u8 ctrl_byte = data->ctrl_byte[channel];
mutex_lock(&data->lock);
status = max127_select_channel(client, ctrl_byte);
if (status)
goto exit;
status = max127_read_channel(client, &raw);
if (status)
goto exit;
*val = max127_process_raw(ctrl_byte, raw);
exit:
mutex_unlock(&data->lock);
return status;
}
static int max127_read_min(struct max127_data *data, int channel, long *val)
{
u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
static const int min_input_map[4] = {
0, /* RNG=0, BIP=0 */
-MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
0, /* RNG=1, BIP=0 */
-MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
};
*val = min_input_map[rng_bip];
return 0;
}
static int max127_read_max(struct max127_data *data, int channel, long *val)
{
u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
static const int max_input_map[4] = {
MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
};
*val = max_input_map[rng_bip];
return 0;
}
static int max127_write_min(struct max127_data *data, int channel, long val)
{
u8 ctrl;
mutex_lock(&data->lock);
ctrl = data->ctrl_byte[channel];
if (val <= -MAX127_FULL_RANGE) {
ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
} else if (val < 0) {
ctrl |= MAX127_CTRL_BIP;
ctrl &= ~MAX127_CTRL_RNG;
} else {
ctrl &= ~MAX127_CTRL_BIP;
}
data->ctrl_byte[channel] = ctrl;
mutex_unlock(&data->lock);
return 0;
}
static int max127_write_max(struct max127_data *data, int channel, long val)
{
mutex_lock(&data->lock);
if (val >= MAX127_FULL_RANGE)
data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
else
data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
mutex_unlock(&data->lock);
return 0;
}
static umode_t max127_is_visible(const void *_data,
enum hwmon_sensor_types type,
u32 attr, int channel)
{
if (type == hwmon_in) {
switch (attr) {
case hwmon_in_input:
return 0444;
case hwmon_in_min:
case hwmon_in_max:
return 0644;
default:
break;
}
}
return 0;
}
static int max127_read(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long *val)
{
int status;
struct max127_data *data = dev_get_drvdata(dev);
if (type != hwmon_in)
return -EOPNOTSUPP;
switch (attr) {
case hwmon_in_input:
status = max127_read_input(data, channel, val);
break;
case hwmon_in_min:
status = max127_read_min(data, channel, val);
break;
case hwmon_in_max:
status = max127_read_max(data, channel, val);
break;
default:
status = -EOPNOTSUPP;
break;
}
return status;
}
static int max127_write(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long val)
{
int status;
struct max127_data *data = dev_get_drvdata(dev);
if (type != hwmon_in)
return -EOPNOTSUPP;
switch (attr) {
case hwmon_in_min:
status = max127_write_min(data, channel, val);
break;
case hwmon_in_max:
status = max127_write_max(data, channel, val);
break;
default:
status = -EOPNOTSUPP;
break;
}
return status;
}
static const struct hwmon_ops max127_hwmon_ops = {
.is_visible = max127_is_visible,
.read = max127_read,
.write = max127_write,
};
static const struct hwmon_channel_info *max127_info[] = {
HWMON_CHANNEL_INFO(in,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
NULL,
};
static const struct hwmon_chip_info max127_chip_info = {
.ops = &max127_hwmon_ops,
.info = max127_info,
};
static int max127_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
int i;
struct device *hwmon_dev;
struct max127_data *data;
struct device *dev = &client->dev;
data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->client = client;
mutex_init(&data->lock);
for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
data->ctrl_byte[i] = (MAX127_CTRL_START |
MAX127_SET_CHANNEL(i));
hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
data,
&max127_chip_info,
NULL);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
static const struct i2c_device_id max127_id[] = {
{ "max127", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, max127_id);
static struct i2c_driver max127_driver = {
.class = I2C_CLASS_HWMON,
.driver = {
.name = "max127",
},
.probe = max127_probe,
.id_table = max127_id,
};
module_i2c_driver(max127_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");