/*
* Driver for Linear Technology LTC4215 I2C Hot Swap Controller
*
* Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* Datasheet:
* http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/jiffies.h>
/* Here are names of the chip's registers (a.k.a. commands) */
enum ltc4215_cmd {
LTC4215_CONTROL = 0x00, /* rw */
LTC4215_ALERT = 0x01, /* rw */
LTC4215_STATUS = 0x02, /* ro */
LTC4215_FAULT = 0x03, /* rw */
LTC4215_SENSE = 0x04, /* rw */
LTC4215_SOURCE = 0x05, /* rw */
LTC4215_ADIN = 0x06, /* rw */
};
struct ltc4215_data {
struct i2c_client *client;
struct mutex update_lock;
bool valid;
unsigned long last_updated; /* in jiffies */
/* Registers */
u8 regs[7];
};
static struct ltc4215_data *ltc4215_update_device(struct device *dev)
{
struct ltc4215_data *data = dev_get_drvdata(dev);
struct i2c_client *client = data->client;
s32 val;
int i;
mutex_lock(&data->update_lock);
/* The chip's A/D updates 10 times per second */
if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
dev_dbg(&client->dev, "Starting ltc4215 update\n");
/* Read all registers */
for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
val = i2c_smbus_read_byte_data(client, i);
if (unlikely(val < 0))
data->regs[i] = 0;
else
data->regs[i] = val;
}
data->last_updated = jiffies;
data->valid = 1;
}
mutex_unlock(&data->update_lock);
return data;
}
/* Return the voltage from the given register in millivolts */
static int ltc4215_get_voltage(struct device *dev, u8 reg)
{
struct ltc4215_data *data = ltc4215_update_device(dev);
const u8 regval = data->regs[reg];
u32 voltage = 0;
switch (reg) {
case LTC4215_SENSE:
/* 151 uV per increment */
voltage = regval * 151 / 1000;
break;
case LTC4215_SOURCE:
/* 60.5 mV per increment */
voltage = regval * 605 / 10;
break;
case LTC4215_ADIN:
/*
* The ADIN input is divided by 12.5, and has 4.82 mV
* per increment, so we have the additional multiply
*/
voltage = regval * 482 * 125 / 1000;
break;
default:
/* If we get here, the developer messed up */
WARN_ON_ONCE(1);
break;
}
return voltage;
}
/* Return the current from the sense resistor in mA */
static unsigned int ltc4215_get_current(struct device *dev)
{
struct ltc4215_data *data = ltc4215_update_device(dev);
/*
* The strange looking conversions that follow are fixed-point
* math, since we cannot do floating point in the kernel.
*
* Step 1: convert sense register to microVolts
* Step 2: convert voltage to milliAmperes
*
* If you play around with the V=IR equation, you come up with
* the following: X uV / Y mOhm == Z mA
*
* With the resistors that are fractions of a milliOhm, we multiply
* the voltage and resistance by 10, to shift the decimal point.
* Now we can use the normal division operator again.
*/
/* Calculate voltage in microVolts (151 uV per increment) */
const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
/* Calculate current in milliAmperes (4 milliOhm sense resistor) */
const unsigned int curr = voltage / 4;
return curr;
}
static ssize_t ltc4215_show_voltage(struct device *dev,
struct device_attribute *da,
char *buf)
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
const int voltage = ltc4215_get_voltage(dev, attr->index);
return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
}
static ssize_t ltc4215_show_current(struct device *dev,
struct device_attribute *da,
char *buf)
{
const unsigned int curr = ltc4215_get_current(dev);
return snprintf(buf, PAGE_SIZE, "%u\n", curr);
}
static ssize_t ltc4215_show_power(struct device *dev,
struct device_attribute *da,
char *buf)
{
const unsigned int curr = ltc4215_get_current(dev);
const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
/* current in mA * voltage in mV == power in uW */
const unsigned int power = abs(output_voltage * curr);
return snprintf(buf, PAGE_SIZE, "%u\n", power);
}
static ssize_t ltc4215_show_alarm(struct device *dev,
struct device_attribute *da,
char *buf)
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
struct ltc4215_data *data = ltc4215_update_device(dev);
const u8 reg = data->regs[LTC4215_STATUS];
const u32 mask = attr->index;
return snprintf(buf, PAGE_SIZE, "%u\n", !!(reg & mask));
}
/*
* These macros are used below in constructing device attribute objects
* for use with sysfs_create_group() to make a sysfs device file
* for each register.
*/
/* Construct a sensor_device_attribute structure for each register */
/* Current */
static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4215_show_current, NULL, 0);
static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
1 << 2);
/* Power (virtual) */
static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4215_show_power, NULL, 0);
/* Input Voltage */
static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4215_show_voltage, NULL,
LTC4215_ADIN);
static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
1 << 0);
static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
1 << 1);
/* Output Voltage */
static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4215_show_voltage, NULL,
LTC4215_SOURCE);
static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
1 << 3);
/*
* Finally, construct an array of pointers to members of the above objects,
* as required for sysfs_create_group()
*/
static struct attribute *ltc4215_attrs[] = {
&sensor_dev_attr_curr1_input.dev_attr.attr,
&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
&sensor_dev_attr_power1_input.dev_attr.attr,
&sensor_dev_attr_in1_input.dev_attr.attr,
&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
&sensor_dev_attr_in2_input.dev_attr.attr,
&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
NULL,
};
ATTRIBUTE_GROUPS(ltc4215);
static int ltc4215_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct i2c_adapter *adapter = client->adapter;
struct device *dev = &client->dev;
struct ltc4215_data *data;
struct device *hwmon_dev;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
return -ENODEV;
data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->client = client;
mutex_init(&data->update_lock);
/* Initialize the LTC4215 chip */
i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
data,
ltc4215_groups);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
static const struct i2c_device_id ltc4215_id[] = {
{ "ltc4215", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, ltc4215_id);
/* This is the driver that will be inserted */
static struct i2c_driver ltc4215_driver = {
.driver = {
.name = "ltc4215",
},
.probe = ltc4215_probe,
.id_table = ltc4215_id,
};
module_i2c_driver(ltc4215_driver);
MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
MODULE_DESCRIPTION("LTC4215 driver");
MODULE_LICENSE("GPL");
