hwmon: LTC4261 Hardware monitoring driver

Kernel driver ltc4261

=====================

Supported chips:

  * Linear Technology LTC4261

    Prefix: 'ltc4261'

    Addresses scanned: -

    Datasheet:

        http://cds.linear.com/docs/Datasheet/42612fb.pdf

Author: Guenter Roeck <guenter.roeck@ericsson.com>

Description

-----------

The LTC4261/LTC4261-2 negative voltage Hot Swap controllers allow a board

to be safely inserted and removed from a live backplane.

Usage Notes

-----------

This driver does not probe for LTC4261 devices, since there is no register

which can be safely used to identify the chip. You will have to instantiate

the devices explicitly.

Example: the following will load the driver for an LTC4261 at address 0x10

on I2C bus #1:

$ modprobe ltc4261

$ echo ltc4261 0x10 > /sys/bus/i2c/devices/i2c-1/new_device

Sysfs entries

-------------

Voltage readings provided by this driver are reported as obtained from the ADC

registers. If a set of voltage divider resistors is installed, calculate the

real voltage by multiplying the reported value with (R1+R2)/R2, where R1 is the

value of the divider resistor against the measured voltage and R2 is the value

of the divider resistor against Ground.

Current reading provided by this driver is reported as obtained from the ADC

Current Sense register. The reported value assumes that a 1 mOhm sense resistor

is installed. If a different sense resistor is installed, calculate the real

current by dividing the reported value by the sense resistor value in mOhm.

The chip has two voltage sensors, but only one set of voltage alarm status bits.

In many many designs, those alarms are associated with the ADIN2 sensor, due to

the proximity of the ADIN2 pin to the OV pin. ADIN2 is, however, not available

on all chip variants. To ensure that the alarm condition is reported to the user,

report it with both voltage sensors.

in1_input		ADIN2 voltage (mV)

in1_min_alarm		ADIN/ADIN2 Undervoltage alarm

in1_max_alarm		ADIN/ADIN2 Overvoltage alarm

in2_input		ADIN voltage (mV)

in2_min_alarm		ADIN/ADIN2 Undervoltage alarm

in2_max_alarm		ADIN/ADIN2 Overvoltage alarm

curr1_input		SENSE current (mA)

curr1_alarm		SENSE overcurrent alarm

S:	Maintained

F:	drivers/scsi/sym53c8xx_2/

LTC4261 HARDWARE MONITOR DRIVER

M:	Guenter Roeck <linux@roeck-us.net>

L:	lm-sensors@lm-sensors.org

S:	Maintained

F:	Documentation/hwmon/ltc4261

F:	drivers/hwmon/ltc4261.c

LTP (Linux Test Project)

M:	Rishikesh K Rajak <risrajak@linux.vnet.ibm.com>

M:	Garrett Cooper <yanegomi@gmail.com>

	  This driver can also be built as a module. If so, the module will

	  be called ltc4245.

config SENSORS_LTC4261

	tristate "Linear Technology LTC4261"

	depends on I2C && EXPERIMENTAL

	default n

	help

	  If you say yes here you get support for Linear Technology LTC4261

	  Negative Voltage Hot Swap Controller I2C interface.

	  This driver can also be built as a module. If so, the module will

	  be called ltc4261.

config SENSORS_LM95241

	tristate "National Semiconductor LM95241 sensor chip"

	depends on I2C

obj-$(CONFIG_SENSORS_LM95241)	+= lm95241.o

obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o

obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o

obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o

obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o

obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o

obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o

/*

 * Driver for Linear Technology LTC4261 I2C Negative Voltage Hot Swap Controller

 *

 * Copyright (C) 2010 Ericsson AB.

 *

 * Derived from:

 *

 *  Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller

 *  Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>

 *

 * Datasheet: http://cds.linear.com/docs/Datasheet/42612fb.pdf

 *

 * 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; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 */

#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>

/* chip registers */

#define LTC4261_STATUS	0x00	/* readonly */

#define LTC4261_FAULT	0x01

#define LTC4261_ALERT	0x02

#define LTC4261_CONTROL	0x03

#define LTC4261_SENSE_H	0x04

#define LTC4261_SENSE_L	0x05

#define LTC4261_ADIN2_H	0x06

#define LTC4261_ADIN2_L	0x07

#define LTC4261_ADIN_H	0x08

#define LTC4261_ADIN_L	0x09

/*

 * Fault register bits

 */

#define FAULT_OV	(1<<0)

#define FAULT_UV	(1<<1)

#define FAULT_OC	(1<<2)

struct ltc4261_data {

	struct device *hwmon_dev;

	struct mutex update_lock;

	bool valid;

	unsigned long last_updated;	/* in jiffies */

	/* Registers */

	u8 regs[10];

};

static struct ltc4261_data *ltc4261_update_device(struct device *dev)

{

	struct i2c_client *client = to_i2c_client(dev);

	struct ltc4261_data *data = i2c_get_clientdata(client);

	struct ltc4261_data *ret = data;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {

		int i;

		/* Read registers -- 0x00 to 0x09 */

		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {

			int val;

			val = i2c_smbus_read_byte_data(client, i);

			if (unlikely(val < 0)) {

				dev_dbg(dev,

					"Failed to read ADC value: error %d",

					val);

				ret = ERR_PTR(val);

				goto abort;

			}

			data->regs[i] = val;

		}

		data->last_updated = jiffies;

		data->valid = 1;

	}

abort:

	mutex_unlock(&data->update_lock);

	return ret;

}

/* Return the voltage from the given register in mV or mA */

static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)

{

	u32 val;

	val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);

	switch (reg) {

	case LTC4261_ADIN_H:

	case LTC4261_ADIN2_H:

		/* 2.5mV resolution. Convert to mV. */

		val = val * 25 / 10;

		break;

	case LTC4261_SENSE_H:

		/*

		 * 62.5uV resolution. Convert to current as measured with

		 * an 1 mOhm sense resistor, in mA. If a different sense

		 * resistor is installed, calculate the actual current by

		 * dividing the reported current by the sense resistor value

		 * in mOhm.

		 */

		val = val * 625 / 10;

		break;

	default:

		/* If we get here, the developer messed up */

		WARN_ON_ONCE(1);

		val = 0;

		break;

	}

	return val;

}

static ssize_t ltc4261_show_value(struct device *dev,

				  struct device_attribute *da, char *buf)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct ltc4261_data *data = ltc4261_update_device(dev);

	int value;

	if (IS_ERR(data))

		return PTR_ERR(data);

	value = ltc4261_get_value(data, attr->index);

	return snprintf(buf, PAGE_SIZE, "%d\n", value);

}

static ssize_t ltc4261_show_bool(struct device *dev,

				 struct device_attribute *da, char *buf)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct i2c_client *client = to_i2c_client(dev);

	struct ltc4261_data *data = ltc4261_update_device(dev);

	u8 fault;

	if (IS_ERR(data))

		return PTR_ERR(data);

	fault = data->regs[LTC4261_FAULT] & attr->index;

	if (fault)		/* Clear reported faults in chip register */

		i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);

	return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);

}

/*

 * 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.

 */

#define LTC4261_VALUE(name, ltc4261_cmd_idx) \

	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \

	ltc4261_show_value, NULL, ltc4261_cmd_idx)

#define LTC4261_BOOL(name, mask) \

	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \

	ltc4261_show_bool, NULL, (mask))

/*

 * Input voltages.

 */

LTC4261_VALUE(in1_input, LTC4261_ADIN_H);

LTC4261_VALUE(in2_input, LTC4261_ADIN2_H);

/*

 * Voltage alarms. The chip has only one set of voltage alarm status bits,

 * triggered by input voltage alarms. In many designs, those alarms are

 * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin

 * to the OV pin. ADIN2 is, however, not available on all chip variants.

 * To ensure that the alarm condition is reported to the user, report it

 * with both voltage sensors.

 */

LTC4261_BOOL(in1_min_alarm, FAULT_UV);

LTC4261_BOOL(in1_max_alarm, FAULT_OV);

LTC4261_BOOL(in2_min_alarm, FAULT_UV);

LTC4261_BOOL(in2_max_alarm, FAULT_OV);

/* Currents (via sense resistor) */

LTC4261_VALUE(curr1_input, LTC4261_SENSE_H);

/* Overcurrent alarm */

LTC4261_BOOL(curr1_max_alarm, FAULT_OC);

static struct attribute *ltc4261_attributes[] = {

	&sensor_dev_attr_in1_input.dev_attr.attr,

	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,

	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,

	&sensor_dev_attr_in2_input.dev_attr.attr,

	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,

	&sensor_dev_attr_in2_max_alarm.dev_attr.attr,

	&sensor_dev_attr_curr1_input.dev_attr.attr,

	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,

	NULL,

};

static const struct attribute_group ltc4261_group = {

	.attrs = ltc4261_attributes,

};

static int ltc4261_probe(struct i2c_client *client,

			 const struct i2c_device_id *id)

{

	struct i2c_adapter *adapter = client->adapter;

	struct ltc4261_data *data;

	int ret;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))

		return -ENODEV;

	if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {

		dev_err(&client->dev, "Failed to read register %d:%02x:%02x\n",

			adapter->id, client->addr, LTC4261_STATUS);

		return -ENODEV;

	}

	data = kzalloc(sizeof(*data), GFP_KERNEL);

	if (!data) {

		ret = -ENOMEM;

		goto out_kzalloc;

	}

	i2c_set_clientdata(client, data);

	mutex_init(&data->update_lock);

	/* Clear faults */

	i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);

	/* Register sysfs hooks */

	ret = sysfs_create_group(&client->dev.kobj, &ltc4261_group);

	if (ret)

		goto out_sysfs_create_group;

	data->hwmon_dev = hwmon_device_register(&client->dev);

	if (IS_ERR(data->hwmon_dev)) {

		ret = PTR_ERR(data->hwmon_dev);

		goto out_hwmon_device_register;

	}

	return 0;

out_hwmon_device_register:

	sysfs_remove_group(&client->dev.kobj, &ltc4261_group);

out_sysfs_create_group:

	kfree(data);

out_kzalloc:

	return ret;

}

static int ltc4261_remove(struct i2c_client *client)

{

	struct ltc4261_data *data = i2c_get_clientdata(client);

	hwmon_device_unregister(data->hwmon_dev);

	sysfs_remove_group(&client->dev.kobj, &ltc4261_group);

	kfree(data);

	return 0;

}

static const struct i2c_device_id ltc4261_id[] = {

	{"ltc4261", 0},

	{}

};

MODULE_DEVICE_TABLE(i2c, ltc4261_id);

/* This is the driver that will be inserted */

static struct i2c_driver ltc4261_driver = {

	.driver = {

		   .name = "ltc4261",

		   },

	.probe = ltc4261_probe,

	.remove = ltc4261_remove,

	.id_table = ltc4261_id,

};

static int __init ltc4261_init(void)

{

	return i2c_add_driver(&ltc4261_driver);

}

static void __exit ltc4261_exit(void)

{

	i2c_del_driver(&ltc4261_driver);

}

MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");

MODULE_DESCRIPTION("LTC4261 driver");

MODULE_LICENSE("GPL");

module_init(ltc4261_init);

module_exit(ltc4261_exit);