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Commit 69e1ded6 authored by Guenter Roeck's avatar Guenter Roeck
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hwmon: Driver for Linear Technologies LTC4260 



LTC4260 is a Positive Voltage Hot Swap Controller.
The driver currently only supports voltage monitoring, not voltage control.

Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 79ffe859

Documentation/hwmon/ltc4260

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Kernel driver ltc4260

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



Supported chips:

  * Linear Technology LTC4260

    Prefix: 'ltc4260'

    Addresses scanned: -

    Datasheet:

        http://cds.linear.com/docs/en/datasheet/4260fc.pdf



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





Description

-----------



The LTC4260 Hot Swap controller allows a board to be safely inserted

and removed from a live backplane.





Usage Notes

-----------



This driver does not probe for LTC4260 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 LTC4260 at address 0x10

on I2C bus #1:

$ modprobe ltc4260

$ echo ltc4260 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.



in1_input		SOURCE voltage (mV)

in1_min_alarm		Undervoltage alarm

in1_max_alarm		Overvoltage alarm



in2_input		ADIN voltage (mV)

in2_alarm		Power bad alarm



curr1_input		SENSE current (mA)

curr1_alarm		SENSE overcurrent alarm

drivers/hwmon/Kconfig

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@@ -821,6 +821,18 @@ config SENSORS_LTC4245 
	  This driver can also be built as a module. If so, the module will

	  be called ltc4245.



config SENSORS_LTC4260

	tristate "Linear Technology LTC4260"

	depends on I2C

	select REGMAP_I2C

	default n

	help

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

	  Positive Voltage Hot Swap Controller I2C interface.



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

	  be called ltc4260.



config SENSORS_LTC4261

	tristate "Linear Technology LTC4261"

	depends on I2C

drivers/hwmon/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ obj-$(CONFIG_SENSORS_LTC4151) += ltc4151.o 
obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o

obj-$(CONFIG_SENSORS_LTC4222)	+= ltc4222.o

obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o

obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o

obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o

obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o

obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o

drivers/hwmon/ltc4260.c

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/*

 * Driver for Linear Technology LTC4260 I2C Positive Voltage Hot Swap Controller

 *

 * Copyright (c) 2014 Guenter Roeck

 *

 * 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.

 */



#include <linux/kernel.h>

#include <linux/module.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>

#include <linux/regmap.h>



/* chip registers */

#define LTC4260_CONTROL	0x00

#define LTC4260_ALERT	0x01

#define LTC4260_STATUS	0x02

#define LTC4260_FAULT	0x03

#define LTC4260_SENSE	0x04

#define LTC4260_SOURCE	0x05

#define LTC4260_ADIN	0x06



/*

 * Fault register bits

 */

#define FAULT_OV	(1 << 0)

#define FAULT_UV	(1 << 1)

#define FAULT_OC	(1 << 2)

#define FAULT_POWER_BAD	(1 << 3)

#define FAULT_FET_SHORT	(1 << 5)



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

static int ltc4260_get_value(struct device *dev, u8 reg)

{

	struct regmap *regmap = dev_get_drvdata(dev);

	unsigned int val;

	int ret;



	ret = regmap_read(regmap, reg, &val);

	if (ret < 0)

		return ret;



	switch (reg) {

	case LTC4260_ADIN:

		/* 10 mV resolution. Convert to mV. */

		val = val * 10;

		break;

	case LTC4260_SOURCE:

		/* 400 mV resolution. Convert to mV. */

		val = val * 400;

		break;

	case LTC4260_SENSE:

		/*

		 * 300 uV 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 * 300;

		break;

	default:

		return -EINVAL;

	}



	return val;

}



static ssize_t ltc4260_show_value(struct device *dev,

				  struct device_attribute *da, char *buf)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	int value;



	value = ltc4260_get_value(dev, attr->index);

	if (value < 0)

		return value;

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

}



static ssize_t ltc4260_show_bool(struct device *dev,

				 struct device_attribute *da, char *buf)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct regmap *regmap = dev_get_drvdata(dev);

	unsigned int fault;

	int ret;



	ret = regmap_read(regmap, LTC4260_FAULT, &fault);

	if (ret < 0)

		return ret;



	fault &= attr->index;

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

		regmap_update_bits(regmap, LTC4260_FAULT, attr->index, 0);



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

}



/* Voltages */

static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4260_show_value, NULL,

			  LTC4260_SOURCE);

static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4260_show_value, NULL,

			  LTC4260_ADIN);



/*

 * Voltage alarms

 * UV/OV faults are associated with the input voltage, and the POWER BAD and

 * FET SHORT faults are associated with the output voltage.

 */

static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4260_show_bool, NULL,

			  FAULT_UV);

static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4260_show_bool, NULL,

			  FAULT_OV);

static SENSOR_DEVICE_ATTR(in2_alarm, S_IRUGO, ltc4260_show_bool, NULL,

			  FAULT_POWER_BAD | FAULT_FET_SHORT);



/* Current (via sense resistor) */

static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4260_show_value, NULL,

			  LTC4260_SENSE);



/* Overcurrent alarm */

static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4260_show_bool, NULL,

			  FAULT_OC);



static struct attribute *ltc4260_attrs[] = {

	&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_alarm.dev_attr.attr,



	&sensor_dev_attr_curr1_input.dev_attr.attr,

	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,



	NULL,

};

ATTRIBUTE_GROUPS(ltc4260);



static struct regmap_config ltc4260_regmap_config = {

	.reg_bits = 8,

	.val_bits = 8,

	.max_register = LTC4260_ADIN,

};



static int ltc4260_probe(struct i2c_client *client,

			 const struct i2c_device_id *id)

{

	struct device *dev = &client->dev;

	struct device *hwmon_dev;

	struct regmap *regmap;



	regmap = devm_regmap_init_i2c(client, &ltc4260_regmap_config);

	if (IS_ERR(regmap)) {

		dev_err(dev, "failed to allocate register map\n");

		return PTR_ERR(regmap);

	}



	/* Clear faults */

	regmap_write(regmap, LTC4260_FAULT, 0x00);



	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,

							   regmap,

							   ltc4260_groups);

	return PTR_ERR_OR_ZERO(hwmon_dev);

}



static const struct i2c_device_id ltc4260_id[] = {

	{"ltc4260", 0},

	{ }

};



MODULE_DEVICE_TABLE(i2c, ltc4260_id);



static struct i2c_driver ltc4260_driver = {

	.driver = {

		   .name = "ltc4260",

		   },

	.probe = ltc4260_probe,

	.id_table = ltc4260_id,

};



module_i2c_driver(ltc4260_driver);



MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");

MODULE_DESCRIPTION("LTC4260 driver");

MODULE_LICENSE("GPL");