Commit df922703 authored by Mike Looijmans's avatar Mike Looijmans Committed by Guenter Roeck

hwmon: Add LTC2990 sensor driver

This adds support for the Linear Technology LTC2990  I2C System Monitor.
The LTC2990 supports a combination of voltage, current and temperature
monitoring. This driver currently only supports reading two currents
by measuring two differential voltages across series resistors, in
addition to the Vcc supply voltage and internal temperature.

This is sufficient to support the Topic Miami SOM which uses this chip
to monitor the currents flowing into the FPGA and the CPU parts.
Signed-off-by: default avatarMike Looijmans <>
Signed-off-by: default avatarGuenter Roeck <>
parent c32f5eff
Kernel driver ltc2990
Supported chips:
* Linear Technology LTC2990
Prefix: 'ltc2990'
Addresses scanned: -
Author: Mike Looijmans <>
LTC2990 is a Quad I2C Voltage, Current and Temperature Monitor.
The chip's inputs can measure 4 voltages, or two inputs together (1+2 and 3+4)
can be combined to measure a differential voltage, which is typically used to
measure current through a series resistor, or a temperature.
This driver currently uses the 2x differential mode only. In order to support
other modes, the driver will need to be expanded.
Usage Notes
This driver does not probe for PMBus devices. You will have to instantiate
devices explicitly.
Sysfs attributes
The "curr*_input" measurements actually report the voltage drop across the
input pins in microvolts. This is equivalent to the current through a 1mOhm
sense resistor. Divide the reported value by the actual sense resistor value
in mOhm to get the actual value.
in0_input Voltage at Vcc pin in millivolt (range 2.5V to 5V)
temp1_input Internal chip temperature in millidegrees Celcius
curr1_input Current in mA across v1-v2 assuming a 1mOhm sense resistor.
curr2_input Current in mA across v3-v4 assuming a 1mOhm sense resistor.
......@@ -685,6 +685,20 @@ config SENSORS_LTC2945
This driver can also be built as a module. If so, the module will
be called ltc2945.
config SENSORS_LTC2990
tristate "Linear Technology LTC2990 (current monitoring mode only)"
depends on I2C
If you say yes here you get support for Linear Technology LTC2990
I2C System Monitor. The LTC2990 supports a combination of voltage,
current and temperature monitoring, but in addition to the Vcc supply
voltage and chip temperature, this driver currently only supports
reading two currents by measuring two differential voltages across
series resistors.
This driver can also be built as a module. If so, the module will
be called ltc2990.
config SENSORS_LTC4151
tristate "Linear Technology LTC4151"
depends on I2C
......@@ -100,6 +100,7 @@ obj-$(CONFIG_SENSORS_LM95234) += lm95234.o
obj-$(CONFIG_SENSORS_LM95241) += lm95241.o
obj-$(CONFIG_SENSORS_LM95245) += lm95245.o
obj-$(CONFIG_SENSORS_LTC2945) += ltc2945.o
obj-$(CONFIG_SENSORS_LTC2990) += ltc2990.o
obj-$(CONFIG_SENSORS_LTC4151) += ltc4151.o
obj-$(CONFIG_SENSORS_LTC4215) += ltc4215.o
obj-$(CONFIG_SENSORS_LTC4222) += ltc4222.o
* Driver for Linear Technology LTC2990 power monitor
* Copyright (C) 2014 Topic Embedded Products
* Author: Mike Looijmans <>
* License: GPLv2
* This driver assumes the chip is wired as a dual current monitor, and
* reports the voltage drop across two series resistors. It also reports
* the chip's internal temperature and Vcc power supply voltage.
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#define LTC2990_STATUS 0x00
#define LTC2990_CONTROL 0x01
#define LTC2990_TRIGGER 0x02
#define LTC2990_TINT_MSB 0x04
#define LTC2990_V1_MSB 0x06
#define LTC2990_V2_MSB 0x08
#define LTC2990_V3_MSB 0x0A
#define LTC2990_V4_MSB 0x0C
#define LTC2990_VCC_MSB 0x0E
#define LTC2990_CONTROL_MEASURE_ALL (0x3 << 3)
/* convert raw register value to sign-extended integer in 16-bit range */
static int ltc2990_voltage_to_int(int raw)
if (raw & BIT(14))
return -(0x4000 - (raw & 0x3FFF)) << 2;
return (raw & 0x3FFF) << 2;
/* Return the converted value from the given register in uV or mC */
static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int *result)
int val;
val = i2c_smbus_read_word_swapped(i2c, reg);
if (unlikely(val < 0))
return val;
switch (reg) {
case LTC2990_TINT_MSB:
/* internal temp, 0.0625 degrees/LSB, 13-bit */
val = (val & 0x1FFF) << 3;
*result = (val * 1000) >> 7;
case LTC2990_V1_MSB:
case LTC2990_V3_MSB:
/* Vx-Vy, 19.42uV/LSB. Depends on mode. */
*result = ltc2990_voltage_to_int(val) * 1942 / (4 * 100);
case LTC2990_VCC_MSB:
/* Vcc, 305.18μV/LSB, 2.5V offset */
*result = (ltc2990_voltage_to_int(val) * 30518 /
(4 * 100 * 1000)) + 2500;
return -EINVAL; /* won't happen, keep compiler happy */
return 0;
static ssize_t ltc2990_show_value(struct device *dev,
struct device_attribute *da, char *buf)
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
int value;
int ret;
ret = ltc2990_get_value(dev_get_drvdata(dev), attr->index, &value);
if (unlikely(ret < 0))
return ret;
return snprintf(buf, PAGE_SIZE, "%d\n", value);
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ltc2990_show_value, NULL,
static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc2990_show_value, NULL,
static SENSOR_DEVICE_ATTR(curr2_input, S_IRUGO, ltc2990_show_value, NULL,
static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2990_show_value, NULL,
static struct attribute *ltc2990_attrs[] = {
static int ltc2990_i2c_probe(struct i2c_client *i2c,
const struct i2c_device_id *id)
int ret;
struct device *hwmon_dev;
if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
return -ENODEV;
/* Setup continuous mode, current monitor */
ret = i2c_smbus_write_byte_data(i2c, LTC2990_CONTROL,
if (ret < 0) {
dev_err(&i2c->dev, "Error: Failed to set control mode.\n");
return ret;
/* Trigger once to start continuous conversion */
ret = i2c_smbus_write_byte_data(i2c, LTC2990_TRIGGER, 1);
if (ret < 0) {
dev_err(&i2c->dev, "Error: Failed to start acquisition.\n");
return ret;
hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
return PTR_ERR_OR_ZERO(hwmon_dev);
static const struct i2c_device_id ltc2990_i2c_id[] = {
{ "ltc2990", 0 },
MODULE_DEVICE_TABLE(i2c, ltc2990_i2c_id);
static struct i2c_driver ltc2990_i2c_driver = {
.driver = {
.name = "ltc2990",
.probe = ltc2990_i2c_probe,
.id_table = ltc2990_i2c_id,
MODULE_DESCRIPTION("LTC2990 Sensor Driver");
MODULE_AUTHOR("Topic Embedded Products");
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