1/*
  2 * Driver for Linear Technology LTC2990 power monitor
  3 *
  4 * Copyright (C) 2014 Topic Embedded Products
  5 * Author: Mike Looijmans <mike.looijmans@topic.nl>
  6 *
  7 * License: GPLv2
  8 *
  9 * This driver assumes the chip is wired as a dual current monitor, and
 10 * reports the voltage drop across two series resistors. It also reports
 11 * the chip's internal temperature and Vcc power supply voltage.
 12 */
 13
 14#include <linux/err.h>
 15#include <linux/hwmon.h>
 16#include <linux/hwmon-sysfs.h>
 17#include <linux/i2c.h>
 18#include <linux/kernel.h>
 19#include <linux/module.h>
 20
 21#define LTC2990_STATUS	0x00
 22#define LTC2990_CONTROL	0x01
 23#define LTC2990_TRIGGER	0x02
 24#define LTC2990_TINT_MSB	0x04
 25#define LTC2990_V1_MSB	0x06
 26#define LTC2990_V2_MSB	0x08
 27#define LTC2990_V3_MSB	0x0A
 28#define LTC2990_V4_MSB	0x0C
 29#define LTC2990_VCC_MSB	0x0E
 30
 31#define LTC2990_CONTROL_KELVIN		BIT(7)
 32#define LTC2990_CONTROL_SINGLE		BIT(6)
 33#define LTC2990_CONTROL_MEASURE_ALL	(0x3 << 3)
 34#define LTC2990_CONTROL_MODE_CURRENT	0x06
 35#define LTC2990_CONTROL_MODE_VOLTAGE	0x07
 36
 37/* convert raw register value to sign-extended integer in 16-bit range */
 38static int ltc2990_voltage_to_int(int raw)
 39{
 40	if (raw & BIT(14))
 41		return -(0x4000 - (raw & 0x3FFF)) << 2;
 42	else
 43		return (raw & 0x3FFF) << 2;
 44}
 45
 46/* Return the converted value from the given register in uV or mC */
 47static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int *result)
 48{
 49	int val;
 50
 51	val = i2c_smbus_read_word_swapped(i2c, reg);
 52	if (unlikely(val < 0))
 53		return val;
 54
 55	switch (reg) {
 56	case LTC2990_TINT_MSB:
 57		/* internal temp, 0.0625 degrees/LSB, 13-bit  */
 58		val = (val & 0x1FFF) << 3;
 59		*result = (val * 1000) >> 7;
 60		break;
 61	case LTC2990_V1_MSB:
 62	case LTC2990_V3_MSB:
 63		 /* Vx-Vy, 19.42uV/LSB. Depends on mode. */
 64		*result = ltc2990_voltage_to_int(val) * 1942 / (4 * 100);
 65		break;
 66	case LTC2990_VCC_MSB:
 67		/* Vcc, 305.18μV/LSB, 2.5V offset */
 68		*result = (ltc2990_voltage_to_int(val) * 30518 /
 69			   (4 * 100 * 1000)) + 2500;
 70		break;
 71	default:
 72		return -EINVAL; /* won't happen, keep compiler happy */
 73	}
 74
 75	return 0;
 76}
 77
 78static ssize_t ltc2990_show_value(struct device *dev,
 79				  struct device_attribute *da, char *buf)
 80{
 81	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 82	int value;
 83	int ret;
 84
 85	ret = ltc2990_get_value(dev_get_drvdata(dev), attr->index, &value);
 86	if (unlikely(ret < 0))
 87		return ret;
 88
 89	return snprintf(buf, PAGE_SIZE, "%d\n", value);
 90}
 91
 92static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ltc2990_show_value, NULL,
 93			  LTC2990_TINT_MSB);
 94static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc2990_show_value, NULL,
 95			  LTC2990_V1_MSB);
 96static SENSOR_DEVICE_ATTR(curr2_input, S_IRUGO, ltc2990_show_value, NULL,
 97			  LTC2990_V3_MSB);
 98static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2990_show_value, NULL,
 99			  LTC2990_VCC_MSB);
100
101static struct attribute *ltc2990_attrs[] = {
102	&sensor_dev_attr_temp1_input.dev_attr.attr,
103	&sensor_dev_attr_curr1_input.dev_attr.attr,
104	&sensor_dev_attr_curr2_input.dev_attr.attr,
105	&sensor_dev_attr_in0_input.dev_attr.attr,
106	NULL,
107};
108ATTRIBUTE_GROUPS(ltc2990);
109
110static int ltc2990_i2c_probe(struct i2c_client *i2c,
111			     const struct i2c_device_id *id)
112{
113	int ret;
114	struct device *hwmon_dev;
115
116	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
117				     I2C_FUNC_SMBUS_WORD_DATA))
118		return -ENODEV;
119
120	/* Setup continuous mode, current monitor */
121	ret = i2c_smbus_write_byte_data(i2c, LTC2990_CONTROL,
122					LTC2990_CONTROL_MEASURE_ALL |
123					LTC2990_CONTROL_MODE_CURRENT);
124	if (ret < 0) {
125		dev_err(&i2c->dev, "Error: Failed to set control mode.\n");
126		return ret;
127	}
128	/* Trigger once to start continuous conversion */
129	ret = i2c_smbus_write_byte_data(i2c, LTC2990_TRIGGER, 1);
130	if (ret < 0) {
131		dev_err(&i2c->dev, "Error: Failed to start acquisition.\n");
132		return ret;
133	}
134
135	hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
136							   i2c->name,
137							   i2c,
138							   ltc2990_groups);
139
140	return PTR_ERR_OR_ZERO(hwmon_dev);
141}
142
143static const struct i2c_device_id ltc2990_i2c_id[] = {
144	{ "ltc2990", 0 },
145	{}
146};
147MODULE_DEVICE_TABLE(i2c, ltc2990_i2c_id);
148
149static struct i2c_driver ltc2990_i2c_driver = {
150	.driver = {
151		.name = "ltc2990",
152	},
153	.probe    = ltc2990_i2c_probe,
154	.id_table = ltc2990_i2c_id,
155};
156
157module_i2c_driver(ltc2990_i2c_driver);
158
159MODULE_DESCRIPTION("LTC2990 Sensor Driver");
160MODULE_AUTHOR("Topic Embedded Products");
161MODULE_LICENSE("GPL v2");