summaryrefslogtreecommitdiff
path: root/drivers/hwmon/ltc4215.c
blob: 7cef3cb2962b90d5cfa257b3b2bbcbd8cf901224 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller
 *
 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
 *
 * 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_voltage_show(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_current_show(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_power_show(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_alarm_show(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_RO(curr1_input, ltc4215_current, 0);
static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2);

/* Power (virtual) */
static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0);

/* Input Voltage */
static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN);
static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0);
static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1);

/* Output Voltage */
static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE);
static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc4215_alarm, 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)
{
	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_new	= 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");