1/*
2 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller
3 *
4 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; version 2 of the License.
9 *
10 * Datasheet:
11 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/init.h>
17#include <linux/err.h>
18#include <linux/slab.h>
19#include <linux/i2c.h>
20#include <linux/hwmon.h>
21#include <linux/hwmon-sysfs.h>
22#include <linux/jiffies.h>
23
24/* Here are names of the chip's registers (a.k.a. commands) */
25enum ltc4215_cmd {
26	LTC4215_CONTROL			= 0x00, /* rw */
27	LTC4215_ALERT			= 0x01, /* rw */
28	LTC4215_STATUS			= 0x02, /* ro */
29	LTC4215_FAULT			= 0x03, /* rw */
30	LTC4215_SENSE			= 0x04, /* rw */
31	LTC4215_SOURCE			= 0x05, /* rw */
32	LTC4215_ADIN			= 0x06, /* rw */
33};
34
35struct ltc4215_data {
36	struct i2c_client *client;
37
38	struct mutex update_lock;
39	bool valid;
40	unsigned long last_updated; /* in jiffies */
41
42	/* Registers */
43	u8 regs[7];
44};
45
46static struct ltc4215_data *ltc4215_update_device(struct device *dev)
47{
48	struct ltc4215_data *data = dev_get_drvdata(dev);
49	struct i2c_client *client = data->client;
50	s32 val;
51	int i;
52
53	mutex_lock(&data->update_lock);
54
55	/* The chip's A/D updates 10 times per second */
56	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
57
58		dev_dbg(&client->dev, "Starting ltc4215 update\n");
59
60		/* Read all registers */
61		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
62			val = i2c_smbus_read_byte_data(client, i);
63			if (unlikely(val < 0))
64				data->regs[i] = 0;
65			else
66				data->regs[i] = val;
67		}
68
69		data->last_updated = jiffies;
70		data->valid = 1;
71	}
72
73	mutex_unlock(&data->update_lock);
74
75	return data;
76}
77
78/* Return the voltage from the given register in millivolts */
79static int ltc4215_get_voltage(struct device *dev, u8 reg)
80{
81	struct ltc4215_data *data = ltc4215_update_device(dev);
82	const u8 regval = data->regs[reg];
83	u32 voltage = 0;
84
85	switch (reg) {
86	case LTC4215_SENSE:
87		/* 151 uV per increment */
88		voltage = regval * 151 / 1000;
89		break;
90	case LTC4215_SOURCE:
91		/* 60.5 mV per increment */
92		voltage = regval * 605 / 10;
93		break;
94	case LTC4215_ADIN:
95		/*
96		 * The ADIN input is divided by 12.5, and has 4.82 mV
97		 * per increment, so we have the additional multiply
98		 */
99		voltage = regval * 482 * 125 / 1000;
100		break;
101	default:
102		/* If we get here, the developer messed up */
103		WARN_ON_ONCE(1);
104		break;
105	}
106
107	return voltage;
108}
109
110/* Return the current from the sense resistor in mA */
111static unsigned int ltc4215_get_current(struct device *dev)
112{
113	struct ltc4215_data *data = ltc4215_update_device(dev);
114
115	/*
116	 * The strange looking conversions that follow are fixed-point
117	 * math, since we cannot do floating point in the kernel.
118	 *
119	 * Step 1: convert sense register to microVolts
120	 * Step 2: convert voltage to milliAmperes
121	 *
122	 * If you play around with the V=IR equation, you come up with
123	 * the following: X uV / Y mOhm == Z mA
124	 *
125	 * With the resistors that are fractions of a milliOhm, we multiply
126	 * the voltage and resistance by 10, to shift the decimal point.
127	 * Now we can use the normal division operator again.
128	 */
129
130	/* Calculate voltage in microVolts (151 uV per increment) */
131	const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
132
133	/* Calculate current in milliAmperes (4 milliOhm sense resistor) */
134	const unsigned int curr = voltage / 4;
135
136	return curr;
137}
138
139static ssize_t ltc4215_show_voltage(struct device *dev,
140				    struct device_attribute *da,
141				    char *buf)
142{
143	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
144	const int voltage = ltc4215_get_voltage(dev, attr->index);
145
146	return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
147}
148
149static ssize_t ltc4215_show_current(struct device *dev,
150				    struct device_attribute *da,
151				    char *buf)
152{
153	const unsigned int curr = ltc4215_get_current(dev);
154
155	return snprintf(buf, PAGE_SIZE, "%u\n", curr);
156}
157
158static ssize_t ltc4215_show_power(struct device *dev,
159				  struct device_attribute *da,
160				  char *buf)
161{
162	const unsigned int curr = ltc4215_get_current(dev);
163	const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
164
165	/* current in mA * voltage in mV == power in uW */
166	const unsigned int power = abs(output_voltage * curr);
167
168	return snprintf(buf, PAGE_SIZE, "%u\n", power);
169}
170
171static ssize_t ltc4215_show_alarm(struct device *dev,
172					  struct device_attribute *da,
173					  char *buf)
174{
175	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
176	struct ltc4215_data *data = ltc4215_update_device(dev);
177	const u8 reg = data->regs[LTC4215_STATUS];
178	const u32 mask = attr->index;
179
180	return snprintf(buf, PAGE_SIZE, "%u\n", !!(reg & mask));
181}
182
183/*
184 * These macros are used below in constructing device attribute objects
185 * for use with sysfs_create_group() to make a sysfs device file
186 * for each register.
187 */
188
189/* Construct a sensor_device_attribute structure for each register */
190
191/* Current */
192static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4215_show_current, NULL, 0);
193static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
194			  1 << 2);
195
196/* Power (virtual) */
197static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4215_show_power, NULL, 0);
198
199/* Input Voltage */
200static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4215_show_voltage, NULL,
201			  LTC4215_ADIN);
202static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
203			  1 << 0);
204static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
205			  1 << 1);
206
207/* Output Voltage */
208static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4215_show_voltage, NULL,
209			  LTC4215_SOURCE);
210static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
211			  1 << 3);
212
213/*
214 * Finally, construct an array of pointers to members of the above objects,
215 * as required for sysfs_create_group()
216 */
217static struct attribute *ltc4215_attrs[] = {
218	&sensor_dev_attr_curr1_input.dev_attr.attr,
219	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
220
221	&sensor_dev_attr_power1_input.dev_attr.attr,
222
223	&sensor_dev_attr_in1_input.dev_attr.attr,
224	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
225	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
226
227	&sensor_dev_attr_in2_input.dev_attr.attr,
228	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
229
230	NULL,
231};
232ATTRIBUTE_GROUPS(ltc4215);
233
234static int ltc4215_probe(struct i2c_client *client,
235			 const struct i2c_device_id *id)
236{
237	struct i2c_adapter *adapter = client->adapter;
238	struct device *dev = &client->dev;
239	struct ltc4215_data *data;
240	struct device *hwmon_dev;
241
242	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
243		return -ENODEV;
244
245	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
246	if (!data)
247		return -ENOMEM;
248
249	data->client = client;
250	mutex_init(&data->update_lock);
251
252	/* Initialize the LTC4215 chip */
253	i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
254
255	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
256							   data,
257							   ltc4215_groups);
258	return PTR_ERR_OR_ZERO(hwmon_dev);
259}
260
261static const struct i2c_device_id ltc4215_id[] = {
262	{ "ltc4215", 0 },
263	{ }
264};
265MODULE_DEVICE_TABLE(i2c, ltc4215_id);
266
267/* This is the driver that will be inserted */
268static struct i2c_driver ltc4215_driver = {
269	.driver = {
270		.name	= "ltc4215",
271	},
272	.probe		= ltc4215_probe,
273	.id_table	= ltc4215_id,
274};
275
276module_i2c_driver(ltc4215_driver);
277
278MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
279MODULE_DESCRIPTION("LTC4215 driver");
280MODULE_LICENSE("GPL");
281