ds2782_battery.c revision a009d29ea104c1bd8805a20018469897c2c2263c 
1/*
2 * I2C client/driver for the Maxim/Dallas DS2782 Stand-Alone Fuel Gauge IC
3 *
4 * Copyright (C) 2009 Bluewater Systems Ltd
5 *
6 * Author: Ryan Mallon <ryan@bluewatersys.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/types.h>
17#include <linux/errno.h>
18#include <linux/swab.h>
19#include <linux/i2c.h>
20#include <linux/idr.h>
21#include <linux/power_supply.h>
22
23#define DS2782_REG_RARC		0x06	/* Remaining active relative capacity */
24
25#define DS2782_REG_VOLT_MSB	0x0c
26#define DS2782_REG_TEMP_MSB	0x0a
27#define DS2782_REG_CURRENT_MSB	0x0e
28
29/* EEPROM Block */
30#define DS2782_REG_RSNSP	0x69	/* Sense resistor value */
31
32/* Current unit measurement in uA for a 1 milli-ohm sense resistor */
33#define DS2782_CURRENT_UNITS	1563
34
35#define to_ds2782_info(x) container_of(x, struct ds2782_info, battery)
36
37struct ds2782_info {
38	struct i2c_client	*client;
39	struct power_supply	battery;
40	int			id;
41};
42
43static DEFINE_IDR(battery_id);
44static DEFINE_MUTEX(battery_lock);
45
46static inline int ds2782_read_reg(struct ds2782_info *info, int reg, u8 *val)
47{
48	int ret;
49
50	ret = i2c_smbus_read_byte_data(info->client, reg);
51	if (ret < 0) {
52		dev_err(&info->client->dev, "register read failed\n");
53		return ret;
54	}
55
56	*val = ret;
57	return 0;
58}
59
60static inline int ds2782_read_reg16(struct ds2782_info *info, int reg_msb,
61				    s16 *val)
62{
63	int ret;
64
65	ret = swab16(i2c_smbus_read_word_data(info->client, reg_msb));
66	if (ret < 0) {
67		dev_err(&info->client->dev, "register read failed\n");
68		return ret;
69	}
70
71	*val = ret;
72	return 0;
73}
74
75static int ds2782_get_temp(struct ds2782_info *info, int *temp)
76{
77	s16 raw;
78	int err;
79
80	/*
81	 * Temperature is measured in units of 0.125 degrees celcius, the
82	 * power_supply class measures temperature in tenths of degrees
83	 * celsius. The temperature value is stored as a 10 bit number, plus
84	 * sign in the upper bits of a 16 bit register.
85	 */
86	err = ds2782_read_reg16(info, DS2782_REG_TEMP_MSB, &raw);
87	if (err)
88		return err;
89	*temp = ((raw / 32) * 125) / 100;
90	return 0;
91}
92
93static int ds2782_get_current(struct ds2782_info *info, int *current_uA)
94{
95	int sense_res;
96	int err;
97	u8 sense_res_raw;
98	s16 raw;
99
100	/*
101	 * The units of measurement for current are dependent on the value of
102	 * the sense resistor.
103	 */
104	err = ds2782_read_reg(info, DS2782_REG_RSNSP, &sense_res_raw);
105	if (err)
106		return err;
107	if (sense_res_raw == 0) {
108		dev_err(&info->client->dev, "sense resistor value is 0\n");
109		return -ENXIO;
110	}
111	sense_res = 1000 / sense_res_raw;
112
113	dev_dbg(&info->client->dev, "sense resistor = %d milli-ohms\n",
114		sense_res);
115	err = ds2782_read_reg16(info, DS2782_REG_CURRENT_MSB, &raw);
116	if (err)
117		return err;
118	*current_uA = raw * (DS2782_CURRENT_UNITS / sense_res);
119	return 0;
120}
121
122static int ds2782_get_voltage(struct ds2782_info *info, int *voltage_uA)
123{
124	s16 raw;
125	int err;
126
127	/*
128	 * Voltage is measured in units of 4.88mV. The voltage is stored as
129	 * a 10-bit number plus sign, in the upper bits of a 16-bit register
130	 */
131	err = ds2782_read_reg16(info, DS2782_REG_VOLT_MSB, &raw);
132	if (err)
133		return err;
134	*voltage_uA = (raw / 32) * 4800;
135	return 0;
136}
137
138static int ds2782_get_capacity(struct ds2782_info *info, int *capacity)
139{
140	int err;
141	u8 raw;
142
143	err = ds2782_read_reg(info, DS2782_REG_RARC, &raw);
144	if (err)
145		return err;
146	*capacity = raw;
147	return raw;
148}
149
150static int ds2782_get_status(struct ds2782_info *info, int *status)
151{
152	int err;
153	int current_uA;
154	int capacity;
155
156	err = ds2782_get_current(info, &current_uA);
157	if (err)
158		return err;
159
160	err = ds2782_get_capacity(info, &capacity);
161	if (err)
162		return err;
163
164	if (capacity == 100)
165		*status = POWER_SUPPLY_STATUS_FULL;
166	else if (current_uA == 0)
167		*status = POWER_SUPPLY_STATUS_NOT_CHARGING;
168	else if (current_uA < 0)
169		*status = POWER_SUPPLY_STATUS_DISCHARGING;
170	else
171		*status = POWER_SUPPLY_STATUS_CHARGING;
172
173	return 0;
174}
175
176static int ds2782_battery_get_property(struct power_supply *psy,
177				       enum power_supply_property prop,
178				       union power_supply_propval *val)
179{
180	struct ds2782_info *info = to_ds2782_info(psy);
181	int ret;
182
183	switch (prop) {
184	case POWER_SUPPLY_PROP_STATUS:
185		ret = ds2782_get_status(info, &val->intval);
186		break;
187
188	case POWER_SUPPLY_PROP_CAPACITY:
189		ret = ds2782_get_capacity(info, &val->intval);
190		break;
191
192	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
193		ret = ds2782_get_voltage(info, &val->intval);
194		break;
195
196	case POWER_SUPPLY_PROP_CURRENT_NOW:
197		ret = ds2782_get_current(info, &val->intval);
198		break;
199
200	case POWER_SUPPLY_PROP_TEMP:
201		ret = ds2782_get_temp(info, &val->intval);
202		break;
203
204	default:
205		ret = -EINVAL;
206	}
207
208	return ret;
209}
210
211static enum power_supply_property ds2782_battery_props[] = {
212	POWER_SUPPLY_PROP_STATUS,
213	POWER_SUPPLY_PROP_CAPACITY,
214	POWER_SUPPLY_PROP_VOLTAGE_NOW,
215	POWER_SUPPLY_PROP_CURRENT_NOW,
216	POWER_SUPPLY_PROP_TEMP,
217};
218
219static void ds2782_power_supply_init(struct power_supply *battery)
220{
221	battery->type			= POWER_SUPPLY_TYPE_BATTERY;
222	battery->properties		= ds2782_battery_props;
223	battery->num_properties		= ARRAY_SIZE(ds2782_battery_props);
224	battery->get_property		= ds2782_battery_get_property;
225	battery->external_power_changed	= NULL;
226}
227
228static int ds2782_battery_remove(struct i2c_client *client)
229{
230	struct ds2782_info *info = i2c_get_clientdata(client);
231
232	power_supply_unregister(&info->battery);
233	kfree(info->battery.name);
234
235	mutex_lock(&battery_lock);
236	idr_remove(&battery_id, info->id);
237	mutex_unlock(&battery_lock);
238
239	kfree(info);
240	return 0;
241}
242
243static int ds2782_battery_probe(struct i2c_client *client,
244				const struct i2c_device_id *id)
245{
246	struct ds2782_info *info;
247	int ret;
248	int num;
249
250	/* Get an ID for this battery */
251	ret = idr_pre_get(&battery_id, GFP_KERNEL);
252	if (ret == 0) {
253		ret = -ENOMEM;
254		goto fail_id;
255	}
256
257	mutex_lock(&battery_lock);
258	ret = idr_get_new(&battery_id, client, &num);
259	mutex_unlock(&battery_lock);
260	if (ret < 0)
261		goto fail_id;
262
263	info = kzalloc(sizeof(*info), GFP_KERNEL);
264	if (!info) {
265		ret = -ENOMEM;
266		goto fail_info;
267	}
268
269	info->battery.name = kasprintf(GFP_KERNEL, "ds2782-%d", num);
270	if (!info->battery.name) {
271		ret = -ENOMEM;
272		goto fail_name;
273	}
274
275	i2c_set_clientdata(client, info);
276	info->client = client;
277	ds2782_power_supply_init(&info->battery);
278
279	ret = power_supply_register(&client->dev, &info->battery);
280	if (ret) {
281		dev_err(&client->dev, "failed to register battery\n");
282		goto fail_register;
283	}
284
285	return 0;
286
287fail_register:
288	kfree(info->battery.name);
289fail_name:
290	kfree(info);
291fail_info:
292	mutex_lock(&battery_lock);
293	idr_remove(&battery_id, num);
294	mutex_unlock(&battery_lock);
295fail_id:
296	return ret;
297}
298
299static const struct i2c_device_id ds2782_id[] = {
300	{"ds2782", 0},
301	{},
302};
303
304static struct i2c_driver ds2782_battery_driver = {
305	.driver 	= {
306		.name	= "ds2782-battery",
307	},
308	.probe		= ds2782_battery_probe,
309	.remove		= ds2782_battery_remove,
310	.id_table	= ds2782_id,
311};
312
313static int __init ds2782_init(void)
314{
315	return i2c_add_driver(&ds2782_battery_driver);
316}
317module_init(ds2782_init);
318
319static void __exit ds2782_exit(void)
320{
321	i2c_del_driver(&ds2782_battery_driver);
322}
323module_exit(ds2782_exit);
324
325MODULE_AUTHOR("Ryan Mallon <ryan@bluewatersys.com>");
326MODULE_DESCRIPTION("Maxim/Dallas DS2782 Stand-Alone Fuel Gauage IC driver");
327MODULE_LICENSE("GPL");
328