1 /*
2  * I2C client/driver for the Linear Technology LTC2941 and LTC2943
3  * Battery Gas Gauge IC
4  *
5  * Copyright (C) 2014 Topic Embedded Systems
6  *
7  * Author: Auryn Verwegen
8  * Author: Mike Looijmans
9  */
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/of_device.h>
13 #include <linux/types.h>
14 #include <linux/errno.h>
15 #include <linux/swab.h>
16 #include <linux/i2c.h>
17 #include <linux/delay.h>
18 #include <linux/power_supply.h>
19 #include <linux/slab.h>
20 
21 #define I16_MSB(x)			((x >> 8) & 0xFF)
22 #define I16_LSB(x)			(x & 0xFF)
23 
24 #define LTC294X_WORK_DELAY		10	/* Update delay in seconds */
25 
26 #define LTC294X_MAX_VALUE		0xFFFF
27 #define LTC294X_MID_SUPPLY		0x7FFF
28 
29 #define LTC2941_MAX_PRESCALER_EXP	7
30 #define LTC2943_MAX_PRESCALER_EXP	6
31 
32 enum ltc294x_reg {
33 	LTC294X_REG_STATUS		= 0x00,
34 	LTC294X_REG_CONTROL		= 0x01,
35 	LTC294X_REG_ACC_CHARGE_MSB	= 0x02,
36 	LTC294X_REG_ACC_CHARGE_LSB	= 0x03,
37 	LTC294X_REG_THRESH_HIGH_MSB	= 0x04,
38 	LTC294X_REG_THRESH_HIGH_LSB	= 0x05,
39 	LTC294X_REG_THRESH_LOW_MSB	= 0x06,
40 	LTC294X_REG_THRESH_LOW_LSB	= 0x07,
41 	LTC294X_REG_VOLTAGE_MSB	= 0x08,
42 	LTC294X_REG_VOLTAGE_LSB	= 0x09,
43 	LTC294X_REG_CURRENT_MSB	= 0x0E,
44 	LTC294X_REG_CURRENT_LSB	= 0x0F,
45 	LTC294X_REG_TEMPERATURE_MSB	= 0x14,
46 	LTC294X_REG_TEMPERATURE_LSB	= 0x15,
47 };
48 
49 #define LTC2943_REG_CONTROL_MODE_MASK (BIT(7) | BIT(6))
50 #define LTC2943_REG_CONTROL_MODE_SCAN BIT(7)
51 #define LTC294X_REG_CONTROL_PRESCALER_MASK	(BIT(5) | BIT(4) | BIT(3))
52 #define LTC294X_REG_CONTROL_SHUTDOWN_MASK	(BIT(0))
53 #define LTC294X_REG_CONTROL_PRESCALER_SET(x) \
54 	((x << 3) & LTC294X_REG_CONTROL_PRESCALER_MASK)
55 #define LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED	0
56 
57 #define LTC2941_NUM_REGS	0x08
58 #define LTC2943_NUM_REGS	0x18
59 
60 struct ltc294x_info {
61 	struct i2c_client *client;	/* I2C Client pointer */
62 	struct power_supply *supply;	/* Supply pointer */
63 	struct power_supply_desc supply_desc;	/* Supply description */
64 	struct delayed_work work;	/* Work scheduler */
65 	unsigned long num_regs;	/* Number of registers (chip type) */
66 	int charge;	/* Last charge register content */
67 	int r_sense;	/* mOhm */
68 	int Qlsb;	/* nAh */
69 };
70 
71 static inline int convert_bin_to_uAh(
72 	const struct ltc294x_info *info, int Q)
73 {
74 	return ((Q * (info->Qlsb / 10))) / 100;
75 }
76 
77 static inline int convert_uAh_to_bin(
78 	const struct ltc294x_info *info, int uAh)
79 {
80 	int Q;
81 
82 	Q = (uAh * 100) / (info->Qlsb/10);
83 	return (Q < LTC294X_MAX_VALUE) ? Q : LTC294X_MAX_VALUE;
84 }
85 
86 static int ltc294x_read_regs(struct i2c_client *client,
87 	enum ltc294x_reg reg, u8 *buf, int num_regs)
88 {
89 	int ret;
90 	struct i2c_msg msgs[2] = { };
91 	u8 reg_start = reg;
92 
93 	msgs[0].addr	= client->addr;
94 	msgs[0].len	= 1;
95 	msgs[0].buf	= &reg_start;
96 
97 	msgs[1].addr	= client->addr;
98 	msgs[1].len	= num_regs;
99 	msgs[1].buf	= buf;
100 	msgs[1].flags	= I2C_M_RD;
101 
102 	ret = i2c_transfer(client->adapter, &msgs[0], 2);
103 	if (ret < 0) {
104 		dev_err(&client->dev, "ltc2941 read_reg failed!\n");
105 		return ret;
106 	}
107 
108 	dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
109 		__func__, reg, num_regs, *buf);
110 
111 	return 0;
112 }
113 
114 static int ltc294x_write_regs(struct i2c_client *client,
115 	enum ltc294x_reg reg, const u8 *buf, int num_regs)
116 {
117 	int ret;
118 	u8 reg_start = reg;
119 
120 	ret = i2c_smbus_write_i2c_block_data(client, reg_start, num_regs, buf);
121 	if (ret < 0) {
122 		dev_err(&client->dev, "ltc2941 write_reg failed!\n");
123 		return ret;
124 	}
125 
126 	dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
127 		__func__, reg, num_regs, *buf);
128 
129 	return 0;
130 }
131 
132 static int ltc294x_reset(const struct ltc294x_info *info, int prescaler_exp)
133 {
134 	int ret;
135 	u8 value;
136 	u8 control;
137 
138 	/* Read status and control registers */
139 	ret = ltc294x_read_regs(info->client, LTC294X_REG_CONTROL, &value, 1);
140 	if (ret < 0) {
141 		dev_err(&info->client->dev,
142 			"Could not read registers from device\n");
143 		goto error_exit;
144 	}
145 
146 	control = LTC294X_REG_CONTROL_PRESCALER_SET(prescaler_exp) |
147 				LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED;
148 	/* Put the 2943 into "monitor" mode, so it measures every 10 sec */
149 	if (info->num_regs == LTC2943_NUM_REGS)
150 		control |= LTC2943_REG_CONTROL_MODE_SCAN;
151 
152 	if (value != control) {
153 		ret = ltc294x_write_regs(info->client,
154 			LTC294X_REG_CONTROL, &control, 1);
155 		if (ret < 0) {
156 			dev_err(&info->client->dev,
157 				"Could not write register\n");
158 			goto error_exit;
159 		}
160 	}
161 
162 	return 0;
163 
164 error_exit:
165 	return ret;
166 }
167 
168 static int ltc294x_read_charge_register(const struct ltc294x_info *info)
169 {
170 	int ret;
171 	u8 datar[2];
172 
173 	ret = ltc294x_read_regs(info->client,
174 		LTC294X_REG_ACC_CHARGE_MSB, &datar[0], 2);
175 	if (ret < 0)
176 		return ret;
177 	return (datar[0] << 8) + datar[1];
178 }
179 
180 static int ltc294x_get_charge_now(const struct ltc294x_info *info, int *val)
181 {
182 	int value = ltc294x_read_charge_register(info);
183 
184 	if (value < 0)
185 		return value;
186 	/* When r_sense < 0, this counts up when the battery discharges */
187 	if (info->Qlsb < 0)
188 		value -= 0xFFFF;
189 	*val = convert_bin_to_uAh(info, value);
190 	return 0;
191 }
192 
193 static int ltc294x_set_charge_now(const struct ltc294x_info *info, int val)
194 {
195 	int ret;
196 	u8 dataw[2];
197 	u8 ctrl_reg;
198 	s32 value;
199 
200 	value = convert_uAh_to_bin(info, val);
201 	/* Direction depends on how sense+/- were connected */
202 	if (info->Qlsb < 0)
203 		value += 0xFFFF;
204 	if ((value < 0) || (value > 0xFFFF)) /* input validation */
205 		return -EINVAL;
206 
207 	/* Read control register */
208 	ret = ltc294x_read_regs(info->client,
209 		LTC294X_REG_CONTROL, &ctrl_reg, 1);
210 	if (ret < 0)
211 		return ret;
212 	/* Disable analog section */
213 	ctrl_reg |= LTC294X_REG_CONTROL_SHUTDOWN_MASK;
214 	ret = ltc294x_write_regs(info->client,
215 		LTC294X_REG_CONTROL, &ctrl_reg, 1);
216 	if (ret < 0)
217 		return ret;
218 	/* Set new charge value */
219 	dataw[0] = I16_MSB(value);
220 	dataw[1] = I16_LSB(value);
221 	ret = ltc294x_write_regs(info->client,
222 		LTC294X_REG_ACC_CHARGE_MSB, &dataw[0], 2);
223 	if (ret < 0)
224 		goto error_exit;
225 	/* Enable analog section */
226 error_exit:
227 	ctrl_reg &= ~LTC294X_REG_CONTROL_SHUTDOWN_MASK;
228 	ret = ltc294x_write_regs(info->client,
229 		LTC294X_REG_CONTROL, &ctrl_reg, 1);
230 
231 	return ret < 0 ? ret : 0;
232 }
233 
234 static int ltc294x_get_charge_counter(
235 	const struct ltc294x_info *info, int *val)
236 {
237 	int value = ltc294x_read_charge_register(info);
238 
239 	if (value < 0)
240 		return value;
241 	value -= LTC294X_MID_SUPPLY;
242 	*val = convert_bin_to_uAh(info, value);
243 	return 0;
244 }
245 
246 static int ltc294x_get_voltage(const struct ltc294x_info *info, int *val)
247 {
248 	int ret;
249 	u8 datar[2];
250 	u32 value;
251 
252 	ret = ltc294x_read_regs(info->client,
253 		LTC294X_REG_VOLTAGE_MSB, &datar[0], 2);
254 	value = (datar[0] << 8) | datar[1];
255 	*val = ((value * 23600) / 0xFFFF) * 1000; /* in uV */
256 	return ret;
257 }
258 
259 static int ltc294x_get_current(const struct ltc294x_info *info, int *val)
260 {
261 	int ret;
262 	u8 datar[2];
263 	s32 value;
264 
265 	ret = ltc294x_read_regs(info->client,
266 		LTC294X_REG_CURRENT_MSB, &datar[0], 2);
267 	value = (datar[0] << 8) | datar[1];
268 	value -= 0x7FFF;
269 	/* Value is in range -32k..+32k, r_sense is usually 10..50 mOhm,
270 	 * the formula below keeps everything in s32 range while preserving
271 	 * enough digits */
272 	*val = 1000 * ((60000 * value) / (info->r_sense * 0x7FFF)); /* in uA */
273 	return ret;
274 }
275 
276 static int ltc294x_get_temperature(const struct ltc294x_info *info, int *val)
277 {
278 	int ret;
279 	u8 datar[2];
280 	u32 value;
281 
282 	ret = ltc294x_read_regs(info->client,
283 		LTC294X_REG_TEMPERATURE_MSB, &datar[0], 2);
284 	value = (datar[0] << 8) | datar[1];
285 	/* Full-scale is 510 Kelvin, convert to centidegrees  */
286 	*val = (((51000 * value) / 0xFFFF) - 27215);
287 	return ret;
288 }
289 
290 static int ltc294x_get_property(struct power_supply *psy,
291 				enum power_supply_property prop,
292 				union power_supply_propval *val)
293 {
294 	struct ltc294x_info *info = power_supply_get_drvdata(psy);
295 
296 	switch (prop) {
297 	case POWER_SUPPLY_PROP_CHARGE_NOW:
298 		return ltc294x_get_charge_now(info, &val->intval);
299 	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
300 		return ltc294x_get_charge_counter(info, &val->intval);
301 	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
302 		return ltc294x_get_voltage(info, &val->intval);
303 	case POWER_SUPPLY_PROP_CURRENT_NOW:
304 		return ltc294x_get_current(info, &val->intval);
305 	case POWER_SUPPLY_PROP_TEMP:
306 		return ltc294x_get_temperature(info, &val->intval);
307 	default:
308 		return -EINVAL;
309 	}
310 }
311 
312 static int ltc294x_set_property(struct power_supply *psy,
313 	enum power_supply_property psp,
314 	const union power_supply_propval *val)
315 {
316 	struct ltc294x_info *info = power_supply_get_drvdata(psy);
317 
318 	switch (psp) {
319 	case POWER_SUPPLY_PROP_CHARGE_NOW:
320 		return ltc294x_set_charge_now(info, val->intval);
321 	default:
322 		return -EPERM;
323 	}
324 }
325 
326 static int ltc294x_property_is_writeable(
327 	struct power_supply *psy, enum power_supply_property psp)
328 {
329 	switch (psp) {
330 	case POWER_SUPPLY_PROP_CHARGE_NOW:
331 		return 1;
332 	default:
333 		return 0;
334 	}
335 }
336 
337 static void ltc294x_update(struct ltc294x_info *info)
338 {
339 	int charge = ltc294x_read_charge_register(info);
340 
341 	if (charge != info->charge) {
342 		info->charge = charge;
343 		power_supply_changed(info->supply);
344 	}
345 }
346 
347 static void ltc294x_work(struct work_struct *work)
348 {
349 	struct ltc294x_info *info;
350 
351 	info = container_of(work, struct ltc294x_info, work.work);
352 	ltc294x_update(info);
353 	schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
354 }
355 
356 static enum power_supply_property ltc294x_properties[] = {
357 	POWER_SUPPLY_PROP_CHARGE_COUNTER,
358 	POWER_SUPPLY_PROP_CHARGE_NOW,
359 	POWER_SUPPLY_PROP_VOLTAGE_NOW,
360 	POWER_SUPPLY_PROP_CURRENT_NOW,
361 	POWER_SUPPLY_PROP_TEMP,
362 };
363 
364 static int ltc294x_i2c_remove(struct i2c_client *client)
365 {
366 	struct ltc294x_info *info = i2c_get_clientdata(client);
367 
368 	cancel_delayed_work(&info->work);
369 	power_supply_unregister(info->supply);
370 	return 0;
371 }
372 
373 static int ltc294x_i2c_probe(struct i2c_client *client,
374 	const struct i2c_device_id *id)
375 {
376 	struct power_supply_config psy_cfg = {};
377 	struct ltc294x_info *info;
378 	int ret;
379 	u32 prescaler_exp;
380 	s32 r_sense;
381 	struct device_node *np;
382 
383 	info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
384 	if (info == NULL)
385 		return -ENOMEM;
386 
387 	i2c_set_clientdata(client, info);
388 
389 	np = of_node_get(client->dev.of_node);
390 
391 	info->num_regs = (unsigned long)of_device_get_match_data(&client->dev);
392 	info->supply_desc.name = np->name;
393 
394 	/* r_sense can be negative, when sense+ is connected to the battery
395 	 * instead of the sense-. This results in reversed measurements. */
396 	ret = of_property_read_u32(np, "lltc,resistor-sense", &r_sense);
397 	if (ret < 0) {
398 		dev_err(&client->dev,
399 			"Could not find lltc,resistor-sense in devicetree\n");
400 		return ret;
401 	}
402 	info->r_sense = r_sense;
403 
404 	ret = of_property_read_u32(np, "lltc,prescaler-exponent",
405 		&prescaler_exp);
406 	if (ret < 0) {
407 		dev_warn(&client->dev,
408 			"lltc,prescaler-exponent not in devicetree\n");
409 		prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
410 	}
411 
412 	if (info->num_regs == LTC2943_NUM_REGS) {
413 		if (prescaler_exp > LTC2943_MAX_PRESCALER_EXP)
414 			prescaler_exp = LTC2943_MAX_PRESCALER_EXP;
415 		info->Qlsb = ((340 * 50000) / r_sense) /
416 				(4096 / (1 << (2*prescaler_exp)));
417 	} else {
418 		if (prescaler_exp > LTC2941_MAX_PRESCALER_EXP)
419 			prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
420 		info->Qlsb = ((85 * 50000) / r_sense) /
421 				(128 / (1 << prescaler_exp));
422 	}
423 
424 	info->client = client;
425 	info->supply_desc.type = POWER_SUPPLY_TYPE_BATTERY;
426 	info->supply_desc.properties = ltc294x_properties;
427 	if (info->num_regs >= LTC294X_REG_TEMPERATURE_LSB)
428 		info->supply_desc.num_properties =
429 			ARRAY_SIZE(ltc294x_properties);
430 	else if (info->num_regs >= LTC294X_REG_CURRENT_LSB)
431 		info->supply_desc.num_properties =
432 			ARRAY_SIZE(ltc294x_properties) - 1;
433 	else if (info->num_regs >= LTC294X_REG_VOLTAGE_LSB)
434 		info->supply_desc.num_properties =
435 			ARRAY_SIZE(ltc294x_properties) - 2;
436 	else
437 		info->supply_desc.num_properties =
438 			ARRAY_SIZE(ltc294x_properties) - 3;
439 	info->supply_desc.get_property = ltc294x_get_property;
440 	info->supply_desc.set_property = ltc294x_set_property;
441 	info->supply_desc.property_is_writeable = ltc294x_property_is_writeable;
442 	info->supply_desc.external_power_changed	= NULL;
443 
444 	psy_cfg.drv_data = info;
445 
446 	INIT_DELAYED_WORK(&info->work, ltc294x_work);
447 
448 	ret = ltc294x_reset(info, prescaler_exp);
449 	if (ret < 0) {
450 		dev_err(&client->dev, "Communication with chip failed\n");
451 		return ret;
452 	}
453 
454 	info->supply = power_supply_register(&client->dev, &info->supply_desc,
455 					     &psy_cfg);
456 	if (IS_ERR(info->supply)) {
457 		dev_err(&client->dev, "failed to register ltc2941\n");
458 		return PTR_ERR(info->supply);
459 	} else {
460 		schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
461 	}
462 
463 	return 0;
464 }
465 
466 #ifdef CONFIG_PM_SLEEP
467 
468 static int ltc294x_suspend(struct device *dev)
469 {
470 	struct i2c_client *client = to_i2c_client(dev);
471 	struct ltc294x_info *info = i2c_get_clientdata(client);
472 
473 	cancel_delayed_work(&info->work);
474 	return 0;
475 }
476 
477 static int ltc294x_resume(struct device *dev)
478 {
479 	struct i2c_client *client = to_i2c_client(dev);
480 	struct ltc294x_info *info = i2c_get_clientdata(client);
481 
482 	schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
483 	return 0;
484 }
485 
486 static SIMPLE_DEV_PM_OPS(ltc294x_pm_ops, ltc294x_suspend, ltc294x_resume);
487 #define LTC294X_PM_OPS (&ltc294x_pm_ops)
488 
489 #else
490 #define LTC294X_PM_OPS NULL
491 #endif /* CONFIG_PM_SLEEP */
492 
493 
494 static const struct i2c_device_id ltc294x_i2c_id[] = {
495 	{"ltc2941", LTC2941_NUM_REGS},
496 	{"ltc2943", LTC2943_NUM_REGS},
497 	{ },
498 };
499 MODULE_DEVICE_TABLE(i2c, ltc294x_i2c_id);
500 
501 static const struct of_device_id ltc294x_i2c_of_match[] = {
502 	{
503 		.compatible = "lltc,ltc2941",
504 		.data = (void *)LTC2941_NUM_REGS
505 	},
506 	{
507 		.compatible = "lltc,ltc2943",
508 		.data = (void *)LTC2943_NUM_REGS
509 	},
510 	{ },
511 };
512 MODULE_DEVICE_TABLE(of, ltc294x_i2c_of_match);
513 
514 static struct i2c_driver ltc294x_driver = {
515 	.driver = {
516 		.name	= "LTC2941",
517 		.of_match_table = ltc294x_i2c_of_match,
518 		.pm	= LTC294X_PM_OPS,
519 	},
520 	.probe		= ltc294x_i2c_probe,
521 	.remove		= ltc294x_i2c_remove,
522 	.id_table	= ltc294x_i2c_id,
523 };
524 module_i2c_driver(ltc294x_driver);
525 
526 MODULE_AUTHOR("Auryn Verwegen, Topic Embedded Systems");
527 MODULE_AUTHOR("Mike Looijmans, Topic Embedded Products");
528 MODULE_DESCRIPTION("LTC2941/LTC2943 Battery Gas Gauge IC driver");
529 MODULE_LICENSE("GPL");
530