xref: /openbmc/linux/drivers/rtc/rtc-isl1208.c (revision e23feb16)
1 /*
2  * Intersil ISL1208 rtc class driver
3  *
4  * Copyright 2005,2006 Hebert Valerio Riedel <hvr@gnu.org>
5  *
6  *  This program is free software; you can redistribute  it and/or modify it
7  *  under  the terms of  the GNU General  Public License as published by the
8  *  Free Software Foundation;  either version 2 of the  License, or (at your
9  *  option) any later version.
10  *
11  */
12 
13 #include <linux/module.h>
14 #include <linux/i2c.h>
15 #include <linux/bcd.h>
16 #include <linux/rtc.h>
17 
18 #define DRV_VERSION "0.3"
19 
20 /* Register map */
21 /* rtc section */
22 #define ISL1208_REG_SC  0x00
23 #define ISL1208_REG_MN  0x01
24 #define ISL1208_REG_HR  0x02
25 #define ISL1208_REG_HR_MIL     (1<<7)	/* 24h/12h mode */
26 #define ISL1208_REG_HR_PM      (1<<5)	/* PM/AM bit in 12h mode */
27 #define ISL1208_REG_DT  0x03
28 #define ISL1208_REG_MO  0x04
29 #define ISL1208_REG_YR  0x05
30 #define ISL1208_REG_DW  0x06
31 #define ISL1208_RTC_SECTION_LEN 7
32 
33 /* control/status section */
34 #define ISL1208_REG_SR  0x07
35 #define ISL1208_REG_SR_ARST    (1<<7)	/* auto reset */
36 #define ISL1208_REG_SR_XTOSCB  (1<<6)	/* crystal oscillator */
37 #define ISL1208_REG_SR_WRTC    (1<<4)	/* write rtc */
38 #define ISL1208_REG_SR_ALM     (1<<2)	/* alarm */
39 #define ISL1208_REG_SR_BAT     (1<<1)	/* battery */
40 #define ISL1208_REG_SR_RTCF    (1<<0)	/* rtc fail */
41 #define ISL1208_REG_INT 0x08
42 #define ISL1208_REG_INT_ALME   (1<<6)   /* alarm enable */
43 #define ISL1208_REG_INT_IM     (1<<7)   /* interrupt/alarm mode */
44 #define ISL1208_REG_09  0x09	/* reserved */
45 #define ISL1208_REG_ATR 0x0a
46 #define ISL1208_REG_DTR 0x0b
47 
48 /* alarm section */
49 #define ISL1208_REG_SCA 0x0c
50 #define ISL1208_REG_MNA 0x0d
51 #define ISL1208_REG_HRA 0x0e
52 #define ISL1208_REG_DTA 0x0f
53 #define ISL1208_REG_MOA 0x10
54 #define ISL1208_REG_DWA 0x11
55 #define ISL1208_ALARM_SECTION_LEN 6
56 
57 /* user section */
58 #define ISL1208_REG_USR1 0x12
59 #define ISL1208_REG_USR2 0x13
60 #define ISL1208_USR_SECTION_LEN 2
61 
62 static struct i2c_driver isl1208_driver;
63 
64 /* block read */
65 static int
66 isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
67 		      unsigned len)
68 {
69 	u8 reg_addr[1] = { reg };
70 	struct i2c_msg msgs[2] = {
71 		{
72 			.addr = client->addr,
73 			.len = sizeof(reg_addr),
74 			.buf = reg_addr
75 		},
76 		{
77 			.addr = client->addr,
78 			.flags = I2C_M_RD,
79 			.len = len,
80 			.buf = buf
81 		}
82 	};
83 	int ret;
84 
85 	BUG_ON(reg > ISL1208_REG_USR2);
86 	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
87 
88 	ret = i2c_transfer(client->adapter, msgs, 2);
89 	if (ret > 0)
90 		ret = 0;
91 	return ret;
92 }
93 
94 /* block write */
95 static int
96 isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
97 		     unsigned len)
98 {
99 	u8 i2c_buf[ISL1208_REG_USR2 + 2];
100 	struct i2c_msg msgs[1] = {
101 		{
102 			.addr = client->addr,
103 			.len = len + 1,
104 			.buf = i2c_buf
105 		}
106 	};
107 	int ret;
108 
109 	BUG_ON(reg > ISL1208_REG_USR2);
110 	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
111 
112 	i2c_buf[0] = reg;
113 	memcpy(&i2c_buf[1], &buf[0], len);
114 
115 	ret = i2c_transfer(client->adapter, msgs, 1);
116 	if (ret > 0)
117 		ret = 0;
118 	return ret;
119 }
120 
121 /* simple check to see whether we have a isl1208 */
122 static int
123 isl1208_i2c_validate_client(struct i2c_client *client)
124 {
125 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
126 	u8 zero_mask[ISL1208_RTC_SECTION_LEN] = {
127 		0x80, 0x80, 0x40, 0xc0, 0xe0, 0x00, 0xf8
128 	};
129 	int i;
130 	int ret;
131 
132 	ret = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
133 	if (ret < 0)
134 		return ret;
135 
136 	for (i = 0; i < ISL1208_RTC_SECTION_LEN; ++i) {
137 		if (regs[i] & zero_mask[i])	/* check if bits are cleared */
138 			return -ENODEV;
139 	}
140 
141 	return 0;
142 }
143 
144 static int
145 isl1208_i2c_get_sr(struct i2c_client *client)
146 {
147 	int sr = i2c_smbus_read_byte_data(client, ISL1208_REG_SR);
148 	if (sr < 0)
149 		return -EIO;
150 
151 	return sr;
152 }
153 
154 static int
155 isl1208_i2c_get_atr(struct i2c_client *client)
156 {
157 	int atr = i2c_smbus_read_byte_data(client, ISL1208_REG_ATR);
158 	if (atr < 0)
159 		return atr;
160 
161 	/* The 6bit value in the ATR register controls the load
162 	 * capacitance C_load * in steps of 0.25pF
163 	 *
164 	 * bit (1<<5) of the ATR register is inverted
165 	 *
166 	 * C_load(ATR=0x20) =  4.50pF
167 	 * C_load(ATR=0x00) = 12.50pF
168 	 * C_load(ATR=0x1f) = 20.25pF
169 	 *
170 	 */
171 
172 	atr &= 0x3f;		/* mask out lsb */
173 	atr ^= 1 << 5;		/* invert 6th bit */
174 	atr += 2 * 9;		/* add offset of 4.5pF; unit[atr] = 0.25pF */
175 
176 	return atr;
177 }
178 
179 static int
180 isl1208_i2c_get_dtr(struct i2c_client *client)
181 {
182 	int dtr = i2c_smbus_read_byte_data(client, ISL1208_REG_DTR);
183 	if (dtr < 0)
184 		return -EIO;
185 
186 	/* dtr encodes adjustments of {-60,-40,-20,0,20,40,60} ppm */
187 	dtr = ((dtr & 0x3) * 20) * (dtr & (1 << 2) ? -1 : 1);
188 
189 	return dtr;
190 }
191 
192 static int
193 isl1208_i2c_get_usr(struct i2c_client *client)
194 {
195 	u8 buf[ISL1208_USR_SECTION_LEN] = { 0, };
196 	int ret;
197 
198 	ret = isl1208_i2c_read_regs(client, ISL1208_REG_USR1, buf,
199 				    ISL1208_USR_SECTION_LEN);
200 	if (ret < 0)
201 		return ret;
202 
203 	return (buf[1] << 8) | buf[0];
204 }
205 
206 static int
207 isl1208_i2c_set_usr(struct i2c_client *client, u16 usr)
208 {
209 	u8 buf[ISL1208_USR_SECTION_LEN];
210 
211 	buf[0] = usr & 0xff;
212 	buf[1] = (usr >> 8) & 0xff;
213 
214 	return isl1208_i2c_set_regs(client, ISL1208_REG_USR1, buf,
215 				    ISL1208_USR_SECTION_LEN);
216 }
217 
218 static int
219 isl1208_rtc_toggle_alarm(struct i2c_client *client, int enable)
220 {
221 	int icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
222 
223 	if (icr < 0) {
224 		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
225 		return icr;
226 	}
227 
228 	if (enable)
229 		icr |= ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM;
230 	else
231 		icr &= ~(ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM);
232 
233 	icr = i2c_smbus_write_byte_data(client, ISL1208_REG_INT, icr);
234 	if (icr < 0) {
235 		dev_err(&client->dev, "%s: writing INT failed\n", __func__);
236 		return icr;
237 	}
238 
239 	return 0;
240 }
241 
242 static int
243 isl1208_rtc_proc(struct device *dev, struct seq_file *seq)
244 {
245 	struct i2c_client *const client = to_i2c_client(dev);
246 	int sr, dtr, atr, usr;
247 
248 	sr = isl1208_i2c_get_sr(client);
249 	if (sr < 0) {
250 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
251 		return sr;
252 	}
253 
254 	seq_printf(seq, "status_reg\t:%s%s%s%s%s%s (0x%.2x)\n",
255 		   (sr & ISL1208_REG_SR_RTCF) ? " RTCF" : "",
256 		   (sr & ISL1208_REG_SR_BAT) ? " BAT" : "",
257 		   (sr & ISL1208_REG_SR_ALM) ? " ALM" : "",
258 		   (sr & ISL1208_REG_SR_WRTC) ? " WRTC" : "",
259 		   (sr & ISL1208_REG_SR_XTOSCB) ? " XTOSCB" : "",
260 		   (sr & ISL1208_REG_SR_ARST) ? " ARST" : "", sr);
261 
262 	seq_printf(seq, "batt_status\t: %s\n",
263 		   (sr & ISL1208_REG_SR_RTCF) ? "bad" : "okay");
264 
265 	dtr = isl1208_i2c_get_dtr(client);
266 	if (dtr >= 0 - 1)
267 		seq_printf(seq, "digital_trim\t: %d ppm\n", dtr);
268 
269 	atr = isl1208_i2c_get_atr(client);
270 	if (atr >= 0)
271 		seq_printf(seq, "analog_trim\t: %d.%.2d pF\n",
272 			   atr >> 2, (atr & 0x3) * 25);
273 
274 	usr = isl1208_i2c_get_usr(client);
275 	if (usr >= 0)
276 		seq_printf(seq, "user_data\t: 0x%.4x\n", usr);
277 
278 	return 0;
279 }
280 
281 static int
282 isl1208_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
283 {
284 	int sr;
285 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
286 
287 	sr = isl1208_i2c_get_sr(client);
288 	if (sr < 0) {
289 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
290 		return -EIO;
291 	}
292 
293 	sr = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
294 	if (sr < 0) {
295 		dev_err(&client->dev, "%s: reading RTC section failed\n",
296 			__func__);
297 		return sr;
298 	}
299 
300 	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SC]);
301 	tm->tm_min = bcd2bin(regs[ISL1208_REG_MN]);
302 
303 	/* HR field has a more complex interpretation */
304 	{
305 		const u8 _hr = regs[ISL1208_REG_HR];
306 		if (_hr & ISL1208_REG_HR_MIL)	/* 24h format */
307 			tm->tm_hour = bcd2bin(_hr & 0x3f);
308 		else {
309 			/* 12h format */
310 			tm->tm_hour = bcd2bin(_hr & 0x1f);
311 			if (_hr & ISL1208_REG_HR_PM)	/* PM flag set */
312 				tm->tm_hour += 12;
313 		}
314 	}
315 
316 	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DT]);
317 	tm->tm_mon = bcd2bin(regs[ISL1208_REG_MO]) - 1;	/* rtc starts at 1 */
318 	tm->tm_year = bcd2bin(regs[ISL1208_REG_YR]) + 100;
319 	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DW]);
320 
321 	return 0;
322 }
323 
324 static int
325 isl1208_i2c_read_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
326 {
327 	struct rtc_time *const tm = &alarm->time;
328 	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
329 	int icr, yr, sr = isl1208_i2c_get_sr(client);
330 
331 	if (sr < 0) {
332 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
333 		return sr;
334 	}
335 
336 	sr = isl1208_i2c_read_regs(client, ISL1208_REG_SCA, regs,
337 				   ISL1208_ALARM_SECTION_LEN);
338 	if (sr < 0) {
339 		dev_err(&client->dev, "%s: reading alarm section failed\n",
340 			__func__);
341 		return sr;
342 	}
343 
344 	/* MSB of each alarm register is an enable bit */
345 	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SCA - ISL1208_REG_SCA] & 0x7f);
346 	tm->tm_min = bcd2bin(regs[ISL1208_REG_MNA - ISL1208_REG_SCA] & 0x7f);
347 	tm->tm_hour = bcd2bin(regs[ISL1208_REG_HRA - ISL1208_REG_SCA] & 0x3f);
348 	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DTA - ISL1208_REG_SCA] & 0x3f);
349 	tm->tm_mon =
350 		bcd2bin(regs[ISL1208_REG_MOA - ISL1208_REG_SCA] & 0x1f) - 1;
351 	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DWA - ISL1208_REG_SCA] & 0x03);
352 
353 	/* The alarm doesn't store the year so get it from the rtc section */
354 	yr = i2c_smbus_read_byte_data(client, ISL1208_REG_YR);
355 	if (yr < 0) {
356 		dev_err(&client->dev, "%s: reading RTC YR failed\n", __func__);
357 		return yr;
358 	}
359 	tm->tm_year = bcd2bin(yr) + 100;
360 
361 	icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
362 	if (icr < 0) {
363 		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
364 		return icr;
365 	}
366 	alarm->enabled = !!(icr & ISL1208_REG_INT_ALME);
367 
368 	return 0;
369 }
370 
371 static int
372 isl1208_i2c_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
373 {
374 	struct rtc_time *alarm_tm = &alarm->time;
375 	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
376 	const int offs = ISL1208_REG_SCA;
377 	unsigned long rtc_secs, alarm_secs;
378 	struct rtc_time rtc_tm;
379 	int err, enable;
380 
381 	err = isl1208_i2c_read_time(client, &rtc_tm);
382 	if (err)
383 		return err;
384 	err = rtc_tm_to_time(&rtc_tm, &rtc_secs);
385 	if (err)
386 		return err;
387 	err = rtc_tm_to_time(alarm_tm, &alarm_secs);
388 	if (err)
389 		return err;
390 
391 	/* If the alarm time is before the current time disable the alarm */
392 	if (!alarm->enabled || alarm_secs <= rtc_secs)
393 		enable = 0x00;
394 	else
395 		enable = 0x80;
396 
397 	/* Program the alarm and enable it for each setting */
398 	regs[ISL1208_REG_SCA - offs] = bin2bcd(alarm_tm->tm_sec) | enable;
399 	regs[ISL1208_REG_MNA - offs] = bin2bcd(alarm_tm->tm_min) | enable;
400 	regs[ISL1208_REG_HRA - offs] = bin2bcd(alarm_tm->tm_hour) |
401 		ISL1208_REG_HR_MIL | enable;
402 
403 	regs[ISL1208_REG_DTA - offs] = bin2bcd(alarm_tm->tm_mday) | enable;
404 	regs[ISL1208_REG_MOA - offs] = bin2bcd(alarm_tm->tm_mon + 1) | enable;
405 	regs[ISL1208_REG_DWA - offs] = bin2bcd(alarm_tm->tm_wday & 7) | enable;
406 
407 	/* write ALARM registers */
408 	err = isl1208_i2c_set_regs(client, offs, regs,
409 				  ISL1208_ALARM_SECTION_LEN);
410 	if (err < 0) {
411 		dev_err(&client->dev, "%s: writing ALARM section failed\n",
412 			__func__);
413 		return err;
414 	}
415 
416 	err = isl1208_rtc_toggle_alarm(client, enable);
417 	if (err)
418 		return err;
419 
420 	return 0;
421 }
422 
423 static int
424 isl1208_rtc_read_time(struct device *dev, struct rtc_time *tm)
425 {
426 	return isl1208_i2c_read_time(to_i2c_client(dev), tm);
427 }
428 
429 static int
430 isl1208_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
431 {
432 	int sr;
433 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
434 
435 	/* The clock has an 8 bit wide bcd-coded register (they never learn)
436 	 * for the year. tm_year is an offset from 1900 and we are interested
437 	 * in the 2000-2099 range, so any value less than 100 is invalid.
438 	 */
439 	if (tm->tm_year < 100)
440 		return -EINVAL;
441 
442 	regs[ISL1208_REG_SC] = bin2bcd(tm->tm_sec);
443 	regs[ISL1208_REG_MN] = bin2bcd(tm->tm_min);
444 	regs[ISL1208_REG_HR] = bin2bcd(tm->tm_hour) | ISL1208_REG_HR_MIL;
445 
446 	regs[ISL1208_REG_DT] = bin2bcd(tm->tm_mday);
447 	regs[ISL1208_REG_MO] = bin2bcd(tm->tm_mon + 1);
448 	regs[ISL1208_REG_YR] = bin2bcd(tm->tm_year - 100);
449 
450 	regs[ISL1208_REG_DW] = bin2bcd(tm->tm_wday & 7);
451 
452 	sr = isl1208_i2c_get_sr(client);
453 	if (sr < 0) {
454 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
455 		return sr;
456 	}
457 
458 	/* set WRTC */
459 	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
460 				       sr | ISL1208_REG_SR_WRTC);
461 	if (sr < 0) {
462 		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
463 		return sr;
464 	}
465 
466 	/* write RTC registers */
467 	sr = isl1208_i2c_set_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
468 	if (sr < 0) {
469 		dev_err(&client->dev, "%s: writing RTC section failed\n",
470 			__func__);
471 		return sr;
472 	}
473 
474 	/* clear WRTC again */
475 	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
476 				       sr & ~ISL1208_REG_SR_WRTC);
477 	if (sr < 0) {
478 		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
479 		return sr;
480 	}
481 
482 	return 0;
483 }
484 
485 
486 static int
487 isl1208_rtc_set_time(struct device *dev, struct rtc_time *tm)
488 {
489 	return isl1208_i2c_set_time(to_i2c_client(dev), tm);
490 }
491 
492 static int
493 isl1208_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
494 {
495 	return isl1208_i2c_read_alarm(to_i2c_client(dev), alarm);
496 }
497 
498 static int
499 isl1208_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
500 {
501 	return isl1208_i2c_set_alarm(to_i2c_client(dev), alarm);
502 }
503 
504 static irqreturn_t
505 isl1208_rtc_interrupt(int irq, void *data)
506 {
507 	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
508 	struct i2c_client *client = data;
509 	struct rtc_device *rtc = i2c_get_clientdata(client);
510 	int handled = 0, sr, err;
511 
512 	/*
513 	 * I2C reads get NAK'ed if we read straight away after an interrupt?
514 	 * Using a mdelay/msleep didn't seem to help either, so we work around
515 	 * this by continually trying to read the register for a short time.
516 	 */
517 	while (1) {
518 		sr = isl1208_i2c_get_sr(client);
519 		if (sr >= 0)
520 			break;
521 
522 		if (time_after(jiffies, timeout)) {
523 			dev_err(&client->dev, "%s: reading SR failed\n",
524 				__func__);
525 			return sr;
526 		}
527 	}
528 
529 	if (sr & ISL1208_REG_SR_ALM) {
530 		dev_dbg(&client->dev, "alarm!\n");
531 
532 		rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);
533 
534 		/* Clear the alarm */
535 		sr &= ~ISL1208_REG_SR_ALM;
536 		sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
537 		if (sr < 0)
538 			dev_err(&client->dev, "%s: writing SR failed\n",
539 				__func__);
540 		else
541 			handled = 1;
542 
543 		/* Disable the alarm */
544 		err = isl1208_rtc_toggle_alarm(client, 0);
545 		if (err)
546 			return err;
547 	}
548 
549 	return handled ? IRQ_HANDLED : IRQ_NONE;
550 }
551 
552 static const struct rtc_class_ops isl1208_rtc_ops = {
553 	.proc = isl1208_rtc_proc,
554 	.read_time = isl1208_rtc_read_time,
555 	.set_time = isl1208_rtc_set_time,
556 	.read_alarm = isl1208_rtc_read_alarm,
557 	.set_alarm = isl1208_rtc_set_alarm,
558 };
559 
560 /* sysfs interface */
561 
562 static ssize_t
563 isl1208_sysfs_show_atrim(struct device *dev,
564 			 struct device_attribute *attr, char *buf)
565 {
566 	int atr = isl1208_i2c_get_atr(to_i2c_client(dev));
567 	if (atr < 0)
568 		return atr;
569 
570 	return sprintf(buf, "%d.%.2d pF\n", atr >> 2, (atr & 0x3) * 25);
571 }
572 
573 static DEVICE_ATTR(atrim, S_IRUGO, isl1208_sysfs_show_atrim, NULL);
574 
575 static ssize_t
576 isl1208_sysfs_show_dtrim(struct device *dev,
577 			 struct device_attribute *attr, char *buf)
578 {
579 	int dtr = isl1208_i2c_get_dtr(to_i2c_client(dev));
580 	if (dtr < 0)
581 		return dtr;
582 
583 	return sprintf(buf, "%d ppm\n", dtr);
584 }
585 
586 static DEVICE_ATTR(dtrim, S_IRUGO, isl1208_sysfs_show_dtrim, NULL);
587 
588 static ssize_t
589 isl1208_sysfs_show_usr(struct device *dev,
590 		       struct device_attribute *attr, char *buf)
591 {
592 	int usr = isl1208_i2c_get_usr(to_i2c_client(dev));
593 	if (usr < 0)
594 		return usr;
595 
596 	return sprintf(buf, "0x%.4x\n", usr);
597 }
598 
599 static ssize_t
600 isl1208_sysfs_store_usr(struct device *dev,
601 			struct device_attribute *attr,
602 			const char *buf, size_t count)
603 {
604 	int usr = -1;
605 
606 	if (buf[0] == '0' && (buf[1] == 'x' || buf[1] == 'X')) {
607 		if (sscanf(buf, "%x", &usr) != 1)
608 			return -EINVAL;
609 	} else {
610 		if (sscanf(buf, "%d", &usr) != 1)
611 			return -EINVAL;
612 	}
613 
614 	if (usr < 0 || usr > 0xffff)
615 		return -EINVAL;
616 
617 	return isl1208_i2c_set_usr(to_i2c_client(dev), usr) ? -EIO : count;
618 }
619 
620 static DEVICE_ATTR(usr, S_IRUGO | S_IWUSR, isl1208_sysfs_show_usr,
621 		   isl1208_sysfs_store_usr);
622 
623 static struct attribute *isl1208_rtc_attrs[] = {
624 	&dev_attr_atrim.attr,
625 	&dev_attr_dtrim.attr,
626 	&dev_attr_usr.attr,
627 	NULL
628 };
629 
630 static const struct attribute_group isl1208_rtc_sysfs_files = {
631 	.attrs	= isl1208_rtc_attrs,
632 };
633 
634 static int
635 isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
636 {
637 	int rc = 0;
638 	struct rtc_device *rtc;
639 
640 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
641 		return -ENODEV;
642 
643 	if (isl1208_i2c_validate_client(client) < 0)
644 		return -ENODEV;
645 
646 	dev_info(&client->dev,
647 		 "chip found, driver version " DRV_VERSION "\n");
648 
649 	if (client->irq > 0) {
650 		rc = request_threaded_irq(client->irq, NULL,
651 					  isl1208_rtc_interrupt,
652 					  IRQF_SHARED,
653 					  isl1208_driver.driver.name, client);
654 		if (!rc) {
655 			device_init_wakeup(&client->dev, 1);
656 			enable_irq_wake(client->irq);
657 		} else {
658 			dev_err(&client->dev,
659 				"Unable to request irq %d, no alarm support\n",
660 				client->irq);
661 			client->irq = 0;
662 		}
663 	}
664 
665 	rtc = rtc_device_register(isl1208_driver.driver.name,
666 				  &client->dev, &isl1208_rtc_ops,
667 				  THIS_MODULE);
668 	if (IS_ERR(rtc)) {
669 		rc = PTR_ERR(rtc);
670 		goto exit_free_irq;
671 	}
672 
673 	i2c_set_clientdata(client, rtc);
674 
675 	rc = isl1208_i2c_get_sr(client);
676 	if (rc < 0) {
677 		dev_err(&client->dev, "reading status failed\n");
678 		goto exit_unregister;
679 	}
680 
681 	if (rc & ISL1208_REG_SR_RTCF)
682 		dev_warn(&client->dev, "rtc power failure detected, "
683 			 "please set clock.\n");
684 
685 	rc = sysfs_create_group(&client->dev.kobj, &isl1208_rtc_sysfs_files);
686 	if (rc)
687 		goto exit_unregister;
688 
689 	return 0;
690 
691 exit_unregister:
692 	rtc_device_unregister(rtc);
693 exit_free_irq:
694 	if (client->irq)
695 		free_irq(client->irq, client);
696 
697 	return rc;
698 }
699 
700 static int
701 isl1208_remove(struct i2c_client *client)
702 {
703 	struct rtc_device *rtc = i2c_get_clientdata(client);
704 
705 	sysfs_remove_group(&client->dev.kobj, &isl1208_rtc_sysfs_files);
706 	rtc_device_unregister(rtc);
707 	if (client->irq)
708 		free_irq(client->irq, client);
709 
710 	return 0;
711 }
712 
713 static const struct i2c_device_id isl1208_id[] = {
714 	{ "isl1208", 0 },
715 	{ "isl1218", 0 },
716 	{ }
717 };
718 MODULE_DEVICE_TABLE(i2c, isl1208_id);
719 
720 static struct i2c_driver isl1208_driver = {
721 	.driver = {
722 		   .name = "rtc-isl1208",
723 		   },
724 	.probe = isl1208_probe,
725 	.remove = isl1208_remove,
726 	.id_table = isl1208_id,
727 };
728 
729 module_i2c_driver(isl1208_driver);
730 
731 MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
732 MODULE_DESCRIPTION("Intersil ISL1208 RTC driver");
733 MODULE_LICENSE("GPL");
734 MODULE_VERSION(DRV_VERSION);
735