xref: /openbmc/linux/drivers/rtc/rtc-isl1208.c (revision e3d786a3)
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/bcd.h>
14 #include <linux/i2c.h>
15 #include <linux/module.h>
16 #include <linux/of_irq.h>
17 #include <linux/rtc.h>
18 
19 /* Register map */
20 /* rtc section */
21 #define ISL1208_REG_SC  0x00
22 #define ISL1208_REG_MN  0x01
23 #define ISL1208_REG_HR  0x02
24 #define ISL1208_REG_HR_MIL     (1<<7)	/* 24h/12h mode */
25 #define ISL1208_REG_HR_PM      (1<<5)	/* PM/AM bit in 12h mode */
26 #define ISL1208_REG_DT  0x03
27 #define ISL1208_REG_MO  0x04
28 #define ISL1208_REG_YR  0x05
29 #define ISL1208_REG_DW  0x06
30 #define ISL1208_RTC_SECTION_LEN 7
31 
32 /* control/status section */
33 #define ISL1208_REG_SR  0x07
34 #define ISL1208_REG_SR_ARST    (1<<7)	/* auto reset */
35 #define ISL1208_REG_SR_XTOSCB  (1<<6)	/* crystal oscillator */
36 #define ISL1208_REG_SR_WRTC    (1<<4)	/* write rtc */
37 #define ISL1208_REG_SR_EVT     (1<<3)	/* event */
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 ISL1219_REG_EV  0x09
45 #define ISL1219_REG_EV_EVEN    (1<<4)   /* event detection enable */
46 #define ISL1219_REG_EV_EVIENB  (1<<7)   /* event in pull-up disable */
47 #define ISL1208_REG_ATR 0x0a
48 #define ISL1208_REG_DTR 0x0b
49 
50 /* alarm section */
51 #define ISL1208_REG_SCA 0x0c
52 #define ISL1208_REG_MNA 0x0d
53 #define ISL1208_REG_HRA 0x0e
54 #define ISL1208_REG_DTA 0x0f
55 #define ISL1208_REG_MOA 0x10
56 #define ISL1208_REG_DWA 0x11
57 #define ISL1208_ALARM_SECTION_LEN 6
58 
59 /* user section */
60 #define ISL1208_REG_USR1 0x12
61 #define ISL1208_REG_USR2 0x13
62 #define ISL1208_USR_SECTION_LEN 2
63 
64 /* event section */
65 #define ISL1219_REG_SCT 0x14
66 #define ISL1219_REG_MNT 0x15
67 #define ISL1219_REG_HRT 0x16
68 #define ISL1219_REG_DTT 0x17
69 #define ISL1219_REG_MOT 0x18
70 #define ISL1219_REG_YRT 0x19
71 #define ISL1219_EVT_SECTION_LEN 6
72 
73 static struct i2c_driver isl1208_driver;
74 
75 /* ISL1208 various variants */
76 enum {
77 	TYPE_ISL1208 = 0,
78 	TYPE_ISL1218,
79 	TYPE_ISL1219,
80 };
81 
82 /* block read */
83 static int
84 isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
85 		      unsigned len)
86 {
87 	u8 reg_addr[1] = { reg };
88 	struct i2c_msg msgs[2] = {
89 		{
90 			.addr = client->addr,
91 			.len = sizeof(reg_addr),
92 			.buf = reg_addr
93 		},
94 		{
95 			.addr = client->addr,
96 			.flags = I2C_M_RD,
97 			.len = len,
98 			.buf = buf
99 		}
100 	};
101 	int ret;
102 
103 	WARN_ON(reg > ISL1219_REG_YRT);
104 	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
105 
106 	ret = i2c_transfer(client->adapter, msgs, 2);
107 	if (ret > 0)
108 		ret = 0;
109 	return ret;
110 }
111 
112 /* block write */
113 static int
114 isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
115 		     unsigned len)
116 {
117 	u8 i2c_buf[ISL1208_REG_USR2 + 2];
118 	struct i2c_msg msgs[1] = {
119 		{
120 			.addr = client->addr,
121 			.len = len + 1,
122 			.buf = i2c_buf
123 		}
124 	};
125 	int ret;
126 
127 	WARN_ON(reg > ISL1219_REG_YRT);
128 	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
129 
130 	i2c_buf[0] = reg;
131 	memcpy(&i2c_buf[1], &buf[0], len);
132 
133 	ret = i2c_transfer(client->adapter, msgs, 1);
134 	if (ret > 0)
135 		ret = 0;
136 	return ret;
137 }
138 
139 /* simple check to see whether we have a isl1208 */
140 static int
141 isl1208_i2c_validate_client(struct i2c_client *client)
142 {
143 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
144 	u8 zero_mask[ISL1208_RTC_SECTION_LEN] = {
145 		0x80, 0x80, 0x40, 0xc0, 0xe0, 0x00, 0xf8
146 	};
147 	int i;
148 	int ret;
149 
150 	ret = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
151 	if (ret < 0)
152 		return ret;
153 
154 	for (i = 0; i < ISL1208_RTC_SECTION_LEN; ++i) {
155 		if (regs[i] & zero_mask[i])	/* check if bits are cleared */
156 			return -ENODEV;
157 	}
158 
159 	return 0;
160 }
161 
162 static int
163 isl1208_i2c_get_sr(struct i2c_client *client)
164 {
165 	return i2c_smbus_read_byte_data(client, ISL1208_REG_SR);
166 }
167 
168 static int
169 isl1208_i2c_get_atr(struct i2c_client *client)
170 {
171 	int atr = i2c_smbus_read_byte_data(client, ISL1208_REG_ATR);
172 	if (atr < 0)
173 		return atr;
174 
175 	/* The 6bit value in the ATR register controls the load
176 	 * capacitance C_load * in steps of 0.25pF
177 	 *
178 	 * bit (1<<5) of the ATR register is inverted
179 	 *
180 	 * C_load(ATR=0x20) =  4.50pF
181 	 * C_load(ATR=0x00) = 12.50pF
182 	 * C_load(ATR=0x1f) = 20.25pF
183 	 *
184 	 */
185 
186 	atr &= 0x3f;		/* mask out lsb */
187 	atr ^= 1 << 5;		/* invert 6th bit */
188 	atr += 2 * 9;		/* add offset of 4.5pF; unit[atr] = 0.25pF */
189 
190 	return atr;
191 }
192 
193 static int
194 isl1208_i2c_get_dtr(struct i2c_client *client)
195 {
196 	int dtr = i2c_smbus_read_byte_data(client, ISL1208_REG_DTR);
197 	if (dtr < 0)
198 		return -EIO;
199 
200 	/* dtr encodes adjustments of {-60,-40,-20,0,20,40,60} ppm */
201 	dtr = ((dtr & 0x3) * 20) * (dtr & (1 << 2) ? -1 : 1);
202 
203 	return dtr;
204 }
205 
206 static int
207 isl1208_i2c_get_usr(struct i2c_client *client)
208 {
209 	u8 buf[ISL1208_USR_SECTION_LEN] = { 0, };
210 	int ret;
211 
212 	ret = isl1208_i2c_read_regs(client, ISL1208_REG_USR1, buf,
213 				    ISL1208_USR_SECTION_LEN);
214 	if (ret < 0)
215 		return ret;
216 
217 	return (buf[1] << 8) | buf[0];
218 }
219 
220 static int
221 isl1208_i2c_set_usr(struct i2c_client *client, u16 usr)
222 {
223 	u8 buf[ISL1208_USR_SECTION_LEN];
224 
225 	buf[0] = usr & 0xff;
226 	buf[1] = (usr >> 8) & 0xff;
227 
228 	return isl1208_i2c_set_regs(client, ISL1208_REG_USR1, buf,
229 				    ISL1208_USR_SECTION_LEN);
230 }
231 
232 static int
233 isl1208_rtc_toggle_alarm(struct i2c_client *client, int enable)
234 {
235 	int icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
236 
237 	if (icr < 0) {
238 		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
239 		return icr;
240 	}
241 
242 	if (enable)
243 		icr |= ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM;
244 	else
245 		icr &= ~(ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM);
246 
247 	icr = i2c_smbus_write_byte_data(client, ISL1208_REG_INT, icr);
248 	if (icr < 0) {
249 		dev_err(&client->dev, "%s: writing INT failed\n", __func__);
250 		return icr;
251 	}
252 
253 	return 0;
254 }
255 
256 static int
257 isl1208_rtc_proc(struct device *dev, struct seq_file *seq)
258 {
259 	struct i2c_client *const client = to_i2c_client(dev);
260 	int sr, dtr, atr, usr;
261 
262 	sr = isl1208_i2c_get_sr(client);
263 	if (sr < 0) {
264 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
265 		return sr;
266 	}
267 
268 	seq_printf(seq, "status_reg\t:%s%s%s%s%s%s (0x%.2x)\n",
269 		   (sr & ISL1208_REG_SR_RTCF) ? " RTCF" : "",
270 		   (sr & ISL1208_REG_SR_BAT) ? " BAT" : "",
271 		   (sr & ISL1208_REG_SR_ALM) ? " ALM" : "",
272 		   (sr & ISL1208_REG_SR_WRTC) ? " WRTC" : "",
273 		   (sr & ISL1208_REG_SR_XTOSCB) ? " XTOSCB" : "",
274 		   (sr & ISL1208_REG_SR_ARST) ? " ARST" : "", sr);
275 
276 	seq_printf(seq, "batt_status\t: %s\n",
277 		   (sr & ISL1208_REG_SR_RTCF) ? "bad" : "okay");
278 
279 	dtr = isl1208_i2c_get_dtr(client);
280 	if (dtr >= 0 - 1)
281 		seq_printf(seq, "digital_trim\t: %d ppm\n", dtr);
282 
283 	atr = isl1208_i2c_get_atr(client);
284 	if (atr >= 0)
285 		seq_printf(seq, "analog_trim\t: %d.%.2d pF\n",
286 			   atr >> 2, (atr & 0x3) * 25);
287 
288 	usr = isl1208_i2c_get_usr(client);
289 	if (usr >= 0)
290 		seq_printf(seq, "user_data\t: 0x%.4x\n", usr);
291 
292 	return 0;
293 }
294 
295 static int
296 isl1208_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
297 {
298 	int sr;
299 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
300 
301 	sr = isl1208_i2c_get_sr(client);
302 	if (sr < 0) {
303 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
304 		return -EIO;
305 	}
306 
307 	sr = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
308 	if (sr < 0) {
309 		dev_err(&client->dev, "%s: reading RTC section failed\n",
310 			__func__);
311 		return sr;
312 	}
313 
314 	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SC]);
315 	tm->tm_min = bcd2bin(regs[ISL1208_REG_MN]);
316 
317 	/* HR field has a more complex interpretation */
318 	{
319 		const u8 _hr = regs[ISL1208_REG_HR];
320 		if (_hr & ISL1208_REG_HR_MIL)	/* 24h format */
321 			tm->tm_hour = bcd2bin(_hr & 0x3f);
322 		else {
323 			/* 12h format */
324 			tm->tm_hour = bcd2bin(_hr & 0x1f);
325 			if (_hr & ISL1208_REG_HR_PM)	/* PM flag set */
326 				tm->tm_hour += 12;
327 		}
328 	}
329 
330 	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DT]);
331 	tm->tm_mon = bcd2bin(regs[ISL1208_REG_MO]) - 1;	/* rtc starts at 1 */
332 	tm->tm_year = bcd2bin(regs[ISL1208_REG_YR]) + 100;
333 	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DW]);
334 
335 	return 0;
336 }
337 
338 static int
339 isl1208_i2c_read_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
340 {
341 	struct rtc_time *const tm = &alarm->time;
342 	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
343 	int icr, yr, sr = isl1208_i2c_get_sr(client);
344 
345 	if (sr < 0) {
346 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
347 		return sr;
348 	}
349 
350 	sr = isl1208_i2c_read_regs(client, ISL1208_REG_SCA, regs,
351 				   ISL1208_ALARM_SECTION_LEN);
352 	if (sr < 0) {
353 		dev_err(&client->dev, "%s: reading alarm section failed\n",
354 			__func__);
355 		return sr;
356 	}
357 
358 	/* MSB of each alarm register is an enable bit */
359 	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SCA - ISL1208_REG_SCA] & 0x7f);
360 	tm->tm_min = bcd2bin(regs[ISL1208_REG_MNA - ISL1208_REG_SCA] & 0x7f);
361 	tm->tm_hour = bcd2bin(regs[ISL1208_REG_HRA - ISL1208_REG_SCA] & 0x3f);
362 	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DTA - ISL1208_REG_SCA] & 0x3f);
363 	tm->tm_mon =
364 		bcd2bin(regs[ISL1208_REG_MOA - ISL1208_REG_SCA] & 0x1f) - 1;
365 	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DWA - ISL1208_REG_SCA] & 0x03);
366 
367 	/* The alarm doesn't store the year so get it from the rtc section */
368 	yr = i2c_smbus_read_byte_data(client, ISL1208_REG_YR);
369 	if (yr < 0) {
370 		dev_err(&client->dev, "%s: reading RTC YR failed\n", __func__);
371 		return yr;
372 	}
373 	tm->tm_year = bcd2bin(yr) + 100;
374 
375 	icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
376 	if (icr < 0) {
377 		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
378 		return icr;
379 	}
380 	alarm->enabled = !!(icr & ISL1208_REG_INT_ALME);
381 
382 	return 0;
383 }
384 
385 static int
386 isl1208_i2c_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
387 {
388 	struct rtc_time *alarm_tm = &alarm->time;
389 	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
390 	const int offs = ISL1208_REG_SCA;
391 	struct rtc_time rtc_tm;
392 	int err, enable;
393 
394 	err = isl1208_i2c_read_time(client, &rtc_tm);
395 	if (err)
396 		return err;
397 
398 	/* If the alarm time is before the current time disable the alarm */
399 	if (!alarm->enabled || rtc_tm_sub(alarm_tm, &rtc_tm) <= 0)
400 		enable = 0x00;
401 	else
402 		enable = 0x80;
403 
404 	/* Program the alarm and enable it for each setting */
405 	regs[ISL1208_REG_SCA - offs] = bin2bcd(alarm_tm->tm_sec) | enable;
406 	regs[ISL1208_REG_MNA - offs] = bin2bcd(alarm_tm->tm_min) | enable;
407 	regs[ISL1208_REG_HRA - offs] = bin2bcd(alarm_tm->tm_hour) |
408 		ISL1208_REG_HR_MIL | enable;
409 
410 	regs[ISL1208_REG_DTA - offs] = bin2bcd(alarm_tm->tm_mday) | enable;
411 	regs[ISL1208_REG_MOA - offs] = bin2bcd(alarm_tm->tm_mon + 1) | enable;
412 	regs[ISL1208_REG_DWA - offs] = bin2bcd(alarm_tm->tm_wday & 7) | enable;
413 
414 	/* write ALARM registers */
415 	err = isl1208_i2c_set_regs(client, offs, regs,
416 				  ISL1208_ALARM_SECTION_LEN);
417 	if (err < 0) {
418 		dev_err(&client->dev, "%s: writing ALARM section failed\n",
419 			__func__);
420 		return err;
421 	}
422 
423 	err = isl1208_rtc_toggle_alarm(client, enable);
424 	if (err)
425 		return err;
426 
427 	return 0;
428 }
429 
430 static int
431 isl1208_rtc_read_time(struct device *dev, struct rtc_time *tm)
432 {
433 	return isl1208_i2c_read_time(to_i2c_client(dev), tm);
434 }
435 
436 static int
437 isl1208_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
438 {
439 	int sr;
440 	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
441 
442 	/* The clock has an 8 bit wide bcd-coded register (they never learn)
443 	 * for the year. tm_year is an offset from 1900 and we are interested
444 	 * in the 2000-2099 range, so any value less than 100 is invalid.
445 	 */
446 	if (tm->tm_year < 100)
447 		return -EINVAL;
448 
449 	regs[ISL1208_REG_SC] = bin2bcd(tm->tm_sec);
450 	regs[ISL1208_REG_MN] = bin2bcd(tm->tm_min);
451 	regs[ISL1208_REG_HR] = bin2bcd(tm->tm_hour) | ISL1208_REG_HR_MIL;
452 
453 	regs[ISL1208_REG_DT] = bin2bcd(tm->tm_mday);
454 	regs[ISL1208_REG_MO] = bin2bcd(tm->tm_mon + 1);
455 	regs[ISL1208_REG_YR] = bin2bcd(tm->tm_year - 100);
456 
457 	regs[ISL1208_REG_DW] = bin2bcd(tm->tm_wday & 7);
458 
459 	sr = isl1208_i2c_get_sr(client);
460 	if (sr < 0) {
461 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
462 		return sr;
463 	}
464 
465 	/* set WRTC */
466 	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
467 				       sr | ISL1208_REG_SR_WRTC);
468 	if (sr < 0) {
469 		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
470 		return sr;
471 	}
472 
473 	/* write RTC registers */
474 	sr = isl1208_i2c_set_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
475 	if (sr < 0) {
476 		dev_err(&client->dev, "%s: writing RTC section failed\n",
477 			__func__);
478 		return sr;
479 	}
480 
481 	/* clear WRTC again */
482 	sr = isl1208_i2c_get_sr(client);
483 	if (sr < 0) {
484 		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
485 		return sr;
486 	}
487 	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
488 				       sr & ~ISL1208_REG_SR_WRTC);
489 	if (sr < 0) {
490 		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
491 		return sr;
492 	}
493 
494 	return 0;
495 }
496 
497 
498 static int
499 isl1208_rtc_set_time(struct device *dev, struct rtc_time *tm)
500 {
501 	return isl1208_i2c_set_time(to_i2c_client(dev), tm);
502 }
503 
504 static int
505 isl1208_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
506 {
507 	return isl1208_i2c_read_alarm(to_i2c_client(dev), alarm);
508 }
509 
510 static int
511 isl1208_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
512 {
513 	return isl1208_i2c_set_alarm(to_i2c_client(dev), alarm);
514 }
515 
516 static ssize_t timestamp0_store(struct device *dev,
517 				struct device_attribute *attr,
518 				const char *buf, size_t count)
519 {
520 	struct i2c_client *client = to_i2c_client(dev->parent);
521 	int sr;
522 
523 	sr = isl1208_i2c_get_sr(client);
524 	if (sr < 0) {
525 		dev_err(dev, "%s: reading SR failed\n", __func__);
526 		return sr;
527 	}
528 
529 	sr &= ~ISL1208_REG_SR_EVT;
530 
531 	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
532 	if (sr < 0)
533 		dev_err(dev, "%s: writing SR failed\n",
534 			__func__);
535 
536 	return count;
537 };
538 
539 static ssize_t timestamp0_show(struct device *dev,
540 			       struct device_attribute *attr, char *buf)
541 {
542 	struct i2c_client *client = to_i2c_client(dev->parent);
543 	u8 regs[ISL1219_EVT_SECTION_LEN] = { 0, };
544 	struct rtc_time tm;
545 	int sr;
546 
547 	sr = isl1208_i2c_get_sr(client);
548 	if (sr < 0) {
549 		dev_err(dev, "%s: reading SR failed\n", __func__);
550 		return sr;
551 	}
552 
553 	if (!(sr & ISL1208_REG_SR_EVT))
554 		return 0;
555 
556 	sr = isl1208_i2c_read_regs(client, ISL1219_REG_SCT, regs,
557 				   ISL1219_EVT_SECTION_LEN);
558 	if (sr < 0) {
559 		dev_err(dev, "%s: reading event section failed\n",
560 			__func__);
561 		return 0;
562 	}
563 
564 	/* MSB of each alarm register is an enable bit */
565 	tm.tm_sec = bcd2bin(regs[ISL1219_REG_SCT - ISL1219_REG_SCT] & 0x7f);
566 	tm.tm_min = bcd2bin(regs[ISL1219_REG_MNT - ISL1219_REG_SCT] & 0x7f);
567 	tm.tm_hour = bcd2bin(regs[ISL1219_REG_HRT - ISL1219_REG_SCT] & 0x3f);
568 	tm.tm_mday = bcd2bin(regs[ISL1219_REG_DTT - ISL1219_REG_SCT] & 0x3f);
569 	tm.tm_mon =
570 		bcd2bin(regs[ISL1219_REG_MOT - ISL1219_REG_SCT] & 0x1f) - 1;
571 	tm.tm_year = bcd2bin(regs[ISL1219_REG_YRT - ISL1219_REG_SCT]) + 100;
572 
573 	sr = rtc_valid_tm(&tm);
574 	if (sr)
575 		return sr;
576 
577 	return sprintf(buf, "%llu\n",
578 				(unsigned long long)rtc_tm_to_time64(&tm));
579 };
580 
581 static DEVICE_ATTR_RW(timestamp0);
582 
583 static irqreturn_t
584 isl1208_rtc_interrupt(int irq, void *data)
585 {
586 	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
587 	struct i2c_client *client = data;
588 	struct rtc_device *rtc = i2c_get_clientdata(client);
589 	int handled = 0, sr, err;
590 
591 	/*
592 	 * I2C reads get NAK'ed if we read straight away after an interrupt?
593 	 * Using a mdelay/msleep didn't seem to help either, so we work around
594 	 * this by continually trying to read the register for a short time.
595 	 */
596 	while (1) {
597 		sr = isl1208_i2c_get_sr(client);
598 		if (sr >= 0)
599 			break;
600 
601 		if (time_after(jiffies, timeout)) {
602 			dev_err(&client->dev, "%s: reading SR failed\n",
603 				__func__);
604 			return sr;
605 		}
606 	}
607 
608 	if (sr & ISL1208_REG_SR_ALM) {
609 		dev_dbg(&client->dev, "alarm!\n");
610 
611 		rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);
612 
613 		/* Clear the alarm */
614 		sr &= ~ISL1208_REG_SR_ALM;
615 		sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
616 		if (sr < 0)
617 			dev_err(&client->dev, "%s: writing SR failed\n",
618 				__func__);
619 		else
620 			handled = 1;
621 
622 		/* Disable the alarm */
623 		err = isl1208_rtc_toggle_alarm(client, 0);
624 		if (err)
625 			return err;
626 	}
627 
628 	if (sr & ISL1208_REG_SR_EVT) {
629 		sysfs_notify(&rtc->dev.kobj, NULL,
630 			     dev_attr_timestamp0.attr.name);
631 		dev_warn(&client->dev, "event detected");
632 		handled = 1;
633 	}
634 
635 	return handled ? IRQ_HANDLED : IRQ_NONE;
636 }
637 
638 static const struct rtc_class_ops isl1208_rtc_ops = {
639 	.proc = isl1208_rtc_proc,
640 	.read_time = isl1208_rtc_read_time,
641 	.set_time = isl1208_rtc_set_time,
642 	.read_alarm = isl1208_rtc_read_alarm,
643 	.set_alarm = isl1208_rtc_set_alarm,
644 };
645 
646 /* sysfs interface */
647 
648 static ssize_t
649 isl1208_sysfs_show_atrim(struct device *dev,
650 			 struct device_attribute *attr, char *buf)
651 {
652 	int atr = isl1208_i2c_get_atr(to_i2c_client(dev->parent));
653 	if (atr < 0)
654 		return atr;
655 
656 	return sprintf(buf, "%d.%.2d pF\n", atr >> 2, (atr & 0x3) * 25);
657 }
658 
659 static DEVICE_ATTR(atrim, S_IRUGO, isl1208_sysfs_show_atrim, NULL);
660 
661 static ssize_t
662 isl1208_sysfs_show_dtrim(struct device *dev,
663 			 struct device_attribute *attr, char *buf)
664 {
665 	int dtr = isl1208_i2c_get_dtr(to_i2c_client(dev->parent));
666 	if (dtr < 0)
667 		return dtr;
668 
669 	return sprintf(buf, "%d ppm\n", dtr);
670 }
671 
672 static DEVICE_ATTR(dtrim, S_IRUGO, isl1208_sysfs_show_dtrim, NULL);
673 
674 static ssize_t
675 isl1208_sysfs_show_usr(struct device *dev,
676 		       struct device_attribute *attr, char *buf)
677 {
678 	int usr = isl1208_i2c_get_usr(to_i2c_client(dev->parent));
679 	if (usr < 0)
680 		return usr;
681 
682 	return sprintf(buf, "0x%.4x\n", usr);
683 }
684 
685 static ssize_t
686 isl1208_sysfs_store_usr(struct device *dev,
687 			struct device_attribute *attr,
688 			const char *buf, size_t count)
689 {
690 	int usr = -1;
691 
692 	if (buf[0] == '0' && (buf[1] == 'x' || buf[1] == 'X')) {
693 		if (sscanf(buf, "%x", &usr) != 1)
694 			return -EINVAL;
695 	} else {
696 		if (sscanf(buf, "%d", &usr) != 1)
697 			return -EINVAL;
698 	}
699 
700 	if (usr < 0 || usr > 0xffff)
701 		return -EINVAL;
702 
703 	if (isl1208_i2c_set_usr(to_i2c_client(dev->parent), usr))
704 		return -EIO;
705 
706 	return count;
707 }
708 
709 static DEVICE_ATTR(usr, S_IRUGO | S_IWUSR, isl1208_sysfs_show_usr,
710 		   isl1208_sysfs_store_usr);
711 
712 static struct attribute *isl1208_rtc_attrs[] = {
713 	&dev_attr_atrim.attr,
714 	&dev_attr_dtrim.attr,
715 	&dev_attr_usr.attr,
716 	NULL
717 };
718 
719 static const struct attribute_group isl1208_rtc_sysfs_files = {
720 	.attrs	= isl1208_rtc_attrs,
721 };
722 
723 static struct attribute *isl1219_rtc_attrs[] = {
724 	&dev_attr_timestamp0.attr,
725 	NULL
726 };
727 
728 static const struct attribute_group isl1219_rtc_sysfs_files = {
729 	.attrs	= isl1219_rtc_attrs,
730 };
731 
732 static int isl1208_setup_irq(struct i2c_client *client, int irq)
733 {
734 	int rc = devm_request_threaded_irq(&client->dev, irq, NULL,
735 					isl1208_rtc_interrupt,
736 					IRQF_SHARED | IRQF_ONESHOT,
737 					isl1208_driver.driver.name,
738 					client);
739 	if (!rc) {
740 		device_init_wakeup(&client->dev, 1);
741 		enable_irq_wake(irq);
742 	} else {
743 		dev_err(&client->dev,
744 			"Unable to request irq %d, no alarm support\n",
745 			irq);
746 	}
747 	return rc;
748 }
749 
750 static int
751 isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
752 {
753 	int rc = 0;
754 	struct rtc_device *rtc;
755 	int evdet_irq = -1;
756 
757 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
758 		return -ENODEV;
759 
760 	if (isl1208_i2c_validate_client(client) < 0)
761 		return -ENODEV;
762 
763 	rtc = devm_rtc_allocate_device(&client->dev);
764 	if (IS_ERR(rtc))
765 		return PTR_ERR(rtc);
766 
767 	rtc->ops = &isl1208_rtc_ops;
768 
769 	i2c_set_clientdata(client, rtc);
770 
771 	rc = isl1208_i2c_get_sr(client);
772 	if (rc < 0) {
773 		dev_err(&client->dev, "reading status failed\n");
774 		return rc;
775 	}
776 
777 	if (rc & ISL1208_REG_SR_RTCF)
778 		dev_warn(&client->dev, "rtc power failure detected, "
779 			 "please set clock.\n");
780 
781 	if (id->driver_data == TYPE_ISL1219) {
782 		struct device_node *np = client->dev.of_node;
783 		u32 evienb;
784 
785 		rc = i2c_smbus_read_byte_data(client, ISL1219_REG_EV);
786 		if (rc < 0) {
787 			dev_err(&client->dev, "failed to read EV reg\n");
788 			return rc;
789 		}
790 		rc |= ISL1219_REG_EV_EVEN;
791 		if (!of_property_read_u32(np, "isil,ev-evienb", &evienb)) {
792 			if (evienb)
793 				rc |= ISL1219_REG_EV_EVIENB;
794 			else
795 				rc &= ~ISL1219_REG_EV_EVIENB;
796 		}
797 		rc = i2c_smbus_write_byte_data(client, ISL1219_REG_EV, rc);
798 		if (rc < 0) {
799 			dev_err(&client->dev, "could not enable tamper detection\n");
800 			return rc;
801 		}
802 		rc = rtc_add_group(rtc, &isl1219_rtc_sysfs_files);
803 		if (rc)
804 			return rc;
805 		evdet_irq = of_irq_get_byname(np, "evdet");
806 	}
807 
808 	rc = rtc_add_group(rtc, &isl1208_rtc_sysfs_files);
809 	if (rc)
810 		return rc;
811 
812 	if (client->irq > 0)
813 		rc = isl1208_setup_irq(client, client->irq);
814 	if (rc)
815 		return rc;
816 
817 	if (evdet_irq > 0 && evdet_irq != client->irq)
818 		rc = isl1208_setup_irq(client, evdet_irq);
819 	if (rc)
820 		return rc;
821 
822 	return rtc_register_device(rtc);
823 }
824 
825 static const struct i2c_device_id isl1208_id[] = {
826 	{ "isl1208", TYPE_ISL1208 },
827 	{ "isl1218", TYPE_ISL1218 },
828 	{ "isl1219", TYPE_ISL1219 },
829 	{ }
830 };
831 MODULE_DEVICE_TABLE(i2c, isl1208_id);
832 
833 static const struct of_device_id isl1208_of_match[] = {
834 	{ .compatible = "isil,isl1208" },
835 	{ .compatible = "isil,isl1218" },
836 	{ .compatible = "isil,isl1219" },
837 	{ }
838 };
839 MODULE_DEVICE_TABLE(of, isl1208_of_match);
840 
841 static struct i2c_driver isl1208_driver = {
842 	.driver = {
843 		.name = "rtc-isl1208",
844 		.of_match_table = of_match_ptr(isl1208_of_match),
845 	},
846 	.probe = isl1208_probe,
847 	.id_table = isl1208_id,
848 };
849 
850 module_i2c_driver(isl1208_driver);
851 
852 MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
853 MODULE_DESCRIPTION("Intersil ISL1208 RTC driver");
854 MODULE_LICENSE("GPL");
855