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1fcbe42c JG |
1 | /* |
2 | * SPI Driver for Microchip MCP795 RTC | |
3 | * | |
4 | * Copyright (C) Josef Gajdusek <atx@atx.name> | |
5 | * | |
6 | * based on other Linux RTC drivers | |
7 | * | |
8 | * Device datasheet: | |
9 | * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf | |
10 | * | |
11 | * This program is free software; you can redistribute it and/or modify | |
12 | * it under the terms of the GNU General Public License version 2 as | |
13 | * published by the Free Software Foundation. | |
14 | * | |
d3e59259 | 15 | */ |
1fcbe42c JG |
16 | |
17 | #include <linux/module.h> | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/device.h> | |
20 | #include <linux/printk.h> | |
21 | #include <linux/spi/spi.h> | |
22 | #include <linux/rtc.h> | |
7f8a5892 | 23 | #include <linux/of.h> |
bcf18d88 | 24 | #include <linux/bcd.h> |
43d0b10f | 25 | #include <linux/delay.h> |
1fcbe42c JG |
26 | |
27 | /* MCP795 Instructions, see datasheet table 3-1 */ | |
28 | #define MCP795_EEREAD 0x03 | |
29 | #define MCP795_EEWRITE 0x02 | |
30 | #define MCP795_EEWRDI 0x04 | |
31 | #define MCP795_EEWREN 0x06 | |
32 | #define MCP795_SRREAD 0x05 | |
33 | #define MCP795_SRWRITE 0x01 | |
d3e59259 | 34 | #define MCP795_READ 0x13 |
1fcbe42c JG |
35 | #define MCP795_WRITE 0x12 |
36 | #define MCP795_UNLOCK 0x14 | |
37 | #define MCP795_IDWRITE 0x32 | |
38 | #define MCP795_IDREAD 0x33 | |
39 | #define MCP795_CLRWDT 0x44 | |
40 | #define MCP795_CLRRAM 0x54 | |
41 | ||
43d0b10f EB |
42 | /* MCP795 RTCC registers, see datasheet table 4-1 */ |
43 | #define MCP795_REG_SECONDS 0x01 | |
44 | #define MCP795_REG_DAY 0x04 | |
45 | #define MCP795_REG_MONTH 0x06 | |
46 | #define MCP795_REG_CONTROL 0x08 | |
644d4c36 EB |
47 | #define MCP795_REG_ALM0_SECONDS 0x0C |
48 | #define MCP795_REG_ALM0_DAY 0x0F | |
43d0b10f | 49 | |
d3e59259 EB |
50 | #define MCP795_ST_BIT BIT(7) |
51 | #define MCP795_24_BIT BIT(6) | |
52 | #define MCP795_LP_BIT BIT(5) | |
43d0b10f EB |
53 | #define MCP795_EXTOSC_BIT BIT(3) |
54 | #define MCP795_OSCON_BIT BIT(5) | |
644d4c36 EB |
55 | #define MCP795_ALM0_BIT BIT(4) |
56 | #define MCP795_ALM1_BIT BIT(5) | |
57 | #define MCP795_ALM0IF_BIT BIT(3) | |
58 | #define MCP795_ALM0C0_BIT BIT(4) | |
59 | #define MCP795_ALM0C1_BIT BIT(5) | |
60 | #define MCP795_ALM0C2_BIT BIT(6) | |
61 | ||
62 | #define SEC_PER_DAY (24 * 60 * 60) | |
1fcbe42c JG |
63 | |
64 | static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count) | |
65 | { | |
66 | struct spi_device *spi = to_spi_device(dev); | |
67 | int ret; | |
68 | u8 tx[2]; | |
69 | ||
70 | tx[0] = MCP795_READ; | |
71 | tx[1] = addr; | |
72 | ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count); | |
73 | ||
74 | if (ret) | |
75 | dev_err(dev, "Failed reading %d bytes from address %x.\n", | |
76 | count, addr); | |
77 | ||
78 | return ret; | |
79 | } | |
80 | ||
81 | static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count) | |
82 | { | |
83 | struct spi_device *spi = to_spi_device(dev); | |
84 | int ret; | |
fed9b186 | 85 | u8 tx[257]; |
1fcbe42c JG |
86 | |
87 | tx[0] = MCP795_WRITE; | |
88 | tx[1] = addr; | |
89 | memcpy(&tx[2], data, count); | |
90 | ||
91 | ret = spi_write(spi, tx, 2 + count); | |
92 | ||
93 | if (ret) | |
94 | dev_err(dev, "Failed to write %d bytes to address %x.\n", | |
95 | count, addr); | |
96 | ||
97 | return ret; | |
98 | } | |
99 | ||
100 | static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state) | |
101 | { | |
102 | int ret; | |
103 | u8 tmp; | |
104 | ||
105 | ret = mcp795_rtcc_read(dev, addr, &tmp, 1); | |
106 | if (ret) | |
107 | return ret; | |
108 | ||
109 | if ((tmp & mask) != state) { | |
110 | tmp = (tmp & ~mask) | state; | |
111 | ret = mcp795_rtcc_write(dev, addr, &tmp, 1); | |
112 | } | |
113 | ||
114 | return ret; | |
115 | } | |
116 | ||
43d0b10f EB |
117 | static int mcp795_stop_oscillator(struct device *dev, bool *extosc) |
118 | { | |
119 | int retries = 5; | |
120 | int ret; | |
121 | u8 data; | |
122 | ||
123 | ret = mcp795_rtcc_set_bits(dev, MCP795_REG_SECONDS, MCP795_ST_BIT, 0); | |
124 | if (ret) | |
125 | return ret; | |
126 | ret = mcp795_rtcc_read(dev, MCP795_REG_CONTROL, &data, 1); | |
127 | if (ret) | |
128 | return ret; | |
129 | *extosc = !!(data & MCP795_EXTOSC_BIT); | |
130 | ret = mcp795_rtcc_set_bits( | |
131 | dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, 0); | |
132 | if (ret) | |
133 | return ret; | |
134 | /* wait for the OSCON bit to clear */ | |
135 | do { | |
136 | usleep_range(700, 800); | |
137 | ret = mcp795_rtcc_read(dev, MCP795_REG_DAY, &data, 1); | |
138 | if (ret) | |
139 | break; | |
140 | if (!(data & MCP795_OSCON_BIT)) | |
141 | break; | |
142 | ||
143 | } while (--retries); | |
144 | ||
145 | return !retries ? -EIO : ret; | |
146 | } | |
147 | ||
148 | static int mcp795_start_oscillator(struct device *dev, bool *extosc) | |
149 | { | |
150 | if (extosc) { | |
151 | u8 data = *extosc ? MCP795_EXTOSC_BIT : 0; | |
152 | int ret; | |
153 | ||
154 | ret = mcp795_rtcc_set_bits( | |
155 | dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, data); | |
156 | if (ret) | |
157 | return ret; | |
158 | } | |
159 | return mcp795_rtcc_set_bits( | |
160 | dev, MCP795_REG_SECONDS, MCP795_ST_BIT, MCP795_ST_BIT); | |
161 | } | |
162 | ||
644d4c36 EB |
163 | /* Enable or disable Alarm 0 in RTC */ |
164 | static int mcp795_update_alarm(struct device *dev, bool enable) | |
165 | { | |
166 | int ret; | |
167 | ||
168 | dev_dbg(dev, "%s alarm\n", enable ? "Enable" : "Disable"); | |
169 | ||
170 | if (enable) { | |
171 | /* clear ALM0IF (Alarm 0 Interrupt Flag) bit */ | |
172 | ret = mcp795_rtcc_set_bits(dev, MCP795_REG_ALM0_DAY, | |
173 | MCP795_ALM0IF_BIT, 0); | |
174 | if (ret) | |
175 | return ret; | |
176 | /* enable alarm 0 */ | |
177 | ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL, | |
178 | MCP795_ALM0_BIT, MCP795_ALM0_BIT); | |
179 | } else { | |
180 | /* disable alarm 0 and alarm 1 */ | |
181 | ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL, | |
182 | MCP795_ALM0_BIT | MCP795_ALM1_BIT, 0); | |
183 | } | |
184 | return ret; | |
185 | } | |
186 | ||
1fcbe42c JG |
187 | static int mcp795_set_time(struct device *dev, struct rtc_time *tim) |
188 | { | |
189 | int ret; | |
190 | u8 data[7]; | |
43d0b10f EB |
191 | bool extosc; |
192 | ||
193 | /* Stop RTC and store current value of EXTOSC bit */ | |
194 | ret = mcp795_stop_oscillator(dev, &extosc); | |
195 | if (ret) | |
196 | return ret; | |
1fcbe42c JG |
197 | |
198 | /* Read first, so we can leave config bits untouched */ | |
43d0b10f | 199 | ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); |
1fcbe42c JG |
200 | |
201 | if (ret) | |
202 | return ret; | |
203 | ||
bcf18d88 EB |
204 | data[0] = (data[0] & 0x80) | bin2bcd(tim->tm_sec); |
205 | data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min); | |
206 | data[2] = bin2bcd(tim->tm_hour); | |
72877b51 | 207 | data[3] = (data[3] & 0xF8) | bin2bcd(tim->tm_wday + 1); |
bcf18d88 | 208 | data[4] = bin2bcd(tim->tm_mday); |
26eeefd5 | 209 | data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1); |
1fcbe42c JG |
210 | |
211 | if (tim->tm_year > 100) | |
212 | tim->tm_year -= 100; | |
213 | ||
bcf18d88 | 214 | data[6] = bin2bcd(tim->tm_year); |
1fcbe42c | 215 | |
43d0b10f EB |
216 | /* Always write the date and month using a separate Write command. |
217 | * This is a workaround for a know silicon issue that some combinations | |
218 | * of date and month values may result in the date being reset to 1. | |
219 | */ | |
220 | ret = mcp795_rtcc_write(dev, MCP795_REG_SECONDS, data, 5); | |
221 | if (ret) | |
222 | return ret; | |
223 | ||
224 | ret = mcp795_rtcc_write(dev, MCP795_REG_MONTH, &data[5], 2); | |
225 | if (ret) | |
226 | return ret; | |
1fcbe42c | 227 | |
43d0b10f EB |
228 | /* Start back RTC and restore previous value of EXTOSC bit. |
229 | * There is no need to clear EXTOSC bit when the previous value was 0 | |
230 | * because it was already cleared when stopping the RTC oscillator. | |
231 | */ | |
232 | ret = mcp795_start_oscillator(dev, extosc ? &extosc : NULL); | |
1fcbe42c JG |
233 | if (ret) |
234 | return ret; | |
235 | ||
72877b51 | 236 | dev_dbg(dev, "Set mcp795: %04d-%02d-%02d(%d) %02d:%02d:%02d\n", |
1fcbe42c | 237 | tim->tm_year + 1900, tim->tm_mon, tim->tm_mday, |
72877b51 | 238 | tim->tm_wday, tim->tm_hour, tim->tm_min, tim->tm_sec); |
1fcbe42c JG |
239 | |
240 | return 0; | |
241 | } | |
242 | ||
243 | static int mcp795_read_time(struct device *dev, struct rtc_time *tim) | |
244 | { | |
245 | int ret; | |
246 | u8 data[7]; | |
247 | ||
43d0b10f | 248 | ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); |
1fcbe42c JG |
249 | |
250 | if (ret) | |
251 | return ret; | |
252 | ||
bcf18d88 EB |
253 | tim->tm_sec = bcd2bin(data[0] & 0x7F); |
254 | tim->tm_min = bcd2bin(data[1] & 0x7F); | |
255 | tim->tm_hour = bcd2bin(data[2] & 0x3F); | |
72877b51 | 256 | tim->tm_wday = bcd2bin(data[3] & 0x07) - 1; |
bcf18d88 | 257 | tim->tm_mday = bcd2bin(data[4] & 0x3F); |
26eeefd5 | 258 | tim->tm_mon = bcd2bin(data[5] & 0x1F) - 1; |
bcf18d88 | 259 | tim->tm_year = bcd2bin(data[6]) + 100; /* Assume we are in 20xx */ |
1fcbe42c | 260 | |
72877b51 EB |
261 | dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d(%d) %02d:%02d:%02d\n", |
262 | tim->tm_year + 1900, tim->tm_mon, tim->tm_mday, | |
263 | tim->tm_wday, tim->tm_hour, tim->tm_min, tim->tm_sec); | |
1fcbe42c | 264 | |
22652ba7 | 265 | return 0; |
1fcbe42c JG |
266 | } |
267 | ||
644d4c36 EB |
268 | static int mcp795_set_alarm(struct device *dev, struct rtc_wkalrm *alm) |
269 | { | |
270 | struct rtc_time now_tm; | |
271 | time64_t now; | |
272 | time64_t later; | |
273 | u8 tmp[6]; | |
274 | int ret; | |
275 | ||
276 | /* Read current time from RTC hardware */ | |
277 | ret = mcp795_read_time(dev, &now_tm); | |
278 | if (ret) | |
279 | return ret; | |
280 | /* Get the number of seconds since 1970 */ | |
281 | now = rtc_tm_to_time64(&now_tm); | |
282 | later = rtc_tm_to_time64(&alm->time); | |
283 | if (later <= now) | |
284 | return -EINVAL; | |
285 | /* make sure alarm fires within the next one year */ | |
286 | if ((later - now) >= | |
287 | (SEC_PER_DAY * (365 + is_leap_year(alm->time.tm_year)))) | |
288 | return -EDOM; | |
289 | /* disable alarm */ | |
290 | ret = mcp795_update_alarm(dev, false); | |
291 | if (ret) | |
292 | return ret; | |
293 | /* Read registers, so we can leave configuration bits untouched */ | |
294 | ret = mcp795_rtcc_read(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); | |
295 | if (ret) | |
296 | return ret; | |
297 | ||
298 | alm->time.tm_year = -1; | |
299 | alm->time.tm_isdst = -1; | |
300 | alm->time.tm_yday = -1; | |
301 | ||
302 | tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec); | |
303 | tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min); | |
304 | tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour); | |
305 | tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1); | |
306 | /* set alarm match: seconds, minutes, hour, day, date and month */ | |
307 | tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | MCP795_ALM0C0_BIT); | |
308 | tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday); | |
309 | tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1); | |
310 | ||
311 | ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); | |
312 | if (ret) | |
313 | return ret; | |
314 | ||
315 | /* enable alarm if requested */ | |
316 | if (alm->enabled) { | |
317 | ret = mcp795_update_alarm(dev, true); | |
318 | if (ret) | |
319 | return ret; | |
320 | dev_dbg(dev, "Alarm IRQ armed\n"); | |
321 | } | |
322 | dev_dbg(dev, "Set alarm: %02d-%02d(%d) %02d:%02d:%02d\n", | |
323 | alm->time.tm_mon, alm->time.tm_mday, alm->time.tm_wday, | |
324 | alm->time.tm_hour, alm->time.tm_min, alm->time.tm_sec); | |
325 | return 0; | |
326 | } | |
327 | ||
328 | static int mcp795_read_alarm(struct device *dev, struct rtc_wkalrm *alm) | |
329 | { | |
330 | u8 data[6]; | |
331 | int ret; | |
332 | ||
333 | ret = mcp795_rtcc_read( | |
334 | dev, MCP795_REG_ALM0_SECONDS, data, sizeof(data)); | |
335 | if (ret) | |
336 | return ret; | |
337 | ||
338 | alm->time.tm_sec = bcd2bin(data[0] & 0x7F); | |
339 | alm->time.tm_min = bcd2bin(data[1] & 0x7F); | |
340 | alm->time.tm_hour = bcd2bin(data[2] & 0x1F); | |
341 | alm->time.tm_wday = bcd2bin(data[3] & 0x07) - 1; | |
342 | alm->time.tm_mday = bcd2bin(data[4] & 0x3F); | |
343 | alm->time.tm_mon = bcd2bin(data[5] & 0x1F) - 1; | |
344 | alm->time.tm_year = -1; | |
345 | alm->time.tm_isdst = -1; | |
346 | alm->time.tm_yday = -1; | |
347 | ||
348 | dev_dbg(dev, "Read alarm: %02d-%02d(%d) %02d:%02d:%02d\n", | |
349 | alm->time.tm_mon, alm->time.tm_mday, alm->time.tm_wday, | |
350 | alm->time.tm_hour, alm->time.tm_min, alm->time.tm_sec); | |
351 | return 0; | |
352 | } | |
353 | ||
354 | static int mcp795_alarm_irq_enable(struct device *dev, unsigned int enabled) | |
355 | { | |
356 | return mcp795_update_alarm(dev, !!enabled); | |
357 | } | |
358 | ||
359 | static irqreturn_t mcp795_irq(int irq, void *data) | |
360 | { | |
361 | struct spi_device *spi = data; | |
362 | struct rtc_device *rtc = spi_get_drvdata(spi); | |
363 | struct mutex *lock = &rtc->ops_lock; | |
364 | int ret; | |
365 | ||
366 | mutex_lock(lock); | |
367 | ||
368 | /* Disable alarm. | |
369 | * There is no need to clear ALM0IF (Alarm 0 Interrupt Flag) bit, | |
370 | * because it is done every time when alarm is enabled. | |
371 | */ | |
372 | ret = mcp795_update_alarm(&spi->dev, false); | |
373 | if (ret) | |
374 | dev_err(&spi->dev, | |
375 | "Failed to disable alarm in IRQ (ret=%d)\n", ret); | |
376 | rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF); | |
377 | ||
378 | mutex_unlock(lock); | |
379 | ||
380 | return IRQ_HANDLED; | |
381 | } | |
382 | ||
34c7b3ac | 383 | static const struct rtc_class_ops mcp795_rtc_ops = { |
1fcbe42c | 384 | .read_time = mcp795_read_time, |
644d4c36 EB |
385 | .set_time = mcp795_set_time, |
386 | .read_alarm = mcp795_read_alarm, | |
387 | .set_alarm = mcp795_set_alarm, | |
388 | .alarm_irq_enable = mcp795_alarm_irq_enable | |
1fcbe42c JG |
389 | }; |
390 | ||
391 | static int mcp795_probe(struct spi_device *spi) | |
392 | { | |
393 | struct rtc_device *rtc; | |
394 | int ret; | |
395 | ||
396 | spi->mode = SPI_MODE_0; | |
397 | spi->bits_per_word = 8; | |
398 | ret = spi_setup(spi); | |
399 | if (ret) { | |
400 | dev_err(&spi->dev, "Unable to setup SPI\n"); | |
401 | return ret; | |
402 | } | |
403 | ||
43d0b10f EB |
404 | /* Start the oscillator but don't set the value of EXTOSC bit */ |
405 | mcp795_start_oscillator(&spi->dev, NULL); | |
1fcbe42c JG |
406 | /* Clear the 12 hour mode flag*/ |
407 | mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0); | |
408 | ||
409 | rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795", | |
d3e59259 | 410 | &mcp795_rtc_ops, THIS_MODULE); |
1fcbe42c JG |
411 | if (IS_ERR(rtc)) |
412 | return PTR_ERR(rtc); | |
413 | ||
414 | spi_set_drvdata(spi, rtc); | |
415 | ||
644d4c36 EB |
416 | if (spi->irq > 0) { |
417 | dev_dbg(&spi->dev, "Alarm support enabled\n"); | |
418 | ||
419 | /* Clear any pending alarm (ALM0IF bit) before requesting | |
420 | * the interrupt. | |
421 | */ | |
422 | mcp795_rtcc_set_bits(&spi->dev, MCP795_REG_ALM0_DAY, | |
423 | MCP795_ALM0IF_BIT, 0); | |
424 | ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL, | |
425 | mcp795_irq, IRQF_TRIGGER_FALLING | IRQF_ONESHOT, | |
426 | dev_name(&rtc->dev), spi); | |
427 | if (ret) | |
428 | dev_err(&spi->dev, "Failed to request IRQ: %d: %d\n", | |
429 | spi->irq, ret); | |
430 | else | |
431 | device_init_wakeup(&spi->dev, true); | |
432 | } | |
1fcbe42c JG |
433 | return 0; |
434 | } | |
435 | ||
7f8a5892 EB |
436 | #ifdef CONFIG_OF |
437 | static const struct of_device_id mcp795_of_match[] = { | |
438 | { .compatible = "maxim,mcp795" }, | |
439 | { } | |
440 | }; | |
441 | MODULE_DEVICE_TABLE(of, mcp795_of_match); | |
442 | #endif | |
443 | ||
1fcbe42c JG |
444 | static struct spi_driver mcp795_driver = { |
445 | .driver = { | |
446 | .name = "rtc-mcp795", | |
7f8a5892 | 447 | .of_match_table = of_match_ptr(mcp795_of_match), |
1fcbe42c JG |
448 | }, |
449 | .probe = mcp795_probe, | |
450 | }; | |
451 | ||
452 | module_spi_driver(mcp795_driver); | |
453 | ||
454 | MODULE_DESCRIPTION("MCP795 RTC SPI Driver"); | |
455 | MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>"); | |
456 | MODULE_LICENSE("GPL"); | |
457 | MODULE_ALIAS("spi:mcp795"); |