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 * 15 */ 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> 23 #include <linux/of.h> 24 #include <linux/bcd.h> 25 #include <linux/delay.h> 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 34 #define MCP795_READ 0x13 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 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 47 #define MCP795_REG_ALM0_SECONDS 0x0C 48 #define MCP795_REG_ALM0_DAY 0x0F 49 50 #define MCP795_ST_BIT BIT(7) 51 #define MCP795_24_BIT BIT(6) 52 #define MCP795_LP_BIT BIT(5) 53 #define MCP795_EXTOSC_BIT BIT(3) 54 #define MCP795_OSCON_BIT BIT(5) 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) 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; 85 u8 tx[257]; 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 } 116 117 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 } 162 163 /* 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 } 186 187 static int mcp795_set_time(struct device *dev, struct rtc_time *tim) 188 { 189 int ret; 190 u8 data[7]; 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; 197 198 /* Read first, so we can leave config bits untouched */ 199 ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); 200 201 if (ret) 202 return ret; 203 204 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); 207 data[3] = (data[3] & 0xF8) | bin2bcd(tim->tm_wday + 1); 208 data[4] = bin2bcd(tim->tm_mday); 209 data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1); 210 211 if (tim->tm_year > 100) 212 tim->tm_year -= 100; 213 214 data[6] = bin2bcd(tim->tm_year); 215 216 /* 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; 227 228 /* 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); 233 if (ret) 234 return ret; 235 236 dev_dbg(dev, "Set mcp795: %ptR\n", tim); 237 238 return 0; 239 } 240 241 static int mcp795_read_time(struct device *dev, struct rtc_time *tim) 242 { 243 int ret; 244 u8 data[7]; 245 246 ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); 247 248 if (ret) 249 return ret; 250 251 tim->tm_sec = bcd2bin(data[0] & 0x7F); 252 tim->tm_min = bcd2bin(data[1] & 0x7F); 253 tim->tm_hour = bcd2bin(data[2] & 0x3F); 254 tim->tm_wday = bcd2bin(data[3] & 0x07) - 1; 255 tim->tm_mday = bcd2bin(data[4] & 0x3F); 256 tim->tm_mon = bcd2bin(data[5] & 0x1F) - 1; 257 tim->tm_year = bcd2bin(data[6]) + 100; /* Assume we are in 20xx */ 258 259 dev_dbg(dev, "Read from mcp795: %ptR\n", tim); 260 261 return 0; 262 } 263 264 static int mcp795_set_alarm(struct device *dev, struct rtc_wkalrm *alm) 265 { 266 struct rtc_time now_tm; 267 time64_t now; 268 time64_t later; 269 u8 tmp[6]; 270 int ret; 271 272 /* Read current time from RTC hardware */ 273 ret = mcp795_read_time(dev, &now_tm); 274 if (ret) 275 return ret; 276 /* Get the number of seconds since 1970 */ 277 now = rtc_tm_to_time64(&now_tm); 278 later = rtc_tm_to_time64(&alm->time); 279 if (later <= now) 280 return -EINVAL; 281 /* make sure alarm fires within the next one year */ 282 if ((later - now) >= 283 (SEC_PER_DAY * (365 + is_leap_year(alm->time.tm_year)))) 284 return -EDOM; 285 /* disable alarm */ 286 ret = mcp795_update_alarm(dev, false); 287 if (ret) 288 return ret; 289 /* Read registers, so we can leave configuration bits untouched */ 290 ret = mcp795_rtcc_read(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); 291 if (ret) 292 return ret; 293 294 alm->time.tm_year = -1; 295 alm->time.tm_isdst = -1; 296 alm->time.tm_yday = -1; 297 298 tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec); 299 tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min); 300 tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour); 301 tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1); 302 /* set alarm match: seconds, minutes, hour, day, date and month */ 303 tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | MCP795_ALM0C0_BIT); 304 tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday); 305 tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1); 306 307 ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); 308 if (ret) 309 return ret; 310 311 /* enable alarm if requested */ 312 if (alm->enabled) { 313 ret = mcp795_update_alarm(dev, true); 314 if (ret) 315 return ret; 316 dev_dbg(dev, "Alarm IRQ armed\n"); 317 } 318 dev_dbg(dev, "Set alarm: %ptRdr(%d) %ptRt\n", 319 &alm->time, alm->time.tm_wday, &alm->time); 320 return 0; 321 } 322 323 static int mcp795_read_alarm(struct device *dev, struct rtc_wkalrm *alm) 324 { 325 u8 data[6]; 326 int ret; 327 328 ret = mcp795_rtcc_read( 329 dev, MCP795_REG_ALM0_SECONDS, data, sizeof(data)); 330 if (ret) 331 return ret; 332 333 alm->time.tm_sec = bcd2bin(data[0] & 0x7F); 334 alm->time.tm_min = bcd2bin(data[1] & 0x7F); 335 alm->time.tm_hour = bcd2bin(data[2] & 0x1F); 336 alm->time.tm_wday = bcd2bin(data[3] & 0x07) - 1; 337 alm->time.tm_mday = bcd2bin(data[4] & 0x3F); 338 alm->time.tm_mon = bcd2bin(data[5] & 0x1F) - 1; 339 alm->time.tm_year = -1; 340 alm->time.tm_isdst = -1; 341 alm->time.tm_yday = -1; 342 343 dev_dbg(dev, "Read alarm: %ptRdr(%d) %ptRt\n", 344 &alm->time, alm->time.tm_wday, &alm->time); 345 return 0; 346 } 347 348 static int mcp795_alarm_irq_enable(struct device *dev, unsigned int enabled) 349 { 350 return mcp795_update_alarm(dev, !!enabled); 351 } 352 353 static irqreturn_t mcp795_irq(int irq, void *data) 354 { 355 struct spi_device *spi = data; 356 struct rtc_device *rtc = spi_get_drvdata(spi); 357 struct mutex *lock = &rtc->ops_lock; 358 int ret; 359 360 mutex_lock(lock); 361 362 /* Disable alarm. 363 * There is no need to clear ALM0IF (Alarm 0 Interrupt Flag) bit, 364 * because it is done every time when alarm is enabled. 365 */ 366 ret = mcp795_update_alarm(&spi->dev, false); 367 if (ret) 368 dev_err(&spi->dev, 369 "Failed to disable alarm in IRQ (ret=%d)\n", ret); 370 rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF); 371 372 mutex_unlock(lock); 373 374 return IRQ_HANDLED; 375 } 376 377 static const struct rtc_class_ops mcp795_rtc_ops = { 378 .read_time = mcp795_read_time, 379 .set_time = mcp795_set_time, 380 .read_alarm = mcp795_read_alarm, 381 .set_alarm = mcp795_set_alarm, 382 .alarm_irq_enable = mcp795_alarm_irq_enable 383 }; 384 385 static int mcp795_probe(struct spi_device *spi) 386 { 387 struct rtc_device *rtc; 388 int ret; 389 390 spi->mode = SPI_MODE_0; 391 spi->bits_per_word = 8; 392 ret = spi_setup(spi); 393 if (ret) { 394 dev_err(&spi->dev, "Unable to setup SPI\n"); 395 return ret; 396 } 397 398 /* Start the oscillator but don't set the value of EXTOSC bit */ 399 mcp795_start_oscillator(&spi->dev, NULL); 400 /* Clear the 12 hour mode flag*/ 401 mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0); 402 403 rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795", 404 &mcp795_rtc_ops, THIS_MODULE); 405 if (IS_ERR(rtc)) 406 return PTR_ERR(rtc); 407 408 spi_set_drvdata(spi, rtc); 409 410 if (spi->irq > 0) { 411 dev_dbg(&spi->dev, "Alarm support enabled\n"); 412 413 /* Clear any pending alarm (ALM0IF bit) before requesting 414 * the interrupt. 415 */ 416 mcp795_rtcc_set_bits(&spi->dev, MCP795_REG_ALM0_DAY, 417 MCP795_ALM0IF_BIT, 0); 418 ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL, 419 mcp795_irq, IRQF_TRIGGER_FALLING | IRQF_ONESHOT, 420 dev_name(&rtc->dev), spi); 421 if (ret) 422 dev_err(&spi->dev, "Failed to request IRQ: %d: %d\n", 423 spi->irq, ret); 424 else 425 device_init_wakeup(&spi->dev, true); 426 } 427 return 0; 428 } 429 430 #ifdef CONFIG_OF 431 static const struct of_device_id mcp795_of_match[] = { 432 { .compatible = "maxim,mcp795" }, 433 { } 434 }; 435 MODULE_DEVICE_TABLE(of, mcp795_of_match); 436 #endif 437 438 static struct spi_driver mcp795_driver = { 439 .driver = { 440 .name = "rtc-mcp795", 441 .of_match_table = of_match_ptr(mcp795_of_match), 442 }, 443 .probe = mcp795_probe, 444 }; 445 446 module_spi_driver(mcp795_driver); 447 448 MODULE_DESCRIPTION("MCP795 RTC SPI Driver"); 449 MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>"); 450 MODULE_LICENSE("GPL"); 451 MODULE_ALIAS("spi:mcp795"); 452