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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 | // SPDX-License-Identifier: GPL-2.0-only /* * SPI Driver for Microchip MCP795 RTC * * Copyright (C) Josef Gajdusek <atx@atx.name> * * based on other Linux RTC drivers * * Device datasheet: * https://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf */ #include <linux/module.h> #include <linux/kernel.h> #include <linux/device.h> #include <linux/printk.h> #include <linux/spi/spi.h> #include <linux/rtc.h> #include <linux/of.h> #include <linux/bcd.h> #include <linux/delay.h> /* MCP795 Instructions, see datasheet table 3-1 */ #define MCP795_EEREAD 0x03 #define MCP795_EEWRITE 0x02 #define MCP795_EEWRDI 0x04 #define MCP795_EEWREN 0x06 #define MCP795_SRREAD 0x05 #define MCP795_SRWRITE 0x01 #define MCP795_READ 0x13 #define MCP795_WRITE 0x12 #define MCP795_UNLOCK 0x14 #define MCP795_IDWRITE 0x32 #define MCP795_IDREAD 0x33 #define MCP795_CLRWDT 0x44 #define MCP795_CLRRAM 0x54 /* MCP795 RTCC registers, see datasheet table 4-1 */ #define MCP795_REG_SECONDS 0x01 #define MCP795_REG_DAY 0x04 #define MCP795_REG_MONTH 0x06 #define MCP795_REG_CONTROL 0x08 #define MCP795_REG_ALM0_SECONDS 0x0C #define MCP795_REG_ALM0_DAY 0x0F #define MCP795_ST_BIT BIT(7) #define MCP795_24_BIT BIT(6) #define MCP795_LP_BIT BIT(5) #define MCP795_EXTOSC_BIT BIT(3) #define MCP795_OSCON_BIT BIT(5) #define MCP795_ALM0_BIT BIT(4) #define MCP795_ALM1_BIT BIT(5) #define MCP795_ALM0IF_BIT BIT(3) #define MCP795_ALM0C0_BIT BIT(4) #define MCP795_ALM0C1_BIT BIT(5) #define MCP795_ALM0C2_BIT BIT(6) #define SEC_PER_DAY (24 * 60 * 60) static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count) { struct spi_device *spi = to_spi_device(dev); int ret; u8 tx[2]; tx[0] = MCP795_READ; tx[1] = addr; ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count); if (ret) dev_err(dev, "Failed reading %d bytes from address %x.\n", count, addr); return ret; } static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count) { struct spi_device *spi = to_spi_device(dev); int ret; u8 tx[257]; tx[0] = MCP795_WRITE; tx[1] = addr; memcpy(&tx[2], data, count); ret = spi_write(spi, tx, 2 + count); if (ret) dev_err(dev, "Failed to write %d bytes to address %x.\n", count, addr); return ret; } static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state) { int ret; u8 tmp; ret = mcp795_rtcc_read(dev, addr, &tmp, 1); if (ret) return ret; if ((tmp & mask) != state) { tmp = (tmp & ~mask) | state; ret = mcp795_rtcc_write(dev, addr, &tmp, 1); } return ret; } static int mcp795_stop_oscillator(struct device *dev, bool *extosc) { int retries = 5; int ret; u8 data; ret = mcp795_rtcc_set_bits(dev, MCP795_REG_SECONDS, MCP795_ST_BIT, 0); if (ret) return ret; ret = mcp795_rtcc_read(dev, MCP795_REG_CONTROL, &data, 1); if (ret) return ret; *extosc = !!(data & MCP795_EXTOSC_BIT); ret = mcp795_rtcc_set_bits( dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, 0); if (ret) return ret; /* wait for the OSCON bit to clear */ do { usleep_range(700, 800); ret = mcp795_rtcc_read(dev, MCP795_REG_DAY, &data, 1); if (ret) break; if (!(data & MCP795_OSCON_BIT)) break; } while (--retries); return !retries ? -EIO : ret; } static int mcp795_start_oscillator(struct device *dev, bool *extosc) { if (extosc) { u8 data = *extosc ? MCP795_EXTOSC_BIT : 0; int ret; ret = mcp795_rtcc_set_bits( dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, data); if (ret) return ret; } return mcp795_rtcc_set_bits( dev, MCP795_REG_SECONDS, MCP795_ST_BIT, MCP795_ST_BIT); } /* Enable or disable Alarm 0 in RTC */ static int mcp795_update_alarm(struct device *dev, bool enable) { int ret; dev_dbg(dev, "%s alarm\n", enable ? "Enable" : "Disable"); if (enable) { /* clear ALM0IF (Alarm 0 Interrupt Flag) bit */ ret = mcp795_rtcc_set_bits(dev, MCP795_REG_ALM0_DAY, MCP795_ALM0IF_BIT, 0); if (ret) return ret; /* enable alarm 0 */ ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL, MCP795_ALM0_BIT, MCP795_ALM0_BIT); } else { /* disable alarm 0 and alarm 1 */ ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL, MCP795_ALM0_BIT | MCP795_ALM1_BIT, 0); } return ret; } static int mcp795_set_time(struct device *dev, struct rtc_time *tim) { int ret; u8 data[7]; bool extosc; /* Stop RTC and store current value of EXTOSC bit */ ret = mcp795_stop_oscillator(dev, &extosc); if (ret) return ret; /* Read first, so we can leave config bits untouched */ ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); if (ret) return ret; data[0] = (data[0] & 0x80) | bin2bcd(tim->tm_sec); data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min); data[2] = bin2bcd(tim->tm_hour); data[3] = (data[3] & 0xF8) | bin2bcd(tim->tm_wday + 1); data[4] = bin2bcd(tim->tm_mday); data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1); if (tim->tm_year > 100) tim->tm_year -= 100; data[6] = bin2bcd(tim->tm_year); /* Always write the date and month using a separate Write command. * This is a workaround for a know silicon issue that some combinations * of date and month values may result in the date being reset to 1. */ ret = mcp795_rtcc_write(dev, MCP795_REG_SECONDS, data, 5); if (ret) return ret; ret = mcp795_rtcc_write(dev, MCP795_REG_MONTH, &data[5], 2); if (ret) return ret; /* Start back RTC and restore previous value of EXTOSC bit. * There is no need to clear EXTOSC bit when the previous value was 0 * because it was already cleared when stopping the RTC oscillator. */ ret = mcp795_start_oscillator(dev, extosc ? &extosc : NULL); if (ret) return ret; dev_dbg(dev, "Set mcp795: %ptR\n", tim); return 0; } static int mcp795_read_time(struct device *dev, struct rtc_time *tim) { int ret; u8 data[7]; ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data)); if (ret) return ret; tim->tm_sec = bcd2bin(data[0] & 0x7F); tim->tm_min = bcd2bin(data[1] & 0x7F); tim->tm_hour = bcd2bin(data[2] & 0x3F); tim->tm_wday = bcd2bin(data[3] & 0x07) - 1; tim->tm_mday = bcd2bin(data[4] & 0x3F); tim->tm_mon = bcd2bin(data[5] & 0x1F) - 1; tim->tm_year = bcd2bin(data[6]) + 100; /* Assume we are in 20xx */ dev_dbg(dev, "Read from mcp795: %ptR\n", tim); return 0; } static int mcp795_set_alarm(struct device *dev, struct rtc_wkalrm *alm) { struct rtc_time now_tm; time64_t now; time64_t later; u8 tmp[6]; int ret; /* Read current time from RTC hardware */ ret = mcp795_read_time(dev, &now_tm); if (ret) return ret; /* Get the number of seconds since 1970 */ now = rtc_tm_to_time64(&now_tm); later = rtc_tm_to_time64(&alm->time); if (later <= now) return -EINVAL; /* make sure alarm fires within the next one year */ if ((later - now) >= (SEC_PER_DAY * (365 + is_leap_year(alm->time.tm_year)))) return -EDOM; /* disable alarm */ ret = mcp795_update_alarm(dev, false); if (ret) return ret; /* Read registers, so we can leave configuration bits untouched */ ret = mcp795_rtcc_read(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); if (ret) return ret; alm->time.tm_year = -1; alm->time.tm_isdst = -1; alm->time.tm_yday = -1; tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec); tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min); tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour); tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1); /* set alarm match: seconds, minutes, hour, day, date and month */ tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | MCP795_ALM0C0_BIT); tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday); tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1); ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp)); if (ret) return ret; /* enable alarm if requested */ if (alm->enabled) { ret = mcp795_update_alarm(dev, true); if (ret) return ret; dev_dbg(dev, "Alarm IRQ armed\n"); } dev_dbg(dev, "Set alarm: %ptRdr(%d) %ptRt\n", &alm->time, alm->time.tm_wday, &alm->time); return 0; } static int mcp795_read_alarm(struct device *dev, struct rtc_wkalrm *alm) { u8 data[6]; int ret; ret = mcp795_rtcc_read( dev, MCP795_REG_ALM0_SECONDS, data, sizeof(data)); if (ret) return ret; alm->time.tm_sec = bcd2bin(data[0] & 0x7F); alm->time.tm_min = bcd2bin(data[1] & 0x7F); alm->time.tm_hour = bcd2bin(data[2] & 0x1F); alm->time.tm_wday = bcd2bin(data[3] & 0x07) - 1; alm->time.tm_mday = bcd2bin(data[4] & 0x3F); alm->time.tm_mon = bcd2bin(data[5] & 0x1F) - 1; alm->time.tm_year = -1; alm->time.tm_isdst = -1; alm->time.tm_yday = -1; dev_dbg(dev, "Read alarm: %ptRdr(%d) %ptRt\n", &alm->time, alm->time.tm_wday, &alm->time); return 0; } static int mcp795_alarm_irq_enable(struct device *dev, unsigned int enabled) { return mcp795_update_alarm(dev, !!enabled); } static irqreturn_t mcp795_irq(int irq, void *data) { struct spi_device *spi = data; struct rtc_device *rtc = spi_get_drvdata(spi); int ret; rtc_lock(rtc); /* Disable alarm. * There is no need to clear ALM0IF (Alarm 0 Interrupt Flag) bit, * because it is done every time when alarm is enabled. */ ret = mcp795_update_alarm(&spi->dev, false); if (ret) dev_err(&spi->dev, "Failed to disable alarm in IRQ (ret=%d)\n", ret); rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF); rtc_unlock(rtc); return IRQ_HANDLED; } static const struct rtc_class_ops mcp795_rtc_ops = { .read_time = mcp795_read_time, .set_time = mcp795_set_time, .read_alarm = mcp795_read_alarm, .set_alarm = mcp795_set_alarm, .alarm_irq_enable = mcp795_alarm_irq_enable }; static int mcp795_probe(struct spi_device *spi) { struct rtc_device *rtc; int ret; spi->mode = SPI_MODE_0; spi->bits_per_word = 8; ret = spi_setup(spi); if (ret) { dev_err(&spi->dev, "Unable to setup SPI\n"); return ret; } /* Start the oscillator but don't set the value of EXTOSC bit */ mcp795_start_oscillator(&spi->dev, NULL); /* Clear the 12 hour mode flag*/ mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0); rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795", &mcp795_rtc_ops, THIS_MODULE); if (IS_ERR(rtc)) return PTR_ERR(rtc); spi_set_drvdata(spi, rtc); if (spi->irq > 0) { dev_dbg(&spi->dev, "Alarm support enabled\n"); /* Clear any pending alarm (ALM0IF bit) before requesting * the interrupt. */ mcp795_rtcc_set_bits(&spi->dev, MCP795_REG_ALM0_DAY, MCP795_ALM0IF_BIT, 0); ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL, mcp795_irq, IRQF_TRIGGER_FALLING | IRQF_ONESHOT, dev_name(&rtc->dev), spi); if (ret) dev_err(&spi->dev, "Failed to request IRQ: %d: %d\n", spi->irq, ret); else device_init_wakeup(&spi->dev, true); } return 0; } #ifdef CONFIG_OF static const struct of_device_id mcp795_of_match[] = { { .compatible = "maxim,mcp795" }, { } }; MODULE_DEVICE_TABLE(of, mcp795_of_match); #endif static const struct spi_device_id mcp795_spi_ids[] = { { .name = "mcp795" }, { } }; MODULE_DEVICE_TABLE(spi, mcp795_spi_ids); static struct spi_driver mcp795_driver = { .driver = { .name = "rtc-mcp795", .of_match_table = of_match_ptr(mcp795_of_match), }, .probe = mcp795_probe, .id_table = mcp795_spi_ids, }; module_spi_driver(mcp795_driver); MODULE_DESCRIPTION("MCP795 RTC SPI Driver"); MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>"); MODULE_LICENSE("GPL"); MODULE_ALIAS("spi:mcp795"); |