drivers/rtc/rtc-mcp795.c

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