drivers/rtc/rtc-ds1302.c

   1 /*
   2  * Dallas DS1302 RTC Support
   3  *
   4  *  Copyright (C) 2002 David McCullough
   5  *  Copyright (C) 2003 - 2007 Paul Mundt
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License version 2. See the file "COPYING" in the main directory of
   9  * this archive for more details.
  10  */
  11
  12 #include <linux/bcd.h>
  13 #include <linux/init.h>
  14 #include <linux/io.h>
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/of.h>
  18 #include <linux/rtc.h>
  19 #include <linux/spi/spi.h>
  20
  21 #define DRV_NAME        "rtc-ds1302"
  22
  23 #define RTC_CMD_READ    0x81            /* Read command */
  24 #define RTC_CMD_WRITE   0x80            /* Write command */
  25
  26 #define RTC_CMD_WRITE_ENABLE    0x00            /* Write enable */
  27 #define RTC_CMD_WRITE_DISABLE   0x80            /* Write disable */
  28
  29 #define RTC_ADDR_RAM0   0x20            /* Address of RAM0 */
  30 #define RTC_ADDR_TCR    0x08            /* Address of trickle charge register */
  31 #define RTC_CLCK_BURST  0x1F            /* Address of clock burst */
  32 #define RTC_CLCK_LEN    0x08            /* Size of clock burst */
  33 #define RTC_ADDR_CTRL   0x07            /* Address of control register */
  34 #define RTC_ADDR_YEAR   0x06            /* Address of year register */
  35 #define RTC_ADDR_DAY    0x05            /* Address of day of week register */
  36 #define RTC_ADDR_MON    0x04            /* Address of month register */
  37 #define RTC_ADDR_DATE   0x03            /* Address of day of month register */
  38 #define RTC_ADDR_HOUR   0x02            /* Address of hour register */
  39 #define RTC_ADDR_MIN    0x01            /* Address of minute register */
  40 #define RTC_ADDR_SEC    0x00            /* Address of second register */
  41
  42 static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
  43 {
  44         struct spi_device       *spi = dev_get_drvdata(dev);
  45         u8              buf[1 + RTC_CLCK_LEN];
  46         u8              *bp;
  47         int             status;
  48
  49         /* Enable writing */
  50         bp = buf;
  51         *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
  52         *bp++ = RTC_CMD_WRITE_ENABLE;
  53
  54         status = spi_write_then_read(spi, buf, 2,
  55                         NULL, 0);
  56         if (status)
  57                 return status;
  58
  59         /* Write registers starting at the first time/date address. */
  60         bp = buf;
  61         *bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
  62
  63         *bp++ = bin2bcd(time->tm_sec);
  64         *bp++ = bin2bcd(time->tm_min);
  65         *bp++ = bin2bcd(time->tm_hour);
  66         *bp++ = bin2bcd(time->tm_mday);
  67         *bp++ = bin2bcd(time->tm_mon + 1);
  68         *bp++ = time->tm_wday + 1;
  69         *bp++ = bin2bcd(time->tm_year % 100);
  70         *bp++ = RTC_CMD_WRITE_DISABLE;
  71
  72         /* use write-then-read since dma from stack is nonportable */
  73         return spi_write_then_read(spi, buf, sizeof(buf),
  74                         NULL, 0);
  75 }
  76
  77 static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
  78 {
  79         struct spi_device       *spi = dev_get_drvdata(dev);
  80         u8              addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
  81         u8              buf[RTC_CLCK_LEN - 1];
  82         int             status;
  83
  84         /* Use write-then-read to get all the date/time registers
  85          * since dma from stack is nonportable
  86          */
  87         status = spi_write_then_read(spi, &addr, sizeof(addr),
  88                         buf, sizeof(buf));
  89         if (status < 0)
  90                 return status;
  91
  92         /* Decode the registers */
  93         time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
  94         time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
  95         time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
  96         time->tm_wday = buf[RTC_ADDR_DAY] - 1;
  97         time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
  98         time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
  99         time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
 100
 101         return 0;
 102 }
 103
 104 static const struct rtc_class_ops ds1302_rtc_ops = {
 105         .read_time      = ds1302_rtc_get_time,
 106         .set_time       = ds1302_rtc_set_time,
 107 };
 108
 109 static int ds1302_probe(struct spi_device *spi)
 110 {
 111         struct rtc_device       *rtc;
 112         u8              addr;
 113         u8              buf[4];
 114         u8              *bp;
 115         int             status;
 116
 117         /* Sanity check board setup data.  This may be hooked up
 118          * in 3wire mode, but we don't care.  Note that unless
 119          * there's an inverter in place, this needs SPI_CS_HIGH!
 120          */
 121         if (spi->bits_per_word && (spi->bits_per_word != 8)) {
 122                 dev_err(&spi->dev, "bad word length\n");
 123                 return -EINVAL;
 124         } else if (spi->max_speed_hz > 2000000) {
 125                 dev_err(&spi->dev, "speed is too high\n");
 126                 return -EINVAL;
 127         } else if (spi->mode & SPI_CPHA) {
 128                 dev_err(&spi->dev, "bad mode\n");
 129                 return -EINVAL;
 130         }
 131
 132         addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
 133         status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 134         if (status < 0) {
 135                 dev_err(&spi->dev, "control register read error %d\n",
 136                                 status);
 137                 return status;
 138         }
 139
 140         if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
 141                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 142                 if (status < 0) {
 143                         dev_err(&spi->dev, "control register read error %d\n",
 144                                         status);
 145                         return status;
 146                 }
 147
 148                 if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
 149                         dev_err(&spi->dev, "junk in control register\n");
 150                         return -ENODEV;
 151                 }
 152         }
 153         if (buf[0] == 0) {
 154                 bp = buf;
 155                 *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
 156                 *bp++ = RTC_CMD_WRITE_DISABLE;
 157
 158                 status = spi_write_then_read(spi, buf, 2, NULL, 0);
 159                 if (status < 0) {
 160                         dev_err(&spi->dev, "control register write error %d\n",
 161                                         status);
 162                         return status;
 163                 }
 164
 165                 addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
 166                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 167                 if (status < 0) {
 168                         dev_err(&spi->dev,
 169                                         "error %d reading control register\n",
 170                                         status);
 171                         return status;
 172                 }
 173
 174                 if (buf[0] != RTC_CMD_WRITE_DISABLE) {
 175                         dev_err(&spi->dev, "failed to detect chip\n");
 176                         return -ENODEV;
 177                 }
 178         }
 179
 180         spi_set_drvdata(spi, spi);
 181
 182         rtc = devm_rtc_device_register(&spi->dev, "ds1302",
 183                         &ds1302_rtc_ops, THIS_MODULE);
 184         if (IS_ERR(rtc)) {
 185                 status = PTR_ERR(rtc);
 186                 dev_err(&spi->dev, "error %d registering rtc\n", status);
 187                 return status;
 188         }
 189
 190         return 0;
 191 }
 192
 193 static int ds1302_remove(struct spi_device *spi)
 194 {
 195         spi_set_drvdata(spi, NULL);
 196         return 0;
 197 }
 198
 199 #ifdef CONFIG_OF
 200 static const struct of_device_id ds1302_dt_ids[] = {
 201         { .compatible = "maxim,ds1302", },
 202         { /* sentinel */ }
 203 };
 204 MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
 205 #endif
 206
 207 static struct spi_driver ds1302_driver = {
 208         .driver.name    = "rtc-ds1302",
 209         .driver.of_match_table = of_match_ptr(ds1302_dt_ids),
 210         .probe          = ds1302_probe,
 211         .remove         = ds1302_remove,
 212 };
 213
 214 module_spi_driver(ds1302_driver);
 215
 216 MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
 217 MODULE_AUTHOR("Paul Mundt, David McCullough");
 218 MODULE_LICENSE("GPL v2");