drivers/rtc/rtc-ds1302.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Dallas DS1302 RTC Support
   4  *
   5  *  Copyright (C) 2002 David McCullough
   6  *  Copyright (C) 2003 - 2007 Paul Mundt
   7  */
   8
   9 #include <linux/bcd.h>
  10 #include <linux/init.h>
  11 #include <linux/io.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/of.h>
  15 #include <linux/rtc.h>
  16 #include <linux/spi/spi.h>
  17
  18 #define RTC_CMD_READ    0x81            /* Read command */
  19 #define RTC_CMD_WRITE   0x80            /* Write command */
  20
  21 #define RTC_CMD_WRITE_ENABLE    0x00            /* Write enable */
  22 #define RTC_CMD_WRITE_DISABLE   0x80            /* Write disable */
  23
  24 #define RTC_ADDR_RAM0   0x20            /* Address of RAM0 */
  25 #define RTC_ADDR_TCR    0x08            /* Address of trickle charge register */
  26 #define RTC_CLCK_BURST  0x1F            /* Address of clock burst */
  27 #define RTC_CLCK_LEN    0x08            /* Size of clock burst */
  28 #define RTC_ADDR_CTRL   0x07            /* Address of control register */
  29 #define RTC_ADDR_YEAR   0x06            /* Address of year register */
  30 #define RTC_ADDR_DAY    0x05            /* Address of day of week register */
  31 #define RTC_ADDR_MON    0x04            /* Address of month register */
  32 #define RTC_ADDR_DATE   0x03            /* Address of day of month register */
  33 #define RTC_ADDR_HOUR   0x02            /* Address of hour register */
  34 #define RTC_ADDR_MIN    0x01            /* Address of minute register */
  35 #define RTC_ADDR_SEC    0x00            /* Address of second register */
  36
  37 static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
  38 {
  39         struct spi_device       *spi = dev_get_drvdata(dev);
  40         u8              buf[1 + RTC_CLCK_LEN];
  41         u8              *bp;
  42         int             status;
  43
  44         /* Enable writing */
  45         bp = buf;
  46         *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
  47         *bp++ = RTC_CMD_WRITE_ENABLE;
  48
  49         status = spi_write_then_read(spi, buf, 2,
  50                         NULL, 0);
  51         if (status)
  52                 return status;
  53
  54         /* Write registers starting at the first time/date address. */
  55         bp = buf;
  56         *bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
  57
  58         *bp++ = bin2bcd(time->tm_sec);
  59         *bp++ = bin2bcd(time->tm_min);
  60         *bp++ = bin2bcd(time->tm_hour);
  61         *bp++ = bin2bcd(time->tm_mday);
  62         *bp++ = bin2bcd(time->tm_mon + 1);
  63         *bp++ = time->tm_wday + 1;
  64         *bp++ = bin2bcd(time->tm_year % 100);
  65         *bp++ = RTC_CMD_WRITE_DISABLE;
  66
  67         /* use write-then-read since dma from stack is nonportable */
  68         return spi_write_then_read(spi, buf, sizeof(buf),
  69                         NULL, 0);
  70 }
  71
  72 static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
  73 {
  74         struct spi_device       *spi = dev_get_drvdata(dev);
  75         u8              addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
  76         u8              buf[RTC_CLCK_LEN - 1];
  77         int             status;
  78
  79         /* Use write-then-read to get all the date/time registers
  80          * since dma from stack is nonportable
  81          */
  82         status = spi_write_then_read(spi, &addr, sizeof(addr),
  83                         buf, sizeof(buf));
  84         if (status < 0)
  85                 return status;
  86
  87         /* Decode the registers */
  88         time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
  89         time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
  90         time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
  91         time->tm_wday = buf[RTC_ADDR_DAY] - 1;
  92         time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
  93         time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
  94         time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
  95
  96         return 0;
  97 }
  98
  99 static const struct rtc_class_ops ds1302_rtc_ops = {
 100         .read_time      = ds1302_rtc_get_time,
 101         .set_time       = ds1302_rtc_set_time,
 102 };
 103
 104 static int ds1302_probe(struct spi_device *spi)
 105 {
 106         struct rtc_device       *rtc;
 107         u8              addr;
 108         u8              buf[4];
 109         u8              *bp;
 110         int             status;
 111
 112         /* Sanity check board setup data.  This may be hooked up
 113          * in 3wire mode, but we don't care.  Note that unless
 114          * there's an inverter in place, this needs SPI_CS_HIGH!
 115          */
 116         if (spi->bits_per_word && (spi->bits_per_word != 8)) {
 117                 dev_err(&spi->dev, "bad word length\n");
 118                 return -EINVAL;
 119         } else if (spi->max_speed_hz > 2000000) {
 120                 dev_err(&spi->dev, "speed is too high\n");
 121                 return -EINVAL;
 122         } else if (spi->mode & SPI_CPHA) {
 123                 dev_err(&spi->dev, "bad mode\n");
 124                 return -EINVAL;
 125         }
 126
 127         addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
 128         status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 129         if (status < 0) {
 130                 dev_err(&spi->dev, "control register read error %d\n",
 131                                 status);
 132                 return status;
 133         }
 134
 135         if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
 136                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 137                 if (status < 0) {
 138                         dev_err(&spi->dev, "control register read error %d\n",
 139                                         status);
 140                         return status;
 141                 }
 142
 143                 if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
 144                         dev_err(&spi->dev, "junk in control register\n");
 145                         return -ENODEV;
 146                 }
 147         }
 148         if (buf[0] == 0) {
 149                 bp = buf;
 150                 *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
 151                 *bp++ = RTC_CMD_WRITE_DISABLE;
 152
 153                 status = spi_write_then_read(spi, buf, 2, NULL, 0);
 154                 if (status < 0) {
 155                         dev_err(&spi->dev, "control register write error %d\n",
 156                                         status);
 157                         return status;
 158                 }
 159
 160                 addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
 161                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
 162                 if (status < 0) {
 163                         dev_err(&spi->dev,
 164                                         "error %d reading control register\n",
 165                                         status);
 166                         return status;
 167                 }
 168
 169                 if (buf[0] != RTC_CMD_WRITE_DISABLE) {
 170                         dev_err(&spi->dev, "failed to detect chip\n");
 171                         return -ENODEV;
 172                 }
 173         }
 174
 175         spi_set_drvdata(spi, spi);
 176
 177         rtc = devm_rtc_device_register(&spi->dev, "ds1302",
 178                         &ds1302_rtc_ops, THIS_MODULE);
 179         if (IS_ERR(rtc)) {
 180                 status = PTR_ERR(rtc);
 181                 dev_err(&spi->dev, "error %d registering rtc\n", status);
 182                 return status;
 183         }
 184
 185         return 0;
 186 }
 187
 188 static int ds1302_remove(struct spi_device *spi)
 189 {
 190         spi_set_drvdata(spi, NULL);
 191         return 0;
 192 }
 193
 194 #ifdef CONFIG_OF
 195 static const struct of_device_id ds1302_dt_ids[] = {
 196         { .compatible = "maxim,ds1302", },
 197         { /* sentinel */ }
 198 };
 199 MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
 200 #endif
 201
 202 static struct spi_driver ds1302_driver = {
 203         .driver.name    = "rtc-ds1302",
 204         .driver.of_match_table = of_match_ptr(ds1302_dt_ids),
 205         .probe          = ds1302_probe,
 206         .remove         = ds1302_remove,
 207 };
 208
 209 module_spi_driver(ds1302_driver);
 210
 211 MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
 212 MODULE_AUTHOR("Paul Mundt, David McCullough");
 213 MODULE_LICENSE("GPL v2");