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