drivers/rtc/rtc-r9701.c

   1 /*
   2  * Driver for Epson RTC-9701JE
   3  *
   4  * Copyright (C) 2008 Magnus Damm
   5  *
   6  * Based on rtc-max6902.c
   7  *
   8  * Copyright (C) 2006 8D Technologies inc.
   9  * Copyright (C) 2004 Compulab Ltd.
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/kernel.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/device.h>
  20 #include <linux/init.h>
  21 #include <linux/rtc.h>
  22 #include <linux/spi/spi.h>
  23 #include <linux/bcd.h>
  24 #include <linux/delay.h>
  25 #include <linux/bitops.h>
  26
  27 #define RSECCNT 0x00    /* Second Counter */
  28 #define RMINCNT 0x01    /* Minute Counter */
  29 #define RHRCNT  0x02    /* Hour Counter */
  30 #define RWKCNT  0x03    /* Week Counter */
  31 #define RDAYCNT 0x04    /* Day Counter */
  32 #define RMONCNT 0x05    /* Month Counter */
  33 #define RYRCNT  0x06    /* Year Counter */
  34 #define R100CNT 0x07    /* Y100 Counter */
  35 #define RMINAR  0x08    /* Minute Alarm */
  36 #define RHRAR   0x09    /* Hour Alarm */
  37 #define RWKAR   0x0a    /* Week/Day Alarm */
  38 #define RTIMCNT 0x0c    /* Interval Timer */
  39 #define REXT    0x0d    /* Extension Register */
  40 #define RFLAG   0x0e    /* RTC Flag Register */
  41 #define RCR     0x0f    /* RTC Control Register */
  42
  43 static int write_reg(struct device *dev, int address, unsigned char data)
  44 {
  45         struct spi_device *spi = to_spi_device(dev);
  46         unsigned char buf[2];
  47
  48         buf[0] = address & 0x7f;
  49         buf[1] = data;
  50
  51         return spi_write(spi, buf, ARRAY_SIZE(buf));
  52 }
  53
  54 static int read_regs(struct device *dev, unsigned char *regs, int no_regs)
  55 {
  56         struct spi_device *spi = to_spi_device(dev);
  57         u8 txbuf[1], rxbuf[1];
  58         int k, ret;
  59
  60         ret = 0;
  61
  62         for (k = 0; ret == 0 && k < no_regs; k++) {
  63                 txbuf[0] = 0x80 | regs[k];
  64                 ret = spi_write_then_read(spi, txbuf, 1, rxbuf, 1);
  65                 regs[k] = rxbuf[0];
  66         }
  67
  68         return ret;
  69 }
  70
  71 static int r9701_get_datetime(struct device *dev, struct rtc_time *dt)
  72 {
  73         int ret;
  74         unsigned char buf[] = { RSECCNT, RMINCNT, RHRCNT,
  75                                 RDAYCNT, RMONCNT, RYRCNT };
  76
  77         ret = read_regs(dev, buf, ARRAY_SIZE(buf));
  78         if (ret)
  79                 return ret;
  80
  81         memset(dt, 0, sizeof(*dt));
  82
  83         dt->tm_sec = bcd2bin(buf[0]); /* RSECCNT */
  84         dt->tm_min = bcd2bin(buf[1]); /* RMINCNT */
  85         dt->tm_hour = bcd2bin(buf[2]); /* RHRCNT */
  86
  87         dt->tm_mday = bcd2bin(buf[3]); /* RDAYCNT */
  88         dt->tm_mon = bcd2bin(buf[4]) - 1; /* RMONCNT */
  89         dt->tm_year = bcd2bin(buf[5]) + 100; /* RYRCNT */
  90
  91         /* the rtc device may contain illegal values on power up
  92          * according to the data sheet. make sure they are valid.
  93          */
  94
  95         return rtc_valid_tm(dt);
  96 }
  97
  98 static int r9701_set_datetime(struct device *dev, struct rtc_time *dt)
  99 {
 100         int ret, year;
 101
 102         year = dt->tm_year + 1900;
 103         if (year >= 2100 || year < 2000)
 104                 return -EINVAL;
 105
 106         ret = write_reg(dev, RHRCNT, bin2bcd(dt->tm_hour));
 107         ret = ret ? ret : write_reg(dev, RMINCNT, bin2bcd(dt->tm_min));
 108         ret = ret ? ret : write_reg(dev, RSECCNT, bin2bcd(dt->tm_sec));
 109         ret = ret ? ret : write_reg(dev, RDAYCNT, bin2bcd(dt->tm_mday));
 110         ret = ret ? ret : write_reg(dev, RMONCNT, bin2bcd(dt->tm_mon + 1));
 111         ret = ret ? ret : write_reg(dev, RYRCNT, bin2bcd(dt->tm_year - 100));
 112         ret = ret ? ret : write_reg(dev, RWKCNT, 1 << dt->tm_wday);
 113
 114         return ret;
 115 }
 116
 117 static const struct rtc_class_ops r9701_rtc_ops = {
 118         .read_time      = r9701_get_datetime,
 119         .set_time       = r9701_set_datetime,
 120 };
 121
 122 static int r9701_probe(struct spi_device *spi)
 123 {
 124         struct rtc_device *rtc;
 125         struct rtc_time dt;
 126         unsigned char tmp;
 127         int res;
 128
 129         tmp = R100CNT;
 130         res = read_regs(&spi->dev, &tmp, 1);
 131         if (res || tmp != 0x20) {
 132                 dev_err(&spi->dev, "cannot read RTC register\n");
 133                 return -ENODEV;
 134         }
 135
 136         /*
 137          * The device seems to be present. Now check if the registers
 138          * contain invalid values. If so, try to write a default date:
 139          * 2000/1/1 00:00:00
 140          */
 141         if (r9701_get_datetime(&spi->dev, &dt)) {
 142                 dev_info(&spi->dev, "trying to repair invalid date/time\n");
 143                 dt.tm_sec  = 0;
 144                 dt.tm_min  = 0;
 145                 dt.tm_hour = 0;
 146                 dt.tm_mday = 1;
 147                 dt.tm_mon  = 0;
 148                 dt.tm_year = 100;
 149
 150                 if (r9701_set_datetime(&spi->dev, &dt) ||
 151                                 r9701_get_datetime(&spi->dev, &dt)) {
 152                         dev_err(&spi->dev, "cannot repair RTC register\n");
 153                         return -ENODEV;
 154                 }
 155         }
 156
 157         rtc = devm_rtc_device_register(&spi->dev, "r9701",
 158                                 &r9701_rtc_ops, THIS_MODULE);
 159         if (IS_ERR(rtc))
 160                 return PTR_ERR(rtc);
 161
 162         spi_set_drvdata(spi, rtc);
 163
 164         return 0;
 165 }
 166
 167 static struct spi_driver r9701_driver = {
 168         .driver = {
 169                 .name   = "rtc-r9701",
 170         },
 171         .probe  = r9701_probe,
 172 };
 173
 174 module_spi_driver(r9701_driver);
 175
 176 MODULE_DESCRIPTION("r9701 spi RTC driver");
 177 MODULE_AUTHOR("Magnus Damm <damm@opensource.se>");
 178 MODULE_LICENSE("GPL");
 179 MODULE_ALIAS("spi:rtc-r9701");