drivers/rtc/rtc-ds1742.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * An rtc driver for the Dallas DS1742
   4  *
   5  * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
   6  *
   7  * Copyright (C) 2006 Torsten Ertbjerg Rasmussen <tr@newtec.dk>
   8  *  - nvram size determined from resource
   9  *  - this ds1742 driver now supports ds1743.
  10  */
  11
  12 #include <linux/bcd.h>
  13 #include <linux/kernel.h>
  14 #include <linux/gfp.h>
  15 #include <linux/delay.h>
  16 #include <linux/jiffies.h>
  17 #include <linux/rtc.h>
  18 #include <linux/of.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/io.h>
  21 #include <linux/module.h>
  22
  23 #define RTC_SIZE                8
  24
  25 #define RTC_CONTROL             0
  26 #define RTC_CENTURY             0
  27 #define RTC_SECONDS             1
  28 #define RTC_MINUTES             2
  29 #define RTC_HOURS               3
  30 #define RTC_DAY                 4
  31 #define RTC_DATE                5
  32 #define RTC_MONTH               6
  33 #define RTC_YEAR                7
  34
  35 #define RTC_CENTURY_MASK        0x3f
  36 #define RTC_SECONDS_MASK        0x7f
  37 #define RTC_DAY_MASK            0x07
  38
  39 /* Bits in the Control/Century register */
  40 #define RTC_WRITE               0x80
  41 #define RTC_READ                0x40
  42
  43 /* Bits in the Seconds register */
  44 #define RTC_STOP                0x80
  45
  46 /* Bits in the Day register */
  47 #define RTC_BATT_FLAG           0x80
  48
  49 struct rtc_plat_data {
  50         void __iomem *ioaddr_nvram;
  51         void __iomem *ioaddr_rtc;
  52         unsigned long last_jiffies;
  53 };
  54
  55 static int ds1742_rtc_set_time(struct device *dev, struct rtc_time *tm)
  56 {
  57         struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  58         void __iomem *ioaddr = pdata->ioaddr_rtc;
  59         u8 century;
  60
  61         century = bin2bcd((tm->tm_year + 1900) / 100);
  62
  63         writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
  64
  65         writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
  66         writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
  67         writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
  68         writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
  69         writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
  70         writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
  71         writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
  72
  73         /* RTC_CENTURY and RTC_CONTROL share same register */
  74         writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
  75         writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
  76         return 0;
  77 }
  78
  79 static int ds1742_rtc_read_time(struct device *dev, struct rtc_time *tm)
  80 {
  81         struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  82         void __iomem *ioaddr = pdata->ioaddr_rtc;
  83         unsigned int year, month, day, hour, minute, second, week;
  84         unsigned int century;
  85
  86         /* give enough time to update RTC in case of continuous read */
  87         if (pdata->last_jiffies == jiffies)
  88                 msleep(1);
  89         pdata->last_jiffies = jiffies;
  90         writeb(RTC_READ, ioaddr + RTC_CONTROL);
  91         second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
  92         minute = readb(ioaddr + RTC_MINUTES);
  93         hour = readb(ioaddr + RTC_HOURS);
  94         day = readb(ioaddr + RTC_DATE);
  95         week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
  96         month = readb(ioaddr + RTC_MONTH);
  97         year = readb(ioaddr + RTC_YEAR);
  98         century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
  99         writeb(0, ioaddr + RTC_CONTROL);
 100         tm->tm_sec = bcd2bin(second);
 101         tm->tm_min = bcd2bin(minute);
 102         tm->tm_hour = bcd2bin(hour);
 103         tm->tm_mday = bcd2bin(day);
 104         tm->tm_wday = bcd2bin(week);
 105         tm->tm_mon = bcd2bin(month) - 1;
 106         /* year is 1900 + tm->tm_year */
 107         tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;
 108
 109         return 0;
 110 }
 111
 112 static const struct rtc_class_ops ds1742_rtc_ops = {
 113         .read_time      = ds1742_rtc_read_time,
 114         .set_time       = ds1742_rtc_set_time,
 115 };
 116
 117 static int ds1742_nvram_read(void *priv, unsigned int pos, void *val,
 118                              size_t bytes)
 119 {
 120         struct rtc_plat_data *pdata = priv;
 121         void __iomem *ioaddr = pdata->ioaddr_nvram;
 122         u8 *buf = val;
 123
 124         for (; bytes; bytes--)
 125                 *buf++ = readb(ioaddr + pos++);
 126         return 0;
 127 }
 128
 129 static int ds1742_nvram_write(void *priv, unsigned int pos, void *val,
 130                               size_t bytes)
 131 {
 132         struct rtc_plat_data *pdata = priv;
 133         void __iomem *ioaddr = pdata->ioaddr_nvram;
 134         u8 *buf = val;
 135
 136         for (; bytes; bytes--)
 137                 writeb(*buf++, ioaddr + pos++);
 138         return 0;
 139 }
 140
 141 static int ds1742_rtc_probe(struct platform_device *pdev)
 142 {
 143         struct rtc_device *rtc;
 144         struct resource *res;
 145         unsigned int cen, sec;
 146         struct rtc_plat_data *pdata;
 147         void __iomem *ioaddr;
 148         int ret = 0;
 149         struct nvmem_config nvmem_cfg = {
 150                 .name = "ds1742_nvram",
 151                 .reg_read = ds1742_nvram_read,
 152                 .reg_write = ds1742_nvram_write,
 153         };
 154
 155
 156         pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 157         if (!pdata)
 158                 return -ENOMEM;
 159
 160         ioaddr = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
 161         if (IS_ERR(ioaddr))
 162                 return PTR_ERR(ioaddr);
 163
 164         pdata->ioaddr_nvram = ioaddr;
 165         pdata->ioaddr_rtc = ioaddr + resource_size(res) - RTC_SIZE;
 166
 167         nvmem_cfg.size = resource_size(res) - RTC_SIZE;
 168         nvmem_cfg.priv = pdata;
 169
 170         /* turn RTC on if it was not on */
 171         ioaddr = pdata->ioaddr_rtc;
 172         sec = readb(ioaddr + RTC_SECONDS);
 173         if (sec & RTC_STOP) {
 174                 sec &= RTC_SECONDS_MASK;
 175                 cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
 176                 writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
 177                 writeb(sec, ioaddr + RTC_SECONDS);
 178                 writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
 179         }
 180         if (!(readb(ioaddr + RTC_DAY) & RTC_BATT_FLAG))
 181                 dev_warn(&pdev->dev, "voltage-low detected.\n");
 182
 183         pdata->last_jiffies = jiffies;
 184         platform_set_drvdata(pdev, pdata);
 185
 186         rtc = devm_rtc_allocate_device(&pdev->dev);
 187         if (IS_ERR(rtc))
 188                 return PTR_ERR(rtc);
 189
 190         rtc->ops = &ds1742_rtc_ops;
 191
 192         ret = devm_rtc_register_device(rtc);
 193         if (ret)
 194                 return ret;
 195
 196         devm_rtc_nvmem_register(rtc, &nvmem_cfg);
 197
 198         return 0;
 199 }
 200
 201 static const struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
 202         { .compatible = "maxim,ds1742", },
 203         { }
 204 };
 205 MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);
 206
 207 static struct platform_driver ds1742_rtc_driver = {
 208         .probe          = ds1742_rtc_probe,
 209         .driver         = {
 210                 .name   = "rtc-ds1742",
 211                 .of_match_table = of_match_ptr(ds1742_rtc_of_match),
 212         },
 213 };
 214
 215 module_platform_driver(ds1742_rtc_driver);
 216
 217 MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
 218 MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
 219 MODULE_LICENSE("GPL");
 220 MODULE_ALIAS("platform:rtc-ds1742");