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