drivers/rtc/rtc-ds1216.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Dallas DS1216 RTC driver
   4  *
   5  * Copyright (c) 2007 Thomas Bogendoerfer
   6  *
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/rtc.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/bcd.h>
  13 #include <linux/slab.h>
  14
  15 struct ds1216_regs {
  16         u8 tsec;
  17         u8 sec;
  18         u8 min;
  19         u8 hour;
  20         u8 wday;
  21         u8 mday;
  22         u8 month;
  23         u8 year;
  24 };
  25
  26 #define DS1216_HOUR_1224        (1 << 7)
  27 #define DS1216_HOUR_AMPM        (1 << 5)
  28
  29 struct ds1216_priv {
  30         struct rtc_device *rtc;
  31         void __iomem *ioaddr;
  32 };
  33
  34 static const u8 magic[] = {
  35         0xc5, 0x3a, 0xa3, 0x5c, 0xc5, 0x3a, 0xa3, 0x5c
  36 };
  37
  38 /*
  39  * Read the 64 bit we'd like to have - It a series
  40  * of 64 bits showing up in the LSB of the base register.
  41  *
  42  */
  43 static void ds1216_read(u8 __iomem *ioaddr, u8 *buf)
  44 {
  45         unsigned char c;
  46         int i, j;
  47
  48         for (i = 0; i < 8; i++) {
  49                 c = 0;
  50                 for (j = 0; j < 8; j++)
  51                         c |= (readb(ioaddr) & 0x1) << j;
  52                 buf[i] = c;
  53         }
  54 }
  55
  56 static void ds1216_write(u8 __iomem *ioaddr, const u8 *buf)
  57 {
  58         unsigned char c;
  59         int i, j;
  60
  61         for (i = 0; i < 8; i++) {
  62                 c = buf[i];
  63                 for (j = 0; j < 8; j++) {
  64                         writeb(c, ioaddr);
  65                         c = c >> 1;
  66                 }
  67         }
  68 }
  69
  70 static void ds1216_switch_ds_to_clock(u8 __iomem *ioaddr)
  71 {
  72         /* Reset magic pointer */
  73         readb(ioaddr);
  74         /* Write 64 bit magic to DS1216 */
  75         ds1216_write(ioaddr, magic);
  76 }
  77
  78 static int ds1216_rtc_read_time(struct device *dev, struct rtc_time *tm)
  79 {
  80         struct ds1216_priv *priv = dev_get_drvdata(dev);
  81         struct ds1216_regs regs;
  82
  83         ds1216_switch_ds_to_clock(priv->ioaddr);
  84         ds1216_read(priv->ioaddr, (u8 *)&regs);
  85
  86         tm->tm_sec = bcd2bin(regs.sec);
  87         tm->tm_min = bcd2bin(regs.min);
  88         if (regs.hour & DS1216_HOUR_1224) {
  89                 /* AM/PM mode */
  90                 tm->tm_hour = bcd2bin(regs.hour & 0x1f);
  91                 if (regs.hour & DS1216_HOUR_AMPM)
  92                         tm->tm_hour += 12;
  93         } else
  94                 tm->tm_hour = bcd2bin(regs.hour & 0x3f);
  95         tm->tm_wday = (regs.wday & 7) - 1;
  96         tm->tm_mday = bcd2bin(regs.mday & 0x3f);
  97         tm->tm_mon = bcd2bin(regs.month & 0x1f);
  98         tm->tm_year = bcd2bin(regs.year);
  99         if (tm->tm_year < 70)
 100                 tm->tm_year += 100;
 101
 102         return 0;
 103 }
 104
 105 static int ds1216_rtc_set_time(struct device *dev, struct rtc_time *tm)
 106 {
 107         struct ds1216_priv *priv = dev_get_drvdata(dev);
 108         struct ds1216_regs regs;
 109
 110         ds1216_switch_ds_to_clock(priv->ioaddr);
 111         ds1216_read(priv->ioaddr, (u8 *)&regs);
 112
 113         regs.tsec = 0; /* clear 0.1 and 0.01 seconds */
 114         regs.sec = bin2bcd(tm->tm_sec);
 115         regs.min = bin2bcd(tm->tm_min);
 116         regs.hour &= DS1216_HOUR_1224;
 117         if (regs.hour && tm->tm_hour > 12) {
 118                 regs.hour |= DS1216_HOUR_AMPM;
 119                 tm->tm_hour -= 12;
 120         }
 121         regs.hour |= bin2bcd(tm->tm_hour);
 122         regs.wday &= ~7;
 123         regs.wday |= tm->tm_wday;
 124         regs.mday = bin2bcd(tm->tm_mday);
 125         regs.month = bin2bcd(tm->tm_mon);
 126         regs.year = bin2bcd(tm->tm_year % 100);
 127
 128         ds1216_switch_ds_to_clock(priv->ioaddr);
 129         ds1216_write(priv->ioaddr, (u8 *)&regs);
 130         return 0;
 131 }
 132
 133 static const struct rtc_class_ops ds1216_rtc_ops = {
 134         .read_time      = ds1216_rtc_read_time,
 135         .set_time       = ds1216_rtc_set_time,
 136 };
 137
 138 static int __init ds1216_rtc_probe(struct platform_device *pdev)
 139 {
 140         struct ds1216_priv *priv;
 141         u8 dummy[8];
 142
 143         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 144         if (!priv)
 145                 return -ENOMEM;
 146
 147         platform_set_drvdata(pdev, priv);
 148
 149         priv->ioaddr = devm_platform_ioremap_resource(pdev, 0);
 150         if (IS_ERR(priv->ioaddr))
 151                 return PTR_ERR(priv->ioaddr);
 152
 153         priv->rtc = devm_rtc_device_register(&pdev->dev, "ds1216",
 154                                         &ds1216_rtc_ops, THIS_MODULE);
 155         if (IS_ERR(priv->rtc))
 156                 return PTR_ERR(priv->rtc);
 157
 158         /* dummy read to get clock into a known state */
 159         ds1216_read(priv->ioaddr, dummy);
 160         return 0;
 161 }
 162
 163 static struct platform_driver ds1216_rtc_platform_driver = {
 164         .driver         = {
 165                 .name   = "rtc-ds1216",
 166         },
 167 };
 168
 169 module_platform_driver_probe(ds1216_rtc_platform_driver, ds1216_rtc_probe);
 170
 171 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 172 MODULE_DESCRIPTION("DS1216 RTC driver");
 173 MODULE_LICENSE("GPL");
 174 MODULE_ALIAS("platform:rtc-ds1216");