linux/drivers/rtc/rtc-ds1216.c
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   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
  15struct 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
  29struct ds1216_priv {
  30        struct rtc_device *rtc;
  31        void __iomem *ioaddr;
  32};
  33
  34static 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 */
  43static 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
  56static 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
  70static 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
  78static 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
 105static 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
 133static const struct rtc_class_ops ds1216_rtc_ops = {
 134        .read_time      = ds1216_rtc_read_time,
 135        .set_time       = ds1216_rtc_set_time,
 136};
 137
 138static 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
 163static struct platform_driver ds1216_rtc_platform_driver = {
 164        .driver         = {
 165                .name   = "rtc-ds1216",
 166        },
 167};
 168
 169module_platform_driver_probe(ds1216_rtc_platform_driver, ds1216_rtc_probe);
 170
 171MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 172MODULE_DESCRIPTION("DS1216 RTC driver");
 173MODULE_LICENSE("GPL");
 174MODULE_ALIAS("platform:rtc-ds1216");
 175